Research on the Finite-Length Probes Related Accuracy of the Measurement of Biological Tissue Thermal Properties Using DPHP Method With CPC Model

The safety and effectiveness of the radio frequency ablation (RFA) depend on the accurate measurement of the thermal properties of tissues. Although the dual-probe heat-pulse (DPHP) method with the cylindrical-perfect-conductors (CPCs) model is widely used for characterizing biological tissues, its accuracy is inherently limited by the model’s neglect of probe length effects. In this study, we used finite element method to investigate the impact of finite-length probes on the accuracy of measurement using DPHP method with the CPCs model. The simulation indicated an overestimation of diffusivity and volumetric heat capacity due to finite-length probes. For probes with the length of 10, 20, and 30 mm, the relative errors in diffusivity reach 9%, 3%, and 1.5%, respectively, while the relative errors in volumetric heat capacity reach 19%, 8%, and 5%, respectively. Based on the simulation, we presented a novel compensation for the errors caused by finite-length probes in the measurement of biological tissues. We conducted measurement of tissue-mimicking phantom to validate the effectiveness of the compensation. The results demonstrate that after applying the compensation, the measurement errors of volumetric heat capacity were reduced from 6.96% to 0.82% with the use of 20-mm probes, and from 4.46% to 1.11% with the use of 30-mm probes.