The plan quality and delivery efficiency of intensity modulated radiotherapy on a new designed linac for left side breast cancer

Objective: To analyze the dosimetric and delivery efficiency differences between IMRT plans based on Halcyon and Trilogy Accelerator for left side breast cancer. Methods: A total of 10 patients with left side breast cancer based on the Trilogy platform were retrospectively analyzed. For each patient, plan based on Halcyon was redesigned using Eclipse Version 15.1 TPS. In order to evaluate plan quality, dose coverage of target and dose to organs at risk, monitor unit efficiency, segment size and delivery time were compared. Results: Halcyon treatment platform could meet the clinical objective. Dose distribution of the target volume had no significant difference with the Trilogy plans (P > 0.05). Volumes receiving 10 Gy, 20 Gy and D_mean of the left lung were significantly reduced (Z = -2.22--1.78, P < 0.05). V₅ of heart for Halcyon and Trilogy was (27.80 ± 7.66)% and (23.18 ± 8.19)%, respectively (Z = -0.71, P < 0.05), while D_mean was (7.03 ± 1.8)Gy and (7.11 ± 2.40)Gy, respectively (P > 0.05). Halcyon increased the monitor unit from 1526.2 ± 227.7 by Trilogy to 1770.5 ± 383.9 (Z = -0.71, P < 0.05), but decreased the delivery time from (12.38 ± 1.49) min by Trilogy to (3.01 ± 0.28) min (Z = -3.42, P < 0.05). Conclusion: Halcyon treatment platform can meet the clinical requirements, reduce dose to normal tissue with high delivery efficiency. (authors)