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Validating TG119 VMAT Commissioning On a Volumetric Phantom

J Delgado, D Brito, D Garcia, S Serrano-Aguirre, Y Rodriguez-Gago, J Delgado*, Sociedad de Lucha contra el Cancer SOLCA - Matriz Guayaquil, Guayaquil, GuayasEC,

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PO-GePV-T-228 (Sunday, 7/10/2022)   [Eastern Time (GMT-4)]

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Purpose: The present work adapts a group of test plans from AAPM TG119 on a volumetric detector array and evaluates its feasibility for VMAT commissioning on different Treatment Planning Systems.

Methods: TG119 structures were inserted on a virtual volumetric phantom, plans were calculated and evaluated with Elekta Monaco (Montecarlo) and Varian Eclipse (AAA), then delivered on 6MV photon beam Elekta Synergy. 6MV FFF plans were generated on Eclipse for Varian Halcyon. Dose distribution was measured on SunNuclear ArcCheck and point doses on Ionization Chamber. Dose constraints and goals were evaluated, global gamma analysis was performed for dose distributions and Confidence Limits (CL) were calculated following TG119 Normal quantile definition. Measured and planned point doses were also compared.

Results: TG119 goals were satisfied except for Head&Neck PTV-D99 (Eclipse) and Multitarget Superior-Target-D10 (Monaco). For 3%3mm range: gamma passing rate was 96.8%-100% and CL 4.7% for plans calculated on Monaco for Synergy, while on Eclipse passing rate was 97.2%-99.9% and CL 3.1%, pass rate was 98.6%-99.8% and CL 1.6% for Halcyon. For 3%2mm: gamma passing rate was 93.5%-100% with CL 8.3% for Monaco, on Eclipse pass rate was 95.6%-98.8% and CL 4.5%. Gamma passing rate range for FFF was 94.5%-99.3% and CL 6.0%. For Synergy an average point dose difference between measured and calculated plans on Monaco was 0.84%, for plans on Eclipse the average dose difference was 1.28%. For Halcyon plans an average dose difference of 0.74% was found.

Conclusion: TG119 tests plans were found adaptable on a volumetric phantom. CL agreed with TG119 reference values even when stricter requirements were used. Despite new criteria is more suitable for modern treatments TG119 methodology remains valid for VMAT. The methodology described for commissioning VMAT technique on a volumetric QA phantom shows to be robust and consistent for various TPS and linacs.

Keywords

Commissioning, Linear Accelerator, Radiation Therapy

Taxonomy

Not Applicable / None Entered.

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