Y Yamanaka¹*, K Inoue², Y Suetsugu³, M Tateishi¹, T Hirose⁴, J Fukunaga⁴, T Yoshitake¹, T Sasaki⁵, K Atsumi¹, (1) Kyushu University, Fukuoka-shi, 40, JP, (2) Steel Memorial Yawata Hosp., Kitakyushu-shi, Fukuoka-ken, 40, JP, (3) Hos. of the Univ. of Occupational and Environmental Health, Kitakyushu-shi, Fukuoka-ken, 40, JP, (4) Kyushu Univ. Hosp., Fukuoka-shi, Fukuoka-ken, 40, JP, (5) Iizuka Hosp.,Iizuka-shi, Fukuoka-ken, 40,JP,

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  Y Yamanaka

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PO-GePV-T-407 (Sunday, 7/10/2022)   [Eastern Time (GMT-4)]

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Purpose: This study aims to analyze the differences of dose calculation algorithms on collimator angle in stereotactic body radiation therapy (SBRT) for lung tumor with volumetric modulated arc therapy (VMAT).

Methods: 20 patients received SBRT of lung tumors using 3D-CRT at Kyushu University Hospital from July to December 2017. All cases were planned with VMAT in 2 arcs. For each plan, dose prescription was 48 Gy in 4 fractions, where at least 95% of the PTV, and the collimator rotation set as 0, 10, 20, 30, 45, and 90 degrees, respectively. The dose calculations were carried out using AcurosXB (AXB) and Anisotropic Analytical Algorithm (AAA) after optimization. The dosimetric parameters (PTV: Conformity Index (CI), Homogeneity Index (HI), Maximum Dose (Dmax), Lung: V5Gy, V20Gy) were calculated for all plans, and the relationship between the dosimetric parameter and collimator angle for each algorithm was analyzed.

Results: Both algorithms had the highest number of patients with the best CI at 45 degrees (AXB:6, AAA:8), and in 11 out of 20 cases, the collimator angle for the best CI was different between AXB and AAA. In 15 cases, the collimator angle for minimum HI in both algorithms matched, and 6 of these cases had the best HI at 0 degrees. For CI, HI, Dmax, V5Gy, and V20Gy, the calculated results of each dosimeter in AAA tended to be lower than those in AXB, with an average difference of 0.329, 0.031, 1.935 Gy, 0.334%, and 0.134%, respectively. There were statistically significant differences for all dosimetric parameters except for V20Gy at 10 degrees.

Conclusion:
Conclusion: In VMAT-SBRT for lung tumors, there is similar trend of CI against collimator angle between AXB and AAA.

Keywords

Treatment Planning, Lung

Taxonomy

TH- External Beam- Photons: IMRT/VMAT dose optimization algorithms

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