Optical diagnosis of tissue freezing depth in cryosurgery using the sapphire cryoprobes

Abstract

The application of cryogenic temperatures to biological tissues has a therapeutic and ablative effect and underlies cryotherapy and cryosurgery. Cryoablation of tissues is currently used for minimally invasive removal of neoplasms of various nosologies. Such a widespread use of cryoablation in clinical practice can be explained by the advantages of this approach, namely, minimal invasiveness, relative painlessness, hemostatic effect, short recovery period for patients, and immunostimulatory effect [1].
For the implementation of cryosurgery methods, special cryoprobs are used, which must meet a number of requirements, such as biocompatibility, the abilities to provide a high rate of tissue cooling and the and to achieve temperatures sufficient for tissue ablation.
In addition, the process of criablation is associated with significant risks of damage to healthy tissues surrounding the pathology with the possibility of incomplete cell death. In this regard, the process of tissue cryoablation requires constant control of the volume of the ice ball during freezing of the area of interest to prevent damage to healthy adjacent tissues [1-3]. The currently existing methods of monitoring the cryoablation process either significantly increase invasiveness, or impose restrictions on the materials for cryoinstruments, or don’t allow determining the size of the freezing area with sufficient accuracy.
To solve this problem, it is proposed to use optical diagnostic methods, in particular, diffuse reflection spectroscopy and terahertz pulsed spectroscopy, since low temperatures lead to scattering and dielectric contrast in tissues that are in different frozen and non-frozen states.
To implement these methods, it is proposed to use cryoprobes based on profiled sapphire crystals. Sapphire is an advantageous material for biomedical applications [4-10] due to a combination of its properties: high hardness, mechanical strength, biocompatibility, chemical inertness, thermal stability, high thermal conductivity at cryogenic temperatures. In addition, it has a high optical transparency, which allows light to be delivered to tissues through the sapphire glass.
In this work, we demonstrate the developed sapphire cryoprobe and experimentally confirm the possibility of monitoring of the ice ball formation in tissues. In addition, we compare the performance of the most commonly used metal probes with the sapphire one. The results reveal the benefits of sapphire for cryosurgical applications.
References
[1] Tumor ablation. Principles and practice. Ed. by E. van Sonnenberg et al. Springer-Verlag New York; (2005).
[2] J. Bischof, K. Christov, B. Rubinsky, “A morphological study of cooling rate response in normal and neoplastic human liver tissue: Cryosurgical implications,” Cryobiology 30, 482–492 (1993).
[3] W.B. Bald and J. Fraser, “Cryogenic Surgery,” Reports on Progress in Physics, 45, 1381 (1982).
[4] G. Katyba et al., “Sapphire shaped crystals for waveguiding, sensing andexposure applications,” Prog. Cryst. Growth Charact. Mater. 64(4), 133–151 (2018).
[5] A. K. Zotov et al., “In situ terahertz monitoring of an ice ball formation during tissue cryosurgery: a feasibility test,” J. Biomed. Opt. 26(4) 043003 (2021)
[6] A. V. Pushkarev et al., “Comparison of Probe Materials for Tissue Cryoablation: Operational Properties of Metal and Sapphire Cryoprobes,” Journal of Biomedical Photonics & Engineering, 8(4), 040501 (2022).
[7] I. N. Dolganova et al., “Feasibility test of a sapphire cryoprobe with optical monitoring of tissue freezing,” J. Biophotonics ,16(3) (2023)
[8] A.K. Zotov et al., “Optical Sensing of Tissue Freezing Depth by Sapphire Cryo-Applicator and Steady-State Diffuse Reflectance Analysis,” Sensors, 24, 3655 (2024).

Speaker

Arsen K. Zotov
Prokhorov General Physics Institute of the Russian Academy of Sciences
Russia

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