The Impact of Corrected-MVCT Images to Dose Distribution on Adaptive Tomotherapy: Hepatocellular Carcinoma Case

Position verification before the treatment is performed to ensure the actual position to the planning position, so the dose distribution received by the tumor target would be in accordance with the planned dose. In Helical Tomotherapy (HT) treatment, the image of Megavoltage CT (MVCT) could be used to verify the patient's position by registering the image to Kilovoltage CT (KVCT) image. The aim of this study was to evaluate the comparison from the dose distribution resulted from MVCT and KVCT image registration with and without automatic position correction at high doses. The correction in MVCT image registration to KVCT image was performed with adjustment in four HT degrees of freedom (lateral, longitudinal, vertical and rotational direction). Nine MVCT patient images with Hepatocellular Carcinoma were used with high doses therapy in 4-10 fractions using HT at Cipto Mangunkusumo Hospital. Evaluation of the dose distribution in the verification variation (the corrected and uncorrected position) was analyzed with Homogeneity Index (HI), Conformity Index (CI) and Organ at Risk. The results show that HI ranges from 0.06 to 0.3, while CI varies from 0.7 to 1. Based on these results, the position correction may less contribute to the dose distribution to the tumor target.