Author: Junsheng Cao, Luis A. Maduro Bustos, Khushdeep Singh 👨🔬
Affiliation: Overlook Medical Center, Atlantic Health System at Morristown Medical Center 🌍
Purpose: To evaluate the agreement between the Sun Nuclear Multi-Met Winston Lutz test (WL) and Varian’s Machine Performance Check (MPC) in assessing isocenter alignment, couch, and collimator rotation on an HD Varian TrueBeam 3.0.
Methods: Eight WL and MPC measurements were conducted, with WL tests divided, half utilizing kV imaging only for phantom setup and the other half using MV only. The results from WL kV setup measurements and MPC’s kV imager projection offset were used to independently evaluate the kV imaging and treatment isocenter coincidence. We then analyzed both solutions to evaluate their consistency. Meanwhile, WL data from MV-based positioning provided the isocenter size in the form of the 3D positional offset, which was subsequently assessed against the isocenter size determined by MPC. Additionally, couch and collimator rotational offsets were directly compared between the two systems.
Results: All the deviations observed in this study fell within < 0.5 mm and < 0.5 degree. The mean WL positional offset recorded for the kV-based setup was 0.30 mm while MPC mean kV-offset was 0.22 mm. For the MV-based setup measurements, the mean WL positional offset was 0.28 mm and MPC’s detected isocenter size was 0.29 mm. MPC and WL both showed collimator and couch rotational offsets of 0.2 and 0.1 degree, respectively.
Conclusion: The Sun Nuclear Multi-Met WL and Varian’s MPC demonstrated excellent agreement in assessing isocenter alignment, couch, and collimator rotations. All measured deviations were within 0.5 mm or 0.5 degree, confirming the consistency and reliability of both solutions for clinical use.