bluuebunny/crossref_metadata_2025 huggingface dataset:
Modification of the ASTM Platelet and Leukocyte Assay: Use of an Alternative and Clinically Relevant Anticoagulant — An In-Vitro Hemocompatibility Assessment of Blood Contacting Medical Devices
Authors: Schatz Tim , Beltrame Abby , Howard Sarah , Smith Mark
Published: October 2017

The purpose of this test method is to assist in the determination of the thrombogenic potential of medical materials exposed to human whole blood. By evaluating surface-induced activation, platelet adherence to a material, and platelet and leukocyte depletion from blood, a material’s potential for thrombus formation can be assessed. If a significant decrease in platelets and/or leukocytes is observed in whole blood when compared to a blank control, the tested material has the potential to induce an in-vivo thrombogenic response.

The present standard for the testing of platelet and leukocyte response to cardiovascular materials, ASTM F2888-13, Standard Test Method for Platelet Leukocyte Count - An In-Vitro Measure for Hemocompatibility Assessment of Cardiovascular Materials [1], mandates the use of several reference materials in the presence of blood anticoagulated with sodium citrate. This study was designed to address the relevance of the assay method when using a potent anticoagulant, 3.2% sodium citrate, to evaluate the thrombogenic potential of medical devices. Current studies on this question are under investigation at the FDA also with the intent of improving the standard methods for this assay by evaluating blood anticoagulated with 2–3 IU/mL of heparin [2]. For this study, the effects of several biomaterials were evaluated when exposed to blood anticoagulated with sodium citrate and, concurrently, an even lower dose of heparin at 1 IU/mL also used by our laboratory in a new circulating in vitro assay for thrombogenicity [3]. We believe this test method allows for a sensitive assay that can more accurately predict potential thrombogenic outcomes of cardiovascular materials, while maintaining appropriate responses in both positive and negative control materials.
Thoracic Volumes Correlated With Pulmonary Function Tests in Adult Scoliosis Patients Following Different Treatments in Adolescence
Authors: Lee Po-Chih , Ledonio Charles , Larson A. Noelle , Erdman Arthur , Polly David
Published: October 2017

In clinical settings, doctors classify pulmonary disorders into two main categories, obstructive lung disease and restrictive lung disease. The former is characterized by the airway obstruction which is associated with several disorders like chronic bronchitis, asthma, bronchiectasis, and emphysema [1]. The latter is caused by different conditions where one of the triggers is tied to the spine deformity. In general, a pulmonary function test (PFT) [2] is used to evaluate and diagnose lung function, and physicians depend on the test results to identify the disease patterns of the patients (obstructive or restrictive lung disease). In the PFT, some parameters including total lung capacity (TLC), vital capacity (VC), and residual volume (RV) can infer the lung volume and lung capacity. Other parameters, such as forced vital capacity (FVC) and forced expiratory volume in the first second (FEV1), 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 (ex: scoliosis, kyphosis, and osteoporosis) can affect thoracic volume. Adequate thoracic volume is needed to promote pulmonary function. 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 [3–4]. In this paper, we aim to correlate thoracic volume and the parameters in PFTs in adult scoliosis patients 25–35 years after receiving treatments during their adolescence, either with physical bracing or spinal fusion surgery.
Thrombogenicity Testing for Blood-Contacting Medical Devices in an In Vitro Ovine Blood Loop: Design Improvements and Continuing Validation
Authors: Cunningham Matthew , Deline Steve , Schatz Tim , Beltrame Abby , Steinmetz Erik , Howard Sarah , Smith Mark
Published: October 2017

Thrombogenicity testing is often a requirement for regulatory approval of many types of blood-contacting medical devices [1, 2]. This study describes the continuing improvement in design and characterization of a minimally-heparinized in vitro blood-loop assay which utilizes freshly drawn ovine blood. These modifications were made after studies using this in vitro model were submitted to the FDA in lieu of the in vivo nonanticoagulated venous implant (NAVI) thrombogenicity test. After extensive discussions with FDA reviewers, several modifications which further characterize and improve the assay have been included: 1). Improved temperature control of the blood before and during the incubation period, 2). Improved uniformity and reproducibility of loop geometry, specifically the length of working space for device deployment and a fixed curvature for the radius of the return segment of the loop, 3). Additional measurement of blood parameters prior to and during the incubation period, complete blood counts and activated clotting time (ACT), 4). More rigorous management of ACT, 5). Measurement of non-adherent thrombus formation in the blood, 6).Incorporation of a legally marketed predicate comparator device in all the assays, and 7).Physical characterization of the positive controls. This validated method with enhanced characterization and more reproducible methods allows for a more robust and reliable assay. These results continue to support the premise that this in vitro blood loop assay may eventually supplant the NAVI model for routine hemocompatibility testing for catheter-like blood contacting medical devices.
Instrument Guidance System for MRI-Guided Percutaneous Spinal Interventions
Authors: Squires Alexander , Oshinski John , Tse Zion Tsz Ho
Published: October 2017

In Amyotrophic Lateral Sclerosis (ALS), neurons controlling voluntary muscles die, resulting in muscle weakness. Small animal studies have shown that neurons experience some regeneration when stem cells are injected into the ventral horn of the spinal cord [1]. These results led to large animal and human trials investigating the effects of injecting stem cells into the spinal cord. Direct injection is used for delivering cells as cells do not have to migrate to the therapy site and visual confirmation is possible [2]. This requires a multi-level laminectomy as well as dissection of the dura mater to expose the cell delivery site. In order to adopt this ALS treatment in regular clinical workflow, a minimally invasive alternative for spinal cord cell therapy is desirable.

