The Effects of Testing Environment on the Viscoelastic Properties of Soft Tissues

Mechanical properties of biological tissues are needed for accurate surgical simulation and diagnostic purposes. These properties change postmortem due to alterations in both the environmental and physical conditions of the tissue. Despite these known changes, the majority of existing data have been acquired ex vivo due to ease of testing. This study seeks to quantify the effects of testing conditions on the measurements obtained when testing the same tissue in the same locations with two different instruments over time. We will discuss measurements made with indentation probes on whole porcine livers in vivo, ex vivo with a perfusion system that maintains temperature, hydration, and physiologic pressure, ex vivo unperfused, and untreated excised lobes. The data show >50% differences in steady state stiffness between tissues in vivo and unperfused, but only 17% differences between in vivo and perfused tests. Variations also exist in the time-domain and frequency domain responses between all test conditions.

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