Acuros XB for Dose Calculations in External Beam Photon Radiotherapy-Mini Review
Trends Journal of Sciences Research, Volume 1, Issue 1, 2018, Pages 26–27.
Received August 30, 2014; Revised November 29, 2014; Accepted December 22, 2014;
Published December 30, 2014
Dose calculations based on Monte Carlo (MC) often require sophisticated treatment planning stations with long processing time, and this could be issue for many cancer centers. Hence, most of the commercial treatment planning system include faster dose calculation engines for the daily clinical routine. Due to advancement in technology and computing power, it is now possible to implement MC based dose calculation algorithms in the clinical environment. This report summarizes the major findings of various researchers who have investigated Acuros XB algorithm, which is the MC based dose calculation algorithm commercially available for dose calculations in radiotherapy.
It is evident that accuracy of dose calculations in radiotherapy is crucial to prevent mistreatment of patients undergoing radiotherapy. The estimation of dose deposited in matter is a complex process which involves the interaction of radiation beam with the matter. 1 In radiation therapy, there are various vendors, which supply treatment planning system (TP), and different TPS are more likely to have different dose calculation engines. This is mainly due to the difference in the radiation beam modeling approach among different TPS. Hence, it is expected that the dose calculations of one TPS may not be similar to that of another TPS. This could create confusion for the clinicians if they have to choose one TPS over the another.
In radiation therapy, Monte Carlo (MC) is considered as gold standard for dose calculations in radiotherapy. 1 MC dose calculations often require sophisticated computing services with long processing time and this may be an issue for the busy cancer centers. Hence, majority of the treatment planning system include faster dose calculation engines for the daily clinical routine. Due to advancement in technology and computing power, it is now possible to implement MC based dose calculation algorithms in the clinical environment. This report summarizes the major clinical findings of various researchers who have investigated Acuros XB algorithm, which is the MC-based dose calculation algorithm commercially available for dose calculations in radiotherapy. Google Scholar and PubMed were used to conduct the literature search of this article. Literature search was carried out using terms "Acuros XB" and "Dose Calculation". Several researchers 2, 3, 4, 5, 6, 7 have investigated the accuracy of one of the most recent dose calculation engines called Acuros XB, which is considered to be MC based engine. As many centers continue to explore the accuracy of Acuros XB, current literature shows the promising results of Acuros XB as it is validated against the measurements and MC simulations. 2, 3, 4, 5, 6, 7 The accuracy of Acuros XB was reported to be within 5% 2 when compared to the MC calculations. Other research groups also reported better results, with accuracy up to 4.4% 3, 3% 4, 2% 5, and 2.8% 6. It was also reported that Acuros XB calculated results showed relatively high level of agreement in 3D gamma analysis and dose volume histogram (DVH) comparison when compared to the MC simulation results. 7 These results suggest high level accuracy of Acuros XB for dose calculations in simple and complex situations.
The literature review suggests that a good number of studies have also investigated the clinical use of Acuros XB. Kroon et al. 8 evaluated the Acuros XB for lung cancer patients and found that Acuros XB calculations lower near-minimum PTV dose and mean PTV dose than the plans calculated by analytical anisotropic algorithm (AAA). Similar finding was reported by Kathirvel et al. 9 with Acuros XB producing slightly lower mean PTV dose against AAA for lung cancer. Liu and colleagues 10 reported lower plan conformation number and higher target dose heterogeneity in the Acuros XB plans than in the AAA plans. Fogliata et al. 11 reported that the AXB predicted lower mean PTV dose in the soft tissue when compared to the AAA for both the 6 MV and 15 MV photon beams. While the target doses from Acuros XB are more favorable than AAA, clinicians must pay special attention to the reduced PTV coverage from Acuros XB calculations in the case of lung cancer as demonstrated by Rana and colleagues. [6, 12, 13] 6, 12, Difference in dose calculations can be dependent on the materials assignment in the Acuros XB and the uncertainty in the CT calibration curve. Difference in dosimetric results of various algorithms may also influence the treatment outcomes of the patients undergoing radiotherapy. Report shows that 5% to 10% lower dose differences may result in 10% to 20% changes in tumor control probability (TCP) or 20% to 30% changes in normal tissue complication probability (NTCP).[7, 14] 7, Hence, it is imperative to perform dose calculations in treatment plans using most accurate dose calculation algorithms. Furthermore, most of the clinical studies on the dose calculation algorithms are done based on DVH results. Treatment plan optimizations are also done using DVH parameters. It is possible to achieve more accurate prediction of TCP and NTCP if treatment plans are evaluated using radiobiological parameters.  In summary, the literature review indicates encouraging results from the Acuros XB. This could be used as an alternative dose calculation engine for calculations in photon radiotherapy.