Image-guided needle targeting and positioning systems have been developed by numerous groups which use computed tomography or ultrasound for image guidance. However, MRI must be used for this ALS study because it is the only imaging system capable of visualizing the necessary anatomical locations for delivering cellular therapeutics to the spinal cord; the cell therapy target is the gray matter within the ventral horn of the spinal cord, and only MRI can detect the contrast between gray and white matter. Innomotion and NeuroArm have been used for MRI-guided interventions [3, 4] but they are complex, take a long time to set up, and take up a great deal of space in the MRI bore. An initial solution by our research group provided targeting solutions using an adjustable template on the spine, but was manually adjusted, targeted solely on a grid, and lacked a second rotation axis[5].

The presented device, SpinoBot, percutaneously directs therapeutics under MRI guidance into the spinal cord, allowing accurate and minimally invasive spinal therapies. This study examines the accuracy and workflow of MRI-guided cellular therapeutics injections using SpinoBot, a targeting and injection needle guidance system.
Defining the Relationship of Magnetohydrodynamic Voltages and Magnetic Field Strength
Authors: Wu Kevin J. , Gregory T. Stan , Lastinger Michael C. , Boland Brian , Tse Zion Tsz Ho
Published: October 2017

The magnetohydrodynamic (MHD) effect is observed in flowing electrolytic fluids and their interactions with magnetic fields. The magnetic field (B0), when perpendicular with the electrolytic fluid flow (μ), causes the shift of the charged particles in the fluid to shift across the length of the vessel (L) normal to the plane of B0 and flow, creating a voltage (VMHD) observable through voltage potential measurements across the flow (Eqn. 1)[1].(1)VMHD=∫0Lu⇀×B0⇀·dL⇀In the medical field, this phenomenon is commonly encountered inside of a human body inside of an MRI machine (Fig. 1).

The effect appears most prominently inside the aortic arch due to orientation and size, and is a large contributing factor to noise observed in intra-MRI ECGs [2, 3]. Traditionally, this MHD induced voltage (VMHD) was filtered out to obtain clean intra-MRI ECGs, but recent studies have shown that the VMHD induced in a vessel is related to the blood flow through it (stroke volume in the case of the aortic arch) [4]. Further proof of this relationship can be shown from the increase in VMHD measured from periphery blood vessels during periods of elevated heart rate from exercise stress, when compared to baseline state [5]. Previously, a portable device was built to utilize induced VMHD as an indicator of flow [6]. The device was capable of showing change in blood flow, utilizing a blood flow metric obtained from VMHD, however a quantitative relationship between VMHD and blood flow has yet to be established.

This study aims to define the relationship between induced VMHD and magnetic field strength in a controlled setting. Through modulating the distance between a pair of magnets around a flow channel, we hope to better realize the relationship between magnetic field strength and induced VMHD with constant flow and electrolytic solution concentration.
Design of a Rotatable One-Element Snake Bone for NOTES
Authors: Zhang Aoyu , Liu Bin , Liu John , Xie Tianyu
Published: October 2017

Over the past decade, natural orifice transluminal endoscopic surgery (NOTES) has developed out of a merger of endoscopy and surgery [1]. NOTES offers the advantages of avoiding external incisions and scars, reducing pain, and shortening recovery time by using natural body orifices as the primary portal of entry for surgeries [2]. The NOTES platform consists of a flexible, hollow body — enabling travel in the interior of the human body — and the distal end (head), the mechanical structure of which is based off of the snake bone. After the distal end passes through a natural orifice, through a transluminal opening of the stomach, vagina, bladder, or colon, and reaches the target working place in the peritoneal cavity, several therapeutic and imaging tools can be passed through the hollow conduit of the NOTES’ body for surgeries [3].

The traditional snake bone design presents two major problems. First, the movement is constrained to two bending degrees-of-freedom (DOF). A need to reorient the tool then often requires the entire body to be rotated by the physician, an unwieldly manipulation that both hinders convenience and results in imprecise control. Second, the traditional fabrication process is tedious and therefore lends to higher manufacturing costs; the bending joints must be first individually machined then assembled together piece-by-piece using rotation pins.

