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Research Papers

J. Med. Devices. 2011;5(2):021001-021001-7. doi:10.1115/1.4003693.

Current gait rehabilitation systems have limited use in community and home settings due to issues of design, cost, and demands on clinical staff. To overcome these challenges, a new gait rehabilitation machine was designed and developed by modifying an existing elliptical trainer. The Intelligently Controlled Assistive Rehabilitation Elliptical (ICARE) provides answers to design limitations that occur in partial-bodyweight-support treadmill systems and other robotic systems by providing a simulated gait motion without the financial and human resource challenges. The ICARE system integrates ergonomic, comfort and safety enhancements with a motor-drive system to optimize usability by individuals with physical disabilities in hospitals, homes, and fitness settings. The affordable new design provides a complete system that reduces physical demands on clinical staff without compromising patient safety. Development and preliminary testing of the ICARE’s motor-drive system are detailed.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):021002-021002-10. doi:10.1115/1.4003736.

Detection of hard inclusions within soft tissue in robotic assisted minimally invasive surgery (MIS), also referred to as laparoscopic surgery, is of great importance, both in clinical and surgical applications. In clinical applications, surgeons need to detect and precisely identify the location and size of all growths, whether cancerous or benign, that are present within surrounding tissue in order to assess the extent and nature of any future treatment plan. In surgical applications, when any solid matter is being removed, it is important to avoid accidental injury to surrounding tissues and blood vessels since, were this to occur, it could then necessitate the need to resort to open surgery. The present study is aimed at developing a three-dimensional tactile display that provides palpation capability to any surgeon performing robotic assisted MIS. The information is collected from two force sensor/pressure matrices and processed with a new algorithm and graphically rendered. Consequently, the surgeon can determine the presence, location, and the size of any hidden superficial tumor/artery by grasping the target tissue in a quasi-dynamic way. The developed algorithm is presented, and the results for various configurations of embedded tumor/arteries inside the tissue are compared with those of the finite element analysis.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):021003-021003-5. doi:10.1115/1.4003822.

Intravenous catheterization is the most common invasive medical procedure today and is designed to introduce medication directly into the blood stream. Common practice is to administer medicine with one syringe, followed by a saline flush to clear the line of any residual medication. The risk of infection due to the introduction of bacteria in the catheter hub is increased with the number of times the hub is accessed. In addition, the two-step process adds millions of nursing hours per year and is prone to error. The goal of this effort was to design and test a dual-chamber syringe that could be reliably used for both dispensing medicine and the saline flush, and be produced at a low cost. The syringe has a novel dual-chamber design with a proximal chamber for medicine and a distal chamber that contains saline. The saline chamber has a fixed volume when the handle is locked into position, which allows the handle to control the variable volume of the medicine chamber. Between the two chambers is a plunger that surrounds the small channel (which is an extension of the distal chamber) that separates the saline from the medicine. When the distal chamber is unlocked, the handle controls the volume of the saline chamber. By this mechanism, the syringe is able inject the medicine followed by the saline flush with a single access to the catheter hub. The smooth operation of the device relies on a locking mechanism to control the rear plunger and volume of the distal saline chamber, and a bubble plug residing in the small channel between the chambers that prevents mixing of the medicine and saline fluids. The bubble plug is held in place by a balance of forces that depend on geometric variables and fluid properties. The chosen design prevents mixing of the two fluids during the operation of the device, which was experimentally validated with mass spectrometry. The dual-chamber syringe has successfully achieved the design goal of a single syringe for the two-step catheter procedure of dispensing medicine and a saline flush. This novel design will reduce the potential for catheter-based infection, medical errors, medical waste, and clinician time. Preliminary test results indicate that this innovation can significantly improve the safety and efficiency of catheter-based administration of medicine.

Commentary by Dr. Valentin Fuster

Technical Briefs

J. Med. Devices. 2011;5(2):024501-024501-6. doi:10.1115/1.4003809.

Clinical gait analysis is the accepted “gold standard” for evaluating an individual’s walking pattern. However, in certain conditions such as idiopathic toe walking (ITW), the degree of voluntary control that a subject may elicit upon their walking pattern in a gait laboratory may not truly reflect their gait during daily activities. Therefore, a battery-powered, wireless data acquisition system was developed to record daily walking patterns to assist in the assessment of treatment outcomes in this patient population. The device was developed to be small (30×50×12mm3), light-weight (15 g), easy to install, reliable, and consumed little power. It could be mounted across the laces of the shoe, while forces and walking activities were recorded to investigate the percentage of toe walking during the assessment. Laboratory tests were performed and preliminary clinical trials at a gait laboratory were done on six normal gait walkers. These volunteers also try to walk on their toes to simulate the toe walking at the gait laboratory. The system was able to track the gait pattern and determine the percentage of toe walking relative to normal gait. Three boys and one girl were diagnosed with ITW then participated into this study. A total of 4 sets thirty-three 10 min data sessions (5.5 h) were collected outside the laboratory. The results showed that the test subjects walked on their toes 70±4% of the total walking time, which was higher than that they performed 64±5% at the gait laboratory. This preliminary study shows promising results that the system should be able to use for clinical assessment and evaluation of children with ITW.

Commentary by Dr. Valentin Fuster

Design Innovation

J. Med. Devices. 2011;5(2):025001-025001-9. doi:10.1115/1.4003675.

This study investigates the design requirements for guiding features that can be incorporated into the shapes of the femoral condyles and the tibial component geometry of a knee replacement system without occupying the intercondylar space of the joint so that the cruciates can be spared and still produce more physiological motions. A conceptual design for a surface-guided knee is introduced to induce effective guiding both in flexion and extension by novel features incorporated in the shape of the lateral condyle. This design can accommodate preservation of either of the cruciates while deficiencies in the functions of the other are compensated by contributions of the articular geometry in guiding the motion and stabilizing the joint. The preliminary kinematic tests on a prototype demonstrated viability of the features in guiding motion under compression.

