The Effect of Contrast Material in Three Dimensional Conformal and Helical Treatment Plans in Rectal Radiotherapy

The aim of this study to investigate the impact of contrast material used for imaging purposes in the treatment of neoadjuvant rectal cancer patients. In rectal radiotherapy, contrast material is used during the simulation phase but the patient enters the treatment without contrast. In our study, we will examine whether CTs taken with contrast material are sufficient for clinical application. A total of eighteen patients with rectal cancer randomly selected. Two different CT scans were conducted for each patient. The patients were initially scanned without contrast enhancement and followed by a second scan with contrast enhancement. The contours were delineated on a non-contrast CT images. Then non-contrast CT were copied to the contrast-enhanced CT with the help of fusion. Subsequently, all plans were generated in Eclipse TPS and Accuray Precision TPS. Finally unenhanced and enhanced plans compared. 3DCRT plans were compared for contrast and non-contrast images, no significant differences were observed in either the target tissue or the maximum and mean values of critical organs. It was observed that the average post-contrast doses increased significantly for small bowel only in helical therapy (p = 0.019). In numerous studies, no significant disparity was observed between 3DCRT and IMRT plans performed with contrast-enhanced CT and non-contrast CT. Consequently, we recommend using a single CT for planning so that the patient does not receive an overdose depending on where the treatment is applied.