Verification of IMRT dose calculations using AAA and PBC algorithms in dose buildup regions

The purpose of this comparative study was to test the accuracy of anisotropic analytical algorithm (AAA) and pencil beam convolution (PBC) algorithms of Eclipse treatment planning system (TPS) for dose calculations in the low‐ and high‐dose buildup regions. AAA and PBC algorithms were used to create two intensity‐modulated radiotherapy (IMRT) plans of the same optimal fluence generated from a clinically simulated oropharynx case in an in‐house fabricated head and neck phantom. The TPS computed buildup doses were compared with the corresponding measured doses in the phantom using thermoluminescence dosimeters (TLD 100). Analysis of dose distribution calculated using PBC and AAA shows an increase in gamma value in the dose buildup region indicating large dose deviation. For the surface areas of 1, 50 and [Formula: see text] , PBC overestimates doses as compared to AAA calculated value in the range of 1.34%–3.62% at 0.6 cm depth, 1.74%–2.96% at 0.4 cm depth, and 1.96%–4.06% at 0.2 cm depth, respectively. In high‐dose buildup region, AAA calculated doses were lower by an average of [Formula: see text] , while PBC was overestimated by [Formula: see text] as compared to TLD measured doses at 0.2 cm depth. However, at 0.4 and 0.6 cm depth, PBC overestimated TLD measured doses by [Formula: see text] and [Formula: see text] , respectively, while AAA underestimated the TLD measured doses by [Formula: see text] and [Formula: see text] at the same respective depth. In low‐dose buildup region, both AAA and PBC overestimated the TLD measured doses at all depths except [Formula: see text] by AAA at 0.2 cm depth. The differences between AAA and PBC at all depths were statistically significant [Formula: see text] in high‐dose buildup region, whereas it is not statistically significant in low‐dose buildup region. In conclusion, AAA calculated the dose more accurately than PBC in clinically important high‐dose buildup region at 0.4 cm and 0.6 cm depths. The use of an orfit cast increases the dose buildup effect, and this buildup effect decreases with depth. PACS number: 87.53.Bn