We propose a novel design for the snake bone that introduces an additional DOF via rotation and is simple and cost-effective to machine. The revised snake bone design features rotation segments controlled by wires that a physician can readily manipulate for increased control and convenience. Further, because surgical tools that pass through the NOTES body conduit are also installed on snake bone structures, the introduction of rotation to the snake bone design increases each tool’s mobility and manipulation. This advance therefore presents the potential to decrease both the number of required tools and the overall diameter of the NOTES body. Finally, the body is machined as a single element and therefore minimizes the work of assembly.
Design and Characterization of Shoe Embedded Pressure Sensors for Gait Analysis and Rehabilitation
Authors: Wachtel SeanWolfgang , Hassett Breanna , Qiao Zhi , Chinimilli Prudhvi Tej , Zhang Wenlong
Published: October 2017

In clinical gait therapy, the quality of gait analysis is critical for developing a training plan and monitoring patient progress. Ground contact forces (GCFs) are often recorded to estimate joint torques which can quantify a patient’s needs and strength development. They are also useful in designing and controlling rehabilitative and assistive devices. In clinical gait analysis, force plates are used to measure GCFs objectively and precisely [1, 2]. Currently, forces sensitive resistors (FSR) are often used as a mobile platform to measure GCFs. FSR based platforms exhibit considerable hysteresis and have low durability, some requiring replacement after only 5-hour long uses. As an alternative to FSR, a pair of sensor-embedded shoes (smart shoes) relying on air pressure sensors has been presented in previous research [3]. Some details regarding the precise characteristics of the sensing abilities were unknown, though, generating unanticipated errors during use.

In this paper, the sensing units of wireless smart shoes are characterized and tested to verify their capability to provide real-time and accurate GCF measurements. For the prototype, silicon tubes were sealed on one end, wound into coils, secured to the underside of the shoe’s insole at four points of interest (heel, toe, the first and fourth metatarsophalangeal joint) routed outside the shoe, and their open ends are connected to air pressure sensors as shown in Fig. 1(a). The pressure sensors were placed on a circuit board along with a battery and microcontroller responsible for reading sensor outputs and wirelessly communicating data to a nearby device, as shown in Fig. 1(c). The sensing unit on the lateral side of the shoe is 1.2″ × 1.3″ × 3.95″. A series of calibration tests were first performed on the tube-insole subsystem in isolation to test linearity, repeatability, and hysteresis. Then practical experiments were performed on a healthy subject to determine the accuracy of GCF measurement. A previously presented hysteresis filter was implemented in practical testing [4].
Assistive Device for Patients Having Spondylitis and Spondylosis
Authors: Deva Anshuj , Nageswaran Sharmila , Vidhya S.
Published: October 2017

Spondylitis is a very common back and neck ailment that is reported to account for one-third of social problems causing difficulty at work. It is caused due to the inflammation in vertebral joints. Its condition goes undetected until the symptoms, such as that of severe pain, develops. It causes stinging pain which is focused around cervical region of vertebra, the shoulders and the lumbar region of the spine. Accordingly, it is classified into three types: cervical, thoracic and lumbosacral spondylosis. This is different from spondylitis which causes pain due to inflammation.

Many existing devices use electric current to bring relief from pain. Transcutaneous electrical nerve stimulation (TENS) is one of the most commonly used devices in this aspect. However, though this has been able to bring effective results to its patients, there is a whole lot of controversy in conditions it should be used to treat.

Studies have shown these devices to bring relief by suppressing the signals from the brain. They are not advised for patients with pacemakers or any kind of electronically powered implantable devices. They are less effective where the skin is numb or in places where there is decreased sensation. It depends entirely on the working of the nerve beneath the surface and may cause irritation on the skin if the current is too high. Moreover, these devices need to be avoided in area where infection is present. High precaution needs to be taken when working with epilepsy patients and pregnant women; the electrical stimulation can interfere with the fetus development.

With such a wide range of drawbacks, there is a need for a mechanical solution which can redress these problems and provide an effective and ergonomic solution. Along with overcoming the present barriers, research has been done to demonstrate the positive effects of vibration in increase of bone density, increase of muscle mass, increase of blood circulation, reduced back pain, reduced joint pain and boost in metabolism. The given paper discusses a device wherein vibrational motors have been incorporated, under the control of a microcontroller, to generate the requisite g-force needed for the purpose of pain alleviation and increase of bone density.
Development of a Dynamically Adjusting Soft Wheelchair Insert for Reduction of Single-Point Pressure
Authors: Hoffmann Alexandra , Gracia Beatriz , Lopez Tracy , Polygerinos Panagiotis
Published: October 2017

Wheelchair-bound patients suffer from a number of constraining ailments that affect the digestive, respiratory, circulatory, and integumentary system. The increased risk of pressure ulcers in wheelchair users can be attributed to the combination of consistent single-point pressure and lack of regional movement for an extended period of time, leading to reduced blood circulation to the lower extremities. Pressure ulcers are especially prevalent in elderly wheelchair-bound patients due to the increased fragility of the skin with age. A study by Stockton and Parker estimated the rate of pressure ulcers in all wheelchair users to be nearly 60% [1] and the 2010 US Census reported that 30.6 million Americans have a major mobility disability that require the assistance of a wheelchair, cane or walker [2].

