The accuracy of the Acuros XB algorithm in external beam radiotherapy – a comprehensive review

Jarkko Ojala


The accuracy of dose calculation algorithms has been a topic of interest among the radiotherapy community throughout last decades. On one hand the advancements in computers and algorithms has improved the accuracy, but on the other hand the developments in other parts of treatment process, in treatment delivery techniques and in treatment devices have always pushed the requirements to the next level. In this review article a comprehensive overview on the accuracy of a new type ‘c’ dose calculation algorithm, the Acuros XB (AXB) algorithm (Varian Medical Systems, Inc., Palo Alto, CA, USA), is provided. All the articles that have applied the AXB algorithm in terms of external beam radiotherapy are included and the research frames with reported deviations to reference methods are described. For the homogeneous water phantoms the reported accuracy was from 1% to 2%, being of similar level for heterogeneous phantoms, in rare occasions lower. In anthropometric and anthropomorphic phantoms the mean deviations were about 2% and slightly larger for single points and/or small regions. With patient plans the reported average discrepancies were less than from 3% to 5%. Almost without exceptions, the algorithm has proven to perform better than other existing commercial dose calculation algorithms. The number of such papers, in which the AXB algorithm is the only dose determination method, is already notable, which indicates that the accuracy of the algorithm is trusted for reference use and it also, with reported dosimetric results, implies that the AXB algorithm has reached its maturity.


Acuros XB; AXB; External Beam Radiotherapy; Dosimetry; Monte Carlo

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Papanikolau N, Battista JJ, Boyer AL, et al. Tissue inhomogeneity corrections for megavoltage photon beams. Report of Task Group No. 65 of the Radiation Therapy Committee of the American Association of Physicist in Medicine. AAPM Report No. 85. Available from:

Ojala JJ, Kapanen MK, Hyödynmaa SJ, et al. Performance of dose calculation algorithms from three generations in lung SBRT: comparison with full Monte Carlo-based dose distributions. J Appl Clin Med Phys 2014; 15:4662.

Ojala J, Kapanen M, Sipilä P, et al. The accuracy of Acuros XB algorithm for radiation beams traversing a metallic hip implant - comparison with measurements and Monte Carlo calculations. J Appl Clin Med Phys 2014; 15:4912.

Failla GA, Wareing T, Archambault Y, Thompson S. Acuros® XB advanced dose calculation for the Eclipse™ treatment planning system. Clinical perspectives 2010.

Wareing TA, McGhee JM, Morel JE, Pautz SD. Discontinuous Finite Element Sn Methods on Three-Dimensional Unstructured Grids. Nucl Sci Eng 2001; 138:256.

Wareing TA, Morel JE, McGhee JM. Coupled electron-photon transport methods on 3-D unstructured grids. Trans Am Nucl Soc 2000; 83:240-42.

Vassiliev ON, Wareing TA, Davis IM, et al. Feasibility of a multigroup deterministic solution method for three-dimensional radiotherapy dose calculations. Int J Radiat Oncol Biol Phys 2008; 72:220-7.

Gifford KA, Horton JL, Wareing TA, Failla G, Mourtada F. Comparison of a finite-element multigroup discrete-ordinates code with Monte Carlo for radiotherapy calculations. Phys Med Biol 2006; 51:2253-65.

Vassiliev ON, Wareing TA, McGhee J, Failla G, Salehpour MR, Mourtada F. Validation of a new grid-based Boltzmann equation solver for dose calculation in radiotherapy with photon beams. Phys Med Biol 2010; 55:581-98.

Ulmer W, Harder D. A triple Gaussian pencil beam model for photon beam treatment planning. Z Med Phys 1995; 5:25-30.

Ulmer W, Harder D. Applications of a triple Gaussian pencil beam model for photon beam treatment planning. Z Med Phys 1996; 6:68-74.

Ulmer W, Kaissl W. The inverse problem of a Gaussian convolution and its application to the finite size of the measurement chambers/detectors in photon and proton dosimetry. Phys Med Biol 2003; 48:707-27.

