Assessment of 6MV flattening filter free (FFF) beam commissioning parameters for Versa HD and TrueBeam: A comparison study.
Versa HD 6 MV flattening filter-free beams penetrate deeper than TB beams
Assessment of 6MV flattening filter free (FFF) beam commissioning parameters for Versa HD and TrueBeam: A comparison study.
Flattening filter-free (flattening filter-free) beams are increasingly deployed for stereotactic body radiotherapy (stereotactic body radiotherapy) and stereotactic radiosurgery (stereotactic radiosurgery).
To quantify the dosimetric differences between the Elekta Versa HD and Varian TrueBeam 6 MV flattening filter-free platforms under equipment-equivalent conditions and to assess their translation into patient treatment plan parameters.
Percentage depth doses (percentage depth doses), lateral beam profiles, and output factors (output factors) were acquired using an identical-model IBA SMARTSCAN three-dimensional water tank, a unified detector set (IBA RAZOR for small fields; CC13 for standard fields), and a fixed source-to-surface distance of 90 cm for both platforms, in conformance with AAPM TG-45, AAPM TG-106, and IAEA TRS-483.
Versa HD beams reach deeper into tissue than TB beams
At 10 cm depth, Versa HD showed a higher percentage depth dose (mean difference = 5.005 ± 0.352%; t(9) = 14.22, p < 0.001, d = 4.498).
The Unflatness conversion index (unflatness conversion index) was strongly correlated with field size (r = 0.916, p = 0.001) and statistically independent of measurement depth (p = 0.292).
At the plan level, TrueBeam required 5.9-17.6% more monitor units (monitor units) than Versa HD across all target sizes, with the differential diminishing as target diameter increased.
Surface dose differences were preserved across all four targets (TrueBeam - Versa HD: 15.9-31.1%).
A harmonized, equipment-equivalent measurement approach demonstrated systematic differences between Versa HD and TrueBeam flattening filter-free beams in penetration, surface dose, and field-size-dependent unflatness.
Treatment planning study across four target sizes (1-12 cm) showed these differences propagate to plan-level parameters in a target-size-dependent manner, with Versa HD advantageous for small targets and TrueBeam for larger ones.