Room: AAPM ePoster Library
As recently reported, water emits a weak luminescence when it is irradiated with high energy protons. The light signal is proportional to the absorbed dose in water and no ?uorescence dye or other additive is required to obtain this signal. We want to present a detailed comparison of the optical range measurement with standard ionization chamber based methods in terms of resolution and measurement time. Also, we have investigated the influence of perturbations such as scattered radiation and Cerenkov light.
A measuring set-up for range measurement consisting of a water tank, a highly sensitive cooled scientific CMOS-Camera and a lightproof cover was built. A series of measurements was performed at the West-German-Proton-Therapy-Center, Essen in order to compare the optical method with the standard range measurement methods for protons in the clinical used energy range. For the optical method, image processing to reduce errors in the images caused by scattered radiation, was performed. The influences of Cerenkov light on the range measurement was evaluated using Monte-Carlo simulations. We used two different ionization chamber-based systems, IBA Gira?e and PTW Bragg Peak chamber, under reference conditions to compare our results.
We could show that it is possible to perform range measurements for clinical proton energies with the optical method. Because the entire Bragg peak is recorded in one shot with high spatial resolution, the measurement time is in the order of magnitude as the IBA Giraffe. For the range resolution, there was a maximum deviation of 0.45mm compared to the PTW Bragg Peak chamber.
The luminescence method is suitable for range measurement with high resolution and short measuring time. Due to measuring directly in water, no corrections from detector material to water are necessary. In future work we will investigate whether further dosimetric parameters can assessed with this method.