Commentary by Dr. Valentin Fuster

2011 Design of Medical Devices Conference Abstracts

J. Med. Devices. 2011;5(2):027501-027501-1. doi:10.1115/1.3590859.
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The following abstracts were submitted, peer reviewed and accepted for presentation at the 2011 University of Minnesota's Design of Medical Devices (DMD) Conference (www.dmd.umn.edu) held April 12–14, 2011 at the Radisson University Hotel in Minneapolis, MN. We especially wish to acknowledge Dr. Just Herder who tirelessly chaired the review process, recruited appropriate reviewers and kept us on schedule.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027502-027502-1. doi:10.1115/1.3587100.
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For some postsurgical patients and stroke victims, a drainage bag is used to discharge urine. As a small and intermittent amount of urine drains down the small tube, urine needs to travel around the confined air bubbles that occupy the tube. As the urine squeezes through the gap between the air and the tube’s wall, the air bubbles slowly rise and allow urine to travel downward. The resistance of such film flow is significant and the urine may become stagnant or backflow, resulting in painful pressure on a sensitive part of the body. Bacterial colonization of catheters is common. Each day of catheter use increases the chance for the appearance of bacteria in the urine by 5%. These infections can have serious consequences, including death. Infections can be prevented by maintaining a closed drainage system, keeping high infection control standards and by preventing backflow from the catheter bag. To prevent the backflow from the catheter bag in a closed drainage system will require the improvement of liquid flow through closed tubes in the presence of confined bubbles. This paper demonstrates the use of a tube with a superhydrophobic coating together with either angular cross section, embedded thin fins, or a spiral thread in order to improve the drainage under the aforementioned situations. Due to the superhydrophobic coating, the liquid will tend to stay away from the tube’s surface and because of the angular geometry or other geometric modifications, liquid will not occupy these corner areas. As a result, liquid will tend to move in the central region of the tube while the air counterflow will use the passage near the corners. The outcome was impressive, with bubbles no longer obstructing the flow. Thus, the combination of the effect of modified cross section geometry and the hydrophobic coating will prevent the confined bubble from obstructing liquid flow in tubes. The applications to the improvement of urinary catheters design are discussed in this paper.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027502-027502-1. doi:10.1115/1.3587101.
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The use of surgically implanted or nonsurgically inserted medical devices has received an escalating interest in modern medical practices. Upon implantation or insertion into patient’s body for exerting the intended purpose like salvage of normal functions of vital organs, the medical devices are unfortunately becoming the sites of competition between host cell integration and microbial adhesion. To control microbial colonization and subsequent biofilm formation onto the medical devices, different approaches either to enhance the efficiency of certain antimicrobial agents or to disrupt the basic physiology of the pathogenic micro-organisms, including novel small molecules and antipathogenic drugs, are being explored. In addition, the various lipid- and polymer-based drug delivery carriers are also investigated for applying antibiofilm coating onto the medical devices especially over catheters. The major objectives of this paper are as follows: (1) to synthesize magnesium fluoride (MgF2) nanoparticles; (2) to prepare MgF2 nanoparticle-stabilized oil-in-water (o/w) nanosized emulsion; (3) to coat biomaterial surfaces (glass coupons) with MgF2 nanoparticles, and MgF2 nanoparticle-stabilized emulsion; (4) to challenge the coated and uncoated glass surfaces with fresh bacterial cultures (i.e., Escherichia coli and Staphylococcus aureus) in 24-well plate over 18 h for biofilm formation; and (5) to compare the efficacy of emulsion-coated and emulsion-uncoated glass coupons in restricting the bacterial growth and biofilm formation.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027503-027503-1. doi:10.1115/1.3587102.
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The orthopedic market offers more than 200 hundred different femoral stems, some with scientific published results. The influence of stem geometry relatively to stress distribution on the cement mantle has been addressed by some authors. Stem geometry influences the fatigue mechanism process at the stem-cement interface and may cause aseptic loosening. This study presents a new cemented hip femoral concept. The study was based on finite element analysis and in vitro hip replacements. The numerical models allowed us to determine the cement mantle stresses of commercial stems that were compared with the ones of the new concept. The stem developed presents innovative collar and tip geometries and “organic” stem sections. The new cemented hip prosthesis reduces the average cement stresses around 25% relatively to the best commercial stems studied.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027503-027503-1. doi:10.1115/1.3589216.
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To increase the cement-implant interface strength and simultaneously prevent the possibility of bone thermal necrosis, an automated electronic control device was designed to be use in cemented arthroplasties. The device developed was specifically adapted for the knee arthroplasty, namely, for tibial-tray cementing. The device controls the heat flux direction between the tibial-tray and the atmosphere through the “Peltier effect,” using Peltier tablets. The device is placed on the upper surface of the tibial tray during the cementing phase, to heating the tibial-tray in a first phase, promoting the polymerization which starts at the warmer cement-implant interface. After the initiation of polymerization, the heat flux in the Peltier tablets is inverted (cooling) to extract the heat generated in bone-cement, avoiding bone thermal necrosis. The efficiency of the device was evaluated by cementing several tibial-trays in bovine fresh bone and by measuring the tray and cement temperatures. The results showed that the use of the device increases the implant temperature at the initial bone-cement polymerization phase and reduces the maximum temperature of the cement in the subsequent polymerization process, preventing the effect of bone thermal necrosis.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027504-027504-1. doi:10.1115/1.3589221.
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Better performance of total knee replacement requires normal kinematics and higher range of motion. A potential solution can be a surface-guided knee with asymmetric configuration including a ball-and-socket articulation in the medial compartment and guiding bearing surfaces on the lateral compartment. An innovative design concept with constant bearing spacing and variable radii for the medial and lateral aspects of the lateral condyle as the guiding features is introduced as a potential design solution. This design allows for normal articulation of the patella and preservation of one or both of the cruciates. In this study, the viability of such surface-guided TKR was tested experimentally. A prototype was built and tested on the joint simulator. The results of the preliminary tests demonstrated that the reference bearing surfaces built based on the novel design concept could successfully generate motion patterns similar to the kinematics of a normal knee joint under compressive forces. The developed concept and methodologies can serve as a basis for development of a TKR with normal kinematics.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027504-027504-1. doi:10.1115/1.3589225.
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Laparascopic surgery required inducing a pneumoperitoneum during surgery and anesthesia this presents unique hemodynamic challenges for the anesthetic management of patients. We monitored hemodynamic management using ECOM endotracheal tubes the parameters are derived using Bioimpedance Cardiac output, stroke volume variability, and systemic vascular resistance were measured using this technology. Pneumoperitoneum results in intra-abdominal pressure of 15–20 mm hg induced by CO2 insufflation Hemodynamic parameters were measured using a new noninvasive device, the endotracheal cardiac output monitor (ECOM) (ConMed Corporation, Utica, NY). This monitor provides measurements—including cardiac output, systemic vascular resistance, and stroke volume variation—which were previously unavailable noninvasively. The results obtained were consistent with those found in the literature (1–4). Based on our assessment, it appears that ECOM derived hemodynamic changes are similar to those obtained invasively. Therefore, ECOM’s noninvasive method to measure cardiac output seems advantageous when considering patient safety, because it is less invasive. A better understanding of the applicability and reliability of this new technology in the clinical setting is important for patient safety.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027505-027505-1. doi:10.1115/1.3589229.
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A powered lower limb prosthesis using a four-bar linkage mechanism was previously optimized, designed, and fabricated. Preliminary bench testing was conducted to demonstrate that it is capable of reproducing the normal ankle moment of a nonamputee. This paper focuses on the control aspect of this prosthesis. A finite state controller, which includes a state selector and a lower level controller, is proposed. Three sets of sensors and a sensing schematic will be used to determine the state of the device. Proportional-integral-derivative (PID) torque or position control will be used to realize the lower level control. Future testing will be done on lower limb amputees to prove the feasibility of this control schematic.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027505-027505-1. doi:10.1115/1.3589227.
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Computer modeling of blood flow in patient-specific anatomies can be a powerful tool for evaluating design of implantable medical devices. In this study, we focused on assessing the design of three different endografts, which are commonly used to treat patients with abdominal aortic aneurysms (AAAs). Once implanted, the endograft may shift within the patient’s aorta creating an endoleak and allowing blood to flow into the aneurismal sac. One potential cause for this type of endoleak is the pulsatile forces experienced by the endograft over the cardiac cycle. We used contrast-enhanced computed tomography angiography (CTA) data of a patient with an AAA to build patient-specific models using 3D segmentation. This 3D technique is better able to capture anatomical details than traditional methods using pathlines and lofting of vessel cross sections. The baseline model constructed from the patient’s pre-operative CTA data was then altered using custom software to reflect two different designs of endografts. An additional model was built from the patient’s CTA data after treatment with a novel endograft. In all, models characterizing three distinct endograft designs were created, with each model representing a different location at which the device bifurcated into two limbs. Computational fluid dynamics (CFD) was used to simulate blood flow, utilizing patient-specific boundary conditions. Pressures, flows, and displacement forces were calculated over the models’ domains. The computed blood pressures matched well with the patient’s measured systolic and diastolic pressures. Average volumetric blood flow at each vessel outlet was very similar across all models, indicating that there is a minimal impact on volumetric flow distribution to surrounding vasculature after endograft treatment, regardless of endograft geometry. The magnitude of the displacement force was similar for all devices, although there were some differences in the direction of individual component forces. This indicates that design may influence the displacement force experienced by an implanted endograft, but no device design offers a clear advantage for minimizing displacement force.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027506-027506-1. doi:10.1115/1.3589230.
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Finite element analysis (FEA) of Nitinol medical devices has become prevalent in the industry. The analysis methods have evolved in time with the knowledge about the material, the manufacturing processes, the testing or in vivo loading conditions, and the FEA technologies and computing power themselves. As a result, some common practices have developed. This paper presents a study in which some commonly made assumptions in FEA of Nitinol devices were challenged and their effect was ascertained. The base model pertains to the simulation of the fabrication of a diamond shape stent specimen, followed by cyclic loading. This specimen is being used by a consortium of several stent manufacturers dedicated to the development of fatigue laws suitable for life prediction of Nitinol devices. The FEA models represent the geometry of the specimens built, for which geometrical tolerances were measured. These models use converged meshes, and all simulations were run in the FEA code ABAQUS making use of its Nitinol material models. Uniaxial material properties were measured in dogbone specimens subjected to the same fabrication process as the diamond specimens. By convention, the study looked at computed geometry versus measured geometry and at the maximum principal strain amplitudes during cyclic loading. The first aspect studied was the effect of simulating a single expansion to the final diameter compared with a sequence of three partial expansions each followed by shape setting. The second aspect was to ascertain whether it was feasible to conduct the full analysis with a model based on the electropolished dimensions or should an electropolish layer be removed only at the end of fabrication, similar to the manufacturing process. Finally, the effect of dimensional tolerances was studied. For this particular geometry and loading, modeling of a single expansion made no discernable difference. The fabrication tolerances were so tight that their effect on the computed fatigue drivers was also very small. The timing of the removal of the electropolished layer showed an effect on the results. This may have been so because the specimen studied is not completely periodic in the circumferential direction.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027506-027506-1. doi:10.1115/1.3589231.
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Hydrocephalus is a disease in which cerebrospinal fluid (CSF) accumulates in the ventricular system of the brain. Clinical therapy involves surgically implanting a catheter system to drain this fluid. These systems typically use a pressure-regulated valve system that diverts CSF into a cavity within the body for patients with chronic hydrocephalus. While the treatment is implanted into patients worldwide, its success is unsatisfactory, often requiring numerous revisions due to shunt malfunction. We have recently suggested that a continuous volume sensor may be an alternative approach for use in hydrocephalus treatment. This article highlights advancement of our novel device, which consists of parylene coated sensors with openings for electrode contacts. The instrumentation is miniaturized with the use of surface mount technology. In order to demonstrate the working principle of the technology, the feasibility of acute volume measurements was assessed in an animal model. 250μl of CSF was removed from a hydrocephalic rat, and measurements are shown. Our vision of an improved therapy consists of incorporating this impedance based volume sensor with a controller and micropump for feedback control of CSF volume.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027507-027507-1. doi:10.1115/1.3589287.
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Arterial coarctation especially that occurs in aorta is an extremely significant health problem. Though it is a result of numerous factors, hemodynamics factors and biomechanical forces have been widely accepted as the key roles in its mechanism, development, and complication. In this study, a 2D model, which incorporates fluid-structure interaction (FSI), has been developed. We investigated the flow field and stress field for coarctation with different lengths and severities. The results show that the existence of coarctation will generate higher velocity at the coarctation region. The severity has great effect on the peak velocity while the length effect is slight. Coarctated vessels demonstrate less distensibility than health vessel by comparing the radial expansion displacement. The stress distribution also has significant variation among health vessel and the series of diseased vessels. The results from this investigation suggest that coarctation inhibit wall motion, resulting in higher blood velocities and higher peak wall stress than health vessel. These factors may contribute to further development and other complications.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027507-027507-1. doi:10.1115/1.3589286.
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In Natural Orifice Translumenal Endoscopic Surgery (NOTES), in vivo robots can be utilized to perform surgical procedures within the peritoneal cavity. A NOTES approach has no external incisions, which decreases overall recovery time and reduces the risk of infection. Fully inserting in vivo robots into the peritoneal cavity eliminates the triangulation and multitasking limitations associated with more traditional endoscope-based NOTES approaches. One major limitation is that once inserted, the in vivo robots are isolated within the abdomen and cannot send or receive materials to the outside world. A steerable material handling system is being developed to bridge this deficiency. This paper presents the design rationale, methodology, and parameters associated with the system.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027508-027508-1. doi:10.1115/1.3589290.
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The development of medical devices is a complex problem from initial conception to final implementation and monitoring. The development process is critical, and attesting to this, the completeness of the process and the experience of the developers are identified as important factors for commercializing medical devices. Meanwhile, regulations, standards, and patents should also be considered in the development process. The Food and Drug Administration (FDA) has been reported as the primary factor affecting companies’ ability to develop new medical technology. The use of standards is voluntary; however, multiple benefits are attributed to their use. Patents are also necessary to protect the inventions employed in novel medical devices from being used/further developed by competitors. This paper addresses the complex nature of the medical device development process and its environment through development of an ontology model. The model describes the components of medical device development and their relationships, including the testing and approval environment that impacts this process. The final ontology model is the result from a document analysis (DA), completed in multiple iterations, and the verifications of source credibility, completeness, terminology, and redundancy. The comprehensiveness of the presented model should aid inexperienced designers understand and implement the development process more effectively.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027508-027508-1. doi:10.1115/1.3589289.
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Laparoscopic surgery requires complex manipulation and movement of internal organs. Current laparoscopic devices succeed in offering surgeons remote access to internal organs but lack the grasping degrees of freedom achieved by the human hand. Specifically, needle nose end effectors engage organs via pinching and can cause tissue perforation. To enhance surgical capacity, a three fingered laparoscopic device was designed, fabricated, and tested. Flexures are used to provide three points of articulation in each finger, while minimizing part count. Flexure joints are modeled as pseudorigid bodies and designed for manufacture with medical grade plastics. Articulation is achieved by tendonlike control cables. To integrate with current laparoscopic procedures, the device fits through a 12 mm trocar port. Furthermore, a handle was designed for this device to offer better control. Testing the device with organlike objects revealed an increased ability to grasp, move, and otherwise engage items.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027509-027509-1. doi:10.1115/1.3589813.
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This paper presents a shirt embedded with simple capacitive sensors that accurately monitors the respiration of a sleeping person through chest expansion. It will also discuss a software package that, when coupled with this device, can determine sleep stages from the acquired data. Current sleep studies are the only medically accepted form of sleep health detection and diagnosis; due to the relatively high price of these studies, only persons with breathing-related disorders are referred to them. These studies depend on polysomnography, the use of various bodily signals for sleep detection; patients are often connected to over 20 sensors ranging from brain wave electrodes to blood oxygen trackers. The Somnus shirt is a comfortable, low-cost solution that could be used in the patient’s regular sleep setting. Through some preliminary testing, our respiration-monitoring prototype was able to produce respiration data similar to that of sensors employed in current sleep laboratories while achieving a higher level of comfort for the user; also, the software package was able to analyze sleep with accuracy comparable to current sleep laboratory technicians.

