Gantry orientation optimization of intensity-modulated radiotherapy for brain glioma
YANG Zhen*, ZHANG Yan-qiu, HONG Ji-dong, LIU Gui, ZHANG Zi-jian, Lv Zhi-ping
*Department of Oncology, Central South University of Xiangya Hospital, Changsha 410008,China Corresponding author:ZHANG Yan-qiu, 421001 Hengyang,Nuclear Science and Technology School of University of South China;Email:zmary198589@163.com
Abstract：Objective To compare the dosimetric characteristics of intensity-modulated radiotherapy (IMRT) treatment plan with gantry orientation optimization. Methods Fifteen post-operation patients with brain glioma were selected randomly. Two plans were designed for each patient with the same dose-volume constraints and number of fields (from 5 to 9 fields). A standard coplanar equi-space gantry angles were used in the first plan (plan 1), whereas the selection of gantry angle was optimized by plan geometry optimization algorithm for the same number of beams in the second plan (plan 2). Under conditions of the same prescription dose requirement, dosimetric parameters of target and organs at risk (OAR) were evaluated by dose-volume-histogram and monitor units (MU). Results The conformity index of GTVtb in Plan 1 is better than in plan 2(0.84∶0.85,t=2.77,P=0.015).The maximum dose of left len, right len and left optical nerve in the plan 2 is lower than in the plan 1(528.91 cGy∶662.40 cGy, t=3.15, P=0.007;535.87 cGy∶631.99 cGy, t=2.72, P=0.017;2189.85 cGy∶2676.41 cGy, t=3.06, P=0.008) respectively. For the dose of normal tissue (defined as the region of the total brain subtracted by plan target volume (PTV), namely B-P), the volume V5,V10,V15 and V20 in plan 2 are obviously lower than in plan 1(52.17%∶55.43%,t=3.76, P=0.002;42.91%∶46.66%, t=4.44, P=0.001;36.05%∶40.01%,t=5.91, P=0.000;29.45%∶32.35%, t=4.89,P=0.000),respectively. MU in plan 2 decreased by 10.7% on average compared with plan 1(851∶760, t=3.60,P=0.003). Conclusions Gantry orientation optimization of IMRT for brain glioma can reduce the dose delivered to OAR to a certain extent, and protect the normal tissue around target better, and also reduce MU. Therefore there are some dosimetric advantages in the IMRT plan with gantry orientation optimization for brain glioma.
YANG Zhen*,ZHANG Yan-qiu,HONG Ji-dong et al. Gantry orientation optimization of intensity-modulated radiotherapy for brain glioma[J]. Chinese Journal of Radiation Oncology, 2012, 21(2): 168-171.
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