Products currently on the market claim to either distribute pressure more evenly across the surface or stimulate the region of pressure. The former include gel cushions which ease stress by distributing the pressure load but do not initiate movement, while the latter regularly alternate mechanical cushions that initiate movement but do not target region of highest load. Because many patients are unable to independently identify, communicate, or adjust their bodies when there is excess pressure being placed on a specific area, a method of reducing a patient’s single-point pressure on a seat without requiring direct user input could greatly improve the quality of life of wheelchair users.
An MRI-Compatible Robot for Intracerebral Hemorrhage Removal
Authors: Chen Yue , Godage Isuru S. , Sengupta Saikat , Liu Cindy Lin , Weaver Kyle D. , Barth Eric J. , Webster Robert J.
Published: October 2017

Intracerebral Hemorrhage (ICH) is the deadliest form of stroke and occurs when blood, leaked from a ruptured vessel pools in the brain forming a pool of semi-coagulated blood called a hematoma. 1 in 50 people will have an ICH in their lifetime [1] and the 30-day mortality rate is 43% with half of the deaths occurring in the acute phase, which motivates the need for safe and rapid treatment. However, literature reviews show no significant benefit of surgical removal vs. “watchful waiting”, despite the potential value of decompressing the brain. It has been hypothesized that this is due to the significant disruption of healthy brain tissue required to reach the hemorrhagic site in open brain surgery.

Recent studies conducted on phantom models have shown that a robotic needle made from curved, concentric, elastic tubes can reach a hemorrhagic site through a needle-sized path to successfully aspirate the hematoma. This approach has the potential to decompress the brain with far less disruption to surrounding brain tissue [4]. Those initial experiments were conducted under guidance from periodic (low rate) CT [2]. The need for intraoperative imaging was motivated by the fact that the brain shifts during aspiration, collapsing to fill the cavity left by voided blood. This approach has the potential advantage of “one stop shopping”, since ICH is typically diagnosed in the CT scanner. It is appealing to treat ICH immediately after diagnosis, while the patient is still in the scanner. However, CT also has the drawback of requiring ionizing radiation, as well as providing only intermittent images rather than real-time information.

In this paper, we consider a Magnetic Resonance Imaging (MRI) guided approach, which provides the converse in terms of both benefits and drawbacks. MRI is not typically used to diagnose ICH, but it can provide detailed soft-tissue and hematoma contrast [3], and fast image updates, enabling real-time monitoring of brain deformation during the aspiration process. Toward performing ICH aspiration with a concentric tube robot in an MRI environment, this paper presents accuracy and MR-compatibility tests for a new MR-compatible robot designed for ICH removal.
Mixed Ionic Electronic Conductors for Improved Charge Transport in Electrotherapeutic Devices
Authors: Shqau Krenar , Heintz Amy
Published: October 2017

Electrotherapeutic devices require an electrode for coupling with the body. The most common electrodes are made of conducting corrosion resistance materials (e.g., TiN, Ir-IrO2, Pt) plus a coupling layer (e.g., electrolyte). The electrode is the location where redox reaction take place between the device and the tissue. As such, it must conduct both electrons and ions. The reactions can be capacitive, involving the charging and discharging of the electrode-electrolyte double layer, or faradaic. Capacitive charge-injection is more desirable than faradic charge-injection because no chemical species are created or consumed during a stimulation pulse. Most noble metal based electrodes are faradic or pseudo-capacitive, which can lead to performance changes over time. In addition, under the high rate of charge injection and high current density conditions of a neuromuscular stimulation pulse, access to all the accessible charges is limited by the interfacial resistance and low surface area at the electrode [1]. A particularly critical point is the passage of current between the surface of the skin and the electrical contact connected by wire to the device, which requires a low stable resistance that does not vary with time, humidity [2].

We have developed new hybrid mixed-ionic-electronic conductors (MIECs) that have the potential to overcome these deficiencies. The MIECs are an interconnected network of electrical and ionic conductors in an elastomeric matrix that provide: (1) high surface area for efficient capacitive charge-discharge; (2) high ionic conductivity for low interfacial resistance; (3) low ohmic resistance; and (4) excellent flexibility and toughness. Carbon nanotubes (CNTs) are the electrical conductors in the MIEC and hyaluronic acid (HA), along with moisture and ions, is the ionic conductor. Unlike the current state-of-the-art, conducting noble metals, this system exhibits good mechanical properties, high conductivity (up to 3000 mS/cm), high moisture retention (up to 100wt%) and high ion mobility, leading to facile electrode kinetics. This simple yet efficient system is promising for the fabrication of a variety of high performance flexible electrodes.
Target Lesion Calcium Arc Influence the Performance of Stenting
Authors: Dong Pengfei , Lin Shengmao , Wilson David L. , Bezerra Hiram G. , Gu Linxia
Published: October 2017

