Gastrointestinal Tissue Mechanics

IEEE Transactions on Biomedical Engineering (2016): An Intestinal Manometry Force Sensor for Robotic Capsule Endoscopy: An Acute, Multi-Patient In vivo Animal and Human Study

Anonymous — Fri, 21 Apr 2017 20:54:11 +0000

IEEE Transactions on Biomedical Engineering (2016): An Intestinal Manometry Force Sensor for Robotic Capsule Endoscopy: An Acute, Multi-Patient In vivo Animal and Human Study Anonymous (not verified) Fri, 04/21/2017 - 14:54

[video:https://youtu.be/FmeW5ITtJ4Y]

Abstract: Goal: Development of a new medical device class generally termed robotic capsule endoscopes (RCE) is currently being pursued by multiple research groups. These maneuverable devices will allow minimally invasive diagnosis and treatment of intestinal pathologies. While the intraluminal pressures related to the migrating motor complex (MMC) are well understood, no previous study has measured the active contact forces exerted by the human small bowel wall on a solid, or near solid bolus such as an RCE. Understanding and quantifying the active contact force are critical for the advancement of RCE technology. Methods: In this study, the authors develop a novel manometric contact force sensor for human studies and validate the feasibility of the design, sterilization method, and minimally invasive surgical procedure in a multianimal study, followed by a multihuman study. Results: Four porcine tests of the sensor were conducted. The mean porcine myenteric contact force measured using the new sensor is 1.20 ± 0.08 N·cm^-1. The mean myenteric contact force recorded for all five human test subjects is 0.18 ± 0.33 N·cm^-1. Conclusion: This study demonstrates the feasibility of operating an MMC force sensor in a live human with a minimally invasive surgical technique and presents force data necessary for RCE design. Significance: This study represents the first known myenteric contact force measurements on a solid bolus in the human small intestine.

Francisco, M., Terry, B.S., Schoen, J.A., Rentschler, M.E., "An Intestinal Manometry Force Sensor for Robotic Capsule Endoscopy: An Acute, Multi-Patient In vivo Animal and Human Study," IEEE Transactions on Biomedical Engineering. 63(5): 943-951, 2016.

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Tribology International (2016): Frictional Resistance Model for Tissue-Capsule Endoscope Sliding Contact in the Gastrointestinal Tract

Anonymous — Fri, 21 Apr 2017 20:52:42 +0000

Tribology International (2016): Frictional Resistance Model for Tissue-Capsule Endoscope Sliding Contact in the Gastrointestinal Tract Anonymous (not verified) Fri, 04/21/2017 - 14:52

Abstract: Wireless capsule endoscopes are becoming prevalent in the medical field as screening, diagnostic and therapeutic tools within the gastrointestinal (GI) tract. However, state-of-the art capsules lack active locomotion systems, which could improve accuracy and broaden applications. The actuation efficiency for direct capsule-tissue contact depends on the frictional resistance between the capsule and the intestinal wall. A model for predicting the resistance force on a capsule was developed and experimentally validated by performing drag force experiments using various cylindrical capsule design parameters and tissue properties. Of the design parameters studied, capsule edge radius influences frictional resistance the most. The average normalized root-mean-square error between the model and experimental results is 6.25%. These results could lead to optimized capsule endoscope actuation systems.

Sliker, L.J., Ciuti, G., Rentschler, M.E., Menciassi, A., "Frictional Resistance Model for Tissue-Capsule Endoscope Sliding Contact in the Gastrointestinal Tract," Tribology International. 102: 472-484, 2016.

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International Journal of Experimental and Computational Biomechanics (2014): A Preconditioning Protocol and Biaxial Mechanical Measurement of the Small Intestine

Anonymous — Fri, 21 Apr 2017 20:51:45 +0000

International Journal of Experimental and Computational Biomechanics (2014): A Preconditioning Protocol and Biaxial Mechanical Measurement of the Small Intestine Anonymous (not verified) Fri, 04/21/2017 - 14:51

