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

Abstract

BackgroundThe study aimed to appraise the dose differences between Acuros XB (AXB) and Anisotropic Analytical Algorithm (AAA) in stereotactic body radiotherapy (SBRT) treatment for lung cancer with flattening filter free (FFF) beams. Additionally, the potential role of the calculation grid size (CGS) on the dose differences between the two algorithms was also investigated.MethodsSBRT plans with 6X and 10X FFF beams produced from the CT scan data of 10 patients suffering from stage I lung cancer were enrolled in this study. Clinically acceptable treatment plans with AAA were recalculated using AXB with the same monitor units (MU) and identical multileaf collimator (MLC) settings. Furthermore, different CGS (2.5 mm and 1 mm) in the two algorithms was also employed to investigate their dosimetric impact. Dose to planning target volumes (PTV) and organs at risk (OARs) between the two algorithms were compared. PTV was separated into PTV_soft (density in soft-tissue range) and PTV_lung (density in lung range) for comparison.ResultsThe dose to PTV_lung predicted by AXB was found to be 1.33 ± 1.12% (6XFFF beam with 2.5 mm CGS), 2.33 ± 1.37% (6XFFF beam with 1 mm CGS), 2.81 ± 2.33% (10XFFF beam with 2.5 mm CGS) and 3.34 ± 1.76% (10XFFF beam with 1 mm CGS) lower compared with that by AAA, respectively. However, the dose directed to PTV_soft was comparable. For OARs, AXB predicted a slightly lower dose to the aorta, chest wall, spinal cord and esophagus, regardless of whether the 6XFFF or 10XFFF beam was utilized. Exceptionally, dose to the ipsilateral lung was significantly higher with AXB.ConclusionsAXB principally predicts lower dose to PTV_lung compared to AAA and the CGS contributes to the relative dose difference between the two algorithms.

Still equivalent for dose calculation in the Monte Carlo era? A comparison of free breathing and average intensity projection CT datasets for lung SBRT using three generations of dose calculation algorithms

“…Huang et al performed a similar study, but using flattening filter free beams. 39 For those beams, they found small differences (within 1%) between the two grid sizes, with slightly higher target dose using 1 mm grid size. Based on these results, we expect the dose differences caused by calculation grid size of 2.5 mm vs. 2 mm in our study to be of even smaller magnitudes.…”

Optimizing the flattening filter free beam selection in RapidArc®-based stereotactic body radiotherapy for Stage I lung cancer

“…Our previous research also indicated that dose difference between AXB and AAA in lung and tumour regions was different. 59 AXB principally predicted lower dose to PTV_lung (PTV with density in lung range) than AAA, whereas the dose difference in PTV_soft (PTV with density in waterequivalent range) was comparable. On the other hand, we also found that AXB predicted only a slightly lower dose to the oesophagus, spinal cord, heart, CW and lung.…”

Dosimetric Comparison of Anisotropic Analytical Algorithm and Acuros XB in Stereotactic Body Radiotherapy and Effect of Calculation Grid Size

“…The accuracy of calculation related the accuracy of these treatments; it is necessary to ensure the dose response in the critical regions of the algorithm used. [18] The presence of different concentrations of tissue in the human body does not have a linear curve on the dose-response relation-…”