Clinical Validation of Open-Source Pylinac Platform for Gamma Analysis In Patient-Specific Quality Assurance
Abstract
Purpose
Open-source software offers a transparent and cost-effective alternative to commercial, patient-specific quality assurance (PSQA) systems; however, clinical validation remains essential. This study aims to validate open-source Pylinac (PL) based gamma analysis by comparing its performance against established commercial QA platforms, MobiusTM(MB) and ArcCHECKTM(AC), across multiple treatment sites.
Methods
Twenty VMAT treatment plans delivered on a TrueBeam™ linear accelerator were retrospectively analyzed, including five patients each from head and neck, thoracic, prostate, and breast/chest wall sites (IRB No. RCR03-0400). Gamma passing rates were calculated using PL from trajectory log derived fluence data, and were compared with MB, which similarly derives dose metrics from trajectory logs, and AC, which provides directly measured dose results. Analyses were conducted using 3%/2 mm and 2%/2 mm criteria with 10% dose threshold. Differences in gamma passing rates were assessed by comparing PL vs. MB and PL vs. AC across all treatment sites and gamma criteria.
Results
Mean gamma passing rates for the PL platform were 99.98 ± 0.04% for 3%/2 mm and 99.96 ± 0.07% for 2%/2 mm. AC results were similarly higher, with mean gamma passing rates of 99.76 ± 0.26% for 3%/2 mm and 99.21 ± 0.57% for 2%/2 mm. In contrast, MB values were lower, averaging 97.9 ± 1.55% for 3%/2 mm and 95.15 ± 2.9% for 2%/2 mm. Across all treatment sites, PL and AC demonstrated excellent agreement, while Mobius tended to produce lower gamma passing rates. Moreover, MB showed the greatest sensitivity to stricter gamma criteria compared to other platforms.
Conclusion
PL based gamma analysis demonstrated clinically acceptable agreement with the commercially available QA platforms, MB and AC across all treatment sites. However, these results warrant further investigation using additional verifications to support the full integration of PL based PSQA into routine clinical practice.