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Accepted Manuscripts

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research-article  
Timothy Schatz, Sarah Howard, Deanna Porter, Kent J Grove, Mark E Smith and Yan Chen
J. Med. Devices   doi: 10.1115/1.4041805
Most blood-contacting medical devices must be assessed for potential thrombogenicity prior to regulatory approval. A common assay for screening and qualifying devices involves monitoring the reduction of platelet and leukocyte counts in whole blood exposed to the device. We have validated an improved method for assessing a device's effect on platelet activation and surface adhesion, offering significant improvement over the current ASTM F2888-13 method which uses blood fully anticoagulated by acidified citrate (known to significantly inhibit platelet responsiveness). Our method uses minimal heparinization (final concentration 1 IU/ml) to optimize the response to commonly used control materials, latex, black rubber, and high-density polyethylene (HPDE). We also have shown the assay's capacity to appropriately assess a legally marketed comparator device (LMCD) with a documented clinical history. The test materials were prepared for incubation and allowed to remain in contact with the citrated or heparinized blood for ~1 hour at 37° C. A complete blood count (CBC) was performed prior to exposure and at the end of the incubation period and reductions in platelet and leukocyte counts were recorded. Results from citrate-anticoagulated assay showed only a marginal response to the positive control, black rubber. Using heparinized blood, the assay generated a robust response to the positive controls, the "intermediate scoring" controls, and also assessed a legally marketed and approved device as clearly non-thrombogenic. This modification adds robustness and sensitivity to this quick and inexpensive thrombogenicity assay and should be incorporated into the next ASTM standards
TOPICS: Blood, Medical devices, Leukocytes, ASTM International, Platelets, Rubber, Testing equipment, Latex, ASTM standards, Robustness, Density, Adhesion
Technical Brief  
John Everingham, Peter Martin and Trevor Lujan
J. Med. Devices   doi: 10.1115/1.4041696
Instrument-assisted soft tissue mobilization (IASTM) is a manual therapy technique that is commonly used to treat dysfunctions in ligaments and other musculoskeletal tissues. Although there is evidence that IASTM can improve the functional restoration of damaged tissue, the specific loading parameters that enhance tissue healing have not been identified. The objective of this study was to develop a simple hand-held device that helps users accurately apply targeted compressive forces and stroke frequencies during IASTM treatments. This portable device uses a force sensor, tablet computer, and custom software to guide the application of user-specified loading parameters. To measure performance, the device was used to apply a combination of targeted forces and stroke frequencies to foam and silicone pads. Three operators using the device applied targeted forces between 0.3-125N with less than 10% error and applied targeted stroke frequencies between 0.25-1.0Hz with less than 3% error. The mean error in applying targeted forces increased significantly at compressive forces less than 0.2N and greater than 125N. For experimental validation, the device was used to apply a series of IASTM treatments over three weeks to rodents with a ligament injury, and the targeted compressive force and stroke frequency were repeatedly applied with an average error less than 5%. This validated device can be used to investigate the effect of IASTM loading parameters on tissue healing in animal and human studies, and therefore can support the optimization and adoption of IASTM protocols that improve patient outcomes.
TOPICS: Instrumentation, Compression, Soft tissues, Biological tissues, Errors, Force sensors, Patient treatment, Silicones, Wounds, Optimization, Performance, Computers, Musculoskeletal system, Computer software
Technical Brief  
Po-Chih Lee, Arthur Erdman, Charles Ledonio, A. Noelle Larson and David Polly
J. Med. Devices   doi: 10.1115/1.4041634
In clinical settings, restrictive lung disease is caused by different conditions where one of the triggers is tied to the spine deformity. In general, a pulmonary function test is used to evaluate and diagnose lung function, and physicians depend on the test results to identify the disease patterns of the patients. In the pulmonary function test, some parameters including total lung capacity, vital capacity, and residual volume can infer the lung volume and lung capacity. Other parameters, such as forced vital capacity and forced expiratory volume in the first second, are often employed to assess the pulmonary mechanics. Scoliosis is an abnormal lateral curvature of the spine which involves not only the curvature from side to side but also an axial rotation of the vertebrae. Restrictive lung disease often happens in scoliosis patients, especially with severe spine deformity. Spine deformity, if left untreated, may lead to progression of the spinal curve, respiratory complications, and the reduction of life expectancy due to the decrease in thoracic volume for lung expansion. However, the relationship between thoracic volume and pulmonary function is not broadly discussed, and anatomic abnormalities in spine deformity can affect thoracic volume. Previous literature has shown that the deformity of the thoracic rib cage will have detrimental effects on the respiratory function in adolescent idiopathic scoliosis patients. In this paper, we aim to correlate thoracic volume to the parameters in pulmonary function tests in adult scoliosis patients 25-35 years after receiving treatments during their adolescence.