Percutaneous coronary intervention (PCI) is the most common revascularization procedure, in which, fibrocalcific plaques are found in 17–35% of patients undergoing PCI [1]. Numbers will rise with population aging and prolonged statin treatment. Calcifications often lead to stent under expansion and strut malapposition, with increased risk of thrombosis and in-stent restenosis [2]. Presence of calcium strongly inhibits stent performance, a well-documented metric for outcome [3]. The goal of this work is to develop the finite element models for inspecting the influence of the calcium arc extent on the stenting outcomes, such as the stress and strain distribution within the plaque, and the lumen gain following stenting. Finite element method is an effective tool to reveal the mechanism of the stent expansion and its interaction with target lesion, provide guidance for optimal clinical outcomes.
Improving Automatic Control of an Ankle-Foot Prosthesis Using Machine Learning Algorithms
Authors: Fairhurst Stuart R. , Koehler-McNicholas Sara R. , Slater Billie C. S. , Nickel Eric A. , Koester Karl A. , Voss Gregory O. , Hansen Andrew H. , Ferguson John E.
Published: October 2017

Most commercially available lower-limb prostheses are designed for walking, not for standing. The Minneapolis VA Health Care System has developed a bimodal prosthetic ankle-foot system with distinct modes for walking and standing [1]. With this device, a prosthesis user can select standing or walking mode in order to maximize standing stability or walking functionality, depending on the activity and context. Additionally, the prosthesis was designed to allow for an “automatic mode” to switch between standing and walking modes based on readings from an onboard Inertial Measurement Unit (IMU) without requiring user interaction to manually switch modes. A smartphone app was also developed to facilitate changing between walking, standing and automatic modes.

The prosthesis described in [1] was used in a pilot study with 18 Veterans with lower-limb amputations to test static, dynamic, and functional postural stability. As part of the study, 17 Veterans were asked for qualitative feedback on the bimodal ankle-foot system (Table 1).

The majority of participants (82%) expressed an interest in having an automatic mode. The participants also indicated that the automatic mode would need to reach walking mode on their first step and to lock the ankle quickly once the standing position was achieved. When asked about how they wanted to control the modes of the prosthesis, 82% wanted to use a physical switch and only 12% wanted to use a smartphone app. The results indicated that the following major design changes would be needed:

1) A fast and accurate automatic mode

2) A physical switch for mode changes

This paper describes the use of machine learning algorithms to create an improved automatic mode and the use of stakeholder feedback to design a physical switch for the bimodal ankle-foot system.
Accurate Non-Invasive Temperature Monitoring Device
Authors: Augustine Garrett , Augustine Scott
Published: October 2017

Core temperature is one of the most tightly auto-regulated physiological processes. Anesthetic drugs compromise the body’s ability to thermoregulate. When core temperature is outside of the normothermia range, patients are at increased risk of myriad complications. Hypothermic patients are at higher risk of, among other things, increased wound infections2, increased blood loss3, increased ICU times and hospital stays2, higher mortality rates4, increased transfusion requirements3. “Even mildly hypothermic patients could suffer an increase in adverse outcomes that can add costs of as much as $2,500–$7,000 per patient.”5 These risks are great such that clinicians actively warm hypothermic patients to achieve normothermia.

Given the importance of the core temperature on outcomes, there is a clear necessity for accurate core temperature measurement. Core temperature measurement is often misunderstood. Perhaps due to the pervasive home use of oral mercury thermometers to “take your temperature,” many wrongly assume that non-invasive core temperature is measured easily and accurately. Oral, axilla, nasal are all unreliable. Temporal/forehead and ear are particularly inaccurate. “Global authorities in anesthesiology and medicine have cited inadequacies with virtually all thermometry”6 False assurance or false alarm are both dangerous. There is currently no non-invasive way to reliably and accurately measure core temperature. Why is this?

The peripheral compartment is not in equilibrium with core. Fat and other layers further complicate the matter. Fat has the thermal conductivity of oak, and thus non-invasive methods to measure core are as Abreu puts it “taking measurements on the outside surface of an oak cask to determine the temperature of its contents.”6 Laws of Thermodynamics notwithstanding, many still try.

Invasive esophageal or rectal and to a lesser extent bladder, are the only way to accurately measure core. The fact is, in order to measure their patients’ core temperature vital sign accurately, clinicians have only available to them the medical equivalent of a meat thermometer.

Intubated patients under general anesthesia are perfectly suited for invasive core temperature monitoring. They are not going to gag the esophageal stethoscope, nor would they find rectal or bladder probing uncomfortable in their unconsciousness. Clinicians may find probing mildly unpleasant and a minor time consumption, but once again, given the lack of alternatives, the only real option is to grin and bear it.

