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# Accepted Manuscripts

BASIC VIEW  |  EXPANDED VIEW
research-article
J. Med. Devices   doi: 10.1115/1.4037052
Shape memory polymer (SMP) foams have been developed for various embolic applications. These polyurethane materials can be stored in a secondary shape, from which they can recover their primary shape after exposure to an external stimulus, such as heat and water exposure. Tailored actuation temperatures of SMPs provide benefits for minimally invasive biomedical applications, but incur significant challenges for SMP-based medical device sterilization. Most sterilization methods require high temperatures or high humidity to effectively reduce the bioburden of the device, but the environment must be tightly controlled after device fabrication. Here, two probable sterilization methods (non-traditional ethylene oxide (ntEtO) gas sterilization and electron beam irradiation) are investigated for SMP medical devices. Thermal characterization of the sterilized foams indicated that ntEtO gas sterilization significantly decreased the glass transition temperature. Further material characterization was undertaken on the electron beam (ebeam) sterilized samples, which indicated minimal changes to the thermomechanical integrity of the bulk foam and to the device functionality.
TOPICS: Urethane elastomers, Shapes, Sterilization, Medical devices, Cathode ray oscilloscopes, Foams (Chemistry), Electron beams, Manufacturing, Heat, Temperature, Irradiation (Radiation exposure), Glass transition, Water, Thermomechanics, High temperature, Biomedicine, Thermal characterization, Shape memory polymers
Review Article
J. Med. Devices   doi: 10.1115/1.4037053
Introduction This paper deals with the survey of kinematic structures adapted to specific medical robots: minimally invasive surgery and tele-echography. The large diversity of kinematic architectures that can be found in medical robotics leads us to perform a statistical analysis to inform and guide design of medical robots. Safety constraints and some considerations in design evolution of medical robots are presented in this paper. Methods First, we describe the spectrum of medical robots in minimally invasive surgery and tele-echography applications and particularly the variety of kinematic architectures used. We present the robots and their kinematic architectures and highlight differences that occur in each medical application. We perform a statistical analysis which can serve as a resource in topological synthesis for each specific medical application. Safety is an important specification in medical robotics, and for that reason we show the means used to take into account this constraint. Conclusion This study demonstrates that the nature of medical robots implies specific requirements leading to different kinematic structures. The statistical analysis gives information on choice of kinematic structures for medical applications (minimally invasive surgery and echography). The safety constraint as well as the interaction between doctor and robot leads to investigate new mechanical solutions to enhance medical robot safety and compliance. We expect that this paper will serve as a significant resource and help the design of future medical robots.
TOPICS: Kinematics, Robots, Surgery, Biomedicine, Safety, Design, Architecture, Statistical analysis, Robotics
Technical Brief
J. Med. Devices   doi: 10.1115/1.4037054
The induction of a mild reduction in body core temperature has been demonstrated to provide neuroprotection for patients who have suffered a medical event resulting in ischemia to the brain or vital organs. Temperatures in the range of 32 - 34°C provide the required level of protection. Rewarming from hypothermia must be conducted slowly to avoid serious adverse consequences and usually is performed under control of the thermal therapeutic device based on a closed loop feedback strategy based on the patient’s core temperature. Given the sensitivity and criticality of this process, it is important that the device control system be able to interact with the human thermoregulation system, which itself is highly nonlinear. The therapeutic hypothermia device must be calibrated periodically to ensure that its performance is accurate and safe for the patient. In general calibration processes are conducted with the hypothermia device operating on a passive thermal mass that behaves much differently than a living human. This project has developed and demonstrated an active human thermoregulation simulator that embodies major governing thermal functions such as central metabolism, tissue conduction, and convective transport between the core and the skin surface via the flow of blood and that replicates primary dimensions of the torso. When operated at physiological values for metabolism and cardiac output, the temperature gradients created across the body layers and the heat exchange with both an air environment and a clinical water-circulating cooling pad system match that which occur in a living body.