Abstract: Understanding the biomechanical properties of the small intestine is necessary for developing in vivo mobility systems for miniature robots. In this work, we have experimentally determined preconditioning parameters and then performed in-plane biaxial biomechanical characterisation of small intestinal tissue. Excised tissue samples underwent uniaxial tension tests for two physiological Piola-stress values and multiple cycles. The percent change in the length of the tissue reached equilibrium after approximately 13 preconditioning cycles for both loading values. The mechanical behaviour of the tissue did not appear to be affected by the loading values. Thirty-three tissue samples from the proximal, middle, and distal regions of the small intestine of three pigs underwent preconditioning and subsequent in-plane biaxial biomechanical characterisation. The mean moduli for all samples in the low and high modulus regions were, respectively, 307.25 ± 29.67 kPa and 2,211.72 ± 316.88 kPa along the longitudinal direction, and 180.07 ± 17.01 kPa and 1,388.89 ± 206.15 kPa along the circumferential direction. For the low modulus region, the proximal tissue was significantly stiffer than the distal tissue in the circumferential direction (p = 0.0356). Overall, the longitudinal direction was stiffer for both the high and low modulus regions (p = 0.0056 and 0.0004, respectively).

Terry, B.S., Wang, X., Schoen, J.A., Rentschler, M.E., "A Preconditioning Protocol and Biaxial Mechanical Measurement of the Small Intestine," International Journal of Experimental and Computational Biomechanics. 2(4): 293-309, 2014.

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Medical Engineering and Physics (2013): A Quasi-static Model of Wheel-Tissue Interaction for Surgical Robotics

Anonymous — Fri, 21 Apr 2017 20:51:28 +0000

Medical Engineering and Physics (2013): A Quasi-static Model of Wheel-Tissue Interaction for Surgical Robotics Anonymous (not verified) Fri, 04/21/2017 - 14:51

Abstract: Wheel-driven mobile in vivo robotic devices can provide an unconstrained platform for visualization and task performance. Careful understanding of the wheel–tissue interaction is necessary to predict in vivo performance of medical mobility systems. Here, an analytical study of the friction involving rolling contact of a surgical wheel, moving at constant velocities over soft tissue, is presented and verified. A quasi-static frictionless solution is first derived from existing theory, and newly developed theory considering frictional effects is later introduced. In this analysis, the effect of friction on wheel mobility over a viscoelastic substrate is analyzed with wheel velocity as the only changing variable. The analytical model is later verified by experiments and Finite Element Method (FEM) simulations. A simple application of this model to help design a surgical robot is also presented. Additional results indicate that the resistance force, which arises from the tissue viscosity, approaches zero for small and very large wheel velocities.

Wang, X., Sliker, L.J., Qi, H., Rentschler, M.E., "A Quasi-static Model of Wheel-Tissue Interaction for Surgical Robotics," Medical Engineering and Physics. 35(9): 1368-1376, 2013.

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Tribology Letters (2013): Preliminary Friction Force Measurements on Small Bowel Lumen when Eliminating Sled Edge Effects

Anonymous — Fri, 21 Apr 2017 20:16:09 +0000

Tribology Letters (2013): Preliminary Friction Force Measurements on Small Bowel Lumen when Eliminating Sled Edge Effects Anonymous (not verified) Fri, 04/21/2017 - 14:16

Abstract: This study aims to produce experimental results for the coefficient of friction (COF) between the small bowel lumen and an edgeless, translating sled. Friction was measured as a function of sled speed under in situ and in vitro conditions. The results indicate that by eliminating edge effects, the COF between a stainless steel sled and the inner surface of the small bowel lumen is decreased. The average COF for in situ testing was found to be slightly lower than in vitro tests. Friction increased with increasing velocity. The friction forces ranged from 0.013 to 0.08 N, and COF values ranged from 0.007 to 0.054 under these conditions.

Lyle, A.B., Terry, B.S., Schoen, J.A., Rentschler, M.E., "Preliminary Friction Force Measurements on Small Bowel Lumen when Eliminating Sled Edge Effects," Tribology Letters. 51(3): 377-383, 2013.

