Program Information
A Comprehensive Evaluation of Volumetric Modulated Arc Therapy (VMAT)
S Jang1*, M Kuckarski1 , A Pyakuryal2 , T Sio3 , J Hanley1 , (1) Princeton Radiation Oncology, Monroe Twp, NJ, (2) U. of District of Columbia, DC (3) Mayo Clinic, Scottsdale, AZ.
Presentations
SU-I-GPD-T-302 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: The purpose of this study is to evaluate the plan quality, arc statistics, and QA results in volumetric modulated arc therapy. The advances in linac systems have been made the changes of dose rates and MLC leaf positions possible during the gantry rotions in order to deliver highly conformal dose distributions and reduce treatment delivery time with a 360 degree gantry rotation in multi-arc treatment.
Methods: The first thirty VMAT plans in various treatment sites (n=24 patients) were retrospectively analyzed in order to evaluate VMAT plans (Pinnacle v.P14). The target coverage index (TCI=PTV(PD)/PTV), dose homogeneity index (HI=Dmax/PD), radiation conformity index (RCI=PTV(PD)/PTV(0.95PD)), and 50% PD volume conformity index (50%VCI=V(0.5 PD)/PTV) were measured for plan quality. The total MUs, control points, and estimated delivery time were analyzed in regards to the fractional dose (FD in cGy) and size of PTV. Also, the arc QA results using ArcCHECK were analyzed with the gamma analysis (3% dose, 3 mm, 10% threshold).
Results: Plan quality meausrements yielded good TCI=1.05, HI=1.08, and RCI=0.82 in coventional FD cases for mean PTV of 615.1 cc+/-448.5 while excellent 50%VCI=4.29 for mean PTV of 23.5 cc+/-12.4 in SBRT/SRT plans. Arc statistics showed MU/FD, control points/FD, and beam delivery time/FD were 3.94 and 1.12, and 1.13, respectively in coventional FD cases while 2.41, 0.31, and 0.39, respectively in SBRT/SRT cases. The arc QA results were reliable and consistend with high mean passing rates (97.6%+/-2.4; n=76 arcs) with gammay analysis.
Conclusion: The benefits of VMAT have been recognized; and currently VMAT is more widely accepted as an accurate dose delivery modality in radiation treatment. This study also demonstrated that VMAT is a highly reliable and conformal dose delivery modality. A further study will be undertaken for greater number of VMAT cases with more plan quality indices, beam statistics, and QA analyses.
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