Showing papers in "Journal of Medical Devices-transactions of The Asme in 2017"

Design, Fabrication, and Testing of a Needle-Sized Wrist for Surgical Instruments

Abstract: This paper presents a miniature wrist that can be integrated into needle-sized surgical instruments. The wrist consists of a nitinol tube with asymmetric cutouts that is actuated by a single tendon to provide high distal curvature. We derive and experimentally validate kinematic and static models for the wrist and describe several prototype wrists, illustrating the straightforward fabrication and scalability of the design. We experimentally investigate fatigue life, the concept of tip-first bending, and practical use of the wrist with a concentric tube robot in an endonasal surgical scenario.

The Role of Computational Modeling and Simulation in the Total Product Life Cycle of Peripheral Vascular Devices.

Abstract: The total product life cycle (TPLC) of medical devices has been defined by four stages: discovery and ideation, regulatory decision, product launch, and postmarket monitoring. Manufacturers of medical devices intended for use in the peripheral vasculature, such as stents, inferior vena cava (IVC) filters, and stent-grafts, mainly use computational modeling and simulation (CM&S) to aid device development and design optimization, supplement bench testing for regulatory decisions, and assess postmarket changes or failures. For example, computational solid mechanics and fluid dynamics enable the investigation of design limitations in the ideation stage. To supplement bench data in regulatory submissions, manufactures can evaluate the effects of anatomical characteristics and expected in vivo loading environment on device performance. Manufacturers might also harness CM&S to aid root-cause analyses that are necessary when failures occur postmarket, when the device is exposed to broad clinical use. Once identified, CM&S tools can then be used for redesign to address the failure mode and re-establish the performance profile with the appropriate models. The Center for Devices and Radiological Health (CDRH) wants to advance the use of CM&S for medical devices and supports the development of virtual physiological patients, clinical trial simulations, and personalized medicine. Thus, the purpose of this paper is to describe specific examples of how CM&S is currently used to support regulatory submissions at different phases of the TPLC and to present some of the stakeholder-led initiatives for advancing CM&S for regulatory decision-making.

Disposable Fluidic Actuators for Miniature In-vivo Surgical Robotics

Abstract: Fusion of robotics and minimally invasive surgery (MIS) has created new opportunities to develop diagnostic and therapeutic tools. Surgical robotics is advancing from externally actuated systems to miniature in-vivo robotics. However, with miniaturization of electric-motor-driven surgical robots, there comes a trade-off between the size of the robot and its capability. Slow actuation, low load capacity, sterilization difficulties, leaking electricity and transferring produced heat to tissues, and high cost are among the key limitations of the use of electric motors in in-vivo applications. Fluid power in the form of hydraulics or pneumatics has a long history in driving many industrial devices and could be exploited to circumvent these limitations. High power density and good compatibility with the in-vivo environment are the key advantages of fluid power over electric motors when it comes to in-vivo applications. However, fabrication of hydraulic/pneumatic actuators within the desired size and pressure range required for in-vivo surgical robotic applications poses new challenges. Sealing these types of miniature actuators at operating pressures requires obtaining very fine surface finishes which is difficult and costly. The research described here presents design, fabrication, and testing of a hydraulic/pneumatic double-acting cylinder, a limited-motion vane motor, and a balloon-actuated laparoscopic grasper. These actuators are small, seal-less, easy to fabricate, disposable, and inexpensive, thus ideal for single-use in-vivo applications. To demonstrate the ability of these actuators to drive robotic joints, they were modified and integrated in a robotic arm. The design and testing of this surgical robotic arm are presented to validate the concept of fluid-power actuators for in-vivo applications.

pneuRIPTM: A Novel Respiratory Inductance Plethysmography Monitor.

Abstract: Objective pulmonary function (PF) evaluation is essential for the diagnosis, monitoring, and management of many pediatric respiratory diseases as seen in the emergency room, intensive care, and outpatient settings. In this paper, the development and testing of a new noninvasive PF instrument, pneuRIPTM, which utilizes respiratory inductance plethysmography (RIP) are discussed. The pneuRIPTM hardware includes a small circuit board that connects to the RIP bands and measures and wirelessly transmits the band inductance data to any designated wirelessly connected tablet. The software provides indices of respiratory work presented instantaneously in a user-friendly graphical user interface on the tablet. The system was tested with ten normal children and compared with an existing system, Respitrace (Sensormedics, Yorba Linda, CA), under normal and loaded breathing conditions. Under normal breathing, the percentage differences between the two systems were 2.9% for labored breathing index (LBI), 31.8% for phase angle (Φ), 4.8% for percentage rib cage (RC%), and 26.7% for respiratory rate (BPM). Under loaded breathing, the percentage differences between the two systems were 1.6% for LBI, 4.1% for Φ, 8.5% for RC%, and 52.7% for BPM. For LBI, Φ, and RC%, the two systems were in general agreement. For BPM the pneuRIPTM is shown to be more accurate than the respitrace when compared to manually counting the breaths: 13.2% versus 36.4% accuracy for normal breathing and 16.9% versus 60.7% accuracy for breathing under load, respectively.

