Abstract
Cryospray is a process of destructing cancerous lesions occurring on the skin. Cryogen is sprayed on the affected area and ablation is achieved through rapid freezing of the cell. Metabolic heat generation, blood perfusion and thermal properties of tissue affect the heat sink in the skin. However, these terms are neglected in in-vitro experiments because they are performed on the tissue phantom. So, the outcomes of such studies will only provide direction to dermatologist but cannot be used in clinical applications. Hence, in-vivo thermal analysis must be conducted in order to obtain precise values before proceeding for clinical application. Present study is an attempt to explore the difference between in-vivo and in-vitro experiments. An in-vivo experiment is performed on healthy male rats (Charles Foster rats) weighing about 150–200 g while the in-vitro experiment is performed on tissue phantom. Single freeze–thaw cycle (freezing 120 s and thawing 130 s) with a spraying distance of 18 mm is selected for both the experiments. Non-invasive thermal imaging technique is used to record the temperature profile on the surface. Cryoablation beneath the surface is estimated through thermocouples. A comparative study between customised multihole nozzle (MHN) and commercial single hole nozzle (SHN) is also conducted to analyze the impact of number of holes on cryoablation in in-vivo conditions. Data extracted through thermocouples advocates that biological factors have negligible impact on cryoablation. However, histopathological results suggest that in-vivo necrotic zone is larger than the in-vitro necrotic zone. Natural thawing is responsible for such behavior. The area of cryoablation on the surface of rat skin is 50 % larger when cryogen is sprayed through MHN as compared to SHN.
Published Version
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