NUMERICAL AND EXPERIMENTAL INVESTIGATION ON TRACKING OF FREEZING FRONT DURING THE CRYOSURGICAL FREEZING OF A TISSUE-MIMICKING MEDIUM

Abstract

We report a combined numerical and experimental approach to determine the transient three-dimensional temperature distribution in a biogel medium subjected to freezing operation by a single cryoprobe. The cryoprobe tip temperature was measured using thermocouples and imposed as a boundary condition in numerical simulations. Numerical simulations have been supported by optics-based experiments conducted under similar operating conditions wherein the principles of lens-less Fourier transform digital holographic interferometry (DHI) have been employed to map the freezing phenomenon in a completely non-intrusive manner. The combined numerical and experimental findings have been made use of to propose a novel methodology for assessing the cooling performance of the cryoprobe. Three different cryoprobe insertion depths (id) viz., 2, 4, and 6 mm, were considered. The numerical estimations for the freezing front were within ± 1 mm margin when compared with the DHI-based intensity data. In the context of temperature values, the numerical predictions were within a ± 5 K margin as compared to the thermocouple data placed at some select locations inside the freezing medium. In addition to the freezing front, we successfully tracked planning isotherm propagation, a parameter that holds importance during cryosurgical planning. Furthermore, the whole-field temperature data predicted using numerical simulations were used to determine the transient cooling capacity of the cryoprobe. The lens-less Fourier transform DHI, in conjunction with numerical simulations, provided a reliable way to obtain the whole-field temperature, which could potentially be used to investigate the cryoprobe cooling characteristics.