Clinical implementation and evaluation of the Acuros dose calculation algorithm

Purpose The main aim of this study is to validate the AcurosXBdose calculation algorithm for a Varian ClinaciXlinac in our clinics, and subsequently compare it with the wildely usedAAAalgorithm. Methods and materials The source models for both AcurosXBandAAAwere configured by importing the same measured beam data into Eclipse treatment planning system. Both algorithms were validated by comparing calculated dose with measured dose on a homogeneous water phantom for field sizes ranging from 6 cm × 6 cm to 40 cm × 40 cm. Central axis and off‐axis points with different depths were chosen for the comparison. In addition, the accuracy of Acuros was evaluated for wedge fields with wedge angles from 15 to 60°. Similarly, variable field sizes for an inhomogeneous phantom were chosen to validate the Acuros algorithm. In addition, doses calculated by Acuros andAAAat the center of lung equivalent tissue from three differentVMATplans were compared to the ion chamber measured doses inQUASARphantom, and the calculated dose distributions by the two algorithms and their differences on patients were compared. Computation time onVMATplans was also evaluated for Acuros andAAA. Differences between dose‐to‐water (calculated byAAAand AcurosXB) and dose‐to‐medium (calculated by AcurosXB) on patient plans were compared and evaluated. Results For open 6MVphoton beams on the homogeneous water phantom, both AcurosXBandAAAcalculations were within 1% of measurements. For 23MVphoton beams, the calculated doses were within 1.5% of measured doses for AcurosXBand 2% forAAA. Testing on the inhomogeneous phantom demonstrated thatAAAoverestimated doses by up to 8.96% at a point close to lung/solid water interface, while AcurosXBreduced that to 1.64%. The test onQUASARphantom showed that Acuros achieved better agreement in lung equivalent tissue whileAAAunderestimated dose for allVMATplans by up to 2.7%. AcurosXBcomputation time was about three times faster thanAAAforVMATplans, and computation time for other plans will be discussed at the end. Maximum difference between dose calculated byAAAand dose‐to‐medium by AcurosXB(Acuros_Dm,m) was 4.3% on patient plans at the isocenter, and maximum difference between D100calculated byAAAand by Acuros_Dm,mwas 11.3%. When calculating the maximum dose to spinal cord on patient plans, differences between dose calculated byAAAand Acuros_Dm,mwere more than 3%. Conclusion Compared withAAA, AcurosXBimproves accuracy in the presence of inhomogeneity, and also significantly reduces computation time forVMATplans. Dose differences betweenAAAand Acuros_Dw,mwere generally less than the dose differences betweenAAAand Acuros_Dm,m. Clinical practitioners should consider making AcurosXBavailable in clinics, however, further investigation and clarification is needed about which dose reporting mode (dose‐to‐water or dose‐to‐medium) should be used in clinics.