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Tribology International (2013): A Tribological Investigation of the Small Bowel Lumen Surface

Anonymous — Fri, 21 Apr 2017 20:15:16 +0000

Tribology International (2013): A Tribological Investigation of the Small Bowel Lumen Surface Anonymous (not verified) Fri, 04/21/2017 - 14:15

Abstract: Robotic capsule endoscopy (RCE), where a robotically controlled capsule endoscope is used to navigate the gastrointestinal tract, is a developing technology currently hindered by mobility challenges within the small bowel. This research seeks to engage the frictional characterization of the small bowel with a formally designed experiment which samples the variability within the porcine animal population while parameters such as engineering material, contact area and bowel region were varied. Friction force measurements were collected within an environmental chamber which closely simulates in vivo conditions. The results indicate that micro-patterned polydimethylsiloxane (PDMS) yields a statistically significantly higher coefficient of friction (COF) than stainless steel or polycarbonate. The effects of contact area and bowel region vary across the porcine animal population. The COF under these conditions ranged from 0.0004 to 0.018.

Lyle, A.B., Luftig, J.T., Rentschler, M.E., "A Tribological Investigation of the Small Bowel Lumen Surface," Tribology International. 62: 171-176, 2013.

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Journal of Mechanical Behavior of Biomedical Materials (2013): A Quantitative Comparison of Soft Tissue Compressive Viscoelastic Model Accuracy

Anonymous — Thu, 20 Apr 2017 22:05:46 +0000

Journal of Mechanical Behavior of Biomedical Materials (2013): A Quantitative Comparison of Soft Tissue Compressive Viscoelastic Model Accuracy Anonymous (not verified) Thu, 04/20/2017 - 16:05

Abstract: Viscoelastic models are generally considered a good option for modeling biological tissue due to tissue time-dependency. However, although various forms of viscoelastic models have been developed, only a few have shown a good balance between model mathematical simplicity and experimental fit accuracy. Starting from a basic Standard Linear Solid (SLS) model, a systematic modification of the viscoelastic model leading to a more accurate tissue model is presented. A five-element model family, with a Double Maxwell-arm Wiechert (DMW) representative model, is selected for its mathematical simplicity and mathematical loading accuracy. This DMW model is then used to fit experimental data collected from stress relaxation indentation tests performed on fresh porcine liver and spleen. The results show that this DMW model provides a closer fit with the experimental liver (SLS R²=0.731, DMW R²=0.991) and spleen (SLS R²=0.720, DMW R²=0.981) data, compared to an SLS model, while maintaining appreciable mathematical simplicity by using only five model elements, compared to seven-element models. Thus, any model from this five-element model family can be used as a base compressive model for complex soft tissue with an approximate 35% improved model fit over SLS. Finally, model element parameters for in vitro fresh porcine liver and spleen are determined from the associated indentation tests.

Wang, X., Schoen, J.A., Rentschler, M.E., "A Quantitative Comparison of Soft Tissue Compressive Viscoelastic Model Accuracy," Journal of Mechanical Behavior of Biomedical Materials. 20: 126-136, 2013.

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Journal of Robotic Surgery (2013): Measurements of the Contact Force from Myenteric Contractions on a Solid Bolus

Anonymous — Thu, 20 Apr 2017 22:04:40 +0000

Journal of Robotic Surgery (2013): Measurements of the Contact Force from Myenteric Contractions on a Solid Bolus Anonymous (not verified) Thu, 04/20/2017 - 16:04

Abstract: The development of robotic capsule endoscopes (RCEs) is one avenue presently investigated by multiple research groups to minimize invasiveness and enhance outcomes of enteroscopic procedures. Understanding the biomechanical response of the small bowel to RCEs is needed for design optimization of these devices. In previous work, the authors developed, characterized, and tested the migrating motor complex force sensor (MFS), a novel sensor for quantifying the contact forces per unit of axial length exerted by the myenteron on a solid bolus. This work is a continuation, in which the MFS is used to quantify the contractile strength in the small intestine proximal, middle, and distal regions of five live porcine models. The MFSs are surgically implanted in a generally anesthetized animal, and force data from 5 min of dwell time are analyzed. The mean myenteric contact force from all porcine models and locations within the bowel is 1.9 ± 1.0 N cm⁻¹. Examining the results based on the small bowel region shows a statistically significant strengthening trend in the contractile force from proximal to middle to distal with mean forces of 1.2 ± 0.5, 1.9 ± 0.9, and 2.3 ± 1.0 N cm⁻¹, respectively (mean ± one standard deviation). Quantification of the contact force against a solid bolus provides developers of RCEs with a valuable, experimentally derived parameter of the intraluminal environment.