TOPICS: Cooling, Water, Temperature, Heat, Physiology, Biomedicine, Blood flow, Temperature gradient, Electromagnetic induction, Control systems, Dimensions, Heat conduction, Biological tissues, Brain, Calibration, Feedback, Skin
research-article
J. Med. Devices   doi: 10.1115/1.4036650
Aim of this study was to develop an rotationally stable intramedullary telescopic nail that is firmly anchored in the bone proximally and distally, without containing any extraosseous components that may alter the surrounding soft tissue. Three prototypes for a positive-locking adapted telescopic intramedullary nail (PLATIN) were developed. In a series of biomechanical tests, the prototypes were compared with two Fassier-Duval telescopic nails, which represent the clinical standard. Axial pressure, torsion and four-point bending measurements were carried out in a materials testing machine, with the telescopic nails implanted into composite bone. Tests were conducted without failure and up to failure. Specifically, the force required for telescoping, as well as torsional stiffness and bending stiffness, were investigated. Taking into account differences that were inherent to the materials, the prototypes showed similar results in the four-point bending tests. In the pressure tests the prototypes required greater forces than the Fassier-Duval nails. The torsional stiffness was between 0.020 Nm/° and 0.135 Nm/°, depending on the diameter of the nail. Positive-locking effect was achieved by a hexagonal shape of an inner rod part and a hexagonal form-fitting outer tube part. Proximal and distal locking of the telescopic nail in the bone was performed by usage of K-Wires in specific arranged drill holes at the end of both parts. Based on these satisfactory results, clinical application of positive-locking irrotational telescopic nails can be expected, furthermore redesign for existing telescopic nails is recommended.
TOPICS: Pressure, Machinery, Composite materials, Drills (Tools), Materials testing, Wire, Biomechanics, Torsion, Engineering prototypes, Bone, Design, Failure, Fittings, Shapes, Stiffness, Soft tissues, Intramedullary rods
research-article
J. Med. Devices   doi: 10.1115/1.4036652
A new type of therapeutic equipment is designed herein, using concepts of convective heat transfer and spray cooling, to treat patients suffering from brain-hyperthermia. The equipment is aimed to provide emergency treatment in order to prevent disability or possible mortality because thermoregulatory system of the patients fails to maintain a homeostasis. The equipment uses non-contact method of forced convection, applied uniformly at body exteriors. The heat exchanger is designed to contain four independent pipe-sections with orifice openings around the body. The cool-air, maintained within ASHRAE’s thermal comfort bounds, is sprayed through the orifices. Design improvements have been made on the basis of image analysis of the flow. The boundary layer analysis has also been performed over a specially designed mannequin with induced hyperthermia characteristics. The testing indicates a decay of ~6? in 280min with a time constant of 2hrs. Comparative to existing techniques, in addition to being a non-contact approach, the equipment shows better thermoregulatory performance along with a flexibility to accommodate different body contours.
TOPICS: Cooling, Sprays, Brain, Orifices, Emergencies, Testing, Boundary layers, Convection, Design, Forced convection, Heat exchangers, Pipes, Flow (Dynamics)
research-article
J. Med. Devices   doi: 10.1115/1.4036654
Instrument-assisted soft tissue manipulation (IASTM) is a form of mechanotherapy, e.g. massage, that uses rigid devices which may be machined or casted. The delivered force, which is a critical parameter during IASTM, has not been measured or standardized for use during clinical practice. In addition to the force, the angle of treatment and stroke frequency play an important role during IASTM. As a result, there is a strong need to characterize the IASTM delivered force, angle of treatment, and stroke frequency. This paper presents a novel, mechatronic design of an IASTM device used to clinically deliver localized pressure to the soft tissue. The proposed design uses a 3D load cell, which can measure all three force components force simultaneously. The device design was implemented using IMUduino microcontroller chip which can provide tool orientation angles. These orientation angles were used for coordinate transformation of the measured forces to the skin interface. Additionally, the measured force data was used to compute the stroke frequency. This mechatronic IASTM tool was validated for force measurements using an electronic plate scale that provided the baseline force values to compare with the applied force values measured by the tool. The load cell measurements and the scale readings were found to be in agreement within the expected degree of accuracy.
