Experimental validation of deterministic Acuros XB algorithm for IMRT and VMAT dose calculations with the Radiological Physics Center's head and neck phantom.

PURPOSE The purpose of this study was to verify the dosimetric performance of Acuros XB (AXB), a grid-based Boltzmann solver, in intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT). METHODS The Radiological Physics Center (RPC) head and neck (H&N) phantom was used for all calculations and measurements in this study. Clinically equivalent IMRT and VMAT plans were created on the RPC H&N phantom in the Eclipse treatment planning system (version 10.0) by using RPC dose prescription specifications. The dose distributions were calculated with two different algorithms, AXB 11.0.03 and anisotropic analytical algorithm (AAA) 10.0.24. Two dose report modes of AXB were recorded: dose-to-medium in medium (D(m,m)) and dose-to-water in medium (D(w,m)). Each treatment plan was delivered to the RPC phantom three times for reproducibility by using a Varian Clinac iX linear accelerator. Absolute point dose and planar dose were measured with thermoluminescent dosimeters (TLDs) and GafChromic® EBT2 film, respectively. Profile comparison and 2D gamma analysis were used to quantify the agreement between the film measurements and the calculated dose distributions from both AXB and AAA. The computation times for AAA and AXB were also evaluated. RESULTS Good agreement was observed between measured doses and those calculated with AAA or AXB. Both AAA and AXB calculated doses within 5% of TLD measurements in both the IMRT and VMAT plans. Results of AXB_D(m,m) (0.1% to 3.6%) were slightly better than AAA (0.2% to 4.6%) or AXB_D(w,m) (0.3% to 5.1%). The gamma analysis for both AAA and AXB met the RPC 7%/4 mm criteria (over 90% passed), whereas AXB_D(m,m) met 5%/3 mm criteria in most cases. AAA was 2 to 3 times faster than AXB for IMRT, whereas AXB was 4-6 times faster than AAA for VMAT. CONCLUSIONS AXB was found to be satisfactorily accurate when compared to measurements in the RPC H&N phantom. Compared with AAA, AXB results were equal to or better than those obtained with film measurements for IMRT and VMAT plans. The AXB_D(m,m) reporting mode was found to be closer to TLD and film measurements than was the AXB_D(w,m) mode. AXB calculation time was found to be significantly shorter (× 4) than AAA for VMAT.

[1]  Firas Mourtada,et al.  Dosimetric comparison of Acuros XB deterministic radiation transport method with Monte Carlo and model-based convolution methods in heterogeneous media. , 2011, Medical physics.

[2]  J. Mechalakos,et al.  IMRT commissioning: multiple institution planning and dosimetry comparisons, a report from AAPM Task Group 119. , 2009, Medical physics.

[3]  P. Mancosu,et al.  Dosimetric validation of the Acuros XB Advanced Dose Calculation algorithm: fundamental characterization in water , 2011, Physics in medicine and biology.

[4]  Barbara Vanderstraeten,et al.  Accuracy of patient dose calculation for lung IMRT: A comparison of Monte Carlo, convolution/superposition, and pencil beam computations. , 2006, Medical physics.

[5]  A. Ahnesjö.  Collapsed cone convolution of radiant energy for photon dose calculation in heterogeneous media. , 1989, Medical physics.

[6]  J. Battista,et al.  Three-dimensional dose verification for intensity-modulated radiation therapy in the radiological physics centre head-and-neck phantom using optical computed tomography scans of ferrous xylenol-orange gel dosimeters. , 2008, International journal of radiation oncology, biology, physics.

[7]  R. Mohan,et al.  Converting absorbed dose to medium to absorbed dose to water for Monte Carlo based photon beam dose calculations. , 2000, Physics in medicine and biology.

[8]  Michael J Price,et al.  Optimization of deterministic transport parameters for the calculation of the dose distribution around a high dose-rate 192Ir brachytherapy source. , 2008, Medical physics.

[9]  Karl Otto,et al.  Volumetric modulated arc therapy: IMRT in a single gantry arc. , 2007, Medical physics.

[10]  G. Ibbott,et al.  Dosimetric considerations for validation of a sequential IMRT process with a commercial treatment planning system. , 2002, Physics in medicine and biology.

[11]  A. Ahnesjö,et al.  A pencil beam model for photon dose calculation. , 1992, Medical physics.

[12]  E Sterpin,et al.  Monte carlo evaluation of the AAA treatment planning algorithm in a heterogeneous multilayer phantom and IMRT clinical treatments for an Elekta SL25 linear accelerator. , 2007, Medical physics.

[13]  Avraham Eisbruch,et al.  Design and implementation of an anthropomorphic quality assurance phantom for intensity-modulated radiation therapy for the Radiation Therapy Oncology Group. , 2005, International journal of radiation oncology, biology, physics.

[14]  C. Ma,et al.  Clinical implementation of a Monte Carlo treatment planning system. , 1999, Medical physics.

[15]  Peter Dunscombe,et al.  Experimental validation of the Eclipse AAA algorithm , 2007, Journal of applied clinical medical physics.

[16]  M. Oldham,et al.  Investigation of the feasibility of relative 3D dosimetry in the Radiologic Physics Center Head and Neck IMRT phantom using presage/optical-CT. , 2009, Medical physics.

[17]  C. Börgers.  Complexity of Monte Carlo and deterministic dose-calculation methods. , 1998, Physics in medicine and biology.

[18]  Firas Mourtada,et al.  Validation of a new grid-based Boltzmann equation solver for dose calculation in radiotherapy with photon beams , 2010, Physics in medicine and biology.

[19]  Luca Cozzi,et al.  On the dosimetric behaviour of photon dose calculation algorithms in the presence of simple geometric heterogeneities: comparison with Monte Carlo calculations , 2007, Physics in medicine and biology.

[20]  Firas Mourtada,et al.  Comparison of a finite-element multigroup discrete-ordinates code with Monte Carlo for radiotherapy calculations , 2006, Physics in medicine and biology.

[21]  K. Bush,et al.  Dosimetric validation of Acuros XB with Monte Carlo methods for photon dose calculations. , 2011, Medical physics.

[22]  K. Bush,et al.  Monte Carlo evaluation of RapidArc™ oropharynx treatment planning strategies for sparing of midline structures , 2010, Physics in medicine and biology.

[23]  I. Kawrakow,et al.  Dose to medium versus dose to water as an estimator of dose to sensitive skeletal tissue , 2010, Physics in medicine and biology.

[24]  J. Galvin,et al.  Radiochromic film dosimetry: recommendations of AAPM Radiation Therapy Committee Task Group 55. American Association of Physicists in Medicine. , 1998, Medical physics.

[25]  L. Cozzi,et al.  Dosimetric validation of the anisotropic analytical algorithm for photon dose calculation: fundamental characterization in water , 2006, Physics in medicine and biology.

[26]  I. Kawrakow,et al.  3D electron dose calculation using a Voxel based Monte Carlo algorithm (VMC). , 1996, Medical physics.

[27]  C. Ma,et al.  BEAM: a Monte Carlo code to simulate radiotherapy treatment units. , 1995, Medical physics.