Ulmer W, Pyyry J, Kaissl W. A 3D photon superposition/convolution algorithm and its foundation on results of Monte Carlo calculations. Phys Med Biol 2005; 50:1767-90.

Tillikainen L, Siljamäki S, Helminen H, et al. Determination of parameters for a multiple-source model of megavoltage photon beams using optimization methods. Phys Med Biol 2007; 52:1441-67.

Tillikainen L, Helminen H, Torsti T, et al. A 3D pencil-beam-based superposition algorithm for photon dose calculation in heterogeneous media. Phys Med Biol 2008; 53:3821-39.

Han T, Mikell JK, Salehpour M, Mourtada F. Dosimetric comparison of Acuros XB deterministic radiation transport method with Monte Carlo and model-based convolution methods in heterogeneous media. Med Phys 2011; 38:2651-64.

Bush K, Gagne IM, Zavgorodni S, et al. Dosimetric validation of Acuros XB with Monte Carlo methods for photon dose calculations. Med Phys 2011; 38: 2208-21.

Fogliata A, Nicolini G, Clivio A, et al. Dosimetric validation of the Acuros XB Advanced Dose Calculation algorithm: fundamental characterization in water. Phys Med Biol 2011; 56:1879-904.

Kan MW, Yu PK, Leung LH. A review on the use of grid-based Boltzmann equation solvers for dose calculation in external photon beam treatment planning. Biomed Res Int 2013; 2013:692874.

Chetty IJ, Curran B, Cygler JE, et al. Report of the AAPM Task Group No. 105: Issues associated with clinical implementation of Monte Carlo-based photon and electron external beam treatment planning. Med Phys 2007; 34:4818-53.

Hoffmann L, Jørgensen MB, Muren LP, Petersen JB. Clinical validation of the Acuros XB photon dose calculation algorithm, a grid-based Boltzmann equation solver. Acta Oncol 2012; 51:376-85.

Mißlbeck M, Kneschaurek P. Comparison between Acuros XB and Brainlab Monte Carlo algorithms for photon dose calculation. Strahlenther Onkol 2012; 188:599-605.

Fogliata A, Nicolini G, Clivio A, et al. Accuracy of Acuros XB and AAA dose calculation for small fields with reference to RapidArc(®) stereotactic treatments. Med Phys 2011; 38:6228-37.

Torsti T, Korhonen L, Petäjä V. Using Varian Photon Beam Source Model for Dose Calculation of Small Fields. Clinical Perspectives. 2013. 20 p.

Kan MW, Leung LH, Yu PK. The performance of the progressive resolution optimizer (PRO) for RapidArc planning in targets with low-density media. J Appl Clin Med Phys 2013; 14:4382.

Kron T, Clivio A, Vanetti E, et al. Small field segments surrounded by large areas only shielded by a multileaf collimator: comparison of experiments and dose calculation. Med Phys 2012; 39:7480-9.

Fogliata A, Clivio A, Vanetti E, et al. Dosimetric evaluation of photon dose calculation under jaw and MLC shielding. Med Phys 2013; 40:101706.

Tan YI, Metwaly M, Glegg M, Baggarley S, Elliott A. Evaluation of six TPS algorithms in computing entrance and exit doses. J Appl Clin Med Phys 2014; 15:4739.

Jeevanandam P, Rajasekaran D, Sukumar P, Nagarajan V. In-house spread sheet based monitor unit verification program for volumetric modulated arc therapy. Phys Med 2014; 30:509-12.

Rogers DWO, Mohan R. Questions for comparison of clinical Monte Carlo codes. 13th Int. Conf. on the Use of Computers in Radiotherapy (Heidelberg). 2000:120-2.

Kroon PS, Hol S, Essers M. Dosimetric accuracy and clinical quality of Acuros XB and AAA dose calculation algorithm for stereotactic and conventional lung volumetric modulated arc therapy plans. Radiat Oncol 2013; 8:149.

Fogliata A, Nicolini G, Clivio A, et al. Dosimetric evaluation of Acuros XB Advanced Dose Calculation algorithm in heterogeneous media. Radiat Oncol 2011; 6:82.