General anesthesia is not without risks, especially with increasingly increasing patients, and as sedation or blocks become more popular, invasive core temperature monitoring is unpractical. This highlights the stark question: Is it possible to accurately and reliably ascertain core temperature non-invasively?
Assessing the Relationship Between Right Atrial Stiffness and Chamber Pressure to Quantitatively Define Myocardial Tensile Properties
Authors: Mattson Alexander R. , Eggen Michael D. , Grubac Vladimir , Iaizzo Paul A.
Published: October 2017

Developing a successful cardiac device requires detailed knowledge of cardiac mechanical properties. For example, tissue failure characteristics and compliance feed into design criteria for many pacemaker leads (Zhao et al., 2011).

In the right atrium, tensile forces are exerted on the right atrial appendage in multiple clinical procedures. In a traditional lead implant, mechanical manipulations with a stylet aid a clinician in assessing lead fixation, with a seldom used “tug” test providing additional input. Atrial lead dislodgement remains one of the top complications for bradycardia pacing leads (Chahuan et al., 1994), in part because there is no standard mechanical assessment at implant to verify fixation. Thus, a deeper understanding of forces exerted on the atrium during implant, is fundamental to understanding the problem. Further characterization of the biomechanics relevant to atrial device implants will provide valuable design input for fixation tests and help drive research toward new atrial fixation mechanisms.

This study aims to better define the relationships between right atrial stiffness and the chamber pressures within the right atrium, so to characterize the link between tensile displacement within the right atrium, and the force exerted on an implanted device in a functional heart. These experiments quantitatively define the fixation force of a fixed cardiac device with a given pulled displacement; i.e. displacing the device a given distance will effectively ensure the experimentally derived fixation force.
Design of a Portable Position, Velocity, and Resistance Meter (PVRM) for Convenient Clinical Evaluation of Spasticity or Rigidity
Authors: Song Seung Yun , Pei Yinan , Liang Jiahui , Hsiao-Wecksler Elizabeth T.
Published: October 2017

Spasticity is a common consequence of the upper motor neuron syndrome and usually associated with brain lesion, stroke, cerebral palsy, spinal cord injury, and etc. On the other hand, rigidity is a neuromuscular disorder often found in Parkinson’s disease patients. Both of spasticity and rigidity are characterized by abnormal hypertonic muscle behaviors that will cause discomfort and hinder daily activities. Worldwide, the estimated affected population of spasticity is around 12 million [1], and rigidity affects more than 10 million people [2]. Clinical evaluation of spasticity or rigidity involves personal assessment using qualitative scales, such as the Modified Ashworth Scale (MAS) or Modified Tardieu Scale (MTS) for spasticity and Unified Parkinson’s Disease Rating Scale (UPDRS) for rigidity. However, this evaluation method heavily relies on the rater’s personal experience/interpretation and usually results in poor consistency and low reliability. The goal of this design was to develop a quantitative measurement device that can be used to assist clinical evaluation of spasticity or rigidity. This portable device, the Position, Velocity, and Resistance Meter (PVRM), can be strapped around a patient’s limb to measure angular position, angular velocity and muscle resistance of a given joint while the patient’s limb is passively stretched by the clinician. Acquiring this quantitative data from patients will not only allow clinicians to make more reliable assessments but also help researchers gain additional insights into the quantification of spasticity and rigidity.
Design and Biomechanical Evaluation Methodology of Pneumatic Ergonomic Crutch
Authors: Xiao Chenzhang , Jahanian Omid , Schnorenberg Alyssa , Slavens Brooke , Hsiao-Wecksler Elizabeth
Published: October 2017

Lofstrand, or forearm, crutch users experience a concerning amount of force in their wrists that can approach 30% of body weight during swing-through gait, along with hyperextension of the wrist [1]. Such repetitive large loads and poor wrist posture could cause joint pain, injury and carpal tunnel syndrome in long-term crutch users [2].

To address these issues in Lofstrand crutch users, we previously reported two different designs. The first involved attaching a passive orthosis to the grip handle and shaft that directly supported the wrist [3]. The second proposed a soft pneumatic sleeve attached to the forearm cuff of the crutch along with a concept to harvest pneumatic energy during walking via a piston pump at the crutch tip, i.e., the Pneumatic Ergonomic Crutch (PEC) [4].

This paper first describes the full system design of the PEC, which contains an improved pneumatic sleeve orthosis, an energy-harvesting shock-absorbing crutch tip, and a control system with three modes of operation and safety protection. We also present pilot data from one healthy control subject performing a proposed biomechanical evaluation of the pneumatic sleeve orthosis. More tests will be conducted with a group of able-bodied subjects to evaluate the overall effectiveness of the PEC.
Design of a Passive Ankle Prosthesis With Energy Return That Increases With Increasing Walking Velocity
Authors: Folz Alexander J. , Schimmels Joseph M.
Published: October 2017

An estimated 623,000 individuals are living with a major lower leg amputation in the United States [1]. Of these amputations, 78% were due to peripheral vascular disease (PVD) and 45% were due to PVD in individuals with type I or II diabetes [2]. With diabetes and PVD incidence levels on the rise [1] and those in a depressed socio-economic situation more susceptible to develop type II diabetes [3], the demand for affordable, high quality ankle prostheses has never been higher. Prostheses currently available on the market include both passive and active devices, neither of which fully satisfies user requirements.

