Purpose: The purpose of this work was to investigate the afterglow effect, which refers to continued light emittance post-irradiation, of a chromium-doped alumina scintillation screen (Chromox) when irradiated with a proton beam. To our knowledge, the afterglow effect has not previously been quantified in the literature.
Methods: Chromox is a desirable scintillation material for visualization of proton beam profiles due to its high light yield and radiation hardness. The afterglow effect was studied using a clinical IBA Proteus Plus delivery system to irradiate a 1 mm thick 10x10 cm² Chromox scintillation screen. A uniform planar dose (7x7 cm²) with a single energy (150 MeV and 9125 total monitor units) was delivered to the screen. Following the irradiation, the afterglow images were acquired every 3 minutes for 18 minutes.
Results: The afterglow was still detectable after 10 minutes using and IR-filtered camera with the exposure time set to 7 seconds. The afterglow half-life was calculated to be approximately 110 seconds.
Conclusion: While Chromox appears to be very suitable for static beam diagnostics, the afterglow will be present if consecutive, varied images are acquired. Ideally, use of a Chromox scintillation screen should be limited to applications that require a high light output for single static exposures. In some applications, the afterglow could be viewed as an advantage as imaging can be completed post exposure rather than in real time.
Funding Support, Disclosures, and Conflict of Interest: Research reported in this abstract was supported by the National Cancer Institute of the National Institutes of Health under award number R37CA226518. Hyer and Flynn are co-inventors on a patent that has been licensed to IBA.