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### Research Papers

J. Med. Devices. 2018;12(2):021001-021001-6. doi:10.1115/1.4039209.

Current techniques for diagnosing skin cancer lack specificity and sensitivity, resulting in unnecessary biopsies and missed diagnoses. Automating tissue palpation and morphology quantification will result in a repeatable, objective process. LesionAir is a low-cost skin cancer diagnostic tool that measures the full-field compliance of tissue by applying a vacuum force and measuring the precise deflection using structured light three-dimensional (3D) reconstruction. The technology was tested in a benchtop setting on phantom skin and in a small clinical study. LesionAir has been shown to measure deflection with a 0.085 mm root-mean-square (RMS) error and measured the stiffness of phantom tissue to within 20% of finite element analysis (FEA) predictions. After biopsy and analysis, a dermatopathologist confirmed the diagnosis of skin cancer in tissue that LesionAir identified as noticeably stiffer and the regions of this stiffer tissue aligned with the bounds of the lesion. A longitudinal, full-scale study is required to determine the clinical efficacy of the device. This technology shows initial promise as a low-cost tool that could rapidly identify and diagnose skin cancer.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2018;12(2):021002-021002-9. doi:10.1115/1.4039390.

This paper investigates the energy transmitted to and harvested by a camera pill traveling along the gastrointestinal (GI) tract. It focuses on the transmitted electromagnetic (EM) energy in the frequency range of 0.18 to 2450 MHz and compares it to the mechanical energy due to the motion of the pill and the force exerted from the intestine in its peristalsis onto the pill, and the electrochemical energy due to the change of pH along the path of the pill. A comprehensive multilayer EM power transmission model is constructed and implemented in a numerical code, including power attenuation through each layer and multireflections at material interfaces. Computer simulations of EM power transmission through a multilayer abdomen to a pill traveling in the intestine are presented for the human abdominal cavity as well as phantom organs and phantom environments, coupled with corresponding experimental studies using these phantom components and environments. Two types of phantom abdomen are investigated: a ballistic gel and a multilayer duck breast. Phantom small intestine involves gelatin gel layers with embedded phantom chyme. Due to limitations related to the energy safety limit of skin exposure and energy losses in the transmission through the abdomen and intestines, inductive range frequencies are recommended which may yield energy harvesting of 10–50 mWh during 8 h of pill journey, complemented by about 10 mWh of mechanical energy and 10 mWh of electrochemical energy harvesting, in addition to about 330 mWh typically stored in the coin batteries of a camera pill.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2018;12(2):021003-021003-10. doi:10.1115/1.4039389.

A system was developed for computed tomography (CT)-guided needle placement in the thorax and abdomen, providing precise aiming of a needle guide (NG) to reach a user-specified target in a single manual insertion. The objective of this work is to present its technical design and analyze its performance in terms of placement error in air. The individual contributions to the placement error of a fiducial marker based system-to-CT registration system, a two degrees-of-freedom (2DOFs) drive system to aim the NG, and a structural link between NG and CT table were experimentally determined, in addition to the placement error of the overall system. An error contribution of 0.81 ± 0.34 mm was determined for the registration system, <1.2 mm and <3.3 mm for the drive system, and 0.35 mm and 0.43 mm for two load cases of the structural link. The overall unloaded system achieved 1.0 ± 0.25 mm and 2.6 ± 0.7 mm at 100 mm and 250 mm depth, respectively. The overall placement errors in air do not exceed the $≤$5 mm error specified as a clinical user requirement for needle placement in tissue.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2018;12(2):021004-021004-6. doi:10.1115/1.4039593.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2018;12(2):021005-021005-11. doi:10.1115/1.4039434.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2018;12(2):021006-021006-8. doi:10.1115/1.4039592.

The distal head of the natural orifice transluminal endoscopic surgery (NOTES) platform commonly uses the structure of a snake bone, which cannot rotate, and the manufacturing is often time-consuming. A novel rotatable, one-element snake bone for NOTES is proposed. This paper first describes the movement mechanism and actuation. The new structure, which is composed of hinge pairs for bending and track-sled rings for rotation, was designed to reach a 90 deg bending angle and 62 deg rotational angle. The workspace of the snake bone was derived using screw theory and was simulated on matlab. The relationship between the angle and wire displacement was analyzed in detail. The new snake bone system bent and rotated by manipulating control wires that were actuated by DC motors, and its angular movements were measured by motion sensors with an angle error within ±2.6 deg. The snake bone was mounted on a flexible tube, inserted into a colonoscopy model, and navigated by motor actuation to eventually reach the cecum. The experimental results demonstrate the new snake bone's ability to travel through a natural orifice by rotating and bending, which satisfies the mobility requirement for NOTES.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2018;12(2):021007-021007-7. doi:10.1115/1.4040043.

Design by Dragging (DBD) [1] is a virtual design tool, which displays three-dimensional (3D) visualizations of many simulation results obtained by sampling a large design space and ties this visual display together with a new user interface. The design space is explored through mouse-based interactions performed directly on top of the 3D data visualizations. Our previous study [1] introduced the realization of DBD with a simplistic example of biopsy needle design under a static bending force. This paper considers a realistic problem of designing a vacuum-assisted biopsy (VAB) needle that brings in more technical challenges to include dynamic tissue reaction forces, nonlinear tissue deformation, and progressive tissue damage in an integrated visualization with design suggestions. The emphasis is placed on the inverse design strategy in DBD, which involves clicking directly on a stress (or other output field parameter) contour and dragging it to a new (usually preferable) position on the contour. Subsequently, the software computes the best fit for the design variables for generating a new output stress field based on the user input. Three cases demonstrated how the inverse design can assist users in intuitively and interactively approaching desired design solutions. This paper illustrates how virtual prototyping may be used to replace (or reduce reliance on) purely experimental trial-and-error methods for achieving optimal designs.

Commentary by Dr. Valentin Fuster

### Technical Brief

J. Med. Devices. 2018;12(2):024501-024501-5. doi:10.1115/1.4039753.

Endoscopic closure is an essential procedure in gastrointestinal (GI) surgery, but currently it is difficult to close large defects endoscopically because of the lack of an appropriate device. Previously, we developed an endoscopic clipping device that has multifiring function and is equipped with an independent clamp. The goal of this study is to provide a new closure method with this device and 4S-modified Roeder (4SMR) slipknot. The feasibility of the closure method is examined by deploying two clips during one insertion onto the 4SMR slipknot to close a 5 cm full-thickness linear defect of an ex vivo porcine stomach from the center. Mechanical strengths of clip-knot closure and the slipknot as regards to tensioning forces are also evaluated. Specifically, the mechanical strength of the 4SMR slipknot is verified by mean peak forces to failure, while the knot is tensioning by 2.5, 5, 7.5, and 10 N force (n = 20 for each group), respectively. Experimental results indicate the clip-slipknot closure can withstand a distracting force of 6.3 $±$ 5.6 N. Tensioning force has a great influence on the mechanical strength of slipknot, with the mean peak force (tensioning force) being 7.1$±$ 6.5, 16.3 $±$ 9.3, 18.9 $±$ 10.4, and 24.2 $±$ 12.0 N, respectively. The proposed closure method can be used for large defects. Tensioning force higher than 5 N is suitable to ensure a stronger 4SMR slipknot.

Commentary by Dr. Valentin Fuster