Dosimetry of three-dimensional confonnal, IMRT and simplified IMRT on rectal cancer post operative pelvic radiotherapy / 中华放射医学与防护杂志

ABSTRACT

Objective To compare the dosimetry difference among three-dimensional conformal radiotherapy (3 DCRT),simplified intensity-modulated radiotherapy (sIMRT) and intensity-modulated radiotherapy (IMRT) in whole pelvic irradiation in postoperative rectal carcinoma,in order to optimize the protocol for clinical practice.Methods From 2006 to 2008,10 patients with stage II and ID rectal cancer after radical resection (Dixon surgery) participated in this study.3DCRT,sIMRT and IMRT were performed for each patient.The dose distribution of target volume and normal tissues,conformal index (CI) and HI were analyzed using the dose-volume histogram (DVH).Results The CI for PTV of IMRT and sIMRT was superior to that of 3DCRT.3DCRT had the best HI in PTV target area dose distribution,while IMRT was similar with sIMRT,however,there were no significant difference among them.As regarded as the protection on organs at risk,for bladder,IMRT was superior to 3DCRT and slightly better than sIMRT;for small intestine,sIMRT showed better performance than 3DCRT while IMRT was better than sIMRT but with no significant difference;for colon,no dosimetry difference was found among three plans;for caput femoris,IMRT and sIMRT were better than 3DCRT.Additionally,sIMRT was similar to 3DCRT in MU of segments,but significantly lower than IMRT.The mean values of total MU for 3DCRT,sIMRT and IMRT were 569.73 ±48.69,542.97 ±69.78,and 770.25 ±73.12,respectively.Conclusions All of 3DCRT,sIMRT and IMRT could provide target area with sufficient and accurate dose,meanwhile they could also protect organs at risk well on rectal cancer after radical resection.Compared with 3DCRT plan and IMRT plan,sIMRT plan might be the optimal plan for clinical practice.