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Friday
May 07
14:15 - 15:30
21st century brachytherapy: is it available, affordable and relevant?
There are several reports of declining use of brachytherapy worldwide despite its well-documented advantages. Brachytherapy is often perceived to be resource-intensive and expensive and its role in the era of increasingly sophisticated external beam radiotherapy techniques has been questioned. This session discusses some of the issues that influence availability and utilisation of brachytherapy. Topics include current status of cervix cancer brachytherapy availability worldwide and global initiatives to improve access, socio-economic factors impacting brachytherapy treatment trends in the United States, a literature review of time activity based costing studies of brachytherapy, and brachytherapy training and interest amongst European radiation oncology residents.
Symposium
00:00 - 00:00
Comparison of Acuros and Anisotropic Analytical Algorithm for dose calculations in VMAT treatments
PO-1366

Abstract

Comparison of Acuros and Anisotropic Analytical Algorithm for dose calculations in VMAT treatments
Authors: Ambroa Rey|, Eva Maria(1)*[eva.ambroa@gmail.com];Rodríguez Meijide|, Pablo(1);Pérez Fernández|, María(1);López Sánchez|, Miguel (1);
(1)Hospital Universitario Lucus Augusti, Medical Physics, Lugo, Spain;
Show Affiliations
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.