Terry, B.S., Schoen, J.A., Rentschler, M.E., "Measurements of the Contact Force from Myenteric Contractions on a Solid Bolus," Journal of Robotic Surgery. 7(1): 53-57, 2013.

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Journal of Mechanical Behavior of Biomedical Materials (2012): Small Intestine Mucusal Adhesivity to In vivo Capsule Robot Materials

Anonymous — Thu, 20 Apr 2017 22:03:37 +0000

Journal of Mechanical Behavior of Biomedical Materials (2012): Small Intestine Mucusal Adhesivity to In vivo Capsule Robot Materials Anonymous (not verified) Thu, 04/20/2017 - 16:03

Abstract: Multiple research groups are investigating the feasibility of miniature, swallowable, in vivo, untethered robots that are capable of traversing the small intestine for the purpose of acquiring biometrics and performing simple surgical procedures. A mathematical model of the intraluminal environment will speed the development of these so-called Robotic Capsule Endoscopes (RCEs), and to this end, the authors, in previous work, initiated a comprehensive program for characterizing both the active and passive forces exerted by the small intestine on an RCE-sized solid bolus. In this work, forces due to adhesivity between RCE materials and the mucosa are investigated. The experimental factors are adhesive modality (peel and tack), material (polycarbonate, micropatterned polydimethylsiloxane, stainless steel, and mucosa), and bowel region (proximal, middle, and distal). The mucosa is excised from a fasting pig, stored in lactated ringer's solution at 3 °C, and then tested at room temperature within 43 h of excision. The results show the mean tack strength of the mucosa to engineering materials was 0.198±0.070 mJ cm⁻². The mean peel strength was 0.055±0.016 mJ cm⁻². This study marks the first time, to the authors' knowledge, that adhesivity between small intestinal mucosa and RCE engineering materials has been measured. The adhesivity values acquired from this study will provide a valuable input into analytical and numerical models of the gastrointestinal tract, specifically models that account for the interfacial properties of the tissue.

Terry, B.S., Passernig, A.C., Hill, M., Schoen, J.A., Rentschler, M.E., "Small Intestine Mucusal Adhesivity to In vivo Capsule Robot Materials," Journal of Mechanical Behavior of Biomedical Materials. 15: 24-32, 2012.

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IEEE Transactions on Biomedical Engineering (2012): Characterization and Experimental Results of a Novel Sensor for Measuring the Contact Force from Myenteric Contractions

Anonymous — Thu, 20 Apr 2017 22:02:30 +0000

IEEE Transactions on Biomedical Engineering (2012): Characterization and Experimental Results of a Novel Sensor for Measuring the Contact Force from Myenteric Contractions Anonymous (not verified) Thu, 04/20/2017 - 16:02

Abstract: The intraluminal pressures and traction forces associated with the migrating motor complex are well understood; however, the contact forces directly exerted by the bowel wall on a solid, or near solid, bolus have not previously been measured. Quantifying contact forces is an important component to understanding the net force experienced by an in vivo robotic capsule endoscope. In this paper, we develop a novel sensor, the migrating motor complex force sensor (MFS), for measuring the contact force generated by the contracting myenteron of the small intestine. The MFS consists of a perfused manometer connected to four torus-shaped balloons custom formed of natural latex rubber and embedded with temperature and pressure sensors. Force exerted on the balloon causes sensor pressure change. In vivo, the MFS measures the magnitude and axial location of contact pressure exerted by the myenteron. The device is tested in vivo in a live porcine model on the middle small bowel. The mean total force per centimeter of axial length of intestine that occurred over a 16-min interval in vivo was 1.04 N·cm^-1 in the middle region of the small intestine; the measured force is in the range of theoretical values.

Terry, B.S., Schoen, J.A., Rentschler, M.E., "Characterization and Experimental Results of a Novel Sensor for Measuring the Contact Force from Myenteric Contractions," IEEE Transactions on Biomedical Engineering. 59(7): 1971-1977, 2012.

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