(Sunday, 7/14/2019)
Room: ePoster Forums
Purpose: Tp analyze the efficiency and accuracy of delivery of VMAT plans based on the Halcyon and Vitalbeam linear accelerators.
Methods: Ten patients with cervical cancer based on the Vitalbeam platform were retrospectively analyzed. For each patient, a VMAT plan based on Halcyon was created using the Eclipse Version 15.1.15 TPS. Delivery efficiency was evaluated by comparing monitor units (MU), gantry rotation speed, leaf speed and segment area. Delivery accuracy was evaluated by comparing gantry angle error, MU error and leaf position error using log files.
Results: The Halcyon treatment platform met the clinical objectives. The number of MU (844.4±55.5 MU vs. 710.3±77.5.5 MU, P=0.00) was significantly higher for Halcyon than for Vitalbeam. Gantry angular speed (10.31±2.40º/sec vs.5.92±0.51º/sec), dose rate (732.51±160.78 MU/min vs. 357.17±112.63MU/min) and leaf speed (2.25±1.73 cm/sec vs.1.23±0.91cm/sec) were also significantly higher for Halcyon than for Vitalbeam. The average segment areas of proximal (upper) and distal (lower) layer leaves of the dual layer collimator in the Halcyon plans were 125.77±29.76 cm2 and 77.31±24.80 cm2 (P=0.00), respectively, with a mean ratio of proximal to distal segment areas of 1.65±0.21 (range, 1.2–3.25)，whereas the average segment areas of Vitalbeam plans were 67.7±23.96 cm2. The delivery time per fraction for Halcyon (1.1min) was much lower than for Vitalbeam(2.07min). The mean gantry, leaf and MU error was 0.013°，0.03mm and 0.035MU for Halcyon and 0.037°,0.024mm and 0.0067MU for Vitalbeam.
Conclusion: The Halcyon treatment platform achieved its clinical requirements, with more efficient delivery and a better sparing effect on normal tissues than Vitalbeam. In addition, Halcyon machine parameter errors are comparable to Vitalbeam.
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