Passive prostheses, the more commonly prescribed style, are economically priced but lack the powered push-off observed in a natural ankle [4] due to the absence of an actuator. As a result, passive prostheses cause a multitude of quality of life detriments to the end user including asymmetrical gait (for unilateral amputees), slower self-selected walking speeds, higher metabolic cost per distance traveled and increased pain in the residual limb [5–6].

Conversely, active devices can nearly match the functionality and powered push-off of a natural ankle [7] but are cost prohibitive. Among active devices, one of the most successful models is the BiOM. Initially developed at MIT, the BiOM uses an actuator in series with a spring to achieve near natural ankle behavior. In 2013, two years after the product’s official launch, the device cost approximately $50,000 and had only sold about 1,000 units [7].

The limitations of currently available ankle prostheses motivates work on a new solution, the EaSY-Walk (Early Stance Y-deflection), a passive ankle device that mimics several key aspects of a natural ankle joint, especially nonlinear rotational stiffness and rotational work output (powered push-off) that increases with walking velocity while remaining relatively inexpensive.
Soft-Robotic Endoscope Tip Design
Authors: Nuriyev Mikhail , Montayre Rudy , Taylor Austin , Tse Zion Tsz Ho
Published: October 2017

Endoscopic procedures are minimally invasive and are commonly used in surgeries and various diagnoses. Endoscopes allow vision in very delicate and constricted areas of the human body. Although the endoscope is a very beneficial tool, it still has its disadvantages. Today’s metallic endoscopes are rigid and tend to be hard to manipulate on the fine scales necessary to work within the human body while minimizing harm. Endoscopes made of metal can easily puncture an internal organ if not directed properly [1].

Soft robotics is a new and unique system for designing and creating a new generation of medical devices [2]. With soft robotics, silicone-based molds can be controlled and driven using nothing more than tubing and air pressure (Fig. 1) [3]. Employing the principles of soft robotics, we are attempting to create a new kind of endoscope made from a silicon-based material. Ideally, a silicone-based endoscope would be cheap to produce and require almost no training to operate, while still maintaining the same benefits of metallic endoscopes. Endoscopes made from soft robotic actuators will have better dexterity due to the wall thickness allowing a full range of motion and flexion. In this study, it was hypothesized that additional controllability in the soft robotic endoscope design could be achieved by controlling the combination of wall thicknesses of the silicone molds during the fabrication process.
Analysis of Postural Stability After Concussion Using Empirical Mode Decomposition: A Pilot Study
Authors: Schneider Charles M. , Verma Ajay K. , Munia Tamanna T. K. , Romanick Mark , Tavakolian Kouhyar , Fazel-Rezai Reza
Published: October 2017

Maintaining upright stance is a complex process, it requires appropriate functioning of a postural control system which consists of inputs from somatosensory, vestibular, musculoskeletal, and proprioceptive systems as well as from several brain regions [1–4]. A concussion is defined as a brain injury caused due to unexpected acceleration/deceleration of the head causing temporary alteration of brain function and it is a prevalent source of injury to football athletes [1]. With the altered function of the brain, the ability to maintain postural equilibrium becomes challenging due to the inability of individuals to respond promptly to stressors, thus, making maintenance of postural equilibrium rather difficult for individuals with a concussion. Effects of concussion on postural ability are shown to last up to three days post injury [5]. Postural stability test, therefore, can be performed to make a valid return to play (RTP) decision, pre-mature RTP is shown to have been catastrophic due to its potential to permanently impair previously affected region/functioning [1,5]. Postural sway data (center of pressure, COP) is traditionally analyzed to study the postural control. Therefore, COP can provide critical information regarding individual’s ability to maintain upright stance post injury.

A more sensitive concussion assessment tool based on electroencephalogram (EEG) is used to accurately track effects of concussion [6]. However, sophisticated electrode placement requirement inhibits its immediate applicability. In current preliminary research, we attempt to differentiate athletes with a history of concussion (experimental) from healthy (control) using postural data. In order to do so, a concept of empirical mode decomposition (EMD) was adopted. EMD has shown evidence in the literature to infer vital information pertaining to the complex underlying physiological phenomenon [4, 7–8]. In the current research, the resultant COP (COPr) was decomposed into its finite set of band-limited signals termed as intrinsic mode functions (IMFs) [8], a set of linear and nonlinear features were extracted from COPr and its IMfs. Lastly, a test of significance was conducted to infer the potential of postural data for differentiating concussed from healthy athletes.
Numerical Analysis of Blood Flow Through Discrete Stenosis: Role of Eccentricity and Spacing Ratio
Authors: Ju Siyeong , Gu Linxia
Published: October 2017