TOPICS: Scoliosis, Lung, Diseases, Rotation
research-article  
Oleg Vesnovsky, Liang Zhu, Laurence W Grossman, Jon P. Casamento, Alireza Chamani, Nadeesri Wijekoon and L D Timmie Topoleski
J. Med. Devices   doi: 10.1115/1.4041589
The objective of this study was to determine real-world, clinical design parameters to create next generation, accurate, digital thermometers. The accuracies of three currently available store brand thermometers were compared to those measured by a calibrated reference thermometer. More than 300 healthy or sick pediatric subjects were enrolled in this study. The reference thermometer was placed at the measurement site simultaneously with the store brand thermometer and recorded the temperature continuously. Temperatures were measured both in the mouth and under the arm. The store brand thermometer measurements characteristically deviated from the reference thermometer temperature after 120 seconds, up to 3.7F, and the deviations were not consistent. The store brand thermometers had lower accuracy than the ±0.2F indicated in their Instructions for Use. The data indicated that the transient temperature profiles may not be represented by an exponential function with a single time constant. The store brand thermometers stated in their documentation that they are able to predict a body temperature based on the first 5 to 10 seconds of transient measurements, implying that they use an embedded algorithm to extrapolate to the steady-state temperature. The accuracy of those embedded algorithms was not verified by our study. A thermometer with an error of several degrees Fahrenheit may result in a false positive or negative diagnosis of fever in children. The transient temperature measurements from our clinical study represent unique and critical data for designing the next generation of readily available, highly accurate, home thermometers.
TOPICS: Design, Temperature measurement, Thermometers, Temperature, Transients (Dynamics), Algorithms, Errors, Pediatrics, Steady state, Temperature profiles
research-article  
Judith M. Burnfield, Thad W. Buster, Chase Pfeifer, Sonya L. Irons, Guilherme Cesar and Carl Nelson
J. Med. Devices   doi: 10.1115/1.4041588
Many children with physical disabilities experience difficulty using traditional exercise equipment for gait rehabilitation and fitness training, and the clinician resources required to deliver intensive overground or treadmill-based therapies are infrequently available in most clinics, hospitals, and school settings. This work describes design and testing of a comprehensive set of modifications that enabled children to use a commercially available robotic exercise device (i.e., ICARE) initially developed to address walking and fitness goals of adults with physical disabilities and chronic conditions. Fifteen children (3 to 11 years old) concurrently enrolled in physical therapy due to varied neurologic conditions were recruited with their parent(s) to evaluate the safety, comfort, and usability of the adult ICARE and pediatric-modified ICARE. After children tried each device, feedback was recorded. To assess feasibility, each child then participated in up to 10 sessions (two to five sessions per week; average session length: 38 minutes, range 21-66 minutes) using the pediatric-modified ICARE. Parents, on average, perceived that the pediatric-modified ICARE was significantly safer, more comfortable and usable than the adult ICARE. Children's perceptions of the pediatric-modified ICARE were similar, although not statistically significant. Children used the prototype device during 133 sessions for over 3800 minutes and more than 162,000 cycles. In conclusion, this study demonstrated the feasibility of using the pediatric-modified ICARE with children as young as three years old as an adjunct to ongoing therapy.
TOPICS: Safety, Engines, Motors, Engineering prototypes, Design, Robotics, Testing, Cycles, Feedback, Pediatrics, Patient treatment, Nervous system
research-article  
Dale Podolsky, Eric Diller, David M Fisher, Karen W Wong Riff, Thomas Looi, James Drake and Christpher R Forrest
J. Med. Devices   doi: 10.1115/1.4041591
Pin-jointed wrist mechanisms provide compact articulation for surgical robotic applications, but are difficult to miniaturize at scales suitable for small body cavity surgery. Solid surface cable guide channels, which eliminate the need for pullys and reduce overall length to facilitate miniaturization were developed within a 3-degree-of-freedom cable driven pin-jointed wrist mechanism. A prototype was 3D printed in steel at 5 mm diameter. Friction generated by the guide channels was experimentally tested to determine increases in cable tension during constant cable velocity conditions. Cable tension increased exponentially from 0 to 37% when the wrist pitched from 0° to 90°. The shape of the guide channel groove and angle where the cable exits the channel impacts the magnitude of cable tension. A spring tensioning and cam actuation mechanism were developed to account for changing cable circuit path lengths during wrist pitch. This work shows that pully-free cable wrist mechanisms can facilitate miniaturization below current feasible sizes while retaining compact articulation, at the expense of increases in friction under constant cable velocity conditions.
