Simultaneous tracking of freezing front and associated temperature-distribution using lensless Fourier transform digital holographic interferometry with potential application in cryosurgery

•Lens-less Fourier transform-based digital holography interferometry.•Cryoprobe-based freezing phenomena.•Non-intrusive measurements.•Real time tracking of freezing front and whole field temperature distribution.•Potential therapeutic applications into cryosurgery. Real-time tracking of the freezing front and the associated temperature distribution is central to optimize the efficacy of cryosurgery for the selective destruction of cancerous cells. The conventional approaches for temperature measurements in the medium undergoing freezing phenomenon rely on the strategic placement of thermocouples within the medium. However, such approaches are severely limited by the challenges associated with the number as well as the placement of thermocouple probes and their finite time response. As a definite advancement, we report the first-ever application of lensless Fourier transform based digital holographic interferometry (DHI) for simultaneous tracking of the freezing front and whole field temperature distribution in the freezing medium in a complete non-intrusive, and real-time manner. The approach becomes important in the context of cryosurgery due to the fact that the holograms recorded at any given time instant enable the determination of a complete intensity map as well as quantitative distribution of temperature field in the entire domain. While the time history of intensity maps allows real-time tracking of the freezing front, the whole field temperature data can be used to precisely follow the 273 K isotherm representing the moving frozen front. Single cryoprobe-based freezing experiments have been conducted with water and agar biogel. The temperature values retrieved through the DHI technique have been compared with the thermocouple-based temperature data as well as the temperature field determined through numerical simulations. These comparative studies revealed a reasonably good agreement between the predictions made through the holography technique and those on the basis of thermocouples and numerical simulations.