체적조절호형방사선치료 시 갠트리 회전과 다엽콜리메이터의 이동 속도에 따른 선량분포 평가

The Effect of MLC Leaf Motion Constraints on Plan Quality and Delivery Accuracy in VMAT

The purpose of this study is to evaluate the dose distribution by gantry rotation and MLC moving speed on treatment planning system(TPS) and linear accelerator. The dose analyzer phantom(Delta 4) was scanned by CT simulator for treatment planning. The planning target volumes(PTVs) of prostate and pancreas was prescribed 6,500 cGy, 5,000 cGy on VMAT(Volumetric Modulated Arc Therapy) by TPS while MLC speed changed. The analyzer phantom was irradiated linear accelerator using by planned parameters. Dose distribution of PTVs were evaluated by the homogeneity index, conformity index, dose volume histogram of organ at risk(rectum, bladder, spinal cord, kidney). And irradiated dose analysis were evaluated dose distribution and conformity by gamma index. The PTV dose of pancreas was 4,993 cGy during 0.1㎝/deg leaf and gantry that was the most closest prescribed dose(5,000 cGy). The dose of spinal cord, left kidney, and right kidney were accessed the lowest during 0.1 ㎝/deg, 1.5 ㎝/deg, 0.3 ㎝/deg. The PTV dose of prostate was 6,466 cGy during 0.1 ㎝/deg leaf and gantry that was the most closest prescribed dose(6,500 cGy). The dose of bladder and rectum were accessed the lowest during 0.3 ㎝/deg, 2.0 ㎝/deg. For gamma index, pancreas and prostate were analyzed the lowest error 100% at 0.8, 1.0 ㎝/deg and 99.6% at 0.3, 0.5 ㎝/deg. We should used the optimal leaf speed according to the gantry rotation if the treatment cases are performed VMAT.