TOPICS: Cables, Surgery, Tension, Friction, Steel, Engineering prototypes, Robotics, Cavities, Circuits, Shapes, Springs, Additive manufacturing
Technical Brief  
Xuelian Gu, Fangqiu Hu, Chi-Lun Lin, Arthur Erdman and Licheng Lu
J. Med. Devices   doi: 10.1115/1.4041487
Needle biopsy is a routine medical procedure for examining tissue or biofluids for the presence of disease using standard methods of pathology. The FEA (Finite Element Analysis) methodology can provide guiding for optimizing the geometric design. The needle biopsy is simulated and analyzed while varying the needle angle, the aperture size and the effect of the rotation/translation ratio k on extracting and cutting process. The results shows that tissue reaction force in the axial direction of needle gradually reduces and the stress and strain is more concentrated at the tip of needle with the increases of tip angle; the tissue reaction force is reduced and the torque is increase with increasing the slice-push ratio; and higher slice-push ratio can increase the peak stress concentration on the cutting edge and larger deformation of tissue; In the process of core needle cutting, the increasing slice-push ratio reduces the tissue reaction force significantly, the aperture on distal wall of outer cannula became wider, the increase of tissue reaction force is significant and the cutting process was more unstable. The results have the potential to provide important insight for improving the needle biopsy design process.
TOPICS: Vacuum, Simulation, Design, needles, Biological tissues, Cutting, Finite element analysis, Torque, Rotation, Deformation, Stress, Stress concentration, Diseases, Biomedicine
research-article  
Steven Chopski, Kevin Whitehead, George Englehardt and Amy Throckmorton
J. Med. Devices   doi: 10.1115/1.4041414
Mechanical circulatory support options are limited for patients with dysfunctional single ventricle physiology. To address this unmet clinical need, we are developing an axial-flow blood pump to provide mechanical assistance to the cavopulmonary circulation. In this study, we investigate the use of high-resolution cardiac MRI to visualize the complex fluid flow conditions of mechanical circulatory assist in two patient-specific Fontan anatomies. A 3-bladed axial-flow impeller coupled to a supportive cage with a 4-bladed diffuser was positioned in the inferior vena cava of each Fontan anatomy. CMR imaging and power efficiency studies were conducted at physiologic relevant parameters with cardiac output of 2, 3, and 4 L/min with impeller rotational speeds of 2000 and 4000 RPM. The axial-flow impeller was able to generate improved flow in the total cavopulmonary connection (TCPC). The higher rotational speed was able to redistribute flow in the TCPC anastomosis aiding in removing stagnant blood. No retrograde flow was observed or measured in the superior vena cava. As an extension of the CMR data, a scalar stress analysis was performed on both models and found a maximum scalar stress of approximately 42 Pascal for both patient anatomies. The power efficiency experiments demonstrated a maximum energy gain of 8.6 mW for TCPC Anatomy 1 and 12.58 mW for TCPC Anatomy 2 for a flow rate of 4 L/min and at 4000 RPM. These findings support the continued the development of axial blood pumps for mechanical cavopulmonary assist.
