Design and Clinical Implementation of a 3D-Printed Arccheck-MR Supporting Solution for Lateral QA on a 1.5T MR-Linac System
Abstract
Purpose
Patient-specific quality assurance (PSQA) for lateral targets on a 1.5T MR-Linac (MRL) is limited by restricted couch motion and lack of dedicated positioning aids for off-axis measurements. While lateral ArcCheck-MR configurations can improve detector coverage for lateral targets, achieving consistent and reproducible setup remains challenging. This work describes the design and implementation of a customized, 3D-printed stand to provide reliable and repeatable positioning of ArcCheck-MR for lateral PSQA measurements on the MRL.
Methods
A dedicated ArcCheck-MR stand was designed using Autodesk Fusion CAD software with the goal of enforcing reproducible placement without reliance on manual alignment. The stands were printed using an Ultimaker S5. The ArcCheck-MR was scanned with the stands in place to generate a PSQA planning image set in the Monaco treatment planning system. Electron density (ED) for the phantom was determined using single-beam measurements to account for energy spectrum changes associated with off-axis beam delivery. Clinical MRL treatment plans for lateral targets were recalculated on the phantom geometry and delivered using the custom stand without additional setup aids or post-delivery shifts.
Results
The design constrains lateral offset, stabilizes vertical height, and ensures consistent longitudinal positioning by docking against two indexed couch bars, minimizing rotational and translational variability between setups. A 0.5% difference in the optimal overwritten ED was observed relative to centered measurements, reflecting energy spectrum changes for off-axis beams. Three lateral PSQA plans were delivered successfully using the customized stand, with all plans achieving gamma index pass rates greater than 95% using 2 mm/3% criteria. Compared to conventional centered phantom placement, the use of the 3D-printed stand increased detected fluence by an average of 56%, improving measurement sensitivity for lateral targets.
Conclusion
The customized ArcCheck-MR stand enables the delivery of PSQA on MRL plans targeting lateral clinical sites with an intuitive, reliable, and repeatable setup.