Linear accelerator selection: impact on feasibility dose-volume histograms and practicality in dose reduction for...

The quality of volumetric-modulated arc therapy (VMAT) plans depends on the planner's expertise. A feasibility dose-volume histogram (FDVH) may help reduce planning variability.

This study evaluated the impact of two linear accelerators - Halcyon and TrueBeam - on FDVH in prostate VMAT planning and their effectiveness in reducing doses to organs at risk (OARs). VMAT plans were generated for 30 patients with prostate cancer, with planning target volume excluding the rectum (PTV-R) and OAR contours created by three planners. An FDVH was created, and plans were classified as "difficult" (0 < F ≤ 0.1) based on OAR dose reduction.

The D98% and D2% of PTV-R were analyzed, showing that TrueBeam had a higher mean dose at D98% and a lower mean dose at D2% compared to Halcyon, but these differences were not statistically significant (D98%: p = 0.123, D2%: p = 0.167). For the rectum, TrueBeam resulted in significantly lower doses for all dose constraints compared to Halcyon (p < 0.001). In the bladder, TrueBeam showed a significantly lower dose at V40Gy (p < 0.001). The upper limits of feasible F-values were 0.00-0.12 (TrueBeam) and 0.00-0.17 (Halcyon) for the rectum, and 0.01-0.20 (TrueBeam) and 0.00-0.20 (Halcyon) for the bladder, depending on dose parameters.

These findings highlight that the choice of the linear accelerator significantly impacts OAR dose reduction. In prostate VMAT, TrueBeam demonstrated superior rectal and bladder dose reduction compared to Halcyon, underscoring the importance of selecting the appropriate device to optimize treatment planning and minimize variability.