Three-dimensional dose verification with x-ray films in conformal carbon ion therapy

A three-dimensional dose verification with photographic emulsions (x-ray films) was realized within the tumour therapy project at GSI Darmstadt, using carbon ions. We present Bragg-peak measurements for 88, 100 and 200 MeV/u carbon ion beams as the simplest case of dose verification. An actual patient treatment plan, composed by the superposition of Bragg-peaks having different energies and intensities, was used to perform a three-dimensional dose verification of an irregularly formed target volume. The shape of the measured dose distribution from film closely matches the intended irradiation volume. Furthermore, the calculated and measured optical density distribution is in good agreement with a maximum deviation of less than 10%.