Radioluminescence-based fibre-optic dosimeters in radiotherapy: a review

Since their conception in the early 1990s, radioluminescence-based fibre-optic dosimeters (FODs) have attracted great interest for dosimetric applications in radiotherapy (RT). Over the years, many scintillating materials, both organic and inorganic, have been developed and tested by multiple research groups around the world. In parallel, reliable techniques for removing or subtracting the stem effect, one of the main drawbacks of FODs, have been proposed in the literature. To date, several prototype systems are widespread, some of which prove to be viable commercial solutions. This review aims to trace the efforts over the years that have enabled FODs to become reliable tools for dosimetry in the current RT procedures and promising options for future scenarios. After a first section devoted to a thorough discussion of the stem effect issue, the use of FODs in various applications of interest to RT, primarily small-field dosimetry and in vivo dosimetry, are addressed. Their use both in external beam RT, including hadrontherapy, and in brachytherapy are considered. A special focus is given to the peculiarities of MRI LINAC dosimetry and the contributions of FODs in this context. Finally, the state of the art concerning the development and characterization of FODs for monitoring ultra-high dose rate radiation beams, typical of FLASH therapy and microbeam RT are presented, highlighting the challenges still open.