TOPICS: Instrumentation, Soft tissues, Design, Stress, Pressure, Force measurement, Skin
research-article
J. Med. Devices   doi: 10.1115/1.4035983
Anticoagulants are the treatment of choice for pulmonary embolism. When these fail or are contraindicated, vena cava filters are effective devices for preventing clots from the legs from migrating to the lung. Many uncertainties exist when a filter is inserted, especially during physiological activity such as normal breathing and the Valsalva manoeuvre. These activities are often connected with filter migration and vena cava damage due to the various related vein geometrical configurations. In this work we analysed the response of the vena cava during normal breathing and Valsalva manoeuvre, for a healthy vena cava and after insertion of a commercial Günther-Tulip filter. Computational fluid dynamics (CFD) and patient specific data are used for analysing blood flow inside the vena cava during these manoeuvres. While during normal breathing the vena cava flow can be considered almost stationary with a very low pressure gradient, during Valsalva the extravascular pressure compresses the vena cava resulting in a drastic reduction of the vein section, a global flow decrease through the cava but increasing the velocity magnitude. This change in section is altered by the presence of the filter which forces the section of the vena cava before the renal veins to keep open. The effect of the presence of the filter is investigated during these manoeuvres showing changes in wall shear stress and velocity patterns.
TOPICS: Filters, Blood flow, Flow (Dynamics), Computational fluid dynamics, Pressure, Uncertainty, Damage, Shear stress, Kidney, Lung, Pressure gradient, Physiology
research-article
J. Med. Devices   doi: 10.1115/1.4035984
This paper introduces a new design for individually controlled magnetic artificial cilia for use in fluid devices, and specifically intended to improve the mixing in DNA microarray experiments. The design has been implemented using a low-cost prototype that can be fabricated using polydimethylsiloxane (PDMS) and off-the-shelf parts, and achieves large cilium deflections (59% of the cilium length). The device's performance is measured via a series of mixing experiments using different actuation patterns inspired by the blinking vortex theory. The experimental results, quantified using the relative standard deviation of the color when mixing two colored inks, show that exploiting the individual control leads to faster mixing (38% reduction in mixing time) than when operating the device in a simultaneous-actuation mode with the same average cilium beat frequency. Furthermore, the experimental results show an optimal beating pattern that minimizes the mixing time. The existence and character of this optimum is predicted by simulations using a blinking-vortex approach for 2D ideal flow, suggesting that the blinking-vortex model can be used to predict the effect of parameter variation on the experimental system.
TOPICS: Flow (Dynamics), Fluids, Simulation, Inks, Plasma desorption mass spectrometry, Engineering prototypes, Design, Engineering simulation, Vortices, Deflection, DNA
research-article
J. Med. Devices   doi: 10.1115/1.4036580
To reform diabetes management painless and reliable noninvasive blood glucose (NIBG) measurement technique has been explored since last three decades. In the present work photoplethysmogram (PPG) signal is used to measure the variations in blood glucose concentration. However, the literature reveals that physiological perturbations such as temperature, skin moisture and sweat cause poor accuracy of NIBG measurement. The task of minimizing the effect of these perturbations and to improve accuracy is an important research area. Therefore, along with PPG sensor, Galvanic Skin Response (GSR) and temperature sensors are also used to achieve more accurate NIBG measurement. The accuracy of the proposed Multi-sensor system is evaluated by pairing and comparing non-invasively measured data with invasively measured readings. The study is made on 50 non-diabetic subjects with BMI 27.3±3 kg/m2. Two machine learning techniques, i.e. Multiple Linear Regression (MLR) and Artificial Neural Network (ANN) are used to estimate the glucose concentration from extracted data. The results reveal that the MAPE and correlation coefficient are significantly improved in comparison to the techniques reported in the literature.
TOPICS: Sensors, Blood glucose measurement, Skin, Artificial neural networks, Diabetes, Blood glucose, Signals, Temperature, Machinery, Temperature sensors, Physiology, Glucose
Technical Brief
J. Med. Devices   doi: 10.1115/1.4036581
Interventional catheter ablation treatment is a non-invasive approach for normalizing heart rhythm in patients with arrhythmia. Catheter ablation can be assisted with magnetic resonance imaging (MRI) to provide high-contrast images of the heart vasculature for diagnostic and intra-procedural purposes. Typical MRI images are captured using surface imaging coils which are external to the tissue being imaged. The image quality and the scanning time required for producing an image are directly correlated to the distance between the tissue being imaged and the imaging coil. The objective of this work is to minimize the spatial distance between the target tissue and the imaging coil by placing the imaging coil directly inside the heart through the use of an expandable origami catheter structure. In this study, geometrical analysis is utilized to optimize the size and shape of the origami structure and MRI scans are taken to confirm the MRI compatibility of the structure. The origami expandable mechanism could also be applied to other medical device designs that require expandable structures.
