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Technical Brief

Measurement and Modeling of Tissue Thermal Conductivity With Variable Water Content and Compression

[+] Author and Article Information
Matthew W. Chastagner

Department of Mechanical Engineering,
University of Michigan,
Ann Arbor, MI 48109-2125

Robert E. Dodde

Department of Biomedical Engineering,
University of Michigan,
Ann Arbor, MI 48109-2125

Albert J. Shih

Department of Mechanical Engineering,
University of Michigan,
Ann Arbor, MI 48109-2125;
Department of Biomedical Engineering,
University of Michigan,
Ann Arbor, MI 48109-2125

Wei Li

Department of Mechanical Engineering,
University of Texas at Austin,
Austin, TX 78712-1591

Roland K. Chen

School of Mechanical and Materials Engineering,
Washington State University,
PO Box 642920,
Pullman, WA 99164-2920
e-mail: roland.chen@wsu.edu

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received September 19, 2014; final manuscript received March 15, 2016; published online April 19, 2016. Assoc. Editor: Zhixiong Guo.

J. Heat Transfer 138(7), 074503 (Apr 19, 2016) (5 pages) Paper No: HT-14-1631; doi: 10.1115/1.4033078 History: Received September 19, 2014; Revised March 15, 2016

The effects of water content and compression level on tissue thermal conductivity were studied. These effects are important in electrosurgery, as tissue is subjected to both compression and thermal heating. Ex vivo canine spleen tissue was used in this study. A thermal diffusion probe technique was employed to measure the tissue thermal conductivity in three different conditions. First, the tissue thermal conductivity with different water content levels was measured. The measured thermal conductivity decreased as the percentage of water within the tissue decreased. Second, the tissue thermal conductivity under compression, up to 77%, was measured and it showed a 9% reduction as the load was applied. Third, desiccated tissue was compressed, and the thermal conductivity was measured. The compression effect on thermal conductivity was less prominent in the desiccated tissue because less water was squeezed out due to compression. A three-phase Maxwell–Eucken model was developed to predict the tissue thermal conductivity for varying water content and compression levels. The model used the ratio of air, tissue fiber, and water to predict the thermal conductivity and showed a good agreement with the experimental data.

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Figures

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Fig. 1

The electrical circuit used to apply power to the thermistor during the self-heating experiments

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Fig. 2

The device used to determine the thermal conductivity of the tissue under compression: (a) schematic showing the key components of the device and (b) the device in use during tissue compression

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Fig. 3

Tissue thermal conductivity of spleen tissue as the water content level of the tissue is reduced

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Fig. 4

Spleen thermal conductivity as a function of compression level for 71% tissue water content level. Maxwell–Eucken model is shown by the solid black line.

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Fig. 5

Spleen thermal conductivity as a function of compression level for (a) 64% and (b) 54% tissue water content level. The Maxwell–Eucken model is shown by the solid black line.

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