Zarza-Moreno, M.Souto, A. C.Teixeira, NunoJesus, A. P.Mora, G.2017-12-282017-12-282009-09Zarza-Moreno A, Souto AC, Teixeira N, Jesus AP, Mora G. Evaluation of multileaf collimator effect on the build-up dose region using different ionization chambers. In: Dössel O, Schlegel WC, editors. World Congress on Medical Physics and Biomedical Engineering, Munich (Germany), September 7-12, 2009. IFMBE Proceedings, vol. 25/1. Berlin: Springer; 2009. p. 1051-4.http://hdl.handle.net/10400.21/7825In the present work, we studied the effect of a multileaf collimator (MLC) on the build-up region. Ionization measurements (PDI) were performed in a water phantom for a 6 MV photon beam emerging from a Varian 2100C/D accelerator with a 120 – MILLENIUM MLC. We used two different detectors: a PTW 31002 cylindrical ionization chamber (IC) and a Roos parallel-plate chamber. Several MLC-JAWS configurations were investigated and the contribution of MLC for the build-up region was determined by comparing PDIs measured for MLC defined field sizes (from 2 x 2 to 10 x 10 cm2) and the corresponding PDIs measured for open fields. Our results were also compared with previous Monte Carlo (MC) simulated depth dose curves for the same experimental set-up [1].The Roos chamber measured dose values agree with MC values within 2% for all MLC openings and depths greater than 2 mm. We observed differences of about 4% between the values measured with cylindrical IC and previously calculated MC values. A negligible effect (less than 1%) of the MLC on the build-up dose was observed for all MLC defined field sizes. Our measurements cannot predict the MC calculated surface dose values.engBuild-up doseSurface doseMultileaf collimatorMonte Carlo simulationIonization chamberconference object10.1007/978-3-642-03474-9_295