Three-dimensional dose verification in complex particle radiation fields based on X-ray films

In the framework of the heavy ion therapy at GSI a three-dimensional dose verification with films is performed. Due to the complex composition of the irradiation field, the knowledge of the film response depending on particle energy and atomic number is essential. Basic experiments were performed to investigate the response of films to heavy ion irradiation. Moreover a model was developed to calculate the respective film response and a look-up table of film responses for the therapy relevant particle and energy spectrum was established. This look-up table allows to calculate the expected optical density distribution of an exposed film. A three-dimensional dose verification with an array of films was yielded by comparing the calculated with the measured optical density distribution of the exposed films. These experiments were performed at the GSI facility using a carbon ion beam. The irradiated field shape was mapped perfectly by the films due to their high spatial resolution. Moreover, the applied physical dose distribution was quantitatively verified with high precision in three dimensions. (C) 2002 Elsevier B.V. All rights reserved.