Fast generation of lung SBRT plans with a knowledge‐based planning model on ring‐mounted Halcyon Linac

Abstract

Purpose To demonstrate fast treatment planning feasibility of stereotactic body radiation therapy (SBRT) for centrally located lung tumors on Halcyon Linac via a previously validated knowledge‐based planning (KBP) model to support offline adaptive radiotherapy. Materials/methods Twenty previously treated non‐coplanar volumetric‐modulated arc therapy (VMAT) lung SBRT plans (c‐Truebeam) on SBRT‐dedicated C‐arm Truebeam Linac were selected. Patients received 50 Gy in five fractions. c‐Truebeam plans were re‐optimized for Halcyon manually (m‐Halcyon) and with KBP model (k‐Halcyon). Both m‐Halcyon and k‐Halcyon plans were normalized for identical or better target coverage than clinical c‐Truebeam plans and compared for target conformity, dose heterogeneity, dose fall‐off, and dose tolerances to the organs‐at‐risk (OAR). Treatment delivery parameters and planning times were evaluated. Results k‐Halcyon plans were dosimetrically similar or better than m‐Halcyon and c‐Truebeam plans. k‐Halcyon and m‐Halcyon plan comparisons are presented with respect to c‐Truebeam. Differences in conformity index were statistically insignificant in k‐Halcyon and on average 0.02 higher (p = 0.04) in m‐Halcyon plans. Gradient index was on average 0.43 (p = 0.006) lower and 0.27 (p = 0.02) higher for k‐Halcyon and m‐Halcyon, respectively. Maximal dose 2 cm away in any direction from target was statistically insignificant. k‐Halcyon increased maximal target dose on average by 2.9 Gy (p < 0.001). Mean lung dose was on average reduced by 0.10 Gy (p = 0.004) in k‐Halcyon and increased by 0.14 Gy (p < 0.001) in m‐Halcyon plans. k‐Halcyon plans lowered bronchial tree dose on average by 1.2 Gy. Beam‐on‐time (BOT) was increased by 2.85 and 1.67 min, on average for k‐Halcyon and m‐Halcyon, respectively. k‐Halcyon plans were generated in under 30 min compared to estimated dedicated 180 ± 30 min for m‐Halcyon or c‐Truebeam plan. Conclusion k‐Halcyon plans were generated in under 30 min with excellent plan quality. This adaptable KBP model supports high‐volume clinics in the expansion or transfer of lung SBRT patients to Halcyon.

Dosimetric performance evaluation of the Halcyon treatment platform for stereotactic radiotherapy: A pooled study

“…Wada et al [35] used a simplified knowledge-based planning model to design the Halcyon VMAT-SBRT plans for lung cancer, and the plan quality was clinically acceptable. In order to validate the feasibility of Halcyon-based rapid SBRT plans for central lung cancer, Visak et al [36] designed lung cancer SBRT plans using the KBP model, and new plans similar or better in dosimetry to the TB plans were obtained within 30 min, where the CI difference was not significant ( P > .05). Halcyon SBRT plans had a mean lower GI of 0.43 ( P = .006), an increase in maximum target dose of 2.9 Gy ( P < .001), and a mean reduction in lung mean lung dose of 0.10 Gy ( P = .004).…”

Comparative dosimetric analysis of volumetric modulated arc therapy based craniospinal irradiation plans between Halcyon ring gantry and TrueBeam C-arm linear accelerator

“…Several research groups have compared the performance of the Halcyon linear accelerator to that of the TrueBeam and Novalis Tx linear accelerators for various sites and techniques such as CSI, head neck, liver SBRT, spine SBRT, prostate SBRT, and pelvic node SBRT 14 , 23 – 28 . In terms of target coverage, dose conformity, and OAR dose constraints, all authors reported acceptable Halcyon dosimetric plans.…”