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

Tao Han, Firas Mourtada, Kelly Kisling, Justin Mikell, David Followill, Rebecca Howell

Research output: Contribution to journalArticlepeer-review

55 Scopus citations


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 (HN) phantom was used for all calculations and measurements in this study. Clinically equivalent IMRT and VMAT plans were created on the RPC HN 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 (Dm,m) and dose-to-water in medium (Dw,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-Dm,m (0.1 to 3.6) were slightly better than AAA (0.2 to 4.6) or AXB-Dw,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-Dm,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 HN phantom. Compared with AAA, AXB results were equal to or better than those obtained with film measurements for IMRT and VMAT plans. The AXB-Dm,m reporting mode was found to be closer to TLD and film measurements than was the AXB-Dw,m mode. AXB calculation time was found to be significantly shorter (× 4) than AAA for VMAT.

Original languageEnglish
Pages (from-to)2193-2202
Number of pages10
JournalMedical physics
Issue number4
StatePublished - Apr 2012


  • Acuros XB
  • IMRT
  • RPC
  • VMAT
  • deterministic method


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