Experiment on building a real-time temperature field distribution model of the prostate using special data encryption multi-pole radiofrequency ablation and a visualization phantom

Abstract

The aim of this study was to explore the utility of a visualization phantom for building a real-time temperature field distribution model of the prostate created by the application of special data encryption (SDE) multi-pole radiofrequency (RF) ablation. We prepared phantoms (phantom group) using acrylamide as the raw material and egg-white as a color developing reagent. The prostate specimens of male adult dogs were fixed in this phantom to create a prostate phantom (prostate group). The SDE multi-pole RF electrode was inserted into the two groups for RF ablation, and the temperature changes at relevant points in space were detected. We set the x-axis as the left and right direction, the y-axis as the fore and aft direction, and the z-axis as the insertion direction of the RF electrode. After this process, the effect of RF ablation on the appearance of each of the two groups was observed. Using temperature measurements taken during the operation, a three-dimensional (3D) surface model of temperature was constructed by drawing the boundary areas of different temperatures on the maximum x-z plane of the two groups of ablation lesions, with y equivalent to 0. Further comparison of the temperature-time change curves of four space points were made by setting y equivalent to 0, z equivalent to 0.5, and x equivalent to 0, 0.25, 0.5 and 0.75. White solid lesions with a diameter of approximately 12 mm could be found in both groups after RF ablation. During the ablation of the phantom group, the temperature ascended faster in a zone 1 cm from the needlepoint to the needle body, and 0.5 cm about the radiofrequency needle. The time-property result of the x-z plane with y equivalent to 0 showed that the boundary areas of the two groups were closer at 50 and 60°C, but the difference between the two groups at 70°C in the high temperature zone was relatively large. The 3D temperature surface model further proved that the 3D temperature outline at 60°C was in better concordance with the actual effect of RF ablation in the prostate tissue. In the comparison of temperature-time changing curves of the two groups at the four space points, despite there being a significant difference in the changing process (P=0.0001), there was no significant statistical difference in the final temperature of the two groups (P>0.05). The results of this work indicated that ablation appearance was in good agreement with in-vitro biologic tissues and that the RF temperature field distribution can be obtained by using a visualization phantom. In particular, the shape of the isothermal line at 60°C was close to the actual ablation lesion. These results may serve as a valuable reference to future clinical trials.