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Evaluation of Treatment Plan Quality Between Two Treatment Planning Systems for VMAT

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S Xu

T Yang1 , W Xu2 , R Ge3 , B Qu4 , S Xu5*, (1) PLA General Hospital, Beijing, Beijing, (2) PLA General Hospital, Beijing, Beijing, (3) PLA General Hospital, Beijing, Beijing, (4) PLA General Hospital, Beijing, Beijing, (5) Chinese PLA General Hospital, Beijing,


SU-E-T-411 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To investigate the treatment plan quality between two treatment planning systems (TPS) for volumetric modulated Arc therapy (VMAT).
Methods: VMAT plans based on Varian Eclipse (Ver10.0) and Philips Pinnacle (Ver9.10) TPS were respectively generated by 10 cervical cancer patients by using 2, 3 arcs , controlling the gantry movement with the space of 2 degrees and setting the same optimization constraint as soon as possible. The delivery system with VMAT was Varian Clinac iX machine. The prescription dose was 50Gy/23f for regions at high risk (PTV1), and 45Gy/23f for regions at low risk (PTV). The difference of treatment plans was evaluated by dose distribution and delivery efficiency.
Results: The VMAT 2-arcs plans based on Pinnacle in the conformal indexes of PTV(CI: 0.77±0.05 vs 0.75±0.02, p>0.05), and OARs (such as V30, V40 of rectum and bladder) showed slightly better than those of Eclipse TPS, and the homogeneity indexes (HI) of in Pinnacle were slightly worse than the Eclipse (PTV: 0.17±0.01 vs 0.14±0.01, p <0.05; PTV1: 0.06±0.01 vs 0.04±0.002, p <0.05), there were statistical difference. The MUs with 2-arcs (750±91 vs 1118±84, p <0.05) and 3-arcs (837±86 vs 1215±208, p <0.05) of the Eclipse plans had a clear advantages over the Pinnacle ones, with the statistical difference. The 3-arc plans in Eclipse showed an advantage over the 2-arcs ones and the plan quality of 3-arcs in Pinnacle had no advantage comparing with 2 arcs, but the MUs of 3 Arcs in both Eclipse (837±86 vs 750±92, p <0.05) and Pinnacle (1215±208 vs 1118±84, p >0.05) were more than those of 2-arcs.
Conclusion:For patients with cervical cancer, the VMAT treatment plans of two TPSs could achieve clinical acceptable dose distribution. However, we will still need more cases to further study and determine the optimization and performance characteristics of the two commercial TPSs.

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