SU-E-T-144: Study of the Effect of the Optical Density to Dose Conversion Calibration Curves on the Measurement of Transverse Lateral Dose Profiles of Proton Beams Using Kodak XV Films

Abstract

Purpose: To investigate the effect of the optical density (OD) to dose conversion calibration curves on the measurement of transverse lateral dose profiles of proton beams using Kodak XV films. Methods: A number of XV films were exposed to different doses in a 10 cm × 10 cm field of passively scattered range modulated beams of different incident energies. The films were placed at the center of spread out Bragg peak of the beam inside plastic water phantoms. The films were scanned by a Vidar Scanner using Scanditronix/ Wellhofer OmniPro‐Accept6.4 software. Different OD‐dose calibration curves were generated and compared. Transverse lateral dose profiles were obtained from an irradiated film using different OD‐dose calibration curves and were compared to evaluate the differences. The lateral dose profiles of proton pencil beam spots (PPBS) were also obtained using the XV films and one of these OD‐dose calibration curves and were compared with ion chamber measurement. Results: OD‐dose calibration curves obtained by giving same doses, but with beams of different incident energies were found to have differences in all dose regions. But, the relative lateral dose profiles (LDP) were not affected by the differences in the calibration curves. Thus, the incident energy of the range modulated beam is not an important consideration for obtaining the film OD‐dose calibration curves for relative LDP measurements. The XV film measured relative LDP of the PPBS agreed well with that from ion chamber measurement in the high dose region, but was seen to be noisier in the long tail region. Conclusions: OD‐dose calibration curves created with given doses from any range modulated passively scattered beam, irrespective of the energy of the incident beam, are found to be suitable for measuring the relative LDP of broad fields of passively scattered proton beams and PPBS with XV films.