SU-E-T-529: Dosimetric Evaluation with Heterogeneity in Acuros XB Advanced Dose Calculation Algorithm and Anisotropic Analytical Algorithm (AAA)

Medical Physics
Suresh Rana, Kevin Rogers

Abstract

To evaluate accuracy of Acuros XB Advanced Dose Calculation Algorithm and Anisotropic Analytical Algorithm (AAA) with measurements in predicting doses beyond air gaps. Three virtual phantoms with layers were created in Eclipse Treatment Planning System. Each layer in phantoms was assigned in terms of water (top), air (middle) and water (bottom) medium. Central axis depth dose in water (bottom medium) beyond 2, 4 and 6 cm air gaps were computed for 5 cm water equivalent material positioned before air gaps. Dose computation was performed for 6MV photon beam with 3×3 and 5×5 cm(2) field sizes at 100 cm SSD to surface of phantoms using AAA_10.0.28 and Acuros XB_10.0.28. Next, solid water and Styrofoam were manufactured to mimic virtual phantoms. By keeping identical field, beam parameters, and geometries that were used for dose computation, 100 MUs were delivered to phantoms, and measurements at selected depths were acquired with cylindrical ionization chamber. Measured central axis depth doses were compared against calculated central axis depth doses computed from Acuros XB and AAA. Acuros XB predicted doses within ±2% of measured doses except at 1cm depth in phantoms with 4 cm air gap (-2.4%) and 6 cm air gap (-2.8%) for field si...Continue Reading

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