Design and Fabrication of a Low-Cost Three-Dimensional Bioprinter.

Abstract: Three-dimensional (3D) bioprinting offers innovative research vectors for tissue engineering. However, commercially available bioprinting platforms can be cost prohibitive to small research facilities, especially in an academic setting. The goal is to design and fabricate a low-cost printing platform able to deliver cell-laden fluids with spatial accuracy along the X, Y, and Z axes of 0.1 mm. The bioprinter consists of three subassemblies: a base unit, a gantry, and a shuttle component. The platform utilizes four stepper motors to position along three axes and a fifth stepper motor actuating a pump. The shuttle and gantry are each driven along their respective horizontal axes via separate single stepper motor, while two coupled stepper motors are used to control location along the vertical axis. The current shuttle configuration allows for a 5 mL syringe to be extruded within a work envelope of 180 mm × 160 mm × 120 mm (X, Y, Z). The shuttle can easily be reconfigured to accommodate larger volume syringes. An attachment for a laser pen is located such that printing material may be light-activated pre-extrusion. Positional fidelity was established with calipers possessing a resolution to the nearest hundredth millimeter. The motors associated with the X and Y axes were calibrated to approximately 0.02 mm per motor impulse. The Z axis has a theoretical step distance of ∼51 nm, generating 0.04% error over a 10 mm travel distance. The A axis, or pump motor, has an impulse distance of 0.001 mm. The volume extruded by a single impulse is dictated by the diameter of the syringe used. With a 5 mL syringe possessing an inner diameter of 12.35 mm, the pump pushes as little as 0.119 μL. While the Z axis is tuned to the highest resolution settings for the motor driver, the X, Y, and A axes can obtain higher or lower resolution via physical switches on the motor drivers.

Toward Medical Devices With Integrated Mechanisms, Sensors, and Actuators Via Printed-Circuit MEMS

Abstract: Recent advances in medical robotics have initiated a transition from rigid serial manipulators to flexible or continuum robots capable of navigating to confined anatomy within the body. A desire for further procedure minimization is a key accelerator for the development of these flexible systems where the end goal is to provide access to previously inaccessible anatomical workspaces and enable new minimallyinvasive surgical (MIS) procedures. While sophisticated navigation and control capabilities have been demonstrated for such systems, existing manufacturing approaches have limited the capabilities of mm-scale end-effectors for these flexible systems to date and, to achieve next generation highlyfunctional end-effectors for surgical robots, advanced manufacturing approaches are required. We address this challenge by utilizing a disruptive 2D layer-by-layer precision fabrication process (inspired by printed circuit board manufacturing) that can create functional 3D mechanisms by folding 2D layers of materials which may be structural, flexible, adhesive, or conductive. Such an approach enables actuation, sensing and circuitry to be directly integrated with the articulating features by selecting the appropriate materials during the layer-by-layer manufacturing process. To demonstrate the efficacy of this technology, we use it to fabricate three modular robotic components at the millimeter-scale: (1) sensors, (2) mechanisms, and (3) actuators. These modules could potentially be implemented into transendoscopic systems, enabling bilateral grasping, retraction and cutting, and could potentially mitigate challenging MIS interventions performed via endoscopy or flexible means. This research lays the ground work for new mechanism, sensor and actuation technologies that can be readily integrated via new mm-scale layer-by-layer manufacturing approaches.

Design of a Magnetic Resonance Imaging Guided Magnetically Actuated Steerable Catheter.

Abstract: This paper presents design optimization of a magnetic resonance imaging (MRI) actuated steerable catheter for atrial fibrillation ablation in the left atrium. The catheter prototype, built over polymer tubing, is embedded with current-carrying electromagnetic coils. The prototype can be deflected to a desired location by controlling the currents passing through the coils. The design objective is to develop a prototype that can successfully accomplish the ablation task. To complete the tasks, the catheter needs to be capable of reaching a set of desired targets selected by a physician on the chamber and keeping a stable contact with the chamber surface. The design process is based on the maximization of the steering performance of the catheter by evaluating its workspace in free space. The selected design is validated by performing a simulation of an ablation intervention on a virtual model of the left atrium with a real atrium geometry. This validation shows that the prototype can reach every target required by the ablation intervention and provide an appropriate contact force against the chamber.

Novel Solutions Applied in Transseptal Puncture: A Systematic Review

Abstract: Fundacao para a Ciencia e a Tecnologia, in Portugal, and the European Social Found, European Union, for funding support through the Programa Operacional Capital Humano (POCH) in through the first author’s PhD grant with reference SFRH/BD/95438/2013. This work was supported by ON.2 SR&TD Integrated Program (NORTE -07-0124-FEDER-000017)” co-funded by Programa Operacional Regional do Norte (ON.2-O Novo Norte), Quadro de Referencia Estrategico Nacional (QREN), through Fundo Europeu de Desenvolvimento Regional (FEDER). Authors gratefully acknowledge the funding of Project NORTE-01-0145-FEDER-000022 - SciTech -Science and Technology for Competitive and Sustainable Industries, cofinanced by “Programa Operacional Regional do Norte” (NORTE2020), through “Fundo Europeu de Desenvolvimento Regional” (FEDER)

Finite Element Analysis of the Implantation Process of Overlapping Stents.