Stenosis or narrowing of arteries induces a turbulent flow region downstream. Multiple stenosis may lead to flow interference and further disturb the blood flow. This has important clinical implications [1], such as disturbed blood flow and flow recirculation which were correlated with the development of atherosclerosis by upregulating the endothelial cells genes and proteins that cause atherogenesis [2]. Numerical simulation of concentric stenoses by Lee et al [3] have shown that the recirculation zone following the first concentric stenosis affected the flow field at the downstream of the second one, which was dependent on the spacing ratio and degree of stenosis. However, the majority of stenosis is eccentric [2] and the detailed fluid dynamics of multiple stenoses with eccentric constrictions is lacking. The aim of this study is to investigate the interactions between double stenoses with eccentricity using computational fluid dynamics (CFD) simulation. The role of spacing ratio on the recirculation zone and turbulence intensity (TI) were characterized and also compared to concentric cases.
Design and Analysis of a Novel 5-DoF Bimanual Laparoscopic Impedance Skills Trainer With Haptics Feedback
Authors: Raghu Prasad M. S. , Manivannan M.
Published: October 2017

Laparoscopic surgery has widely replaced open surgery due to the advantages it has for patients both during surgery and post-surgery recovery. Due to inversion and remote access to the surgical site, haptics feedback is altered with laparoscopic surgical instruments [1]. This leads to excessive exertion of force [2]. Many intra operative errors like tissue injury in laparoscopic surgery are due to texertion of large forces [2]. Over the years, virtual reality (VR) based laparoscopic surgical simulators with haptics feedback have been instrumental in teaching basic and advanced laparoscopic skills to residents and surgeons [3]. However, a major limitation in modern day VR based simulator training systems is that they do not effectively teach the bimanual impedance-based laparoscopic skills. Past studies on VR based laparoscopic training have captured the skills sets of residents and surgeons using force and psychomotor metrics [3, 4]. However, till date none have explored the effects of experience on impedance based training. In this study, we analyze the impedance skills of residents and surgeons using custom developed novel bimanual laparoscopic skills trainer.
Endogenous retinoid X receptor ligands in mouse hematopoietic cells
Authors: Niu Haixia , Fujiwara Hideji , di Martino Orsola , Hadwiger Gayla , Frederick Thomas E. , Menéndez-Gutiérrez María P. , Ricote Mercedes , Bowman Gregory R. , Welch John S.
Published: October 2017

The long-chain fatty acid C24:5 is likely an endogenous ligand of the retinoid X receptor α in mouse hematopoietic cells.
Endogenous defense against helminths
Authors: VanHook Annalisa M.
Published: October 2017

Secreted phospholipase A
2
protects against helminth infection by damaging parasite larvae.
Papers of note in
Nature
550
(7677)
Authors: VanHook Annalisa M.
Published: October 2017

This week’s articles highlight inflammatory memory in epithelial stem cells; ubiquitin-specific protease inhibitors that target cancer cells; the identification of a sphingosine 1-phosphate exporter; and G protein signaling hotspots on the plasma membrane.
Calculating the individual probability of successful ocriplasmin treatment in eyes with VMT syndrome: a multivariable prediction model from the EXPORT study
Authors: Paul Christoph , Heun Christine , Müller Hans-Helge , Hoerauf Hans , Feltgen Nicolas , Wachtlin Joachim , Kaymak Hakan , Mennel Stefan , Koss Michael Janusz , Fauser Sascha , Maier Mathias M , Schumann Ricarda G , Mueller Simone , Chang Petrus , Schmitz-Valckenberg Steffen , Kazerounian Sara , Szurman Peter , Lommatzsch Albrecht , Bertelmann Thomas
Published: October 2017

Background/Aims

To evaluate predictive factors for the treatment success of ocriplasmin and to use these factors to generate a multivariate model to calculate the individual probability of successful treatment.

Methods

Data were collected in a retrospective, multicentre cohort study. Patients with vitreomacular traction (VMT) syndrome without a full-thickness macular hole were included if they received an intravitreal injection (IVI) of ocriplasmin. Five factors (age, gender, lens status, presence of epiretinal membrane (ERM) formation and horizontal diameter of VMT) were assessed on their association with VMT resolution. A multivariable logistic regression model was employed to further analyse these factors and calculate the individual probability of successful treatment.

Results

167 eyes of 167 patients were included. Univariate analysis revealed a significant correlation to VMT resolution for all analysed factors: age (years) (OR 0.9208; 95% CI 0.8845 to 0.9586; p<0.0001), gender (male) (OR 0.480; 95% CI 0.241 to 0.957; p=0.0371), lens status (phakic) (OR 2.042; 95% CI 1.054 to 3.958; p=0.0344), ERM formation (present) (OR 0.384; 95% CI 0.179 to 0.821; p=0.0136) and horizontal VMT diameter (µm) (OR 0.99812; 95% CI 0.99684 to 0.99941, p=0.0042). A significant multivariable logistic regression model was established with age and VMT diameter.

Conclusion

Known predictive factors for VMT resolution after ocriplasmin IVI were confirmed in our study. We were able to combine them into a formula, ultimately allowing the calculation of an individual probability of treatment success with ocriplasmin in patients with VMT syndrome without FTHM.