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Research Papers

Instrumentation for Testing Soft Tissue Undergoing Large Deformation: Ex Vivo and In Vivo Studies

[+] Author and Article Information
Tie Hu

Department of Computer Science, Columbia University, New York, NY 10027th2236@columbia.edu

Alan C. Lau

Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, PA 19104lau@drexel.edu

Jaydev P. Desai1

Robotics, Automation, Manipulation, and Sensing (RAMS) Laboratory, University of Maryland, College Park, MD 20742jaydev@umd.edu

1

Corresponding author.

J. Med. Devices 2(4), 041001 (Oct 23, 2008) (6 pages) doi:10.1115/1.2996594 History: Received October 29, 2007; Revised August 13, 2008; Published October 23, 2008

Biomechanical property of soft tissue derived from experimental measurements is critical to develop a reality-based soft-tissue model for minimally invasive surgical training and simulation. In our research, we have focused on developing a biomechanical model of the liver with the ultimate goal of using this model for local tool-tissue interaction tasks and providing feedback to the surgeon through a haptic (sense of touch) display. In this paper, we present two devices that we have designed and built, namely, ex vivo and in vivo testing devices. We used them to measure the experimental force and displacement data of pig liver tissue. The device for ex vivo experiments uses a PC-based control system to control the motion of the probe and acquire the experimental force and displacement data. The force resolution for ex vivo testing was 0.002N (as per the resolution information provided by the manufacturer) and the probe velocity ranged from 0.1mms to 25.4mms. The device was designed so that it could be easily used for both small probe (tissue sample larger than the indenting probe surface area) testing as well as large probe (tissue sample smaller than the indenting probe surface area) testing. The device for in vivo experiments used a microcontroller-based instrumentation to control the motion and acquire and store the data on a multimedia memory disk. This device is designed for the purpose of acquiring experimental force and displacement data in vivo. The primary challenge in the design of the device for in vivo experiments was the limited workspace for device operation. The force resolution for in vivo testing was 0.015N and the displacement resolution was 0.02mm. The sampling frequency for data acquisition for in vivo testing was 50Hz.

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Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 12

LEEM value computed for the liver from in vivo experiments. © [2006] IEEE.

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Figure 11

Plot of force versus displacement data from in vivo tests. © [2006] IEEE.

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Figure 10

Experimental data from the ex vivo probing of soft tissue. © [2005] IEEE.

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Figure 9

In vivo probe attached to a surgical tractor and the overall probe fixturing assembly

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Figure 8

In vivo experimental setup. © [2006] IEEE.

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Figure 7

Velocity profile: displacement of the probe versus time

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Figure 6

Calibration curve: output voltage from the load cell versus the measured force

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Figure 5

Diagram of motion control, data acquisition, and data storage. © [2006] IEEE.

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Figure 4

LCD display for the user interface

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Figure 3

Prototype of the portable probe for in vivo tests. © [2006] IEEE.

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Figure 2

Schematic of the in vivo soft-tissue testing device

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Figure 1

Experimental setup for ex vivo testing. © [2005] IEEE.

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