Demonstration of 2D dosimetry using Al₂O₃ optically stimulated luminescence films for therapeutic megavoltage x-ray and ion beams

This work gives an overview of the performance of a laser-scanning 2D dosimetry system developed for Al₂O₃ optically stimulated luminescence dosimetric (OSLD) films, particularly for applications in radiotherapy using external beams. Al₂O₃:C and Al₂O₃:C,Mg OSLD films were irradiated using a 6 MV X-ray beam, a 221 MeV proton and 430 MeV/u ¹²C scanned pencil beams, and read using a specially-developed OSL system. The data obtained show that the OSLD films allow 2D dosimetry with sub-millimetric resolution, with approximately linear photon dose response over a wide dynamic range (20 mGy - 3 Gy), no film saturation up to > 76 Gy, and a minimum detectable dose < 1.0 mGy. No field size dependence within the investigated range of 4–15 cm was observed, based on the agreement with ionization chamber within 1%. The image signal-to-noise ratio is higher for Al₂O₃:C,Mg films than for Al₂O₃:C films due to the higher intensity of fast F⁺-center emission in Al₂O₃:C,Mg films. The results demonstrate that the 2D dosimetry system based on Al₂O₃ films may provide a convenient and precise tool in medical dosimetry, with potential application in small field dosimetry.