Numerical investigation of the effect of vascular network complexity on the efficiency of cryosurgery of a liver tumor

Cryosurgery is a minimally invasive treatment method used to ablate some internal tumors, including the liver. The convection heat transfer from the adjacent vessels can affect the ice ball formation and surgery success. To investigate this effect, patient-specific geometries of hepatic and portal vein networks were reconstructed from the CT images, and the cryoablation of a liver tumor was modeled. The cryoprobe was inserted into five positions with different vascular complexities, and the temperature distribution was obtained. To study the efficiency of the cryosurgery quantitatively, two parameters were introduced; cryoablation coverage ratio (CACR) and ice-ball irregularity (IBI). The CACR values, which altered in the range of 0.81-1.75 for a 3 cm diameter tumor, decreased with increasing the network complexity. Also, the relevant IBI increased from 0.3 to 0.44. Therefore, the results revealed that more irregular ice balls formed by the thermal effect of vessels-decreased the CACR. It is not possible to continue the freezing procedure because it may harm the surrounding healthy tissue. Therefore, a tool should be developed to determine the number and position of the cryoprobes and predict surgery outcomes. This type of patient-specific numerical model can be used as the platform.