Tsuruta Y, Nakata M, Nakamura M, et al. Dosimetric comparison of Acuros XB, AAA, and XVMC in stereotactic body radiotherapy for lung cancer. Med Phys 2014;41:081715.

Stathakis S, Esquivel C, Quino LV, et al. Accuracy of the Small Field Dosimetry Using the Acuros XB Dose Calculation Algorithm within and beyond Heterogeneous Media for 6 MV Photon Beams. Int J Med Phys Clin Eng Radiat Oncol 2012; 1:78-87.

Kan MW, Leung LH, Yu PK. Verification and dosimetric impact of Acuros XB algorithm on intensity modulated stereotactic radiotherapy for locally persistent nasopharyngeal carcinoma. Med Phys 2012; 39:4705-14.

Kan MW, Leung LH, Yu PK. Dosimetric impact of using the Acuros XB algorithm for intensity modulated radiation therapy and RapidArc planning in nasopharyngeal carcinomas. Int J Radiat Oncol Biol Phys 2013; 85:e73-80.

Kan MW, Leung LH, So RW, Yu PK. Experimental verification of the Acuros XB and AAA dose calculation adjacent to heterogeneous media for IMRT and RapidArc of nasopharygeal carcinoma. Med Phys 2013;40:031714.

Rana S, Rogers K. Dosimetric evaluation of Acuros XB dose calculation algorithm with measurements in predicting doses beyond different air gap thickness for smaller and larger field sizes. J Med Phys 2013; 38:9-14.

Rana S, Rogers K, Pokharel S, et al. Acuros XB Algorithm vs. Anisotropic Analytical Algorithm: A Dosimetric Study Using Heterogeneous Phantom and Computed Tomography (CT) Data Sets of Esophageal Cancer Patients. J Cancer Ther 2013; 4:138-44.

Rana S, Rogers K, Lee T, et al. Verification and Dosimetric Impact of Acuros XB Algorithm for Stereotactic Body Radiation Therapy (SBRT) and RapidArc Planning for Non-Small-Cell Lung Cancer (NSCLC) Patients. Int J Med Phys Clin Eng Radiat Oncol 2013; 2:6-14.

Rana S, Rogers K, Pokharel S, Cheng C. Evaluation of Acuros XB algorithm based on RTOG 0813 dosimetric criteria for SBRT lung treatment with RapidArc. J Appl Clin Med Phys 2014; 15:4474.

Lloyd SA, Ansbacher W. Evaluation of an analytic linear Boltzmann transport equation solver for high-density inhomogeneities. Med Phys 2013; 40:011707.

Han T, Mourtada F, Kisling K, et al. Experimental validation of deterministic Acuros XB algorithm for IMRT and VMAT dose calculations with the Radiological Physics Center's head and neck phantom. Med Phys 2012; 39:2193-202.

Han T, Followill D, Mikell J, et al. Dosimetric impact of Acuros XB deterministic radiation transport algorithm for heterogeneous dose calculation in lung cancer. Med Phys 2013; 40:051710.

Warren S, Panettieri V, Panakis N, et al. Optimizing collimator margins for isotoxically dose-escalated conformal radiation therapy of non-small cell lung cancer. Int J Radiat Oncol Biol Phys 2014; 88: 1148-53.

Gimeno J, Pujades MC, García T, et al. Commissioning and initial experience with a commercial software for in vivo volumetric dosimetry. Phys Med 2014: S1120-1797(14)00108-2.

Tomiyama Y, Araki F, Kanetake N, et al. Comparison of dose calculation algorithms in stereotactic radiation therapy in lung. Nihon Hoshasen Gijutsu Gakkai Zasshi 2013; 69:663-8.

Chetty IJ, Devpura S, Liu D, et al. Correlation of dose computed using different algorithms with local control following stereotactic ablative radiotherapy (SABR)-based treatment of non-small-cell lung cancer. Radiother Oncol 2013; 109:498-504.

Fogliata A, Nicolini G, Clivio A, et al. Critical appraisal of Acuros XB and Anisotropic Analytic Algorithm dose calculation in advanced non-small- -cell lung cancer treatments. Int J Radiat Oncol Biol Phys 2012; 83:1587-95.