TOPICS: Cardiovascular system, Catheters, Magnetic resonance imaging, Imaging, Biological tissues, Ablation (Vaporization technology), Medical devices, Arrhythmias, Shapes
research-article
J. Med. Devices   doi: 10.1115/1.4036490
Background: Drilling through bone is a common task during otologic procedures. Currently, the drilling tool is manually held by the surgeon. This project was to demonstrate the feasibility of using the da Vinci Research Kit (dVRK) to hold the drill and provide force feedback for temporal bone drilling. Methods: A modified da Vinci surgical instrument with force sensing was developed to enable robotically assisted drilling for otologic surgery. To provide intuitive motion and force feedback, the master–slave kinematics were analyzed and a suitable mapping was implemented. Results: Several experiments were completed including trajectory tracking of master–slave motion, drill instrument calibration, and force feedback using a temporal bone model. The results showed that good trajectory tracking performance, and minor calibration errors were achieved. In addition, force feedback from the drill instrument could be felt at the master arm. Conclusions: A robotically assisted surgical drill for otologic surgery was developed and demonstrated using the dVRK. In the future, it may be feasible to use master–slave surgical robot systems for temporal bone drilling.
TOPICS: Drills (Tools), Instrumentation, Surgery, Force feedback, Drilling, Bone, Trajectories (Physics), Calibration, Errors, Kinematics, Robots, Surgical tools
Expert View
J. Med. Devices   doi: 10.1115/1.4036333
The Food and Drug Administration’s (FDA) Humanitarian Device Exemption (HDE) is a unique marketing approval pathway for medical devices targeting diseases affecting small (rare) patient populations. Analyses of HDE approvals from 2007-2015 revealed that approvals were based on a broad range of data constituting valid scientific evidence to support a finding of safety and probable benefit and demonstrated that the FDA exercises a high degree of flexibility when reviewing HDE applications.
TOPICS: Diseases, Frequency-domain analysis, Food and Drug Administration, Drugs, Food products, Safety, Medical devices
research-article
J. Med. Devices   doi: 10.1115/1.4036335
Objective: To develop and evaluate the clinical application of a multimodal colposcopy combining multispectral reflectance, autofluorescence and RGB imaging for early screening of cervical intraepithelial neoplasia (CIN). Methods: We developed a multimodal colposcopy system that combined multispectral reflectance, autofluorescence, and RGB imaging for early screening of CIN. We studied the optical properties of cervical tissue first, then the imaging system was designed and tested in clinical trial where comprehensive datasets were acquired and analyzed to differentiate between squamous normal and high grade types of cervical tissue. Results: The specially designed multimodal colposcopy is capable of acquiring multispectral reflectance images, autofluorescence images, and RGB images of cervical tissue consecutively. The classification algorithm was employed on both normal and abnormal cases for image segmentation. The sensitivity and specificity performance of this system related to gold standard of histopathology show statistical significance. Conclusions: Our pilot study demonstrated the clinical potential of this multimodal colposcopic system for early screening of CIN. The low-cost portable characteristics, the simple operating process, and the simple image segmentation algorithm of this system make it possibility to address the needs for CIN early screening in a rapid, cost-effective, and non-invasive fashion in the developing countries.