Topics: Sleep
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027509-027509-1. doi:10.1115/1.3589811.
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One of the most challenging tasks in minimal invasive surgeries is the knotting of suture strands due to the lack of space for performing a free hand knotting. Furthermore, the differences between knotting performances of each individual surgeon, sutures are barely uniform from one closure to the other or even from one surgery to another. This may result in suboptimal healing processes due to insufficiencies or dead tissue at the wound area leading to necessary reoperations. Therefore, a new process and device has been developed by the Fraunhofer-Institute for Production Technology to replace conventional knots in minimal invasive surgeries by a new laser welding process. In this paper, the process concept, which is based on small fasteners, will be presented. After some insights on the design and production of the fasteners, results from proof-of-concept experiments will be discussed, which show the outstanding robustness and reproducibility of the welding process. In conclusion, a first prototype of a corresponding minimal invasive suturing device will be presented that has successfully been tested in first laboratory experiments. The new process and device for minimal invasive surgical suturing promises to enable an easier, faster, more reproducible, more uniform, and more sufficient performance of sutures with defined suture tensioning compared with conventional, difficult knotting procedures.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027510-027510-1. doi:10.1115/1.3589815.
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Herein we present a new helical slit tip for the nasogastric (NG) tube to reduce clogging, as well as an accompanying modular in-line flusher to simplify flow restoration to a clogged tube. Nasogastric tubes are one of the most ubiquitous medical devices used in urgent and intensive care situations. Most commonly used to evacuate the stomach during cases of small obstructive bowel syndrome and surgical operations, the NG tube is prone to clogging. A detailed analysis of nasogastric tube obstruction in an ex vivo model was performed. The proposed NG tube tip is an improvement over the current state of the art. Clogging by suction to the mucosa is prevented by the continuous and helical nature of the suction area. Clogging by food particles is avoided by introducing slits rather than holes, and thus inhibiting close packing and clogging of the particulate on the suction tip. The modular in-line flusher is a device that combines into one push the many steps a caregiver usually takes to unclog the tube via flushing, with no disconnections required. Use of the redesigned NG tube and modular in-line flusher will reduce the need to troubleshoot and replace NG tubes, saving care providers’ time, reducing hospital costs, and reducing patient discomfort.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027510-027510-1. doi:10.1115/1.3589826.
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During product development, ideas are narrowed down to a single one by the designers in order to satisfy the customers’ needs. This process is called concept selection and is crucial to the development of new products because, from this point onward, the design team is committed to a concept whose modification implies delays and additional costs. Decisions made during the concept selection phase are often difficult due to the uncertainty caused by the lack of objective data. However, it is possible to reduce this uncertainty assessing each concept’s expected costs and benefit. Medical devices, before entering the market, are scrutinized by several agencies around the world to assess their clinical- and cost-effectiveness. In order to reduce the uncertainty associated with concept selection, the parameters evaluated by the multiple agencies should be used to support the idea to pursue. However, as that data are not available yet, in this paper, several parameters were identified to evaluate each concept and, for each metric, the most adequate measurement technique was described. This paper also presents a specific implementation of the design process for a new stent-graft.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027511-027511-1. doi:10.1115/1.3589827.
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In order to improve dexterity and tactile feedback during grasping in laparoscopic surgery, a pressure-sensing, ergonomic laparoscopic grasper with parallel motion grasper jaws has been designed, prototyped, and tested to provide surgeons with a safer and more user-friendly instrument than what is currently available. Parallel motion grasping creates a uniform pressure distribution along the length of the grasper jaws. Moreover, a pressure sensor located in one of the grasper jaws helps surgeons control the pressure applied during grasping. Ease-of-use of the grasper was enhanced through ergonomic handle design. Results from force and motion testing of a 2x prototype of the design were consistent with analytical predictions. These improvements demonstrate that this new laparoscopic grasper can both improve the dexterity of grasping tasks and reduce the incidence of tissue injury during laparoscopic surgery.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027511-027511-1. doi:10.1115/1.3589828.
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This paper describes a magnetic, nonoperative device and control system designed to treat long-gap esophageal atresia (LEA). This congenital disorder occurs in approximately 100 newborn infants every year and is characterized by a discontinuity in the esophagus between the mouth and stomach. Our device builds upon previous work investigating the use of internal permanent magnets to stretch the proximal and distal esophageal pouches together until anastomosis occurs. We implement a hydraulic standoff device for the proximal magnet assembly to control the distance between the two magnets independent of the esophageal gap size. The standoff allows for controllable, intermittent force between the two pouches and provides a layer of safety from runaway magnetic forces that could potentially damage delicate esophageal tissue. The proximal device comes in two variations: a convex tip for stretching the esophagus and a concave mating tip for meeting the distal end during anastomosis. A light emitting diode (LED) and phototransistor pair estimates the esophageal gap size for the duration of the procedure, and a fluid pressure sensor enables the force on the esophageal tissue to be calculated. The external control circuitry, physician interface, and pump are described that demonstrate the core functionality of the system.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027512-027512-1. doi:10.1115/1.3589829.
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An overlying problem with shunting cerebrospinal fluid (CSF) is that there is no way to directly measure the volume being drained through a shunt once it has been implanted. Therefore, it becomes very difficult to determine if the shunt is working properly. If the patient’s symptoms remain unchanged, the shunt may not be draining fluid, the pressure setting on the shunt may need to be changed, or the patient may simply be unresponsive to shunt treatment. The objective is to develop a prototype shunt device which is capable of measuring, recording, and controlling the amount of CSF that passes through it on a daily basis. By using a positive displacement pump and controlling the stroke frequency, a volume of fluid similar to CSF (water) is controlled, measured, and recorded. If the volume of CSF being drained could be measured and controlled, this would make troubleshooting much easier. By using a bicorporeal device, power supply, and pumping device, it is hypothesized that shunting can be achieved with success.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027512-027512-1. doi:10.1115/1.3589830.
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Laparoscopic surgery is a widespread and rapidly growing surgical technique. One of the challenges facing surgeons performing laparoscopic procedures is the retraction of anatomical structures that restrict vision and access to the surgical site. Current solutions to this problem involve opening additional incisions, which causes increased risk and discomfort to the patient. This study proposes a design for a laparoscopic retractor that can be inserted and operated without the need for additional incisions. The anatomical principles relevant to the design are introduced. The inventive problem is investigated and the design requirements for the device are listed and explained. The processes of initial concept generation and selection are described, as well as the various stages of design refinement and prototyping performed on the chosen concept. User feedback regarding the alpha prototype of the device is presented. Finally, recommendations are made for future development of the device.

Topics: Design , Surgery
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027513-027513-1. doi:10.1115/1.3589832.
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Ultrasound Guided Foam Sclerotherapy is a treatment where a physician injects sclerosant foam along the length of a patient’s varicose vein. The same hypodermic needle is used to perform multiple injections on the same patient and in this example patient discomfort is a common complaint. If hypodermic needles were more efficient at passing through skin tissue, patient discomfort could be reduced. To develop solutions to achieve this, a method for testing hypodermic needle performance was required. For this investigation, a purpose built injection simulator was developed, which had the ability to perform injections in a consistent automated manner while measuring the forces exerted by the needle. Two possible skin substitutes were tested; the first was a synthetic material referred to as basic synthetic skin. This was medium density foam based and was highly consistent in structure. Butchered porcine belly was also used as a substitute. This material was selected as porcine skin bears an acceptable resemblance to human skin. Hypodermic needles were tested in two different states into both skin substitutes. The first group consisted of unmodified needles; the second, unlubricated needles. Normally hypodermic needles are coated with silicone lubricant to improve patient comfort. It was removed so that results from both groups could be compared with establish its effectiveness. The injection simulator was used to insert a needle to a depth of 9 mm into the skin substitute at a rate of 4 mm/s, the needle was allowed to dwell for 6 s and then removed at 4 mm/s. Data from each injection were captured and stored later analysis. Both skin substitutes performed differently, with basic synthetic skin requiring a greater force for both insertion and removal, when compared with porcine belly. When injected into basic synthetic skin, standard needles displayed performance degradation throughout use, with insertion and removal force gradually increasing after each injection whereas unlubricated needles required a constant insertion force. This performance degradation was attributed to the lubricant coating wearing. When injected into porcine belly, standard needles did not display performance degradation; this was attributed to the pickup of oily fluid from the skin tissue. Unlubricated needles displayed slight performance degradation, which was attributed to debris pickup by surface imperfections on the needle surface. The injection simulator designed was suitable for purpose; however, different skin substitutes may be required. Basic synthetic skin was suitable for testing friction reduction techniques; however, porcine belly provided inconsistent results. The lubricant used on hypodermic needles was significant in needle performance and needle tips were not blunted after 25 injections.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027513-027513-1. doi:10.1115/1.3589835.
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The lack of donated blood available for emergency transfusions in the developing world is a critically important issue that can significantly affect the prognosis and recovery of hemorrhaging patients. Autologous transfusion, in which a patient receives a transfusion of his or her own blood, is often used to reduce the need for donated blood. Clinicians in resource-limited settings have developed an improvised method of performing autologous transfusion using a soup ladle and simple gauze filter. This procedure is commonly used in cases of ruptured ectopic pregnancy, during which patients can lose up to 2 l of blood through internal hemorrhage. The process involves several labor- and material-intensive steps, which can cause complications due to excessive environmental exposure and handling of the blood. The aim of this research was to develop a low-cost blood salvage device applicable to resource-limited settings capable of replacing the current method.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027514-027514-1. doi:10.1115/1.3589902.
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Surgical manipulation has been successfully demonstrated using a robotic spherical serial mechanism (called CoBRASurge) having a remote center of rotation driven through a compact bevel-geared system. This cost-effective prototype confirmed surgical robots do not have to be large and expensive machines to operate effectively. After testing and assessing the device, several key design changes were proposed for a second CoBRASurge robot, which would significantly increase the overall effectiveness of the device. These design changes were found after considering the following desirable characteristics: reliability, compactness, precision, protection from contamination, and flexibility in initial setup. These redesign characteristics led to improvements including an increase in gear transmission accuracy by decreasing gear module, implementation of a motor housing to protect against outside contamination, a new rack and pinion driving assembly for a more robust tool translation, decreased volume and weight for ease of use and overall effectiveness, and a new mounting system for a quicker and easier initial setup process. It is believed that these features will further allow the operating surgeon to more effectively complete tasks in less time, and with increased ease as compared with current laparoscopic surgery techniques, while also making multirobot cooperating interventions more feasible.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027514-027514-1. doi:10.1115/1.3589903.
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The British Columbia Institute of Technology’s (BCIT) Health Technology Research Group (HTRG) is a team of multidisciplinary researchers that provides medical device development and evaluation services to clients from medical device companies, health care organizations, and academia. Researchers include biomedical engineers, biomechanics and anthropology scientists, plastics, mechanical, electrical, robotics/automation technologists, trades researchers, and industrial designers. In 2000 the HTRG embarked on the development of a quality system that complied with the design and risk management requirements of the U.S. Food and Drug Administration (FDA) Design Controls, Health Canada’s Canadian Medical Device Conformity Assessment System (CMDCAS), and the ISO 13485 Medical devices—Quality management systems—Requirements for regulatory purposes (ISO 13485). An initial system was developed and launched in 2002. In 2005 we further developed the system to be fully compliant with all requirements of ISO 13485 and obtained certification of the system in 2007. The BCIT HTRG is currently the only ISO 13485 certified academic medical device research group in Canada. The benefits of the quality system for industry clients, students, and the academic research team are discussed as well as the challenges faced in implementing a quality system in an academic research setting. The HTRG has worked with a number of multinational and international companies and would not have been able to attract these clients without operating under a certified system. Our research team is able to shorten the development time from concept to commercialization as prototypes that are developed under a certified quality system can be evaluated in surgical settings. The research staff has been able to access new research funding in part due to the quality system. The major benefit to BCIT’s biomedical and other engineering students is hands-on experience with a working quality system prior to graduation. The challenges associated with introduction and acceptance of a quality system in an academic setting are also discussed along with strategies to increase acceptance of the system. Challenges include overcoming resistance from researchers that perceive quality systems as a constraint on their creativity and as a new administrative burden, managing the costs associated with developing and maintaining a certified quality system, and interfacing with outside departments in an academic environment. Strategies for overcoming these challenges include involving all researchers in the initial development of a system and creating an efficient electronic system that is easily accessed.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027515-027515-1. doi:10.1115/1.3589905.
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An automated method for the creation of patient-specific volumetric articular cartilage elements in the human foot is presented. The algorithm generates visually accurate (based on depictions in the literature) articular cartilage elements by identifying contact surfaces on adjacent bones in a computationally effective manner based on a distance threshold criterion. This method provides an automated and practical cartilage model when compared with current methods, which include scan-by-scan identification and selection, a highly user-biased and tedious process.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027515-027515-1. doi:10.1115/1.3589904.
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The goal of this research is to determine how customer ratings affect the final outcome, which is to determine the optimal number of modules for medical device design. Medical devices have a 90% failure rate in their first prototype tests according to the international testing body, Intertek. To address this key issue of quality, we present an integrated, collaborative modular architecture method for medical device design and development. A typical glucometer is used as proof of concept to demonstrate the methodology and analyze the impact of changing the customer ratings on the optimal number of modules and minimum deviation. The implication of this research is to generate scholarly work and to reduce the number of potential failure points in medical devices by determining the optimal number of modules.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027516-027516-1. doi:10.1115/1.3589907.
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A synergistic experimental and numerical investigation has provided quantitative information on the response of human tissue temperatures to misalignment of the implant and antenna of neuromodulation devices during recharging. It was found that misalignment increases tissue temperatures for all of the investigated devices. These increases ranged from 0.5°C to 2.7°C. Notwithstanding these increases, the lowest temperatures were attained by the Restore Ultra device for all operating conditions. The temperature levels achieved by the Precision Plus and Eon Mini devices were found to be greater than those for the Restore Ultra, but their relative rankings depend on the thermal boundary conditions and the duration of the recharging period.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027516-027516-1. doi:10.1115/1.3590366.
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Medical device start-ups are increasingly being challenged to justify the economic value of their innovation at an early stage, in a manner that is acceptable to the health technology assessment (HTA) community. The experience of introducing a medical device start-up company to health economics methods is described, outlining the construction of a basic Markov model to assess the potential cost-effectiveness of their wound healing innovation for treating diabetic foot ulcer. The model provided the start-up with the means to articulate their innovation in health economic terms. A common understanding of value between innovator and assessors is essential to improving the efficiency of taking innovations though the HTA process and into adoption.

