Dosimetric study of intensity-modulated radiotherapy with different gantry angle for lumbar spinal metastases / 中国辐射卫生

ABSTRACT

Objective To compare the dose difference of intensity-modulated radiotherapy (IMRT) with different gantry angle between target volumes and surrounding normal tissues in lumbar spinal metastases therapy. Methods Ten patients with lumbar spinal metastases were enrolled in the study. Three plans with the same prescription dose of 3000 cGy/10f were designed by seven-equal beams (plan-A), five-back beams (plan-B) and seven-back beams (plan-C). All the plans were designed with the same objective function and dose limiting condition. The difference of dosimetric parameters of planning target volume (PTV), organ at risk (OAR), normal tissues, and treatment parameters in all the plans were compared with SPSS 21.0 statistical software. Results All the plans satisfied the clinical requirement. There was no significant difference in the Dmean, D2%, D98%, CI and HI of PTV between plan-A and plan-C (P >0.05), and these parameters of plan-A and plan-C were better than plan-B (P < 0.05). Compared with the other two plans, plan-B reduced the dosimetric parameters of bilateral kidney (P < 0.05), whereas plan-B increased the Dmax of spinal cord (P < 0.05). The V5 and V10 of normal tissue of plan-B were lower than the other two plans while the V15, V20 and V25 showed inverse relationship (P < 0.05). plan-B had certain advantages in shortening the monitor units and treatment time (P < 0.05).. Conclusions The seven-equal beams (plan-A) and seven-back beams (plan-C) IMRT plans can provide better target dose distribution, and reduce the Dmax of spinal cord. Five-back beams (plan-B) IMRT plan had certain advantages in protecting bilateral kidney and shortening treatment time.