In the last decade, the interest in scintillating fiber optics for ionizing radiation monitoring is constantly increasing.
Among the fields of possible applications of these sensors, radiation therapy represents a driving force for the research
and development of new devices. In fact, the small dimensions of fiber optics based detectors, together with their realtime
response, make these systems extremely promising both in quality assurance measurements of intensity modulated
radiotherapy beams, and in in-vivo dosimetry. On the other hand, two specific aspects might represent limiting factors:
(i) the “stem effect”, that is the spurious luminescence originating as a consequence of the irradiation of the light guide,
and (ii) the “memory effect”, that is the radioluminescence sensitivity increase during prolonged exposition to ionizing
radiation, typical of many scintillating materials.
These two issues, representing the main challenges to face for the effective use of scintillating fiber as dosimeters in
radiotherapy, were studied considering amorphous silica matrices prepared by sol-gel method and doped with europium.
The origin of the stem effect was investigated by means of spectral measurements of the doped fibers irradiated with Xrays
and electrons of different energies, field sizes and orientations. New approaches for removing the stem effect on the
basis of the radioluminescent spectral analysis are presented and discussed. Furthermore, the causes and phenomenology
of the memory effect are described, considering also the effect of dose accumulation with different dose rates and
energies of ionizing radiation.