An Experimental and Numerical Study on Nodular Gel Phantom during Cryotherapy.

Area of Science:

• Biomedical Engineering
• Thermal Physics

Background:

• Cryogen spray cooling (CSC) is a viable treatment for nodular basal cell carcinoma.
• Understanding CSC parameters is crucial for optimizing therapeutic outcomes.

Purpose of the Study:

• To investigate the impact of varying spraying distances (9 mm, 18 mm, 27 mm) on a nodular gel phantom.
• To validate a two-dimensional numerical model simulating CSC for basal cell carcinoma treatment.

Main Methods:

• Liquid nitrogen was sprayed onto an agarose gel phantom with a 0.8 mm nozzle.
• A two-dimensional Pennes equation incorporating phase change was solved using an axisymmetric non-orthogonal grid.

Main Results:

• The lethal front, indicating tissue damage, was consistently observed at 4 mm from the gel surface.
• While the initiation of necrosis and maximum ablation volume depended heavily on nozzle height, the final ablation volume showed less dependence on spraying distance.
• Isotherms at -50°C and -25°C demonstrated a weaker correlation with spraying distance compared to the 0°C isotherm.

Conclusions:

• The numerical model accurately predicted experimental outcomes, showing good agreement.
• Reducing spraying distance accelerates the maximum ablation volume during freezing.
• Final ablation volumes were largely consistent across different spraying distances, suggesting robustness in treatment planning.