Planning of Spherical Volumes for Treating Renal Tumors by Thermal Ablation with Tissue Shrinkage Estimation

Percutaneous thermal ablation techniques represent viable alternatives and minimally-invasive treatment methods for renal tumors. For treating larger tumors, multiple overlapping ablations are imperative. Currently, there is limited software available that incorporates tissue shrinkage into planning for ablation therapy while predicting the lowest number of ablation zones with complete tumor coverage. In this work, a time-power-dependent model to automatically estimate the microwave heating-induced tissue shrinkage is presented. The ablation extent of two commercially available microwave ablation (MWA) systems is modeled as a mathematical function of time and power, too. These models were implemented in a planning software to simulate the process ofMWA more realistically and thus, enhance treatment planning. Seven clinical renal T1a, T1b and T2a tumors were tested with and without integrated models, and the proposed ablation plans of which were compared to manual plans of an experienced physician. In the case of built-in models, the software achieved improved planning proposals for all tumors in terms of zone number and total time of ablation.