TOPICS: Tumors, Imaging, Reflectance, Biological tissues, Image segmentation, Algorithms, Developing nations
research-article
J. Med. Devices   doi: 10.1115/1.4036337
The purpose of this study was to evaluate the suitability of a novel radio-frequency identification (RFID)-based tracking system for intraoperative magnetic resonance imaging (MRI). A RFID tracking system was modified to fulfill MRI-compatibility and tested according to ASTM and NEMA. The influence of the RFID tracking system on MRI was analyzed in a phantom study using a HASTE and TrueFISP sequence. The RFID antenna was gradually moved closer to the isocenter of the MR scanner from 90 to 210 cm to investigate the influence of the distance. Furthermore the RF was gradually changed between 865-869 MHz for a distance of 90 cm, 150 cm and 210 cm to the isocenter of the magnet to investigate the influence of the frequency. The specific spatial resolution was measured with and without a permanent line of sight (LOS). After the modification of the reader no significant change of the SNR could be observed with increasing distance of the RFID tracking system to the isocenter of the MR scanner. Also different radio frequencies of the RFID tracking system did not influence the SNR of the MR images significantly. The specific spatial resolution deviated on average by 8.97 ± 7.33 mm with LOS and 11.23 ± 12.03 mm without LOS from the reference system. The RFID tracking system had no relevant influence on the MR image quality. RFID tracking solved the LOS problem. However the spatial accuracy of the RFID tracking system has to be improved for medical usage.
TOPICS: Magnetic resonance imaging, Navigation, Resolution (Optics), Magnets, Phantoms, Biomedicine, ASTM International
Technical Brief
J. Med. Devices   doi: 10.1115/1.4036338
Objectives: Accurate needle guidance is essential for a number of MRI-guided percutaneous procedures, such as radiofrequency ablation (RFA) of metastatic liver tumors. A promising technology to obtain real-time tracking of the shape and tip of a needle is by using high frequency (up to 20 kHz) fiber Bragg grating (FBG) sensors embedded in optical fibers, which are insensitive to external magnetic fields. Methods: We fabricated an MR-compatible needle designed for percutaneous procedures with a series of FBG sensors which would be tracked in an image-guidance system, allowing to display the needle shape within a navigation image. Results: A series of phantom experiments demonstrated needle tip tracking errors of 1.05 ± 0.08 mm for a needle deflection up to 16.82 mm on a ground-truth model and shown nearly similar accuracy to electromagnetic tracking (i.e. 0.89 ± 0.09 mm). Conclusion: We demonstrated feasibility of the FBG-based tracking system for MR guided interventions with differences under 1 mm between tracking systems. Significance: This study establishes the needle tracking accuracy of FBG needle tracking for image-guided procedures.
TOPICS: needles, Shapes, Fiber Bragg gratings, Sensors, Radiofrequency ablation, Tumors, Magnetic fields, Magnetic resonance imaging, Optical fiber, Phantoms, Deflection, Errors, Liver, Navigation
Technical Brief
J. Med. Devices   doi: 10.1115/1.4036336
This work exploits the advantages of compliant mechanisms (devices that achieve their motion through the deflection of flexible members) to enable the creation of small instruments for minimally invasive surgery. Using flexures to achieve motion presents challenges, three of which are considered in this work. First, compliant mechanisms generally perform inadequately in compression. Second, for a $\pm90^{\circ}$ range of motion desired for each jaw, the bending stresses in the flexures are prohibitive considering materials used in current instruments. Third, for cables attached at fixed points on the mechanism the mechanical advantage will vary considerably during actuation. Research results are presented that address these challenges using compliant mechanism principles as demonstrated in a 2-degree-of-freedom L-Arm gripper.
TOPICS: Grippers, Compliant mechanisms, Instrumentation, Surgery, Compression, Deflection, Cables, Bending (Stress)
Technical Brief
J. Med. Devices   doi: 10.1115/1.4036136
Surgical endoscopy has gained traction over the past several decades as a viable option for therapeutic interventions in the gastrointestinal tract. It utilizes natural orifice access which shortens hospital stay, minimizes patient discomfort, and decreases overall healthcare costs. However, the inability to effectively retract and position target tissue is a significant limitation for these procedures. Current instruments are unable to triangulate and can only be manually withdrawn or advanced through the channels. There is a need to provide better access and control of soft tissue to be able to perform more complex and complete endoscopic resections. We have developed a novel device to provide optimal tissue retraction for endoscopic procedures. Our device consists of an articulating tissue retractor and a specialized handle. Two articulating curves were created that can manipulate the position and direction of the retractor tip. Each curve is independently adjusted by locking thumb sliders, allowing for increased range of motion and retraction independent of endoscope position. With a diameter of 2.8mm, the proposed device can be used in current endoscopic equipment. Preliminary testing showed that our retractor has comparable slip strength to a commercially available device (1.13N +/- 0.53N vs. 1.10N +/- 0.51N, p-value: 0.416), but has much greater range of motion (maximum deflection of 72 compared to 0). This increased range of motion allows the articulating grasper to better triangulate and preserve visualization of the dissection plane, allowing it to overcome the most significant barrier restricting endoscopic surgery.
