INVITATION to the Public defence of
To obtain the academic degree of ‘DOCTOR IN MEDICAL SCIENCES’
CT guided thermal ablation of malignant lesions: technique and evaluation of success.
Summary of the dissertation
Thermal ablation is a minimally invasive cancer treatment that aims to totally eradicate the tumor. Lesions up to 3-5 cm can be eradicated with lethal heat. The ablation zone is recognized as an absent perfusion zone on imaging. Reliable imaging for treatment evaluation plays an important role in improving the efficacy of this approach. In this work, we aimed to investigate methods which allow for early and reliable evaluation of thermal ablation of focal tumors. We analyzed the predictive value of image patterns on ce-CT and PET/CT scans one day after the RF ablation procedure of liver metastases. The absence of FDG uptake was found to be indicative of successfully treated tumors. Early focal nodular enhancement or tracer distribution are very likely corresponding to residual tumor. The diagnostic performance of ce-CT and PET/CT were investigated using ROC analysis. PET/CT did not demonstrate an improved diagnostic performance over ce-CT alone in the early evaluation of RF ablation of liver metastases. Dual Energy CT (DECT) technology has a high sensitivity for the detection of focal lesions. The low keV monochromatic reconstruction images and iodine maps show an improved delineation of the treated avascular regions after RF ablation of tumors in liver, lung and kidney from the surrounding parenchyma. We believe that DECT can be a valuable asset in the differentiation of residual tumors from benign inflammatory changes, commonly found after ablation. We assessed the value of geometric coverage as a predictive factor for local tumor progression (LTP). The liver on ce-CT before and 24h after RF ablation was geometrically aligned using an interactive approach. On the fusion image, the margin between the index tumor and the ablation zone was an excellent predictive factor for LTP of liver metastases treated with thermal ablation.