TOPICS: Magnetic resonance imaging, Flow (Dynamics), Impellers, Blood, Axial flow, Anatomy, Physiology, Pumps, Energy efficiency, Scalars, Fluid dynamics, Stress, Stress analysis (Engineering), Resolution (Optics), Diffusers, Imaging
research-article  
Oscar Chuy, Jonathan Herrero, Asma Al-Selwadi and Adam Mooers
J. Med. Devices   doi: 10.1115/1.4041336
Attendant wheelchairs provide a means to transport patients or mobility to people with walking disability. They can be attendant propelled, which are highly maneuverable in confined spaces, but offer no power assistance. Also, they can be electric powered with joystick control interface, which provide power assistance, but not as maneuverable as the attendant propelled wheelchair. With the objective of providing power assistance and having excellent maneuverability, this paper presents a motorized attendant wheelchair with haptic interface. Its control approach is based on virtual/desired dynamics, which is not the true dynamics of the wheelchair, but a mathematical model describing the motion behavior of a desired system. The desired dynamics takes the user's applied force/torque and yields desired velocities of the wheelchair. In the evaluation, tasks in confined spaces and require a lot of maneuvers were given and performed using the motorized wheelchair with haptic and joystick control interfaces. The results in terms of task completion times showed that motorized wheelchair with haptic significantly outperformed the motorized wheelchair with joystick interface. In addition, the performance of the motorized with haptic interface and attendant propelled wheelchairs were evaluated at two different loads. At heavy load, the task completion times of motorized wheelchair with haptic interface were comparable to the attendant propelled wheelchair.
TOPICS: Haptics, Wheelchairs, Dynamics (Mechanics), Stress, Space, Torque, Mechanical admittance
Design Innovation Paper  
Chase Pfeifer, Douglas Rowen, Thad W. Buster, Guilherme Cesar, Sonya L. Irons and Judith M. Burnfield
J. Med. Devices   doi: 10.1115/1.4041337
Cardiovascular assessment and fitness training are often overlooked in physical rehabilitation. is often overlooked. Many current rehabilitation exercise devices do not allow for the recording and exportation of variables related to cardiovascular fitness.meaningful fashion. Therefore, the purpose of this work was to design, prototype, and validate a Data Logger that measures, records, and exports time, heart rate, and speed data with the commercially available rehabilitation device called the ICARE. Validation involved using the Data Logger device in parallel with Gold Standard devices currently used in research environments for measuring heart rate (TrueOne® 2400 metabolic cart with Polar heart rate monitoring chest strap) and speed (the ICARE's console). Ten healthy individuals without known disability impacting walking or ability to use the ICARE, free from significant conditions impacting walking and exercise participated by training exercised on the ICARE while heart rate and ICARE speed were measured. It was found that the Data Logger can be used to accurately measure, record, and export heart rate (Linear Regression: P < 0.001; R2 = 0.892) and speed (Linear Regression: P < 0.001; R2 = 0.997) data when used with the ICARE.
TOPICS: Design, Cardiovascular system, Engineering prototypes, Rehabilitation devices
Design Innovation Paper  
Mohamad Abbass, Stacy Fan, Kevin Barker, Aaron Fenster and Jeremy Cepek
J. Med. Devices   doi: 10.1115/1.4041335
Error and uncertainty in needle placement can drastically impact the clinical outcome of both diagnostic and therapeutic needle-based procedures. In this work we aim to estimate the shape of a bent needle during insertion and provide a prototype design of a handheld steerable needle whose deflection is tracked in real-time. We calculate slope along a needle by measuring the movement of fixed wires running along its length with a compact image-based sensor. Through the use of the Euler-Bernoulli beam theory, we calculate shape and trajectory of a needle. We constructed a prototype needle with two wires fixed along its length, and measure wire-movement using a VCSEL mouse sensor. This method was able to estimate needle tip deflection within 1 mm in a variety of deflection scenarios in real-time. We then provide designs for a steerable needle device, and a handheld needle that provides the user with a simple display to convey needle deflection in tissue. We present a prototype estimating the shape of a bent needle during insertion in real-time, and designs for steerable needle device with a display to convey needle deflection in tissue. These methods could be applied to needle-based biopsy or therapy procedures to improve diagnostic accuracy or treatment delivery quality.
TOPICS: Surgery, Encryption, Shapes, Biomedicine, needles, Deflection, Wire, Engineering prototypes, Biological tissues, Sensors, Patient treatment, Uncertainty, Euler-Bernoulli beam theory, Design, Performance, Trajectories (Physics), Errors
Technical Brief  
Tomasz Bugajski, Douglas Kondro, Kartikeya Murari and Janet L. Ronsky
J. Med. Devices   doi: 10.1115/1.4041190
Pectus Carinatum (PC) presents itself as a protrusion located on the chest of adolescent individuals. The current treatment for PC is performed with a Pectus Carinatum Orthosis (PCO) that applies a compressive force to the protrusion. While this treatment is widely accepted, the magnitude of compressive forces applied remains unknown leading to conditions of excessive or deficient compression. Although the crucial need for this quantitative data is recognized, no studies reporting the data or methods are available. The purpose of this study was to design an accurate force measurement system (FMS) that could be incorporated into a PCO with minimal bulk. The FMS was effortlessly implemented into the PCO and was able to withstand the applied forces. The system calibration revealed an increase in load cell error with increased magnitude of applied force (mean error of 0.58 V [standard deviation = 0.34 V]). This response was speculated to be attributed to the congruency of the FMS with the surface it resided on. Participants recruited to evaluate the FMS demonstrated reliable forces with smaller standard deviations than those during the calibration. The successful FMS is the foundational component in a wireless, minimalistic sensor system to provide real time force feedback to both the clinician and patient.
