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Dosimetric validation of Acuros ® XB with Monte Carlo methods for photon dose calculations

Dosimetric validation of Acuros ® XB with Monte Carlo methods for photon dose calculations Purpose: The dosimetric accuracy of the recently released Acuros ® XB advanced dose calculation algorithm (Varian Medical Systems, Palo Alto, CA) is investigated for single radiation fields incident on homogeneous and heterogeneous geometries, and a comparison is made to the analytical anisotropic algorithm (AAA). Methods: Ion chamber measurements for the 6 and 18 MV beams within a range of field sizes (from 4.0×4.0 to 30.0×30.0 cm 2 ) are used to validate Acuros ® XB dose calculations within a unit density phantom. The dosimetric accuracy of Acuros ® XB in the presence of lung, low-density lung, air, and bone is determined using BEAMnrc/DOSXYZnrc calculations as a benchmark. Calculations using the AAA are included for reference to a current superposition/convolution standard. Results: Basic open field tests in a homogeneous phantom reveal an Acuros ® XB agreement with measurement to within ±1.9% in the inner field region for all field sizes and energies. Calculations on a heterogeneous interface phantom were found to agree with Monte Carlo calculations to within ±2.0% (σ MC =0.8 % ) in lung (ρ=0.24 g cm -3 ) and within ±2.9% (σ MC =0.8 % ) in low-density lung (ρ=0.1 g cm -3 ) . In comparison, differences of up to 10.2% and 17.5% in lung and low-density lung were observed in the equivalent AAA calculations. Acuros ® XB dose calculations performed on a phantom containing an air cavity (ρ=0.001 g cm -3 ) were found to be within the range of ±1.5% to ±4.5% of the BEAMnrc/DOSXYZnrc calculated benchmark (σ MC =0.8 % ) in the tissue above and below the air cavity. A comparison of Acuros ® XB dose calculations performed on a lung CT dataset with a BEAMnrc/DOSXYZnrc benchmark shows agreement within ±2%/2mm and indicates that the remaining differences are primarily a result of differences in physical material assignments within a CT dataset. Conclusions: By considering the fundamental particle interactions in matter based on theoretical interaction cross sections, the Acuros ® XB algorithm is capable of modeling radiotherapy dose deposition with accuracy only previously achievable with Monte Carlo techniques. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Medical Physics American Association of Physicists in Medicine

Dosimetric validation of Acuros ® XB with Monte Carlo methods for photon dose calculations

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References (27)

Publisher
American Association of Physicists in Medicine
Copyright
Copyright © 2011 American Association of Physicists in Medicine
ISSN
0094-2405
DOI
10.1118/1.3567146
pmid
21626955
Publisher site
See Article on Publisher Site

Abstract

Purpose: The dosimetric accuracy of the recently released Acuros ® XB advanced dose calculation algorithm (Varian Medical Systems, Palo Alto, CA) is investigated for single radiation fields incident on homogeneous and heterogeneous geometries, and a comparison is made to the analytical anisotropic algorithm (AAA). Methods: Ion chamber measurements for the 6 and 18 MV beams within a range of field sizes (from 4.0×4.0 to 30.0×30.0 cm 2 ) are used to validate Acuros ® XB dose calculations within a unit density phantom. The dosimetric accuracy of Acuros ® XB in the presence of lung, low-density lung, air, and bone is determined using BEAMnrc/DOSXYZnrc calculations as a benchmark. Calculations using the AAA are included for reference to a current superposition/convolution standard. Results: Basic open field tests in a homogeneous phantom reveal an Acuros ® XB agreement with measurement to within ±1.9% in the inner field region for all field sizes and energies. Calculations on a heterogeneous interface phantom were found to agree with Monte Carlo calculations to within ±2.0% (σ MC =0.8 % ) in lung (ρ=0.24 g cm -3 ) and within ±2.9% (σ MC =0.8 % ) in low-density lung (ρ=0.1 g cm -3 ) . In comparison, differences of up to 10.2% and 17.5% in lung and low-density lung were observed in the equivalent AAA calculations. Acuros ® XB dose calculations performed on a phantom containing an air cavity (ρ=0.001 g cm -3 ) were found to be within the range of ±1.5% to ±4.5% of the BEAMnrc/DOSXYZnrc calculated benchmark (σ MC =0.8 % ) in the tissue above and below the air cavity. A comparison of Acuros ® XB dose calculations performed on a lung CT dataset with a BEAMnrc/DOSXYZnrc benchmark shows agreement within ±2%/2mm and indicates that the remaining differences are primarily a result of differences in physical material assignments within a CT dataset. Conclusions: By considering the fundamental particle interactions in matter based on theoretical interaction cross sections, the Acuros ® XB algorithm is capable of modeling radiotherapy dose deposition with accuracy only previously achievable with Monte Carlo techniques.

Journal

Medical PhysicsAmerican Association of Physicists in Medicine

Published: Apr 1, 2011

Keywords: bone; computerised tomography; dosimetry; lung; Monte Carlo methods; phantoms; radiation therapy; Monte Carlo; AAA; Acuros®

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