Fiber optic radioluminescent probes for radiation therapy dosimetry

Radioluminescent fiber optic dosimeters have drawn great attention due to their unique practical advantageous properties including the ability to perform in vivo, real-time, and intracavity measurements with high spatial resolution due to their small physical size and mechanical flexibility. These features make them ideal candidates for many potential applications in radiation therapy dosimetry, such as in brachytherapy, intensity-modulated radiation therapy, superficial therapy, stereotactic radiosurgery, proton therapy, and small-field dosimetry. However, in therapeutic radiation fields, the total optical signal carried by the fiber has undesirable components in addition to the useful radioluminescent signal. The main problem with fiber optic dosimeters in photon and electron therapies is these undesirable signals that are primarily the Čerenkov radiation generated in the irradiated portion of the guide fiber. Another significant issue related to scintillation fiber optic dosimetry that occurs in proton therapy and other beams with high linear energy transfer (LET) is the non-proportionality between the scintillation signal and the proton dose due to the ionization quenching. In this work, recent progress toward minimizing the impact of Čerenkov radiation and ionization quenching through using spectroscopic methods, specialty fiber optics, and undoped fibers is briefly reviewed.