An Experimental and Numerical Study on Nodular Gel Phantom during Cryotherapy

Cryogen spray cooling is an effective method to treat nodular basal cell carcinoma.

To study the effect of spraying distance (z = 27 mm, 18 mm and 9 mm) on a nodular gel phantom and to validate the numerical model.

Liquid nitrogen is sprayed on agarose gel phantom using 0.8 mm nozzle diameter. A two-dimensional Pennes equation with phase change is solved on the axisymmetric non-orthogonal grid.

The lethal front is obtained at 4 mm from the gel surface, irrespective of spraying distance and the same is validated with numerical results. The maximum necrotic volume and lethal front achieved by -50C and -25C isotherms seem to have a lower dependence on the spraying distance as opposed to those corresponding to the 0C isotherm. In contrast, the initiation of these parameters is highly dependent on the nozzle to gel height.

The numerical study presents good agreement with experimental data. The decrease in spraying distance leads to higher rate of maximum ablation volume during freezing, but final ablation volume remained approximately similar.