Topics: Medical devices
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027517-027517-1. doi:10.1115/1.3590369.
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Through the use of a cadaveric porcine model, forces necessary for manipulation of the abdominal organs were evaluated using an instrumented probe. Additionally, forces for tissue puncture, knot tightening, and suture breakage have been measured in order to determine the requirements placed upon the design of novel robotic surgical tools. The break forces for a variety of suture sizes and types were evaluated including sizes 3-0 through 7-0 polypropylene, size 1 polybutestor, size 4-0 chromic gut, and size 6-0 braided polyester. Tests of the tissue puncture force and knot tightening forces were carried out using the same instrumented probe, while the suture break forces were measured using a tension testing machine. The measured forces were found to compare well against the literature and provide a good basis from which to design robotic surgical tools with the appropriate capabilities.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027517-027517-1. doi:10.1115/1.3590368.
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Sub-Saharan Africa is the region most heavily affected by HIV, accounting for 67% of HIV positive cases and 72% of AIDS deaths globally in 2007. Public health officials believe adult male circumcision can be an effective HIV prevention intervention and recommend task shifting as an approach to increase the volume of male circumcisions performed in sub-Saharan Africa. Current scale up complications in sub-Saharan Africa include high procedural cost, clinical tools complexity, trained human resources shortages and inefficiencies in health delivery methodologies, preventing many countries from reaching their mass circumcision scale up target goals. A task shifting approach is one method that can both reduce costs and improve healthcare services by delegating critical tasks to less specialized healthcare providers. As a result, the aim of this research is to develop a functional, safe, cost effective adult male circumcision device allowing less-trained healthcare providers to perform the circumcision procedure. This paper discusses the design concept and development of an adult male circumcision device for use in a task shifting clinical setting. Preliminary engineering analyses were completed to support the prototype design, and validation tests on human cadavers and bovine adult reproductive organs were completed to prove the device operates effectively and safely.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027518-027518-1. doi:10.1115/1.3590377.
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In the Netherlands, approximately 100,000 people have a muscle disease. Often this disease is progressive, so patients’ disabilities get worse over time. They end up in a wheelchair and will be dependent on technical supports. Head supports are often not used because of bad cosmetics, comfort, and control. This paper presents a slim, disguisable, and body supported innovative head rest. The prototype is tested in two ways: by tilting the setup to simulate accelerations and observing it during a car drive. It proved to withstand accelerations varying up to around 5m/s2, comparable to normal driving conditions in a bus. While there remains scope for improvement, the prototype was appreciated by the patient. A company is willing to further develop the design.

Topics: Design
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027518-027518-1. doi:10.1115/1.3590375.
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Intra-abdominal surgery has taken large steps away from the conventional method of open incisions in the last 2 decades. Minimally invasive methods have proven to be successful replacements in performing these surgeries. Recently, a newer approach known as natural orifice translumenal endoscopic surgery (NOTES) takes minimally invasive surgery further by eliminating external incisions and instead performs surgery via natural orifices such as the esophagus. NOTES concepts have been in existence during the past decade, but this approach is not widely adopted in human surgeries due mainly to the technological limitations imposed by such surgeries. In this paper, a new robotic platform for natural orifice surgery is described. The robot is designed to carry multiple tool tips in a single end-effector arm that is attached to a steerable and shape lockable drive mechanism. Tool changing capability is achieved by indexing the tool cartridge and advancing the tool of choice. The overall diameter of the robot is small enough for it to navigate through a human esophagus. The steerable and lockable drive mechanism allows easy navigation through the twists and turns of an orifice and also provides a stable platform for the robot while surgery is performed. Design and calculations are presented in this paper, followed by experimental validation. Initial results suggest that the new robotic tool will enable dexterous abdominal surgery with improved force transmission.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027519-027519-1. doi:10.1115/1.3590371.
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Low-intensity ultrasound (LIUS) is a special type of sonic waves that can stimulate and/or regulate various cellular functions, and thereby regulate status of related diseases. In our previous study, LIUS was shown to relieve pain and progression of osteoarthritis (OA) in a rabbit model, when co-treated with hyaluronan. In this study, we investigated the LIUS effect on the repair of OA in vitro and in a rabbit OA model at the molecular level. The rabbit OA model was created by dissecting the anterior cruciate ligaments (ACLs) and medial meniscus on the right knee joints of adult male New Zealand white rabbits. The left knee joint was mock-operated as a sham control. The right knee joints with surgery were mock-treated or treated with LIUS every day for 10 min at a frequency of 1 MHz and an intensity of 100mW/cm2. The rabbits were sacrificed at 2 and 4 weeks postoperatively. In the histochemical analyses of joint cartilages, LIUS was shown to reduce progression of OA-phenotypes such as loss of cells, decrease in the levels of sulfated glycosamionoglycans (GAGs) and type II collagen, and increase in the expression of type X collagen and matrix metalloproteinases (MMP-9 and MMP-13). In the experiment in vitro, rat chondrocytes were treated with interleukin-1? (IL-1 beta) to induce OA-phenotypes. Then, LIUS was treated every day for 20 min from day 0 at varying intensities of 30mW/cm2, 70mW/cm2, and 100mW/cm2. When analyzed at 1, 2, and 3 days, IL-1 beta reduced the expression of cartilage-specific genes of type II collagen and aggrecan and induced the expression of type X collagen, MMP-9 and MMP-13. In contrast, co-treatment of LIUS reversed the activity of IL-1 beta particularly at 30mW/cm2 and 70mW/cm2. These results showed that LIUS inhibited the changes in the expression of OA-related genes. The results of this study confirmed our previous result on the LIUS effect at the molecular level and further suggest that LIUS could be a potent intervention to OA and cartilage disorders in clinics.

Topics: Ultrasound
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027519-027519-1. doi:10.1115/1.3590378.
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The anatomical ankle is capable of providing adaptation to sloped surfaces, a function that is unavailable in most traditional lower limb prostheses. Commercially available prostheses that are claimed to adapt to surfaces have limitations such as high cost, delay in response, reduced stability, and loss of energy through damping. The purpose of the present work was to develop a prototype prosthetic ankle that adapts to sloped surfaces and is sufficiently durable for short-term field trials. The prototype switches between low and high rotational stiffnesses by means of a wrap spring clutch, and demonstrates a change of the ankle alignment in the ankle moment-angle curves when subjects walked with the unit on surfaces of different slopes, suggesting the prototype was providing slope adaptation. The arbors of the wrap spring clutch demonstrated significant wear when tested to 100,000 cycles based on ISO 10328 standards, yet the adaptable ankle continued to hold testing loads. Further efforts to reduce the weight and size of the prototype are essential, and continued refinement of the clutch engagement mechanism is recommended.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027520-027520-1. doi:10.1115/1.3590386.
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This paper presents the preliminary development of a novel cryoablation catheter for the delivery of cryo-energy and complimentary pharmacological agents selected to improve lesion formation. The described prototype uses a commercially available cryoablation catheter with a deployable needle injection catheter grafted onto it. The device would be used in endocardial ablation of thick structures and would inject an adjuvant at the desired depth prior to cryotherapy delivery. Adjuvants have been investigated previously to increase the “kill zone” of an ablation lesion and can minimize the zone of incomplete death near the iceball edge. This makes visualization of the iceball via ultrasound a better predictor for lesion size and progression. Transmurality of a lesion can be essential for a clinical ablation procedure to have long-term effectiveness. The secondary goal of such a device may be to increase energy transfer via the metal needle in the myocardium, so to further aid in the creation of transmural lesions in thick tissues (e.g., the ventricles). Added embodiments of such therapeutic devices would be to also have electrical pacing/sensing capabilities and/or temperature monitoring capabilities at the tip of the needle. Such features would likely provide a physician with more precise information regarding lesion progressions and efficacies. One potential device design could therefore have two temperature sensors, one at the ablative tip and one at the needle tip. This will allow the user to monitor how far and how fast the lesion has advanced into the myocardium at the preset depth of the needle. After the lesion is formed, entrance and exit block tests could then be used to evaluate the ability of the lesion to block electrical propagation. A unique feature of this catheter design approach is the method of active deployment. The physician will preset a desired needle deployment depth and then navigate the catheter to the location of treatment. Next, the cryocatheter would be positioned and frozen to the desired location of the endocardium, when appropriate, the needle would then be deployed, perhaps by first applying a rf energy to warm the system within the created iceball so to allow needle to be actively plunged into the myocardium. Subsequently, the contact of the needle to the cryocatheter system will rapidly cool the needle within the engaged myocardium. This approach could potentially reduce the risks of perforations and ensure consistent deployment depths. As found in the literature, and during preliminary testing, lesion size can be readily increased using the focal delivery of a high NaCl infusion, prior to energy application. We consider here that it should be possible to create the final embodiments of such devices with additional pacing/sensing, temperature monitoring, and active deployment: This should be technologically feasible using commercially available products and stereolithography (SLA) rapid prototyping.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027520-027520-1. doi:10.1115/1.3590387.
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In order to regain haptic feedback when utilizing robot-assisted surgical techniques in the telesurgery, various methods have been utilized. Toward this effort, the most widely used method of utilizing sensors to measure the interaction force between tissue and surgical instruments has inherent drawbacks such as increased size and cost due to the additional sensor modules. In this paper, an alternative sensorless method has been proposed to estimate the interaction force for a surgical robot in telesurgery. This novel method utilizes a calculation algorithm based on accurate dynamic modeling of the robot and the relationship between a motor’s current and torque. Employing this algorithm will resume haptic feedback sensorlessly in telesurgery and simplify the robotic structure, thereby reduce the associated costs. This sensorless force estimation method presents an effective haptic feedback approach for general on-board actuated surgical methods or applications. It is still applicative when the master console and the slave robot are built in dissimilar multi-degree-of-freedom architectures. Consequently, this algorithm will significantly usher the revolution of applications in surgical robotic fields.

