A dosimetric study on helical tomotherapy and linear accelerator-based step-and-shoot intensity modulated radiation therapy for prostate cancer

Objective: To study the difference in dosimetric characteristics and protection of organs at risk（OAR） between helical tomotherapy（HT） and routine intensity modulated radiation therapy（IMRT） for prostate cancer. Methods: CT images of 10 patients with local prostate cancer were delineated and transferred to HT and IMRT planning systems.Clinical target volume（CTV） was contoured on CT slices of each patient.The prescription dose of IMRT was 76Gy/35 F for the PTV.Isodose line and dose volume histograms（DVH） were used to evaluate the dose distribution in OAR. Results: No statistically significant difference was found in homogeneity index（HI） between HT and IMRT.Compared with IMRT,HT notably reduced the volume of rectum and bladder at 20,30,40 and 50Gy（P＜0.05）.The volume of femoral head at 20,30 and 40Gy was reduced after HT and IMRT. Conclusion: The two treatment modalities can satisfy clinical requirements.HT has a better dose distribution and protective effect for organs at risk than IMRT.