Room: AAPM ePoster Library
To perform a dosimetric comparison between Acuros-XB and Anisotropic Analytical Algorithm (AAA) (Varian Medical Systems, Palo Alto, CA) for stereotactic body radiotherapy (SBRT) for lung cancer to aid in clinical implementation of Acuros-XB.
A comparison between Acuros-XB version 15.5 and AAA version 13.6 was performed on twenty-five patients’ treatment plans previously calculated using AAA. The AAA plans were normalized such that 95% of the PTV was covered by the prescribed dose. The treatment plans were recalculated with Acuros-XB using dose to water with the identical monitor units and the same optimized MLC patterns and grid size as the AAA plans. The prescription doses used were 52.5 Gy and 54 Gy for peripherally and centrally located tumors. The PTV dose (D95) and the PTV mean dose were evaluated for each plan and algorithm.
The PTV volumes ranged in size from 4.9 to 49.3 cm3 with a median volume of 26.7 cm3. Overall, the PTV doses (D95) and mean doses were lower for the recalculated Acuros-XB plans. The median differences of PTV dose (D95) (AAA – Acuros-XB) were 2.4 Gy (range: -0.7 to 15.0 Gy) and 1.0 Gy (range: 0.0 – 7.4 Gy) for peripherally and centrally located tumors, respectively. The median differences of PTV mean dose were 1.9 Gy (range: -0.5 to 12.5 Gy) and 0.5 Gy (range: -0.7 to 5.4 Gy) for peripherally and centrally located tumors, respectively. Additionally, the difference in PTV dose coverage decreased as the tumor size increased.
AAA tends to overestimate the PTV dose, and the dose difference is amplified in smaller tumors. When using Acuros-XB, we suggested that the prescription for SBRT lung treatment not change given the subtle difference in dose, though the monitor units per treatment plan will change to account for the difference.
Funding Support, Disclosures, and Conflict of Interest: The University of Alabama at Birmingham Department of Radiation Oncology does receive research support from Varian Medical Systems.
Not Applicable / None Entered.