Comparison of Acuros and Anisotropic Analytical Algorithm for dose calculations in VMAT treatments
EVA MARIA AMBROA REY,
Spain
PO-1366
Abstract
Comparison of Acuros and Anisotropic Analytical Algorithm for dose calculations in VMAT treatments
Authors: Eva Maria Ambroa Rey.(Hospital Universitario Lucus Augusti, Medical Physics, Lugo, Spain), Miguel López Sánchez.(Hospital Universitario Lucus Augusti, Medical Physics, Lugo, Spain), María Pérez Fernández.(Hospital Universitario Lucus Augusti, Medical Physics, Lugo, Spain), Pablo Rodríguez Meijide.(Hospital Universitario Lucus Augusti, Medical Physics, Lugo, Spain)
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Purpose or Objective
The purpose of this study is to compare the algorithm Acuros XB and AAA for dose calculations in heterogeneous pathologies such as head and neck (H&N), esophagus and lung VMAT treatments.
Material and Methods
70 VMAT patients were selected for this study (24 lung, 24 H&N and 22 esophagus). Plans were calculated in Eclipse (v13.6).
Treatments plans originally calculated with AAA algorithm were recalculated using Acuros XB (V13.6) using the same number of monitor units (MU) and multileaf collimator as the original plan. No other parameters were changed or twiked during the optimization.
Dose differences in PTV coverage and other dosimetric values were compared for both algorithms. Due to the small sample a Kruskal-Wallis test was performed to analyzed the differences between the two calculations. To estimated precisely how important these differences are, the effect size was also studied.
Results
Table I shows PTV coverage (V95%), minimum and maximum dose to the PTV. The major differences in the V95% were shown for the H&N treatments, where there is a 3% difference, in average. For the esophagus and lung treatments this difference was 2.8% and a 1.1% respectively. Differences in V95% were statistically significant for H&N and esophagus treatments, but not for the lung cases.
According to Cohen criteria, the effect size of these significance was medium (d=0.5) for esophagus treatments and large effect (d=0.7) for HN treatments.
Figure I shows the dosimetric differences between the AAA and Acuros algorithm for the three pathologies.
Furthermore, calculations with Acuros XB shown a higher maximum dose (3% for esophagus, 2.1% for H&N and 2.7% for lung treatments) and a lower minimum dose (in average, 4.6%, 4% and 3.7%, for esophagus, H&N and lung, respectively) in all studied pathologies.
Conclusion
Dose calculations in treatments with heterogeneous regions are more accurate when calculated with Acuros XB. AAA algorithm does not account for this type of heterogeneities and overestimate PTV coverage. These differences are more acute for H&N treatments due to the large section of inhomogenity regions.