A model for the time dependent three‐dimensional thermal distribution within iceballs surrounding multiple cryoprobes

Abstract

A time dependent three-dimensional finite difference model of iceball formation about multiple cryoprobes has been developed and compared to experimental data. Realistic three-dimensional probe geometry is specified and the number of cryoprobes, the cryoprobe cooling rates, and the locations of the probes are arbitrary inputs by the user. The simulation accounts for observed longitudinal thermal gradients along the cryoprobe tips. Thermal histories for several points around commercially available cryoprobes have been predicted within experimental error for one, three, and five probe configurations. The simulation can be used to generate isotherms within the iceball at arbitrary times. Volumes enclosed by the iceball and any isotherms may also be computed to give the ablative ratio, a measure of the iceball's killing efficiency. This ratio was calculated as the volume enclosed by a critical isotherm divided by the total volume of the iceball for assumed critical temperatures of -20 and -40 degrees C. The ablative ratio for a single probe is a continuously decreasing function of time but when multiple probe configurations are used the ablative ratio increases to a maximum and then essentially plateaus. Maximum values of 0.44 and 0.55 were observed for three and five probe configurations, respectively, with an assumed critical temperature of -20 degrees C. Assuming a critical temperature of -40 degrees C, maximum ablative ratios of 0.21 and 0.3 for three and five probe configurations, respectively, were observed.

Multiple-Electrode Radiofrequency Ablation Creates Confluent Areas of Necrosis: In Vivo Porcine Liver Results

“…This effect has been demonstrated for both microwave ablation and cryoablation, where three simultaneously activated applicators create a conglomerate zone of coagulation with a volume greater than three times the volume of a single-applicator ablation (19,28). We believe that thermal synergy in multiple-electrode RF ablation has several mechanisms.…”

Lower Incidence of Thrombus Formation With Cryoenergy Versus Radiofrequency Catheter Ablation

“…33 Single freeze/thaw cycles with 7F catheters are emerging as the procedure of choice and were therefore compared with the original 9F double freeze/thaw cycles. 38,39 The number of freeze/thaw cycles may potentially confound the relationship between catheter size and dimension of ablation lesions as well as thrombus volume. The study design does not permit dissociating the effects of catheter size from number of freeze/thaw cycles.…”

Freezing of Biological Tissues During Cryosurgery Using Hyperbolic Heat Conduction Model

“…Phase change problems can be solved using finite difference method (FDM) [1,15,16,21,22,22,23,28,34], finite element method(FEM) [6,12,19,29,30,35,40,43], boundary element method(FEM) [14,18] or finite volume method (FVM). The finite element method and boundary element method successfully handle complex geometries, but it is recognize that they are consuming more time in computing and programming.…”

“…They applied isothermal and non-isothermal phase change in order to simulate heat transfer in cryopreservation. Blood perfusion and metabolic heat generation also have important effect on heat transfer in tissues [15,34,35,44].…”