Topics: Robots , Haptics , Feedback
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027521-027521-1. doi:10.1115/1.3590552.
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Interwoven self-expandable stents demonstrate distinct characteristics compared with laser-cut ones. In this study, the deployment of interwoven stent in a stenotic artery was evaluated through finite element analysis. Moreover, a laser-cut stent with the same nominal dimensions as the interwoven one was simulated to assess the effect of manufacturing method on mechanical behavior of self-expandable stent. The results showed that relative sliding between struts reduced the strain on the interwoven stent under compressive loadings and larger strain occurred on the struts of laser-cut stent due to its restricted longitudinal extension. After deployment, the interwoven stent restored the patency of the stenotic artery; however, the dogbone shape was observed immediately after the releasing of the stent, which may lead to less lumen gains and higher risk of arterial dissection at both ends of the stent. Lesion preparation prior to the deployment of the stent may help relieve underexpansion of the stent.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027521-027521-1. doi:10.1115/1.3590584.
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Percutaneous treatments for heart disease have created new challenges for both physicians and medical device developers and manufacturers. In order to deliver the highest-quality care to patients, developers and physicians must be able to more easily access the intracardiac environment during the initial phases of device development and while learning to implement new tools and methods. We have developed a pulsatile flow model (PFM), which simulates the intracardiac environment using a bellows-pump and closed fluid flow circuit. The PFM is also outfitted with video imaging and other sensors to provide real-time feedback to a user. The PFM was used to aid in the development of a catheter for the percutaneous treatment of mitral regurgitation via chordal cutting. Knowledge gained from tests with the PFM are now being used by a manufacturer to produce catheters, which would be appropriate for more in-depth trials in both animal and human models. The pulsatile flow model provide physicians and manufacturers of cardiac surgical devices a platform for increasing the efficiency of the development process as well as the physicians ability to better treat patients.

Topics: Pulsatile flow
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027522-027522-1. doi:10.1115/1.3590692.
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The most commonly used stethoscopes in clinics nowadays are the acoustic stethoscopes. They operate on the transmission of sound from the chest piece, via air-filled hollow tubes, to the ears of the healthcare worker. However, even for very experienced healthcare workers, the accuracy of diagnosis of heart murmurs with acoustic stethoscope is limited by the poor ability of the human ears to low frequency heart sounds. This is important, as valuable information from subaudio sounds is present at frequencies below the human hearing range. Thus, the follow-up in-depth tests are needed in order to further distinguish different types of hear murmurs. In this paper, we report the development of a new type of stethoscope using laser technology to make the heartbeat signal “visible.” In this laser-based-stethoscope, the heartbeat signal is correlated with the optical spot from a laser beam reflected from the vibrating diaphragm attached to the patient’s chest skin. Vibration of the diaphragm is generated by the acoustic pressure from the heartbeat. The heartbeat signal is recorded from the movement of optical spot in time domain and it will be transformed to frequency domain to reveal more details on the heartbeat problems. Optical signal processing techniques will be applied to classify and analyze different types of heart murmurs from the visualized heart-sound patterns. This laser-based stethoscope will be helpful in reducing errors in heart-sound classification by practitioners. Additionally, the visual aspect of this stethoscope will provide subaudio (below the human hearing range) and images of sounds to the practitioner. The research results could provide better diagnosis of heart diseases and reduce unnecessary referrals. In the initial demonstration of the system presented in this paper, we set up the prototype of the optical system, in which we use a heart-sound box to simulate the chest of a human being. The movement of optical spot is detected by a linear position sensor and recorded by the USB data acquisition (DA) system. The heart-sound waves collected using iStethoscope Pro (the iPhone App) are applied to activate the vibration of the heart-sound box. With the optical system setup, we successfully acquired the visual display of the heartbeat signal in time domain based on the movement of the reflection spot from the laser beam.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027522-027522-1. doi:10.1115/1.3590627.
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Microhot-embossing is a less complex and inexpensive alternative over standard photolithography for patterning poly(lactic acid) (PLA) films. However, direct patterning of discrete or through-thickness microstructures by conventional microhot-embossing is not possible due to embossing-caused residual film. Use of complex modifications in the embossing process can further prohibit its integration with other standard semiconductor fabrication processes. Plasma-based reactive ion etching (RIE) of embossing-caused PLA residual film can be a viable option potentially allowing integration of the conventional hot-embossing process with standard semiconductor fabrication processes. RIE etch-rates of PLA packaging films, hot-embossed with parylene-based thin-film cochlear implant-shaped stiffener structures, were characterized for oxygen (O2), nitrogen (N2), and argon (Ar) plasmas under two different process conditions. The etch-rates of PLA films for O2, N2, and Ar plasmas were 0.29–0.72 μm/min, 0.09–0.14 μm/min, and 0.11–0.15 μm/min, respectively. Complete removal of embossing-caused residual film has been demonstrated utilizing the etching results for O2 plasma. Also, the effect of RIE etching on resultant PLA film surface roughness has been quantified for the three plasmas.

Topics: Medical devices
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027523-027523-1. doi:10.1115/1.3590649.
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Cardiac catheters allow clinicians to minimally invasively interact with the beating heart without stopping the heart or opening the chest. However, the fast motion of the intracardiac structures makes it difficult to modify and repair the tissue in a controlled and safe manner. To enable surgical procedures on the inside of the beating heart, we have developed an ultrasound-guided catheter system that virtually freezes the heart by compensating for the fast cardiac motions. The device presented in this paper is a resection tool that allows the catheter system to cut moving tissue, a key surgical task required for many intracardiac procedures including valve and leaflet repair. The motion tracking system is demonstrated in vivo and the tissue resection tool is evaluated by resecting tissue mounted on a cardiac motion simulator. The motion compensated catheter is shown to greatly improve the resection cut quality on the moving tissue target while reducing the forces experienced by the tissue by almost 80%.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027523-027523-1. doi:10.1115/1.3590703.
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We describe a specific implementation of the Biodesign process explained by Zenios et al.  and how it may be adapted for use in small teams in an academic or corporate setting. This adaptation is termed disciplined innovation to place emphasis on the rigorous information mining that must occur to truly understand the problem prior to contemplating design solutions. We provide a roadmap with links to online resources for the purpose of navigating the initial stages of the Biodesign process, specifically “Needs Finding” and “Needs Screening.”

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027524-027524-1. doi:10.1115/1.3590704.
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This paper describes the design of the single entry tunneler (SET), devised to create a loop-shaped path in forearm subcutaneous tissue prior to placement of a vascular graft for hemodialysis access. Existing tunnelers are almost universally rigid and require high forces and multiple incisions to complete even the most simple path geometries. Furthermore, they are guided from the handle with limited tip-location feedback. This paper presents a three-stage tunneler design consisting of concentric nested tubes. The first stage is a straight stainless steel tube, the second is a smaller precurved nitinol tube, and the third is a straight inner nitinol tube. By deploying the stages in this order, SET is able to produce an approximately 180 deg looped path in tissue. A tip that is illuminated via a fiber optic cable provides visual feedback of the tip location. The SET outer diameter is limited to ensure that the precurved nitinol will not exceed its yield strain and not require an excessive force to be deployed from the straight outer stage. Therefore, a custom dilator was designed to increase the size of the tunnel to one suitable for the intended graft. A prototype of the SET tunneler and dilator system was manufactured. The device was shown to achieve the desired path in ballistics gel and was capable of at least 100 repeated-use cycles. By reducing the number of required incisions and improving ease of use during graft insertion procedures, the SET has the potential to greatly reduce the risk of infection and degree of unnecessary tissue trauma while increasing tunneling accuracy.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027524-027524-1. doi:10.1115/1.3590705.
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Osseointegration is the direct attachment of a prosthetic device to the bone in order to mimic the use, feel, and behavior of a missing natural limb. In a femoral osseointegrated fixture, the load is transferred directly into the bone using the same force path a natural leg would generate. This leads to better proprioception and sense of the foot contacting the ground. However, traumatic falls or impact loads present a serious concern for the amputee wearing an osseointegrated system. The conceptual device presented here offers a fully mechanical solution to these loading problems by releasing the prosthetic when placed under maximum allowable torsion loads and bending loads in the anteroposterior (AP) and mediolateral (ML) planes. The device is designed to bracket those forces with an upper limit set at 50% greater than the measured gait forces.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027525-027525-1. doi:10.1115/1.3590708.
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Robotic devices have been widely used in biomaterial processing, for example, the cutting operations, also called deboning operations, in a chicken meat harvesting factory. The cutting force will be one of the most useful information for automating the deboning process to maintain the best yield and obtain the satisfied products, i.e., obtaining meat with no bone chips. In this area, a lot of problems need to be studied. This research mainly concentrated on the investigation of the cutting force difference at the initiation of the fracture and those needed to sustain the continuous fracture during the progressive cutting of chicken meat. First, the microstructures of both the blade cutting edges and those of chicken meat were observed and analyzed. The chicken meat cutting fracture was then explained. Based on the parameters measured from the micro-scale analysis, the cutting procedure was simulated and analyzed using a finite element method (FEM). The simulation was realized using software called ABAQUS . From the results, it was observed that the force at cutting fracture initiation is bigger than those to keep the continuous fracture. These results provided the basic understandings for the design of force control algorithms to automate robotic cutting of bio-materials.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027525-027525-1. doi:10.1115/1.3590706.
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An optical wound monitor that is based on diffuse near infrared spectroscopy (DNIRS) was used to interrogate twenty human diabetic foot ulcers. Weekly measurements were conducted until there was wound closure, limb amputation or 20 completed visits without healing. Wound size and degree of wound contraction were measured by image analysis of digital photographs and the results were compared with the NIRS results. Temporal changes of oxy- and total hemoglobin concentration were significantly different in healing versus nonhealing wounds.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027526-027526-1. doi:10.1115/1.3590858.
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This study aims at developing an optical measurement instrument to implement a diffuse optical imaging system that is incorporated with the X-ray mammogram for the purpose of obtaining functional images for breast tumor detection. In this paper, a dual-direction scanning device to project illuminated near infrared (NIR) light with a multiple-channel switching for both sources and detectors was designed and constructed. The device operates to compress breastlike phantoms by two compression plates to reduce the distance between sources and detectors for enhancing the signal to noise ratio (SNR) of measurements and obtaining more reliable data. A dual-direction projection scheme was employed to obtain double information that can benefit image reconstruction. Besides, we also implemented an improved image reconstruction algorithm for a dual-modality imaging scheme by combining the functional images of diffuse optical tomography (DOT) with the structure information of X-ray mammograms. The enhanced computation scheme was validated by using designated cases including various size, contrast, and location of inclusions to background. As a comparison, both simulation and experiments were performed to reconstruct functional optical-coefficient images. A mean square error (MSE) was used for the quantitative evaluation on all reconstruction images.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027526-027526-1. doi:10.1115/1.3590860.
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The dental implantation has been a popular treatment for edentulous and partially dentate patients. To assess osseointegration and discriminate bone defects effectively is demanding for obtaining successful dental implantation. This study aims at developing noncontact a detection technique to measure the severity as well as to locate the orientation of imperfection around bone-implant interface based on resonance frequency analysis (RFA). To justify the effectiveness, both in vitro (artificial bone defects) and in vivo (animal tests) models were performed. A prototype design of an integrated excitation and detection transducer was proposed.

