Investigation of temperature-dependent viscoelastic properties of thermal lesions in ex vivo animal liver tissue

Abstract

The viscoelastic characteristics of thermal lesions in ex vivo animal liver are investigated in this paper. Characterization of the moduli of thermal lesions prepared at several temperatures will provide additional information for the elastographic monitoring of radio frequency ablation of hepatic tumors. In this study, the frequency-dependent complex modulus of thermal lesions prepared at temperatures ranging from 60-90 °C over a frequency range from 0.1-50 Hz are presented. Lesions were prepared using either radio frequency ablation or double immersion boiling. It was found that both the magnitude and phase of the modulus increase with frequency, a behavior that has been noted in the literature. A new result reported shows that the modulus dependence on temperature reveals a local maximum around 70-75 °C corresponding to the temperature at which tissue has released most of its water content. The modulus values at temperatures higher than 70 °C continued to increase, but the extent of increase depend on animal species and other factors.

Dispersion and Shear Modulus Measurements of Porcine Liver

“…24 Previous re sults formed the ba sis for more re cent stud ies exploring the use of elas tic ity im ag ing meth ods to track the growth of ther mal le sions dur ing ab la tion pro ce dures. [25][26][27] Our contribution to these re sults is the find ings of table 2 that the dy namic vis cos ity con stant h in creases three fold af ter ther mal dam age as com pared to a dou bling of µ 1 . Thus h could be a more robust pa ram e ter for viscoelasticity im ag ing of ther mal le sion growth in the 50-300 Hz band width provided its mea sure ment un cer tainty is com pa ra ble to that observed for µ 1 .…”

Thermometry and ablation monitoring with ultrasound

“…The mechanical properties of soft tissue are temperature dependent, and both bulk and shear elastic properties exhibit changes with temperature (104–106). The temperature dependence is non-linear, with a large transition occurring when tissues undergo thermal coagulation (107).…”

A strain-hardening bi-power law for the nonlinear behaviour of biological soft tissues

“…Preconditioning is a common procedure to minimize the disparity of results when investigating soft biological tissues (Fung, 1993;Phan-Thien et al, 2000;Liu et al, 2000;Darvish et al, 2001;Nasseri et al, 2002;Liu et al 2002;Tamura et al, 2002;Hrapko et al, 2006;Kiss et al, 2009). Although Gefen and Margulies (2004) demonstrated that the preconditioning tends to decrease the shear moduli, Cheng et al (2009) recommended performing preconditioning to reduce the variation of tissue properties and ensure a steady-state response.…”