Room: ePoster Forums
Purpose: To investigate the feasibility of proton therapy dosimetry using the radioluminescence of un-doped plastic and silica glass optical fibers.
Methods: Silica glass and poly(methyl methacrylate) (PMMA) optical fibers were embedded in solid water phantoms and irradiated with proton therapy beams. Luminescent spectroscopy was performed by a fiber-coupled spectrometer to analyze the radioluminescent spectrum of the fibers across the visible range (400-700 nm).
Results: Radioluminescent spectrum of the silica fiber showed two peaks at 460 and 650 nm, whose origins are connected to the point defects of the silica, namely oxygen-deficiency centers (ODC) and non-bridging oxygen hole centers (NBOHC), respectively. The intensity of the red emission at 650 nm was proportional to the dose, whereas the intensity of the blue emission at 460 nm significantly under estimated the dose. The ratio of the intensities of these two peaks varied with depth in phantom. The radioluminescent spectrum of the PMMA fiber showed a single peak at 410 nm whose origin is connected with the fluorescence of the fiber material.
Conclusion: The radioluminescent spectra of the irradiated silica glass and PMMA fibers were different from the spectrum of ÄŒerenkov radiation indicating that ÄŒerenkov radiation is not the responsible signal for dose measurement using un-doped optical fibers. The fact that the ratio of the red and blue signal intensities in the silica fiber varies with the depth suggests a dependency on the linear energy transfer (LET) of the beam and can be carefully examined for LET sensing.
Funding Support, Disclosures, and Conflict of Interest: The author received an AAPM Research Seed Funding Award in support of this work.