Small-field measurements in 3D polymer gel dosimetry using optical computed tomography

Polymer gel dosimetry enables three-dimensional measurements. We measured the dose-response characteristics using an optical computed tomography (CT) system and evaluated the scatter correction for polymer gel-optical CT to calculate accurate field output factors. The dose-response can be expressed using an appropriate fitting model in the range of 0-10 Gy. The irradiated four-finger gel phantom with four collimators of different diameters was scanned using optical CT. The corrected optical CT image showed an improved low-intensity signal near the edge closer to the film, resulting in the profile. The field output factors in the 5 mm diameter small irradiation field were calculated using a gel dosemeter-optical CT system and compared with those from several ionization chambers. The polymer gel-optical CT system is suitable for calculating field output factors in small-field measurements.