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Very High Temperature Thermal Ablation of Tumors and Margins.
G. Shafirstein, P. Novak, R. J. Griffin, L. Hennings, Y. Kaufmann, S. L. Ferguson, E. R. Siegel, B. C. Stack, P. Spring, P. Corry, E. G. Moros;
University of Arkansas for Medical Sciences, Little Rock, AR.
Background.
Thermal ablation at very high temperatures (>100° C) can considerably decrease the time for coagulation necrosis of tumors and margins. However it is associated with boiling, bubble formation and carbonization that impede current ablation processes. Here we present a new device for performing conductive interstitial thermal therapy (CITT) that can effectively ablate tumors and margins at probe temperatures of 100° to 170° C. In CITT, heat is delivered by conduction and active pins deployment that penetrate the carbonized layer to enable rapid ablation at high temperatures. The efficacy and safety of very high temperature ablation of tumors and margins via CITT is demonstrated in animal models. Methods.
VX2 tumors implanted in the thigh muscle of New Zealand White live rabbits were ablated with CITT at probe temperatures of 90° to 150° C. Breast tissue of live swine was ablated via CITT at probe temperatures of 80° to 170° C. Following ablation, the ablated regions and approximately 5-10 mm of adjacent tissue were resected and embedded in HistOmerTM (Vibratome Company, St. Louis, MO) a room-temperature embedding polymer for mechanical slicing. The fresh sections were stained for viability with triphenyltetrazolium chloride (TTC) and photographed with a digital camera (Canon ES Rebel 350). The ablation depth was measured as function of thermal dose. Results.
The depth of ablation steadily increases for maximum temperature of 70° to 125°C for 20 to 10 min. At 130°- 170° C the time for maximum ablation depth (50 mm) was shorter (10 to 5 min) but the maximum ablation depth did not increase. A carbonized layer of 1-2 mm was formed at the probe tissue interface did not impede the propagation of heat to the target tissue. The very high temperature ablation reduces the time required to cause coagulation necrosis of highly vascular VX2 carcinoma tumor in the rabbit and breast tissue in an adult swine. Adjacent tissue was spared. Conclusions.
The engineering design of the CITT enables rapid heat flow to the target tissue. CITT ablation at very high temperatures can significantly reduce ablation time of tumors and margins.
Supported by NIH grant CA108678.
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