Topics: Design
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027527-027527-1. doi:10.1115/1.3590863.
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Myotonic dystrophy is a dominantly inherited disorder characterized by myotonia and delayed muscle relaxation due to repetitive action potentials in the muscle fibers (hyperexcitability). In this study, a knockout mouse model for the muscle blind proteins (Mbnl1ΔE3ΔE3), a valid model for myotonic dystrophy, was assessed, using an in vivo force assessment device, used in conjunction with EMG recording. The aim of the study was to verify whether the muscle force assessment device we developed was capable to sensitively detect the typical characteristics of myotonic muscle. To date, two wild-type and four myotonic female mice have been assessed. After anesthetic induction by isoflurane, the mice were positioned in the apparatus. Hindlimb muscles were stimulated noninvasively by electrodes placed on the muscle of the leg being stimulated. After establishing optimal muscle length, muscle force was assessed after single pulse stimulation at supramaximal voltage followed by double, triple and quadruple pulses. Both legs from each animal were tested and included in the analyses. Muscle force characteristics (peak force, half relaxation time, and area under the force curve (AUC)) and EMG data were recorded and analyzed. Peak forces generated in the myotonic mice were significantly lower (P<0.02), half relaxation times significantly prolonged (P<0.02), and AUCs significantly increased (P<0.002) as compared with the wild-type mice. The recorded EMGs showed characteristic after depolarizations for the myotonic mice. In conclusion, the muscle force assessment device we developed here was able to detect the typical myotonic features in both reproducible and sensitive ways. This device can be considered as a valid tool for future projects concentrating on the in vivo effects of anesthetic agents or therapies on mouse models of myotonia.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027527-027527-1. doi:10.1115/1.3590861.
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This paper describes the design of an instrument guidance device for percutaneous interventions in closed bore magnetic resonance (MR) imaging systems. The device consists of a curved arm piece that travels around a circular base and an additional needle holder that travels along the curved arm, thus providing two angular degrees of freedom that enable an ablation probe to pivot about a remote center of motion located at the skin entry point. The device is intended to be mounted onto a custom built MR coil that rests on the patient while they are imaged. Exact constraint design principles were used to incorporate translational bearings into the plastic parts. Thumbscrews were used for preload and locking so that the probe guide could be fixed along a specific trajectory. The device was prototyped via stereolithography as a proof of concept and demonstrated that a probe could be angled about a remote pivot point.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027528-027528-1. doi:10.1115/1.3590866.
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POWER KNEE is the world’s first intelligent motor powered prosthetic knee. The knee replaces lost muscle functions and is designed to increase gait symmetry and to reduce unwanted load in level ground walking, stair and ramp descent/ascent, sitting down and standing up. During the first part of swing phase, in general, the knee joint flexes, lifting the foot off the ground. This is an important part of the swing phase as insufficient ground clearance at initial swing has a rippling effect throughout the whole phase and can cause toe stubbing, insecurity of the user, and as a result some types of gait deviations. User of a passive prosthesis knee joint uses his hip to force the foot off the ground whereas a powered knee joint can actively flex the knee at the right moment, ensuring enough ground clearance throughout the swing phase. Every prosthetic knee joint has some internal resistance, which needs to be overcome in order to transfer from knee flexion to extension in swing. In order to overcome this internal resistance, users of passive knee joints use excessive hip power to force the joint into extension. This can cause gait deviations and insecurity for the user as the center of mass is shifted back. An intelligent motor powered knee joint has the ability to remove this unwanted action by actively extending the knee at the right moment. Another benefit of a motor powered prosthesis is that the motor can be actively locked in any flexed position without the risk of the joint buckling. This means that the joint does not have to be fully extended at heel strike and the extension at terminal swing can be fine tuned to leave the joint in approximately 5 deg flexion, imitating the position of a healthy knee. While the motor is blocked at heel strike, avoiding buckling, a mechanical spring controls a stance flexion angle. The stance flexion works as a shock absorption and ensures more symmetry during walking. In addition to controlling the speed and amount of flexion and extension of the knee joint in every gait cycle, a powered knee prosthesis provides the user with enough lifting power to ascend stairs step over step and stand up from a chair with equal weight on the sound side and the prosthesis side. This important feature reduces the unsymmetrical load put on the sound side, arms, and shoulders in those activities.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027528-027528-1. doi:10.1115/1.3590864.
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Clinical studies for new medical devices are expensive to conduct and, if not designed efficiently or with sufficient scientific rigor, can add years to the product development life cycle. In the United States, since the implementation of the 1976 Medical Device Regulations, medical device companies have been working with FDA to find innovative and effective methods to bring new devices to the market. The randomized, controlled clinical trial is the gold standard; however this gold standard study design has not always been required to prove safety and effectiveness of medical devices. This paper explores the Randomized Withdrawal Study Design as a novel trial design for regulated medical device studies. A mock-up trial is described and the advantages and disadvantages of the design are analyzed. The randomized withdrawal trial has been successfully implemented in the pharmaceutical industry. In this design, all patients receive the study therapy and are randomized to have the therapy withdrawn at a time point near the end of the treatment phase. In some settings, a randomized withdrawal study may solve some of the problems inherent in either a traditional randomized design or a nonrandomized design. The potential benefits to utilizing such a design include a higher level of scientific evidence from a single arm study, minimization of the amount of time subjects are exposed to a placebo control, and in the case of enrichment designs, the potential for increased power and decreased time to market due to a smaller sample size requirement.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027529-027529-1. doi:10.1115/1.3590868.
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In literature, little comparison data are available among various morcellators, which are used to remove large tissue masses minimal invasively. Since a range of morcellators is available on the market, and their use is fairly common, it is important to know whether the devices perform optimally, or if one is more efficient than another, regardless of what the industry claims. To this purpose, a literature research was performed in a companion study to find and compare all previous, current and experimental morcellators. However, due to the lack of a standard in literature to which morcellators are tested, there is little unity in the method of reporting morcellation functionality, which makes a comparison between morcellators difficult. For this reason, a data gathering protocol is suggested to function as a tool to obtain all relevant morcellator related data. This helps surgeons to more objectively assess their morcellation procedures, compare obtained data to statements made by the manufacturers with respect to morcellation speed, and improve future in-literature morcellator data reporting.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027529-027529-1. doi:10.1115/1.3590867.
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In literature, little comparison data are available between various morcellators, which are used to remove large tissue masses minimally invasively. Since various morcellators are available on the market, and they are used fairly frequently, it is important to know whether the devices perform optimally, or if one is more functional than another. To this purpose, a literature research has been performed to find all previous, current and experimental morcellators and compare their morcellation rates (g/min), i.e., the removed mass divided by its removal time. The instruments were categorized by their respective working principles and significant trends were identified in the field of morcellation from the found and calculated data. The main findings are that the newest morcellators on the market, which rely on the principle of “motor peeling,” are indeed the fastest in terms of morcellation rate, yet it seems that improvements are still possible when it comes to speed and safety. Based on literature, these improvements include the use of an endoscopic bag with a custom created environment and the optimization of the continuity of the applied morcellation working principle.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027530-027530-1. doi:10.1115/1.3590872.
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Motivation: Human assist devices such as hand tools and orthotics require high force, low speed, compact size, and light weight, which match hydraulics. Traditionally, hydraulic systems are used in applications that require large amounts of power so components are large and heavy. To apply hydraulic technologies to human assist devices, traditional hydraulic components must be scaled down to appropriate power levels, that is, from thousands of watts to about 100 W. To apply small-scale (10–100 W) hydraulics to human assist devices, three steps were taken. First, a hydraulic ankle foot orthosis (AFO) was built and tested to understand the feasibility of using small-scale hydraulics in human assist devices. Second, a small-scale electrohydraulic actuator (EHA) system was built to identify the gaps between the desired small-scale hydraulic components and the smallest off-the-shelf hydraulic components. Third, basic fluid mechanics and structural equations were used to model the efficiency of small-scale hydraulic components, which is the key to miniaturize traditional hydraulic systems. Results: The AFO platform showed that sufficient torque and range of motion can be realized with a hydraulic system but confirmed the need for small hydraulics to reduce the weight and bulk. The EHA system showed that the smallest off-the-shelf components are oversized for a small-scale hydraulic system and identified the need for custom small-scale hydraulic components. The efficiency models showed that reasonable efficiencies are achievable for small-scale hydraulic components, but different design rules are required.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027530-027530-1. doi:10.1115/1.3590873.
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Chronic pain is a significant public health problem throughout the world. In the United States alone, chronic pain accounts for an estimated $61 billion a year in lost work productivity and is the leading cause of disability and reduced quality of life in the working population. Treatment of pain is therefore an important and active area of research. For each new treatment modality or drug developed, quantitative evaluation is necessary to judge its efficacy and optimal target population. Quantitative Sensory Testing (QST) provides a standardized and quantifiable methodology to study pain sensitivity in humans. A QST protocol describes a series of noxious and nonnoxious stimuli (e.g., heat, pressure, or electrical) delivered to a patient, and a semi-objective method for the patient to rate their perception of each stimulus. Using this information, clinicians are able estimate the level of a patient’s pain sensitivity. This information can be used in the diagnosis of the pain source, the prediction of future pain occurrence, or the assessment of treatment efficacy. In traditional QST, fairly rudimentary devices have been used to deliver stimuli, such as manual dolorimeters or von Frey filaments; however, these methods suffer from inaccuracies primarily due to their operator dependence. More sophisticated QST devices that are also available are large and difficult to use, thus limiting their clinical applicability. This paper presents the motivation, design, and evaluation of a novel pressure-type QST system termed the multimodal automated sensory testing (MAST) system. The system’s primary benefit is that it significantly reduces operator based experimental variability by automatically delivering stimuli and prompting the patient for feedback. In addition, its small size and ease of use allow it to be used clinically at the point-of-care. We present encouraging results illustrating that the MAST system offers reduced experimental variability and is able to discriminate between healthy human subjects and those with chronic pain. The advantages of using this type of device in clinical research will be highlighted with additional data showing that this system permits evaluation of response variability and tissue characteristics previously hidden in the measurement “noise” of current pressure-type QST systems.

Topics: Testing
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027531-027531-1. doi:10.1115/1.3590874.
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While cystoscopic surveillance, which uses a type of endoscope used by urologists to view the interior surface of patient’s bladder, is regarded as the “gold standard” for bladder cancer detection, it remains imperfect. Physicians advance a rigid or flexible scope through a patient’s urethra and into his/her bladder, manually manipulating the probe in order to view the entire inner surface of the bladder. Thus, the completeness of cystoscopic examinations remains completely dependent on the examining physician. We propose a few scanning trajectories, which can be potentially adopted in the mechatronics approach to minimize operator errors. An automated image mosaicing software, which would afford 3D reconstruction of the bladder for more efficient surveillance, is proposed to achieve a high resolution and comprehensive model of the bladder. The software adequately reconstructs the internal surface of the virtual model under all three scan trajectories as a proof-of-concept.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027531-027531-1. doi:10.1115/1.3590875.
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A longstanding controversy in the field of cardiac surgery is whether or not to repair the pericardium on completion of open heart surgery. The device proposed is a multilumen catheter that will allow for delivery and removal of fluids to and from the pericardial space. In more detail, the main lumen will allow for gentle suction. A second lumen will allow for targeted drug delivery if desired. Targeted drug deliver can be especially important in the case of adverse events such as infection or postoperative atrial fibrillation. A temporary pacing lead through the catheter will allow for increased rate control by means of antibradicardic pacing. The catheter can help reduce the complications involved with closing the pericardium and thus encouraging more surgeons to complete this task in more procedures in order to reduce complications among the ever-increasing number of repeat operations.