Liu HW, Nugent Z, Clayton R, et al. Clinical impact of using the deterministic patient dose calculation algorithm Acuros XB for lung stereotactic body radiation therapy. Acta Oncol 2014; 53:324-9.

Khan RF, Villarreal-Barajas E, Lau H, Liu HW. Effect of Acuros XB algorithm on monitor units for stereotactic body radiotherapy planning of lung cancer. Med Dosim 2014; 39:83-7.

Fogliata A, Nicolini G, Clivio A, et al. On the dosimetric impact of inhomogeneity management in the Acuros XB algorithm for breast treatment. Radiat Oncol 2011; 6:103.

Lonski P, Taylor ML, Hackworth W, et al. In vivo verification of radiation dose delivered to healthy tissue during radiotherapy for breast cancer. J Phys Conf Ser 2014; 489:012015.

Petillion S, Swinnen A, Defraene G, et al. The photon dose calculation algorithm used in breast radiotherapy has significant impact on the parameters of radiobiological models. J Appl Clin Med Phys 2014; 15:4853.

Rana S, Rogers K, Lee T, et al. Dosimetric impact of Acuros XB dose calculation algorithm in prostate cancer treatment using RapidArc. J Cancer Res Ther 2013; 9:430-5.

Fogliata A, Scorsetti M, Navarria P, et al. Dosimetric comparison between VMAT with different dose calculation algorithms and protons for soft-tissue sarcoma radiotherapy. Acta Oncol 2013; 52: 545-52.

Krayenbuehl J, Riesterer O, Graydon S, et al. Intensity-modulated radiotherapy and volumetric-modulated arc therapy for malignant pleural mesothelioma after extrapleural pleuropneumonectomy. J Appl Clin Med Phys 2013; 14:4130.

Kathirvel M, Subramanian S, Clivio A, et al. Critical appraisal of the accuracy of Acuros-XB and Anisotropic Analytical Algorithm compared to measurement and calculations with the compass system in the delivery of RapidArc clinical plans. Radiat Oncol 2013; 8:140.

Stroom J, Vieira S, Mateus D, et al. On the robustness of VMAT-SABR treatment plans against isocentre positioning uncertainties. Radiat Oncol 2014; 9:196.

Abacioglu U, Ozen Z, Yilmaz M, et al. Critical appraisal of RapidArc radiosurgery with flattening filter free photon beams for benign brain lesions in comparison to GammaKnife: a treatment planning study. Radiat Oncol 2014; 9:119.

Fogliata A, Cozzi L, Clivio A, et al. Preclinical assessment of volumetric modulated arc therapy for total marrow irradiation. Int J Radiat Oncol Biol Phys 2011; 80:628-36.

Mancosu P, Navarria P, Castagna L, et al. Anatomy driven optimization strategy for total marrow irradiation with a volumetric modulated arc therapy technique. J Appl Clin Med Phys 2012; 13:3653.

Essers M, Osman SO, Hol S, et al. Accelerated partial breast irradiation (APBI): are breath-hold and volumetric radiation therapy techniques useful? Acta Oncol 2014; 53:788-94.

Osman SO, Hol S, Poortmans PM, Essers M. Volumetric modulated arc therapy and breath-hold in image-guided locoregional left-sided breast irradiation. Radiother Oncol 2014; 112:17-22.

Vanetti E, Nicolini G, Nord J, et al. On the role of the optimization algorithm of RapidArc (®) volumetric modulated arc therapy on plan quality and efficiency. Med Phys 2011; 38:5844-56.

Persoon LC, Egelmeer AG, Ollers MC, et al. First clinical results of adaptive radiotherapy based on 3D portal dosimetry for lung cancer patients with atelectasis treated with volumetric-modulated arc therapy (VMAT). Acta Oncol 2013; 52:1484-9.

Gersh JA, Best RC, Watts RJ. The clinical impact of detector choice for beam scanning. J Appl Clin Med Phys 2014; 15:4801.


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