An experimental and numerical study for cutaneous cryotherapy
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ORIGINAL
An experimental and numerical study for cutaneous cryotherapy Chandrika Kumari1 · Amitesh Kumar2 · Sunil Kumar Sarangi3 · Arunachalam Thirugnanam1 Received: 19 July 2019 / Accepted: 3 August 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The present study deals with an experimental and numerical study to quantify the skin necrosis during cryotherapy. Agarose gel (0.6% (w/v)) is used to mimic the thermal properties of the dermis. The spray cooling is performed with 0.8 mm, 0.6 mm and 0.4 mm nozzle diameters for a single freeze-thaw cycle of 120 s freezing and 130 s thawing. The distance from the nozzle to the gel surface (z) is maintained at 9 mm, 18 mm and 27 mm. The numerical modelling for the thermal analysis has been performed with enthalpy equation; the numerical results are well matched with the experimental results. The numerical results are used to calculate the lethal front, ablation volume and gap (distance between lethal and ice front) in the gel. The ablation volume obtained with 0.8 mm nozzle diameter for −50o C and −25o C isothermal surfaces is 83% and 62% smaller than the ice volume respectively for all the spraying distance. Similarly, it is 93% and 78% smaller for z=27 mm while it is 91% and 73±2% respectively for z=18 mm and 9 mm in the case of 0.6 mm nozzle diameter. The present numerical model may help in the computerised planning of cryotherapy. Keywords Cryospray · Skin cancer · Cryotherapy · Freezing · Spray parameters
1 Introduction Owing to increase in skin cancer, various treatment modalities are coming into demand [38] out of which cryosurgery is an effective technique [1, 15, 27, 34, 41]. Cryosurgery utilises a low temperature on the skin surface or inside the tissue to treat the tumours efficiently with higher cure rate [4, 22, 43, 44]. Currently, various cryofreezing techniques are utilised by surgeons such as the cotton swab, cryoprobe, cryospray and intralesional cryosurgery to eradicate the skin tumours [1, 30, 44]. Among them, cryospray is a non-invasive device and causes freezing of the skin surface faster as compared to other techniques. Arunachalam Thirugnanam
[email protected] 1
Department of Biotechnology and Medical Engineering, National Institute of Technology, Rourkela, Odisha 769008, India
2
Department of Mechanical Engineering, Indian Institute of Technology (BHU), Varanasi 221005, India
3
Department of Mechanical Engineering, National Institute of Technology, Rourkela, Odisha 769008, India
The various parameters which play a significant role during liquid nitrogen spray are nozzle diameter, spraying distance and direction of cryogen spray [1, 15, 27, 44]. Besides this, freezing and thawing play an important role in the tumour ablation during cryospray. During freezing, a higher cooling rate leads to necrosis due to intracellular ice formation while the lower cooling rate leads to apoptosis due to cell dehydration. On the other hand, thawing results in the recrystallisation of ice which is injurious to the cell memb
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