Dosimetric effects of multileaf collimator leaf width on inverse intensity-modulated radiotherapy in intracranial stereotactic radiosurgery / 中华放射肿瘤学杂志

ABSTRACT

Objective To compare the dosimetric effects of micro-multileaf collimator (MLC)(2 mm leaf width) and conventional MLC (10 mm leaf width) on inverse intensity-modulated radiotherapy(IMRT) in intracranial stereotactic radiosurgery(SRS). Methods In view of the fact that the micro-MLC has a small open field,30 patients with intracranial tumor with a<10 cm diameter were enrolled in this study. Their inverse dynamic IMRT plans were established using conventional MLC (conventional group) and micro-MLC (micro group) with the same other conditions. The radiation doses to the target volume and the organs at risk (OAR) were compared between the two groups with t test. Results Compared with the conventional group, the micro group had a significantly better dose distribution in the target volume (P=0.019). However, there were no significant differences in D98,D95,D50,and D3between the two groups (P=0.774,0.650,0.170,0.080). The micro group had a 58.7% lower mean homogeneity index and a 20.1% higher mean conformity index than the conventional group (P=0.000). The micro group had significantly lower radiation doses to OAR than the conventional group (P=0.044). The mean Dmeanand Dmaxof the brain stem in the micro group were 10.0% and 8.2%,respectively,lower than those in the conventional group (P=0.768,0.753). The mean Dmeanand Dmax of the right eye and left eye in the micro group were 16.5%,19.3%,21.4%,and 13.4%,respectively,lower than those in the conventional group (P=0.572,0.775 and 0.734,0.630). The mean Dmaxof the left lens, right lens, left optic nerve, right optic nerve, and optic chiasm in the micro group were 50.4%, 24.1%, 38.5%, 27.8%, and 5.7%, respectively, lower than those in the conventional group (P=0.172,0.467, 0.521,0.740,0.899). The PRV100,PRV50,and PRV25of the normal tissue in the micro group were no more than those in the conventional group(P=0.839,0.832,0.972). Conclusions In inverse IMRT in intracranial SRS,micro-MLC is better than conventional MLC because it can improve CI of the target volume and reduce the radiation doses to OAR.