S Gardner*, S Wang, K Snyder, Y Huang, C Smith, I Chetty, B Miller, Henry Ford Health System, Detroit, MI

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  S Gardner

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PO-GePV-T-321 (Sunday, 7/10/2022)   [Eastern Time (GMT-4)]

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Purpose: To evaluate dose level differences for IMRT/VMAT dose calculation using AAA and AcurosXB.

Methods: Two groups of clinical patient plans were evaluated for this study:(1) 49 conventionally fractionated plans treated using TrueBeam linac (6 MV and 5mm central MLC leaf width)-24 IMRT plans and 25 VMAT plans with target volume range[96.9cc,2406.0cc], and(2) 34 stereotactic plans treated with Edge linac (6MV-FFF and 2.5 mm central MLC leaf width)-all VMAT plans with target volume range[0.05cc,156.3cc]. Each plan was calculated using identical parameters for two algorithms(AAA and AcurosXB). To eliminate the effects of tissue heterogeneity, the dose evaluation was performed on phantom dataset. Each algorithm was configured using identical input data, including broad beam data as well as DLG/MLC transmission settings. The dose value at isocenter or a similar meaningful dose point was used for comparison.

Results: For TrueBeam IMRT/VMAT plans(median target volume:705cc), AcurosXB yielded lower dose levels on average: 0.88±0.38%(VMAT) and 1.08±0.31%(IMRT). For 48 of 49 plans, the AcurosXB calculated dose was lower than AAA dose. For Edge plans with smaller target volumes(median target volume:6.8cc), the distribution was more balanced – AAA dose level, on average, was slightly lower than AcurosXB (0.21±1.51%), with AcurosXB yielding higher dose level for 19 of 34 plans.

Conclusion: For algorithm configuration, AAA and AcurosXB utilize identical input data in terms of PDD,profiles,output factors,and MLC parameters. Often, the AcurosXB algorithm is commissioned after AAA is already in clinical use, so a comparison of the dose level between the two algorithms may be useful. Our results indicate a difference in dose level between AAA and AcurosXB, particularly for larger targets with TrueBeam linac. For Edge linac and corresponding smaller target sizes, the relative dose level may be reversed. These results provide some perspective for clinics looking to commission and tune these algorithms for stereotactic and/or IMRT/VMAT delivery.

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