Topics: Drainage , Catheters
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027532-027532-1. doi:10.1115/1.3590876.
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In vivo animal models have been and remain the “gold standard” for medical device testing. However, these models sometimes present disadvantages in terms of similarity to human anatomy, associated high cost, and other complexities. This is especially true when considering devices that are to be introduced via the peripheral cardiovascular system and navigated to their destination using catheter-based techniques. Hence, the utilization of fresh human cadavers for such investigations has become an attractive alternative or complement to animal in vivo testing. The main drawbacks to using a cadaver for such testing are the lack of perfusion and heart movement, which can cause difficulties in simulating device placement. To overcome these issues, we constructed a pump system consisting of a centrifugal pump and solenoid valve to generate a pulsatile flow through an intact cadaver heart, causing cardiac movements meant to approximate right heart physiologic conditions. The system was able to generate an approximately sinusoidal right ventricle pressure with a mean of 22 mm Hg and amplitude of 4 mm Hg at 60 beats/min. Heart movements were observable and the physicians testing device delivery methods reported that they could perceive catheter movements during placement. It is planned that in the next iteration the system will be modified to likely include a positive displacement pump and varied cannulation strategies. Overall, the system has provided a solid foundation for future work. Improvements to the system will allow for more realistic heart movement and will aid in subsequent device testing.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027532-027532-1. doi:10.1115/1.3590877.
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The design, development, and implementation of health-related technologies for resource-limited settings require a detailed consideration of the end user and target community that goes beyond the traditional engineering design needs assessment. In a broader sense, economic, social, and cultural constraints must be considered for successful implementation of technologies. Such constraints are often difficult or impossible to ascertain a priori, necessitating significant fieldwork; there is currently no database where prospective designers for global health can review how others have fared with similar and diverse challenges. Here we present the concept and preliminary results of a medical device case study database developed through research of best practices in low-cost medical devices designed for diagnosis, treatment, and prevention of the World Health Organization top ten causes of death in low-income countries in addition to Millennium Development Goals 4 and 5. Over 170 identified cases were organized based on device type (e.g., diagnostic, treatment, and preventive), development stage (e.g., preclinical, clinical trial, and market) and geographical implementation.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027533-027533-1. doi:10.1115/1.3590878.
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The transition from multiple-port to single-port robotic systems in minimally invasive surgery (MIS) procedures has made flexible, dexterous manipulation an essential capability. The requirement that single-port MIS devices span an enclosed surgical workspace through only one access point while avoiding collateral damage to surrounding tissues necessitates the employment of mechanically sophisticated, kinematically redundant device architectures. These redundant architectures, while capable of achieving clinically acceptable performance levels on complicated MIS procedures, are difficult to design and can easily result in economically prohibitive or technically impractical solutions. The problem of balancing clinical functionality and design economy in single-port MIS devices becomes even more challenging when the dexterous that uses multiple surgical tools is required for a given procedure. This research presents a design methodology aimed at reducing the number of degrees of freedom needed to achieve dexterous motion for a multiple-arm single-port MIS device. This design methodology exploits the availability of multiple manipulator arms by quantifying device dexterity in terms of cooperative manipulability, such that the dexterity of two or more nonredundant manipulator arms can be synergistically combined to achieve a high level of motion redundancy. This methodology, in theory, can be used to design multiple-arm MIS devices such that each arm is specialized for a particular type of motion, thus obviating the need for more versatile, redundant manipulator arms, which innately require higher DOFs and, by extension, demand greater mechanical sophistication and device cost. The concept of cooperative kinematic isotropy, an extension of prior work on weighted global isotropy indices, is developed as a multiple-arm MIS device fitness metric. This metric quantifies kinematic isotropy as the aggregate isotropy of two or more manipulator arms and allows the treatment surgical procedures as a task-specific, hybrid set of individual and cooperative manipulation tasks. The efficacy of cooperative kinematic isotropy is demonstrated on the design of a four-armed single-port MIS device designed for blood vessel anastomosis procedures that typically require such a hybrid set of manipulation tasks. Results show that cooperative kinematic isotropy is an effective means reducing MIS device complexity while maintaining adequate levels of kinematic dexterity for specific surgical procedures. The author concludes that this new design fitness metric, while heuristic in nature and based on several key design and simulation assumptions, holds the potential to improve both the clinical value and the economy of cutting-edge, multiple-armed single-port MIS systems.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027533-027533-1. doi:10.1115/1.3590880.
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The adoption of laparoendoscopic single-site surgery (LESS) provides potential for surgical procedures to be performed with the use of a single incision into the peritoneal cavity. Benefits of this technique include faster recovery times, decreased chance of infection, and improved cosmetic results as compared with traditional surgery. Current technology in this area relies on multiple laparoscopic tools, which are inserted into the peritoneal cavity through a specialized port. Because of this, poor visualization, limited dexterity, and unintuitive controls occur. To mitigate these problems, this research group is developing a multifunctional, two-armed miniature in vivo surgical robot with a remote user interface for use in LESS. While this platform’s feasibility has been demonstrated in multiple nonsurvival surgeries in porcine models, including four cholecystectomies, previous prototypes have been too large to be inserted through a single incision. Work is currently being performed to reduce the overall size of the robot while increasing dexterity. Using the knowledge gained from the development of a four degree of freedom (DOF) miniature in vivo surgical robot, another robot prototype was designed, which was smaller, yet was able to utilize 5DOFs instead 4. The decreased size of the 5DOF robot allows it to be completely inserted into the peritoneal cavity through a single incision for use in LESS. Each arm of the surgical robot is inserted independently before being mated together and attached to a central control rod. Once inserted, this platform allows for gross repositioning of the robot to provide surgical capabilities in all four quadrants of the abdominal cavity by rotating the control rod. The additional degree of freedom allows for reaching positions in the surgical workspace from varied angles. This paper will provide a comparison of the 4DOF and 5DOF miniature in vivo surgical robots. The implications of the added degree of freedom on the forward and inverse kinematics will be discussed and the workspace of each robot will be compared. Additionally, the increased complexity of the control system for the remote surgical interface in moving from 4DOFs to 5DOFs will be demonstrated. Finally, results from nonsurvival procedures using a porcine model will be presented for both robots. This comparison will provide useful information for further development of miniature in vivo surgical robots as the goals of decreased size and improved dexterity are approached.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027534-027534-1. doi:10.1115/1.3591376.
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Superparamagnetic iron oxide nanoparticles are of interest for use as magnetic resonance imaging contrast agents and in thermal therapies. Silica nanoparticle coatings can increase the thermal stability of particles and provide a biologically inert surface for the attachment of functionalizing ligands. In this study, silica-coated magnetic iron oxide nanoparticles were produced by synthesizing core iron oxide nanoparticles in a thermal plasma followed by coating the particles with silica by photoinduced chemical vapor deposition (photo-CVD). Core particles were shown to be superparamagnetic with a maximum saturation magnetization of 29 emu/g. The photo-CVD process produced silica coatings with thicknesses up to 6 nm. Coatings were found to consist of conformal high-purity silica. The presence of the coating was found to decrease the saturation magnetization when evaluated on a total mass basis (iron oxide and silica).

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027534-027534-1. doi:10.1115/1.3591377.
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It is important to identify and understand variations in the anatomy of the human cardiac venous system in order to best develop and then use minimally invasive cardiac devices. Hence, anatomical mapping of the cardiac venous system of a large sampling of human heart specimens, with and without disease, will be a beneficial aid for cardiac device designers. We utilized fluoroscopy, a Microscribe 3Dx digitizer and IMAGEWARE software to obtain maps of the cardiac veins and to create 3D models. To date, we have created models for 19 perfusion fixed human hearts and will measure the anatomical parameters for each model. We have started and will continue to create a unique anatomical database for the major cardiac veins that will include vessel diameters, arc lengths, tortuousities, and branching angles from the coronary sinus. This novel database of cardiac venous anatomical parameters will allow one to better visualize and understand the degree of anatomical variability that exists between human hearts. We will continue to build this data set, which should be of great value for both device designers and those clinically implanting cardiac devices.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027535-027535-1. doi:10.1115/1.3591380.
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Colorectal cancer is one of the commonly occurring types of cancer and individuals above 50 years of age are considered at a high risk. Everyone is suggested to undergo full colonoscopy every 10 years. Training medical students by operating on patients directly is not safe and not comfortable for the patients. Hence, a training model is being developed to train medical students. In the training sessions, if student gets information regarding the distal end of colonoscope, he can prepare and plan his future moves and he also gets the information concerning the diseased part of the colon. This information also helps the student if he requires inserting a surgical tool along with the colonoscope. In the present study, the distal end of colonoscope is localized using photocells. The colonoscope has a light source for the camera at its distal end. These photocells are connected in basic comparator circuit. The photocells are fitted at specific locations on rubber colon, whose voltage changes on reception of light beam. The photocells are interfaced with a data acquisition system, using which data are acquired. While tracking the distal end, noise created in some photocells at particular instant yields misleading information. In order to avert such occurrence, an algorithm is written separately for advancement and retraction. Using these data, distal end is accurately localized and also specific time required during the test, to pass the colonoscope through specific parts of colon for further analysis.

Topics: Sensors
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027535-027535-1. doi:10.1115/1.3591379.
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Colonoscopy can be associated with many problems, such as mechanical trauma due to the distal tip contacting the colon wall or health issues due to the extended use of anesthesia. In order to eliminate these complications, an automatically adjustable colonoscope was designed. This device uses sensors, actuators, and a control system to automatically position the distal tip in the center of the colon lumen. The sensors were tested to determine their ability to accurately sense the distance from the tip to the surface of a white PVC tube. The actuators were tested to determine the correlation between motor rotation and displacement of the distal tip. The control system was tested to assess the ability of the device to position the tip in the center of the test tube and the ability to navigate through a flat test course. It was determined that the sensors could accurately determine distances from 0 mm to 15 mm from the test surface in all test conditions. The motors for up-down movement and left-right movement of the colonoscope had response times of 0.57 s and 0.69 s, respectively, when the motors were rotated from 0 deg to 90 deg. The control system was able to safely move the colonoscope tip away from all walls of the test apparatus. It was also able to navigate through the flat test course without coming in contact with the walls. The automatically adjustable colonoscope has demonstrated that it can safely and effectively position the distal tip to avoid contact with the walls of the test surface.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027536-027536-1. doi:10.1115/1.3591385.
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Tissue engineered pulmonary valve (TEPV) has been suggested as a potential approach for replacement congenitally defective pediatric heart valves. As with all heart valves, the leaflet shape during systole and diastole is essential to the normal function of PV. In this work, we present a design framework on optimal unloaded shape of TEPV leaflet for single leaflet replacement surgery by incorporating key experimental data within a finite element (FE) simulation framework. The mechanical properties of the material for leaflet replacement are measured by biaxial tensile and flexural deformation modes. The scaffold construct is modeled as a transversely isotropic hyperelastic material using a generalized Fung-type constitutive model. The quasi-static deformation of leaflet from open to close is simulated by finite element method using explicit time integration. The optimal shape of leaflet is determined by minimizing the surface distance between the deformed leaflet shapes obtained from FE simulation of TEPV and the native ovine PV shape as obtained from microCT imaging. This study aims to provide an approach toward designing the shape of leaflet for PV replacement surgery.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027536-027536-1. doi:10.1115/1.3591386.
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Over 58,000 patients suffer from renal cell carcinoma annually in the United States. Treatment for this cancer often requires surgical removal of the cancerous tissue in a partial nephrectomy procedure. In open renal surgery, the kidney is placed on ice to increase allowable ischemia time; however, there is no widely accepted method for reducing kidney temperature during minimally invasive surgery. A novel device has been designed, prototyped, and evaluated to perform effective renal cooling during minimally invasive kidney surgery to reduce damage due to extended ischemia. The device is a fluid-containing bag with foldable cooling surfaces that wrap around the organ like a taco shell. It is deployed through a 12 mm trocar, wrapped around the kidney and secured using bulldog clamps. The device then fills with an ice slurry and remains on the kidney for up to 20 min. The ice slurry is then removed from the device and the device is retracted from the body. Tests of the prototype show that the device successfully cools porcine kidneys from 37°C to 20°C in 5 minutes.

