Experimental verification of Acuros XB in the presence of lung-equivalent heterogeneities M. Bueno, M. A. Duch Institut de T`ecniques Energ`etiques, Universitat Polit`ecnica de Catalunya, 08028 Barcelona,Spain D. Jurado-Bruggeman, S. Agramunt-Chaler and C. Mun ˜oz-Montplet Servei de F´ısica M`edica i Protecci´o Radiol`ogica, Institut Catal`a d’Oncologia—Girona, 17007 Girona, Spain Abstract Acuros XB (AXB) is a deterministic algorithm that directly accounts for the effects of heterogeneities and improves the accuracy of photon dose calculations in radiotherapy. Nevertheless, the accuracy of AXB inside lung has not been yet fully examined by means of experimental measurements. The aim of this study was to evaluate the accuracy of AXB in the presence of lung using 7 Li-based thermoluminescent dosimeters (TLD-700). Percentage depth-dose distributions (PDD) obtained by AXB on a slab water-equivalent phantom with a lung- equivalent heterogeneity were compared with the TLD-700 measurements for 6 MV and 18 MV photon beams and a set of field sizes ranging from 2 × 2 cm 2 to 20 × 20 cm 2 . Dose distributions obtained by the Anisotropic Analytical Al- gorithm (AAA) were also included in the comparison as a reference to a non- deterministic dose calculation algorithm. The agreement between AXB and the TLD results was kept within clinical tolerance levels (3%) for all beam configu- rations. On the contrary, AAA failed at correctly predicting the absorbed dose when the lateral electronic equilibrium was lost. AXB is capable of providing reliable dose estimations in the presence of lung and clearly outperforms AAA. Keywords: Acuros XB, TLD, heterogeneities, lung 1. Introduction Li-based thermoluminescent detectors (TLDs) are suitable for the experi- mental verification of dose calculation algorithms in radiotherapy [1, 2]. The thermoluminescent material is tissue-equivalent, which makes it especially use- 5 ful for validation inside lung where ionization chambers (IC) cannot generally ∗ Corresponding author Email address: mbuenovizcarra@gmail.com (M. Bueno, M. A. Duch)