Computer simulation based analysis of transient two-phase thermal evolutions during multiprobe cryosurgery of hepatic tissues embedded without or with blood vessels

Abstract

Cryosurgery is demarcated as cell annihilation by freezing temperature yielded through a cryogenic probe. Thermal distributions nearby the adjacent blood vessels can impede the iceball evolution and surgery success. Hence it is indispensable to predict the dynamic temperature and iceball propagations in biological tissues and its implications earlier through simulation methods. In this study, a transient two-phase flow and heat transfer model is presented to envisage the thermal extents inside and outside cryoprobes. The bioheat transfer model is adopted to inspect the temperature evolutions during multiprobe cryosurgery of hepatic tissues embedded without or with blood vessels. During computer simulation, a 3D geometry model is introduced as the living tissue vicinities embedded with two simplified hepatic arteries when multiple cryogenic probes are injected into the tissues with uniform insertion depth system. The tissues are pondered as non-ideal materials in which phase transition occurs over a temperature range, and the effects of blood perfusion and metabolic heat generation in the tissues are also considered. Computational analyses are then carried out to scrutiny the impact of the blood vessels on the temperature developments of tissues. The results show that when blood vessels are treated as a heat source during treatment, oscillatory thermal outlines are found along the anticipated pathways during multiprobe cryosurgery, and the relative maximum temperature increased upto ∼98 % at the midpoint of the route BB′ for the ablation time of 100 s. The irregular ice fronts are also obtained with the manifestation of blood vessels compared with no blood vessel case, and the iceball volume enclosed by the − 40°C isothermal front decreased significantly from 22.94 cm3 (without blood vessels) to 6.92 cm3 (with blood vessels) for the ablation time of 300 s. The simulation outcomes indicate that multiprobe cryosurgery is more effective to destroy the tumor tissue properly when the target tissue is located faraway from blood vessels. The simulation platform is anticipated to be valuable in optimizing pre-treatment plans of cryosurgery schemes while determining the number and position of cryoprobes in the neighborhood of blood vessels.

Keywords

• Cryosurgery
• Cryoprobe
• Bioheat transfer
• Two-phase flow
• Blood vessel
• Finite volume method (FVM)