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Accepted Manuscripts

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research-article  
Elizabeth Shumbayawonda, Ali Salifu, Constantina Lekakou and John Cosmas
J. Med. Devices   doi: 10.1115/1.4039390
This paper investigates the energy transmitted to and harvested by a camera pill travelling along the gastrointestinal 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 multi-reflections at material interfaces. Computer simulations of EM power transmission through a multilayer abdomen to a pill travelling 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 hours 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.
research-article  
Maarten Arnolli, Martijn Buijze, Michel Franken, Ivo Broeders and Dannis Brouwer
J. Med. Devices   doi: 10.1115/1.4039389
Background A system was developed for CT-guided needle placement in the thorax and abdomen, providing precise aiming of a needle guide 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. Methods The individual contributions to the placement error of a fiducial marker based system-to-CT registration system, a 2-DOFs drive system to aim the needle guide, and a structural link between needle guide and CT table were experimentally determined, in addition to the placement error of the overall system. Results 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. Conclusions The overall placement errors in air do not exceed the =5 mm error specified as a clinical user requirement for needle placement in tissue.
Design Innovation Paper  
Danuel Laan, Trang Ngoc Diem Vu, Matthew Hernandez and Henry Schiller
J. Med. Devices   doi: 10.1115/1.4039208
Background: Chest tubes serve as life-saving adjuncts in thoracic trauma. Unfortunately, suboptimal positioning using the open, standard of care technique is associated with complications resulting in impaired tube thoracostomy (TT) function. Using a porcine model, we aimed to determine whether a Magnetic Chest Tube Positioning System (MCTPS) could be utilized to direct the intrathoracic position of a chest tube. Methods: Using recently deceased cross-bred domestic swine, we performed TT using our MCTPS and the standard of care open technique. The operator held one magnet on the outside of the chest. The second magnet was positioned at the distal aspect of the chest tube. The operator was tasked with moving the tube to distinct pre-marked intrathoracic locations under blinded conditions. The experiment was video-recorded through an open sternotomy incision. Control maneuvers were performed using the standard of care open technique. Results: The MCTPS was successful in directing a chest tube from one pre-marked location to another on 4 of 5 attempts (80%). Conversely, the control chest tube with no magnet failed to navigate the intra-thoracic cavity from one pre-marked location to the next with 0 of 5 attempts successful (p=0.05). Conclusion: Positional flaws in chest tube placement are common. We demonstrate the MCTPS efficacy as an alternative to the traditional hand-guided method under simulated placement conditions. The MCTPS is possibly superior to the current standard of care technique of TT. Additional studies are needed to develop this emerging technology in humans.
TOPICS: Magnets, Cavities
research-article  
Tyler D Wortman, Jay Carlson, Edward Perez and Alexander Slocum
J. Med. Devices   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 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 RMS error and measured the stiffness of phantom tissue to within 20% of 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. LesionAir is capable of replicating the palpation of a lesion through an automated, repeatable process that increases the spatial resolution and sensitivity over a physician's finger. A longitudinal study is required to further validate the technology. This technology shows initial promise as a low-cost tool to rapidly identify and diagnose skin cancer.
TOPICS: Cancer, Skin, Biological tissues, Deflection, Phantoms, Errors, Stiffness, Finite element analysis, Vacuum, Resolution (Optics)
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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