To evaluate volume changes on computerized tomography scan and magnetic resonance imaging-based delineation during radiotherapy treatment planning in prostate cancer.

Abstract

The aim of the present study was to evaluate the impact of magnetic resonance imaging (MRI) on radiotherapy target volume changes in prostate cancer. Ten patients with localized prostate cancer receiving radical radiotherapy were included in the study. Computerized tomography (CT) simulation was done with adequate immobilization, and pelvic MRI was also done at the same time. The two were then registered on eclipse planning system and fused. Target delineation (gross tumor volume [GTV] and clinical target volume [CTV]) was done on both the image sets separately and their volumes were compared. In the current study, it has been found that the CT image-based contouring overestimated the GTV and CTV with 35.4% and 21.7%, respectively, as compared to that by MRI images. The difference observed was statistically significant in the case of GTV, whereas it was not statistically significant for CTV. It can be concluded that MRI is found to be a better modality for GTV delineation, as it gives superior soft-tissue contrast.