TOPICS: Sensors, Bracing (Construction), Flexible manufacturing systems, Errors, Calibration, Compression, Force feedback, Force measurement, Orthotics, Stress, Design
Review Article  
Carlos Herrada, Md Alamgir Kabir, Rommel Altamirano and Waseem Asghar
J. Med. Devices   doi: 10.1115/1.4041086
The Zika virus (ZIKV) is one of the most infamous mosquito-borne flavivirus on recent memory due to its potential association with high mortality rates in foetuses, microcephaly and neurological impairments in neonates, and autoimmune disorders. The severity of the disease, as well as its fast spread over several continents has urged the World Health Organization (WHO) to declare ZIKV a global health concern. In consequence, over the past couple of years, there has been a significant effort for the development of ZIKV diagnostic methods, vaccine development, and prevention strategies. This review focuses on the most recent aspects of ZIKV research which includes the outbreaks, genome structure, multiplication and propagation of the virus, and more importantly the development of serological and molecular detection tools such as Zika IgM Antibody Capture Enzyme-Linked Immunosorbent Assay (Zika MAC-ELISA), plaque reduction neutralization test (PRNT), reverse transcription quantitative real-time polymerase chain reaction (qRT-PCR), reverse transcription-loop mediated isothermal amplification (RT-LAMP), localized surface plasmon resonance (LSPR) biosensors, nucleic acid sequence-based amplification (NASBA) and recombinase polymerase amplification (RPA). Limitations of current methods are described, opportunities are highlighted, and potential solutions are discussed.
TOPICS: Surface plasmon resonance, Chain, Biosensors, Diseases, Enzymes, Nervous system, Modal assurance criterion
Design Innovation Paper  
F. Mark Payne, Tony Connell and Jacob Rice
J. Med. Devices   doi: 10.1115/1.4030812
Background: Tissue expanders are used in breast reconstruction after mastectomy to create a space for placement of permanent breast implants. The AeroForm™ Tissue Expander, developed by AirXpanders™ Inc., utilizes carbon dioxide released from an internal reservoir to inflate the expander. The released gas is contained within a high barrier material pre-formed into a breast shaped shell of the desired volume. During patient travel to higher altitude, a partially inflated expander will increase in volume proportionately to the gas fill volume. At volume levels near full, expansion is governed by the compliance of the inner gas barrier and silicone shell. Therefore, the assessment of the expander performance at altitude consists of the analysis of two operating regimes. The first regime is fill levels < 70% full where the implant, when exposed to cabin pressure, expands without significantly stressing the inner gas barrier. The second is fill levels ~>70% where the response of the inner gas barrier is important, both in terms of structural capability and determination of the volume increase. We assessed the impact of pressurized flight on expander performance in both operating regimes. Findings: The volume increase associated with altitude increase to 8000 feet (maximum cabin altitude per FAA) is typically within the range administered during post-operative fills of saline expanders. Although assessment must be conducted by a clinician, a patient can be typically expected to tolerate the increased volume with some minor discomfort, such as a feeling of tightness. At higher fill levels, the structural capability of shell has been demonstrated to withstand the additional pressure loading. At these fill levels, the expander does not expand as much, due to the structural restraint of the shell. To date, 7 subjects have flown with the expander in situ during clinical trials. All subjects were required to temporarily cease dosing up to two weeks prior. Flight travel was completed uneventfully and they reported discomfort levels ranging from none to moderate. The recommendation to cease dosing two weeks prior to flying was made to allow the expected 1 cc per day of CO2 permeation to occur, which will result in slight deflation to accommodate for the expansion of the CO2 when flying. As expected, subjects reported a sensation of pressure upon ascent which subsided on descent.
TOPICS: Biological tissues, Carbon dioxide, Shells, Pressure, Flight, Reservoirs, Silicones

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