TOPICS: Surgery, Endoscopic devices, Biological tissues, Instrumentation, Testing, Visualization, Deflection, Endoscopes, Health care, Traction, Soft tissues
Technical Brief
J. Med. Devices   doi: 10.1115/1.4036026
Prior studies have linked microbial contamination of intravenous (IV) ports and stopcocks with post-operative infections. Existing technologies to prevent contamination are not consistently utilized because of the time and effort they require. Herein, novel barrier devices were created that form a protective shell to passively prevent contact between injection sites and practitioner hands or environmental surfaces while still allowing rapid connection of a syringe for injection of medications via an opening in the shell. Prototypes were tested using a grossly contaminated environment and ATP-bioluminescence assay. For 8 pairs of unshielded vs. shielded IV ports/stopcocks, average contamination was 4,102 vs. 35 RLU (p<0.02), respectively, indicating that the devices could significantly reduce IV port/stopcock contamination.
TOPICS: Contamination, Gates (Closures), Shells, Engineering prototypes, Drugs
research-article
J. Med. Devices   doi: 10.1115/1.4036024
Objectives: This study sought to determine the feasibility of using Non-Invasive Cardiac Hemodynamics (NICHE), a new non-invasive Doppler-based device, to monitor real-time, simultaneous tissue and blood-flow Doppler measurements in a clinical setting, and to obtain preliminary performance data compared to a commercially available system. Background: Doppler based measurements have been shown to correlate well with invasive hemodynamic data and diastolic function, but their use in clinical applications have been limited by various technical issues. The NICHE device was developed to obtain simultaneous tissue and blood flow Doppler measurements automatically, in real time and in a hands-free manner. Methods: 30 participants (10 normal volunteers and 20 patients in a cardiac rehab program) underwent standard echocardiographic/Doppler studies followed immediately by NICHE monitoring. Early diastolic trans-mitral blood flow velocity (E) and tissue Doppler myocardial wall velocity during early relaxation (E’) were acquired using a standard echo device; and E/E’ was derived post hoc. NICHE measurements included E, E’ and directly measured instantaneous E/E’. Results: NICHE was successfully used in 28 participants. Measurements of ENICHE ranged from 40 cm/s to over 120 cm/s and correlated well with Eecho (R=0.93). E’NICHE ranged from 2 to 23 cm/s and correlated well with the averaged E’echo (R= 0.91). Directly measured E/E’NICHE ratios ranged from 3-23 and correlated well with derived E/E’echo (R= 0.91). Conclusions: The NICHE device can monitor patients in a hands-free manner and can supply real time Doppler derived measurements of hemodynamic parameters and diastolic function that correlate well with measurements from standard echo devices.
TOPICS: Echoes, Hemodynamics, Biological tissues, Blood flow, Doppler measurement, Patient rehabilitation, Relaxation (Physics)
research-article
J. Med. Devices   doi: 10.1115/1.4036025
To facilitate the design of the serialized implants to satisfy the requirements of the population, a novel method is put forward for constructing an average bone model (ABM) with semantic parameters as template. Firstly, ABM is created from the existing bone models, among which each bone has an equal contribution to the ABM. Secondly, combined with medical semantics, some characteristic points and semantic parameters are defined on ABM, and then parameter values for each bone can be automatically obtained through its registration and deformation to the ABM. Lastly, an average bone template (ABT) is constructed by configuring the semantic parameters and building the constraints between parameters. Taking 100 femur models as samples, we construct an average bone template, and the template can be easily extended to generate a new average template.
TOPICS: Bone, Design, Semantics, Biomedicine, Deformation