Towards using secondary gamma-rays from proton-induced radioactivation of titanium implants for off-line field verification

This experimental study investigates the radioactivation of titanium during proton therapy. Titanium is a commonly used material for implants. Because of its fixed position, the activation of those implants might be useful for post-irradiation field. Various titanium samples are irradiated at the West German Proton Therapy Centre Essen. The activities of the produced radionuclides are obtained with a low-level gamma-ray spectrometry system at the Dortmund Low Background Facility. Furthermore, an irradiated titanium sample is placed in a pre-clinic PET/CT scanner to investigate the potential of the implants for range verification. With the gamma-ray spectrometry technique a number of radionuclides are identified as candidates for range verification with delayed secondary gamma-rays. Furthermore, activation cross sections are calculated with the activities for the identified radionuclides. The depth distribution of the activity as obtained with the PET/CT scans has a characteristic rise towards the distal end similar to the depth dose curve.