Abstract: Overlapping stents are widely used in vascular stent surgeries. However, the rate of stent fractures (SF) and in-stent restenosis (ISR) after using overlapping stents is higher than that of single stent implantations. Published studies investigating the nature of overlapping stents rely primarily on medical images, which can only reveal the effect of the surgery without providing insights into how stent overlap influences the implantation process. In this paper, a finite element analysis of the overlapping stent implantation process was performed to study the interaction between overlapping stents. Four different cases, based on three typical stent overlap modes and two classical balloons, were investigated. The results showed that overlapping contact patterns among struts were edge-to-edge, edge-to-surface, and noncontact. These were mainly induced by the nonuniform deformation of the stent in the radial direction and stent tubular structures. Meanwhile, the results also revealed that the contact pressure was concentrated in the edge of overlapping struts. During the stent overlap process, the contact pattern was primarily edge-to-edge contact at the beginning and edge-to-surface contact as the contact pressure increased. The interactions between overlapping stents suggest that the failure of overlapping stents frequently occurs along stent edges, which agrees with the previous experimental research regarding the safety of overlapping stents. This paper also provides a fundamental understanding of the mechanical properties of overlapping stents.

Effects of Sterilization on Shape Memory Polyurethane Embolic Foam Devices.

Abstract: Polyurethane shape memory polymer (SMP) foams have been developed for various embolic medical devices due to their unique properties in minimally invasive biomedical 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 (nontraditional 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.

Influence of a Commercial Antithrombotic Filter on the Caval Blood Flow During Neutra and Valsalva Maneuver

Abstract: This study was supported by the CIBER-BBN financed by the Instituto de Salud Carlos III, by the Spanish Ministry of Science and Technology through the Research Projects Nos. DPI-2010-20746-C03-01 and DPI-2013-44391-P and by the Spanish Ministry of Economy and Competitiveness through the Research Project No. DPI-2016-76630-C2-1-R. The experimental study was supported by the Instituto de Salud Carlos III, through the Research Project No. PI08/1424 and was performed by the Minimally Invasive Techniques Research Group (GITMI) of Aragon Government.

A Laparoscopic Morcellator Redesign to Constrain Tissue Using Integrated Gripping Teeth

Abstract: Laparoscopic hysterectomy is a procedure that involves the removal of the uterus through an abdominal keyhole incision. Morcellators have been specifically designed for this task, but their use has been discouraged by the food and drug administration (FDA) since November 2014 because of risks of cancerous tissue spread. The use of laparoscopic bags to catch and contain tissue debris has been suggested, but this does not solve the root cause of tissue spread. The fundamental problem lies in the tendency of the tissue mass outside the morcellation tube to rotate along with the cutting blade, causing tissue to be spread through the abdomen. This paper presents a bio-inspired concept that constrains the tissue mass in the advent of its rotation in order to improve the overall morcellation efficacy and reduce tissue spread. A design of gripping teeth integrated into the inner diameter of the morcellation tube is proposed. Various tooth geometries were developed and evaluated through an iterative process in order to maximize the gripping forces of these teeth. The maximum gripping force was determined through the measurement of force-displacement curves during the gripping of gelatin and bovine tissue samples. The results indicate that a tooth ring with a diameter of 15mm can provide a torque resistance of 1.9 Ncm. Finally, a full morcellation instrument concept design is provided.

Statistical Shape Modeling for Cavopulmonary Assist Device Development: Variability of Vascular Graft Geometry and Implications for Hemodynamics.

Abstract: Patients born with a single functional ventricle typically undergo three-staged surgical palliation in the first years of life, with the last stage realizing a cross-like total cavopulmonary connection (TCPC) of superior and inferior vena cavas (SVC and IVC) with both left and right pulmonary arteries, allowing all deoxygenated blood to flow passively back to the lungs (Fontan circulation). Even though within the past decades more patients survive into adulthood, the connection comes at the prize of deficiencies such as chronic systemic venous hypertension and low cardiac output, which ultimately may lead to Fontan failure. Many studies have suggested that the TCPC's inherent insufficiencies might be addressed by adding a cavopulmonary assist device (CPAD) to provide the necessary pressure boost. While many device concepts are being explored, few take into account the complex cardiac anatomy typically associated with TCPCs. In this study, we focus on the extra cardiac conduit vascular graft connecting IVC and pulmonary arteries as one possible landing zone for a CPAD and describe its geometric variability in a cohort of 18 patients that had their TCPC realized with a 20mm vascular graft. We report traditional morphometric parameters and apply statistical shape modeling to determine the main contributors of graft shape variability. Such information may prove useful when designing CPADs that are adapted to the challenging anatomical boundaries in Fontan patients. We further compute the anatomical mean 3D graft shape (template graft) as a representative of key shape features of our cohort and prove this template graft to be a significantly better approximation of population and individual patient's hemodynamics than a commonly used simplified tube geometry. We therefore conclude that statistical shape modeling results can provide better models of geometric and hemodynamic boundary conditions associated with complex cardiac anatomy, which in turn may impact on improved cardiac device development.