Vol 26, No 3 (2021)
Technical note
Published online: 2021-04-19

open access

Page views 757
Article views/downloads 569
Get Citation

Connect on Social Media

Connect on Social Media

A comparative analysis of Acuros XB and the analytical anisotropic algorithm for volumetric modulation arc therapy

Raju P. Srivastava12, K. Basta1, Werner De Gersem23, Carlos De Wagter23
Rep Pract Oncol Radiother 2021;26(3):481-488.


BACKGROUND: This study aimed to verify the dosimetric impact of Acuros XB (AXB) (AXB, Varian Medical Systems Palo Alto CA, USA), a two model-based algorithm, in comparison with Anisotropic Analytical Algorithm (AAA) calculations for prostate, head & neck and lung cancer treatment by volumetric modulated arc therapy (VMAT), without primary modification to AAA.

At present, the well-known and validated AAA algorithm is clinically used in our department for VMAT treatments of different pathologies. AXB could replace it without extra measurements. The treatment result and accuracy of the dose delivered depend on the dose calculation algorithm.

MATERIALS AND METHOD: Ninety-five complex VMAT plans for different pathologies were generated using the Eclipse version 15.0.4 treatment planning system (TPS). The dose distributions were calculated using AAA and AXB (dose-to-water, AXBw and dose-to-medium, AXBm), with the same plan parameters for all VMAT plans. The dosimetric parameters were calculated for each planning target volume (PTV) and involved organs at risk (OAR). The patient specific quality assurance of all VMAT plans has been verified by Octavius®‐4D phantom for different algorithms.

RESULTS: The relative differences among AAA, AXBw and AXBm, with respect to prostate, head & neck were less than 1% for PTV D95%. However, PTV D95% calculated by AAA tended to be overestimated, with a relative dose difference of 3.23% in the case of lung treatment. The absolute mean values of the relative differences were 1.1 ± 1.2% and 2.0 ± 1.2%, when comparing between AXBw and AAA, AXBm and AAA, respectively. The gamma pass rate was observed to exceed 97.4% and 99.4% for the measured and calculated doses in most cases of the volumetric 3D analysis for AAA and AXBm, respectively.  

Conclusion: This study suggests that the dose calculated to medium using AXBm algorithm  is better than AAA and it could be used clinically. Switching the dose calculation algorithm from AAA to AXB does not require extra measurements.

Article available in PDF format

View PDF Download PDF file


  1. Van Esch A, Tillikainen L, Pyykkonen J, et al. Testing of the analytical anisotropic algorithm for photon dose calculation. Med Phys. 2006; 33(11): 4130–4148.
  2. Fogliata A, Nicolini G, Clivio A, et al. Dosimetric validation of the anisotropic analytical algorithm for photon dose calculation: fundamental characterization in water. Phys Med Biol. 2006; 51(6): 1421–1438.
  3. Vassiliev ON, Wareing TA, McGhee J, et al. Validation of a new grid-based Boltzmann equation solver for dose calculation in radiotherapy with photon beams. Phys Med Biol. 2010; 55(3): 581–598.
  4. 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(5): 051710.
  5. 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(4): 2208–2221.
  6. 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(3): 430–435.
  7. Huang B, Wu L, Lin P, et al. Dose calculation of Acuros XB and Anisotropic Analytical Algorithm in lung stereotactic body radiotherapy treatment with flattening filter free beams and the potential role of calculation grid size. Radiat Oncol. 2015; 10: 53.
  8. Liu HH. Dm rather than Dw should be used in Monte Carlo treatment planning. For the proposition. Med Phys. 2002; 29(5): 922–923.
  9. Walters BRB, Kramer R, Kawrakow I. Dose to medium versus dose to water as an estimator of dose to sensitive skeletal tissue. Phys Med Biol. 2010; 55(16): 4535–4546.
  10. Zhen H, Hrycushko B, Lee H, et al. Dosimetric comparison of Acuros XB with collapsed cone convolution/superposition and anisotropic analytic algorithm for stereotactic ablative radiotherapy of thoracic spinal metastases. J Appl Clin Med Phys. 2015; 16(4): 181–192.
  11. Allgaier B, Schüle E, Würfel J. Dose reconstruction in the OCTAVIUS 4D phantom and in the patient without using dose information from the TPS. White Paper PTW, Freiburg 2013.
  12. Stathakis S, Myers P, Esquivel C, et al. Characterization of a novel 2D array dosimeter for patient-specific quality assurance with volumetric arc therapy. Med Phys. 2013; 40(7): 071731.
  13. Van Esch A, Basta K, Evrard M, et al. The Octavius1500 2D ion chamber array and its associated phantoms: dosimetric characterization of a new prototype. Med Phys. 2014; 41(9): 091708.
  14. Low DA, Harms WB, Mutic S, et al. A technique for the quantitative evaluation of dose distributions. Med Phys. 1998; 25(5): 656–661.
  15. Nelms BE, Simon JA. A survey on planar IMRT QA analysis. J Appl Clin Med Phys. 2007; 8(3): 76–90.
  16. Kan MWK, Leung LHT, Yu PKN. 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(1): e73–e80.
  17. Hirata K, Nakamura M, Yoshimura M, et al. Dosimetric evaluation of the Acuros XB algorithm for a 4 MV photon beam in head and neck intensity-modulated radiation therapy. J Appl Clin Med Phys. 2015; 16(4): 52–64.
  18. 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(5): 1587–1595.
  19. Bassi S, Tyner E. 6X acuros algorithm validation in the presence of inhomogeneities for VMAT treatment planning. Rep Pract Oncol Radiother. 2020; 25(4): 539–547.
  20. Soh RC, Tay GH, Lew WS, et al. A depth dose study between AAA and AXB algorithm against Monte Carlo simulation using AIP CT of a 4D dataset from a moving phantom. Rep Pract Oncol Radiother. 2018; 23(5): 413–424.
  21. 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.
  22. Robinson D. Inhomogeneity correction and the analytic anisotropic algorithm. J Appl Clin Med Phys. 2008; 9(2): 112–122.
  23. 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(3): 324–329.
  24. Tajaldeen A, Ramachandran P, Alghamdi S, et al. On the use of AAA and AcurosXB algorithms for three different stereotactic ablative body radiotherapy (SABR) techniques: Volumetric modulated arc therapy (VMAT), intensity modulated radiation therapy (IMRT) and 3D conformal radiotherapy (3D-CRT). Rep Pract Oncol Radiother. 2019; 24(4): 399–408.
  25. Kumar L, Kishore V, Bhushan M, et al. Impact of acuros XB algorithm in deep-inspiration breath-hold (DIBH) respiratory techniques used for the treatment of left breast cancer. Rep Pract Oncol Radiother. 2020; 25(4): 507–514.
  26. Kry SF, Feygelman V, Balter P, et al. AAPM Task Group 329: Reference dose specification for dose calculations: Dose-to-water or dose-to-muscle? Med Phys. 2020; 47(3): e52–e64.
  27. Budgell GJ, Perrin BA, Mott JHL, et al. Quantitative analysis of patient-specific dosimetric IMRT verification. Phys Med Biol. 2005; 50(1): 103–119.
  28. Pulliam KB, Huang JY, Howell RM, et al. Comparison of 2D and 3D gamma analyses. Med Phys. 2014; 41(2): 021710.