Temperature-dependent thermal properties of ex vivo liver undergoing thermal ablation.
Thermotherapy uses a heat source that raises temperatures in the target tissue, and the temperature rise depends on the thermal properties of the tissue. Little is known about the temperature-dependent thermal properties of tissue, which prevents us from accurately predicting the temperature distribution of the target tissue undergoing thermotherapy. The present study reports the key thermal parameters (specific heat capacity, thermal conductivity and heat diffusivity) measured in ex vivo porcine liver while being heated from 20 ° C to 90 ° C and then naturally cooled down to 20 ° C. The study indicates that as the tissue was heated, all the thermal parameters resulted in plots with asymmetric quasi-parabolic curves with temperature, being convex downward with their minima at the turning temperature of 35-40 ° C. The largest change was observed for thermal conductivity, which decreased by 9.6% from its initial value (at 20 ° C) at the turning temperature (35 ° C) and rose by 45% at 90 ° C from its minimum (at 35 ° C). The minima were 3.567 mJ/(m(3) ∙ K) for specific heat capacity, 0.520 W/(m.K) for thermal conductivity and 0.141 mm(2)/s for thermal diffusivity. The minimum at the turning temperature was unique, and it is suggested that it be taken as a characteristic value of the thermal parameter of the tissue. On the other hand, the thermal parameters were insensitive to temperature and remained almost unchanged when the tissue cooled down, indicating that their variations with temperature were irreversible. The rate of the irreversible rise at 35 ° C was 18% in specific heat capacity, 40% in thermal conductivity and 38.3% in thermal diffusivity. The study indicates that the key thermal parameters of ex vivo porcine liver vary largely with temperature when heated, as described by asymmetric quasi-parabolic curves of the thermal parameters with temperature, and therefore, substantial influence on the temperature distribution of the tissue undergoing thermotherapy is expected.
Interdisciplinary Postgraduate Program of Biomedical Engineering, Jeju National University, Jeju Special Self-Governing Province, Jeju-Si, Republic of Korea.
Sitaramanjaneya Reddy
SR
Guntur
Kang Il
KI
Lee
Dong-Guk
DG
Paeng
Andrew John
AJ
Coleman
Min Joo
MJ
Choi
D000818:Animals; D001831:Body Temperature / Q000502:physiology* / Q000528:radiation effects*; D003198:Computer Simulation; D006498:Hepatectomy / Q000379:methods*; D019220:High-Energy Shock Waves; D057086:High-Intensity Focused Ultrasound Ablation / Q000379:methods*; D066298:In Vitro Techniques; D008099:Liver / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery*; D008954:Models, Biological; D013552:Swine; D013696:Temperature
Ex vivo porcine liver; Specific heat capacity; Temperature dependent; Thermal conductivity; Thermal diffusivity; Thermal properties; Thermotherapy; Turning temperature