Abstract
The transport‐based dose calculation algorithm Acuros XB (AXB) has been shown to accurately account for heterogeneities primarily through comparisons with Monte Carlo simulations. This study aims to provide additional experimental verification of AXB for clinically relevant flattened and unflattened beam energies in low density phantoms of the same material. Polystyrene slabs were created using a bench‐top 3D printer. Six slabs were printed at varying densities from 0.23 to 0.68 g/cm3, corresponding to different density humanoid tissues. The slabs were used to form different single and multilayer geometries. Dose was calculated with Eclipse™ AXB 11.0.31 for 6MV, 15MV flattened and 6FFF (flattening filter free) energies for field sizes of 2 × 2 and 5 × 5 cm2. EBT3 film was inserted into the phantoms, which were irradiated. Absolute dose profiles and 2D Gamma analyses were performed for 96 dose planes. For all single slab configurations and energies, absolute dose differences between the AXB calculation and film measurements remained <3% for both fields in the high‐dose region, however, larger disagreement was seen within the penumbra. For the multilayered phantom, percentage depth dose with AXB was within 5% of discrete film measurements. The Gamma index at 2%/2 mm averaged 98% in all combinations of fields, phantoms and photon energies. The transport‐based dose algorithm AXB is in good agreement with the experimental measurements for small field sizes using 6MV, 6FFF and 15MV beams adjacent to various low‐density heterogeneous media. This work provides preliminary experimental grounds to support the use of AXB for heterogeneous dose calculation purposes.
Highlights
Radiation therapy relies on accurate patient dose planning and delivery to ensure that the patient receives the prescribed dose
The recently introduced volumetric dose calculation algorithm Acuros XB (AXB) (Varian Medical Systems, Palo Alto, CA, USA) deterministically solves the linear Boltzmann Transport Equation (LBTE).[1,2,3]. This new algorithm distinguishes itself from other methods of dose computation, such as the Analytical Anisotropic Algorithm (AAA)[4,5,6] and the Collapsed Cone Convolution (CCC) algorithm, by directly solving the LBTE compared to the convolution and superposition methods employed by AAA and CCC to calculate dose
Based on the Hounsfield Unit (HU) of each voxel, density and material assignments are performed by AXB Version 11’s material library
Summary
Radiation therapy relies on accurate patient dose planning and delivery to ensure that the patient receives the prescribed dose. With the development of treatment planning systems, fast and accurate algorithms are available for dose calculation. The LBTE describes the macroscopic behavior of the radiation as it interacts with matter, such as the dose deposition over a spatial resolution of roughly 1 mm or greater. Dose in a voxel can be calculated by using an energy-dependent response function based on either dose-to-water or the material properties of the voxel. Unlike convolution and superposition algorithms (e.g., AAA, CCC), where the heterogeneities within a patient are handled using density-based corrections to the dose kernels calculated in water, AXB explicitly models physical interactions with matter using the mass density and material type for each voxel of the CT dataset
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