Clinical implementation of a multifaceted quality assurance phantom for high-precision radiation therapy: an...

This study aimed to evaluate the multifaceted clinical utility of the RUBY phantom as a comprehensive quality assurance (QA) platform in high-precision radiotherapy, particularly for stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT). The objective was to validate its performance in patient positioning, imaging system accuracy, isocenter congruency, and treatment plan verification across various complex clinical scenarios.

A series of QA workflows were conducted using the RUBY phantom and its dedicated modular inserts. These included CBCT and MV/kV planar imaging for patient alignment, the Winston-Lutz insert for isocenter verification, end-to-end testing for full-chain validation, and multi-metastasis and patient-specific inserts for point dose verification. Plans were created in Eclipse TPS (v15.6) and delivered using a Varian TrueBeam STx linear accelerator with high-definition MLC. PTW Semiflex 3D and PinPoint 3D ionization chambers were used for all dosimetric verifications.

CBCT- and planar image-guided alignments showed sub-millimetric deviations, with post-correction alignment verified through coincident laser and surface markers. Winston-Lutz testing across various angles demonstrated maximal deviations of ≤ 0.4 mm, which was within TG-142 recommendations. Point dose measurements for 61 SRS plans showed agreement within ± 3% of TPS calculations. End-to-end testing revealed dose discrepancies of < 1% in both coplanar and non-coplanar beam arrangements. Multi-target plans using single- and multi-isocenter approaches showed deviations of - 0.23% to - 0.50%, confirming excellent dosimetric and geometric accuracy.

The RUBY phantom demonstrated exceptional precision, reproducibility, and clinical adaptability across a spectrum of advanced radiotherapy QA tasks. Its integration enables the end-to-end validation of modern treatment protocols, ensuring alignment, imaging, and accuracy of dose delivery. These findings establish the RUBY phantom as a cornerstone QA solution for enhancing safety, efficacy, and reliability in high-precision radiotherapy.