Accuracy Of Accelerator Photon Dose Anisotropic Analytical Algorithm Evaluated By Monte Carlo

Purpose: To evaluate accuracy of accelerator photon dose Anisotropic Analytical Algorithm inheterogeneous media (air, lung, fat, muscle, bone) using Monte Carlo simulation as benchmarks.Method: A water phantom with a heterogeneous media (air, lung, fat, muscle, bone) slabinserted at the depth of5cm and the size of the phantom and the slab were40cm×40cm×25cm,30cm×30cm×5cm, respectively. The depth dose (DD) and off-axis ratio (OAR) of differentfield(1cm×1cm to10cm×10cm), different energy(6MV,15MV), different media(air, lung, fat,muscle, bone) were calculated and compared in the phantom by AAA algorithms, Pencil BeamConvolution （PBC） algorithms（as comparison）,and Monte Carlo (MC) simulation. Theobjects for the comparison of the DD include heterogeneous region and the region behind it andevaluated by defined dose deviation and dose departure factor. The OARs were evaluated bygamma analysis.Results: In the air,when the energy were6MV and15MV，the dose deviation ranges of the AAAwere40.37%～517.22%,42.55%～560.97%，respectively, and gamma analysis pass rates rangewere12.20%～64.63%,21.95%～65.82%, respectively. The dose deviation of the AAA were allless than PBC and gamma analysis pass rates were close to PBC. In the lung, when the energywere6MV and15MV，the dose deviation range of the AAA were-2.54%～11.63%,-0.92%～26.29%，respectively, and gamma analysis pass rates range were84.15%～92.68%,87.80%～100.00%, respectively. The dose deviation of the AAA were less than PBC except one or twofields and gamma analysis pass rates were all more than AAA. In the fat,when the energy were6MV and15MV，the dose deviation of the AAA were-2.45%～-1.22%,-3.43%～1.26%，respectively, and gamma analysis pass rates range were92.68%～97.56%、93.90%～97.56%,respectively. The dose deviation of the AAA were all less than PBC except the2cm×2cm fieldwhen the energy was6MV and gamma analysis pass rates were close to AAA. In the muscle,when the energy were6MV and15MV,the dose deviation range of the AAA were-0.86%～ 2.79%,1.65%～4.38%, respectively, and gamma analysis rates range were92.68%～97.56%,95.12～97.56%, respectively. The dose deviation of the AAA were all more than PBCexcept the1cm×1cm field when the energy was15MV and gamma analysis rates were close toAAA. In the bone, when the energy were6MV and15MV，the dose deviation range of the AAAwere1.68%～4.22%,1.47～2.60%，respectively, and gamma analysis rates range were91.46%～97.56%,92.68%～97.56%, respectively. The dose deviation of the AAA were all more than PBCexcept the1cm×1cm field when the energy was15MV and gamma analysis rates were close toPBC.Conclusions: The accuracy of AAA in air, lung, fat was higher than PBC，while in the muscleand bone was a little lower than PBC. In the lung and fat, the agreement between the dosecalculated by AAA and MC simulation was better and the accuracy was higher.In the air, theagreement between the dose calculated by AAA and MC simulation was worse and the accuracywas lower. When the energy was6MV, the accuracy of AAA in the air, lung,fat and musle washigher than the energy was15MV,While, the accuracy of AAA in bone was lower than theenergy was15MV. Moreover, the accuracy of AAA, especially, PBC in the field of1cm×1cmwas a little worse.ZHANG Yan-qiu（Radiation and environment protection）Directed by QIU Xiao-ping...