Topics: Cooling , Surgery , Kidney
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027537-027537-1. doi:10.1115/1.3591390.
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5.7 million Americans are clinically diagnosed each year with refractory gastresophageal reflux disease (GERD), characterized by chronic stomach acid reflux that is insensitive to both lifestyle modifications and pharmaceutical treatments. The most widely available treatments for these patients are endoluminal antireflux procedures, including EndoCinch plication and EsophyX transoral incisionless fundoplication, and the more drastic Nissen Fundoplication. These endoluminal treatments involve stitching the gastresophageal tissue in order to restore the natural antireflux barrier of the lower esophageal sphincter (LES), a ring of muscle regulating entry to the stomach, although their efficacy in terms of decreasing long-term acid exposure has not been established. As such, patients often must rely on Nissen Fundoplication for relief. However, because Nissen Fundoplication is invasive, irreversible, and can lead to complications such as dysphagia and bloating, new methods to effectively treat refractory GERD are necessary. We propose a novel, long-term solution to treat refractory GERD by using an esophageal prosthesis to prevent retrograde acid flow while maintaining normal physiological function. Our device, a silicone band molded over a nitinol wire, strengthens the antireflux barrier by adding a compressive pressure on the LES. The prosthesis deforms to allow food to pass uninhibited during swallowing and opens to release air and vomit during belching and regurgitation, respectively. In the absence of these events, however, the band compresses the LES to prevent acid reflux from damaging esophageal tissue. As the prosthesis will be inserted laparoscopically around the distal esophagus and can be adjusted or removed at a later time if necessary, it is both minimally invasive and reversible. The device successfully established a 14 mm Hg pressure differential in an ex vivo porcine esophagus and passed a representative food bolus test. Further development of this design concept is warranted to achieve the goal of long-term acid reflux prevention in refractory GERD patients.

Topics: Prostheses , Diseases
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027537-027537-1. doi:10.1115/1.3591388.
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We present a fuzzy rule-based system for epileptic seizure onset detection. Two features based on temporal evolution of seizure in electroencephalogram (EEG) were extracted from intracranial EEG (iEEG) recordings. Features extracted from multichannel EEGs were combined using fuzzy algorithms in feature domain as well as in spatial (channels) domain. Fuzzy rules were derived from experts’ knowledge and reasoning. Finally, a predefined threshold was used to make the final decision. A total of 40.46 h of iEEG recordings (obtained from Freiburg Seizure Prediction EEG database) selected from 13 patients having 19 seizures was used for the system evaluation. The overall detection rate of 100% was achieved with false detection rate of 0.275/h and the average detection latency of 26.858 seconds.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027538-027538-1. doi:10.1115/1.3591392.
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Concentric tube continuum devices, known as active cannulas, consist of multiple precurved elastic tubes that extend telescopically and rotate axially with respect to each other. Through these degrees of freedom, an active cannula presents a dexterous and versatile “tentaclelike” mechanism for accessing targets in minimally invasive surgery. Deploying an active cannula in a practical surgical setting requires a sterilizable device capable of specifying positions and trajectories for each degree of freedom. While robotic devices will likely enable this to be done most efficiently in the future, initial clinical feasibility studies are best undertaken with manual devices. In this paper, we present specifications, design, and development of a manual (that is, not motorized) active cannula deployment device.

Topics: Design
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027538-027538-1. doi:10.1115/1.3591391.
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All materials experience a force when placed in a region of magnetic field and field gradient. The magnitude of this force depends on the magnetic susceptibility of the material and this varies over a wide range depending on the type of material. Our goal is to develop a technique for evaluating the magnetic susceptibility of cells and subcellular organelles so that scientists can access to develop new methods to modify or modulate internal cellular forces. Research studies have shown that forces in the piconewton range can affect cellular behavior. Internal forces of this magnitude can occur in cells exposed to high intensity magnetic fields, if the difference in magnetic susceptibility of subcellular organelles is as low as 10%. Because the magnetic susceptibility x is expected to be on the order of 9×106, the proposed measurement technique must be extremely sensitive. In this paper, a pilot study is described in which the feasibility of a magnetophoresis technique is explored. Tests implementing magnetophoresis for polystyrene test particles (|x|=8.21×106) with a 100μm diameter explored the sensitivity and accuracy effects of varying fluid flow speeds of 0.63 mm/s, 1.09 mm/s, and 1.44 mm/s, particle radius to channel depth ratios (r/a) of 0.043 and 0.199, and a magnetic field and gradient product (BdB/dz) of 38.91T2/m. The percent uncertainties of the experimental magnetic susceptibilities for the three different flow speeds and r/a ratio combinations studied are 12.3%, 18.3%, and 22.4% (in order of flow speed). The trial runs indicate that a balance of a larger r/a ratio and a slower flow speed is ideal to optimize consistency in flow velocities and calculated magnetic susceptibilities while minimizing uncertainty. Requirements for MEMs device design are also presented.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027539-027539-1. doi:10.1115/1.3591402.
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Clinical access to the left atrium and/or to the left ventricle for medical device delivery, from a nonsurgical standpoint, continues to be a challenge. Currently such procedures involve left heart access via delivery through the arterial system via the aorta or across the atrial septal wall. More specifically, medical devices delivered through the atrial septum require transseptal punctures by utilizing tools and delivery systems, which include puncturing needles, stiff wires, or more sophisticated approaches, such as wire tips using rf energy. Typically, from the right atrium, one hopes to make this approach through the fossa ovalis and thus gain access to the left atrium. Next, a dilator and an outer device delivery sheath/catheter (clinically available between 7°F and 24°F) are employed to pass through the initial puncture and then create a larger hole through the septum. With continued advancements in intracardiac device technologies, it is foreseeable that larger and larger tools may be needed to perform more complicated procedures from such a percutaneous approach (e.g., the transcatheter deliveries of mitral and/or aortic valves). One of the primary aims of the present study was to assess the relative properties of the fossa ovalis within a large sample of large mammalian hearts and/or the relative amount of forces needed to induce anatomical impacts (i.e., tenting, puncturing, and dilating the fossa ovalis). To do so, an experimental platform has been uniquely developed and experiment data collected. Briefly, the interatrial septums from large mammalian hearts were excised and placed on a plate lined with a silicone elastomer. This plate contains a hole where the fossa is centered and then pinned onto the gel. A smaller plate covers the tissue and is also pinned to the plate, preventing the pins from bending or leaning inward as the tissue is being tested. The prepared sample can then be depressed with a rod attached to a force transducer to predetermined distances and cause strain on the tissue: Resulting forces are digitally recorded. Such experimental protocols can be performed multiple times and to date have allowed for consistent measurements of each fossa ovalis tested. This experimental approach has also allowed us to determine the amount of force required to perforate a given fossa ovalis and thus has provided us with insights relative to device designs. Further use of this setup could be employed to study the transseptal passage and imposed forces on larger transseptal devices; e.g., to determine their potential impacts on the native anatomy of the heart. This novel approach to examine the anatomical and physical properties of the cardiac fossa ovalis should be a great value for those designing or clinically deploying transseptal therapies.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027539-027539-1. doi:10.1115/1.3591396.
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Recent advances in cardiac imaging have resulted in a growing understanding of both the form and function of the heart in vivo. Currently, the primary modalities for cardiac imaging are (1) two-dimensional cardiac ultrasound or echocardiography, (2) computed tomography (CT), and (3) magnetic resonance imaging (MRI). Yet, high resolution imaging with these modalities can be complicated by motion artifacts and long acquisition times resulting in most of the high resolution anatomical cardiac imaging protocols being reserved for ex vivo studies. Our laboratory has had the privilege to obtain fresh human heart specimens for educational and research purposes. These specimens have been perfusion fixed in 10% buffered formalin, by attaching cannulas to the great vessels, so to create a pressure head of approximately 50 mm Hg. The hearts were then suspended in containers and positioned in anatomically correct orientations before being embedded in 0.7% agar gel, at approximately 45°C. The cooled specimens were then scanned using the aforementioned clinical imaging modalities (2D and 3D echocardiography, CT, and 3T MRI). The stability of the embedded specimen, the physical properties of the gel, and the lack of motion artifacts allows for the acquisition of extremely high resolution images. These images have subsequently been used in the analysis of cardiac anatomies for a variety of pathologic investigations, not possible with current clinical imaging protocols, and/or for high resolution diffusion tensor MR imaging studies (e.g., of fiber orientations in heart failure in swine ventricles). Future work will include investigations as to whether this gelling approach could be used to prepare other organ specimens for such imaging.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027540-027540-1. doi:10.1115/1.3591405.
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Since the brain-computer interface (BCI) speller was first proposed by Farwell and Donchin, there have been modifications in the visual aspects of P300 paradigms. Most of the changes are based on the original matrix format such as changes in the number of rows and columns, font size, flash/blank time, and flash order. The improvement in the resulting accuracy and speed of such systems has always been the ultimate goal. In this research paper, we have conducted a set of experiments to determine the errors related to various regions in a region-based P300 BCI paradigm (RB), which is not based on the original matrix format. We have designed RB paradigm in which similar characters are distributed in all the seven regions and user input was recorded using electrodes. The results show that the spelling error related to the center region was highest among the subjects.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027540-027540-1. doi:10.1115/1.3591407.
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Early identification of intracranial hematomas in patients with traumatic brain injury is crucial for the successful outcome of the intervention. Infrascanner is a hand-held, noninvasive, near-infrared based mobile imaging device to detect brain hematoma within the “golden period.” This refers to the period following head trauma where assessment of the neurological condition and medical intervention of a victim is most needed and can significantly reduce the mortality and morbidity rate. In Infrascanner, hematoma detection is based on the differential light absorption of the injured versus the noninjured part of brain. When extravascular blood is present due to internal bleeding, there is a greater local concentration of hemoglobin that results in greater absorbance of the light on the bleeding side of the brain as compared with the contralateral uninjured side. This differential can be detected via sources and detectors placed on symmetrical lobes of the skull noninvasively. In a multicenter study, Infrascanner demonstrated high sensitivity (88%) and specificity (91%) in detecting intracranial hematomas larger than 3.5 ml in volume and less than 2.5 cm from the surface of the brain. These results suggest that this technology may be useful to supplement clinical information such as neurological examination in determining need for and urgency of further imaging studies. Infrascanner is intended to be used as an adjunct to the standard diagnostic workup to aid the decision in prioritizing high risk patients with suspected hematomas for urgent CT scans and surgical interventions. It can further facilitate surgical intervention decisions in environments where access to CT scan is restricted or not available.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027541-027541-1. doi:10.1115/1.3591412.
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Bone grafts are used commonly in spinal fusion procedures to induce the fusion of adjacent spinal vertebrae. Autologous bone graft (autograft) is taken from the patient’s own bone. This bone graft provides the best fusion rates; however, obtaining the bone graft requires a secondary incision that is time consuming to the surgeon and very painful to the patient. Alternative commercial bone graft solutions exist as well. However, these alternatives produce worse clinical outcomes and greatly increase the cost of health care. We propose a novel medical device for the minimally invasive extraction of autologous bone graft from the iliac crest of a patient. This device will allow physicians to achieve high fusion rates without burdening the hospital with the high costs of alternative products. Here, we overview our current design at a systems level and we demonstrate the market potential for the proposed device and outline a commercialization strategy for bringing this device to market.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2011;5(2):027541-027541-1. doi:10.1115/1.3591415.
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There is growing and continued interest in the development of new electrical stimulation and sensing devices for diverse biomedical applications such as cochlear prosthetics, deep brain stimulation, and cardiac rhythm management. Biotectix has developed BT DOT electrode coatings made from novel electrically conducting polymer formulations based on based on poly(3,4-ethylenedioxythiophene) commonly known as PEDOT. These coatings enable intimate, long-term electrical and biological connections between implantable electrodes and the target tissue, offering the conductivity and stability of metals with the ease of processing and biological functionality of polymers. In this paper, we compare the in vitro electrical performance of three types of implantable electrostimulation devices: active fixation pacing leads, cochlear electrodes, and spinal cord stimulators with and without the BT DOT coatings. Significant decreases in impedance and polarization were observed along with significant increased charge storage capacity. The results suggest that such coatings may enable future medical device design improvements such as smaller device profiles and extended battery life.

Commentary by Dr. Valentin Fuster

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