Progetti di ricerca

Ionizing radiation, especially X-rays and γ photons, are essential in many tools and techniques developed for bioimaging. The most common application regards their use in direct medical imaging such as radiography and tomography. In such applications, the main building blocks of radiation… Leggi tutto detectors are scintillating materials, that absorb and down-convert the energy deposited by the incoming ionizing radiation to low-energy UV-Vis-IR light, which is then easily read out by common photodetectors. A valuable class of scintillating materials is represented by rare-earth doped garnets; indeed, garnets in the form of single crystals are already used in some medical instrument and are also promising candidates for Time of Flight Positron Emission Tomography (TOF-PET) detectors where stringent requirements on fast time response are crucial to optimize the spatial localization of the tumours and detection accuracy. Moreover, they can be easily obtained as micro- and nano-sized powders and, in this form, they can be used as phosphors in optical bioimaging. The latter technique consists in the inoculation of the nanoparticles in the tissues to be treated and the imaging occurs through laser-stimulated luminescence in the biological window where tissue absorbance is minimal (700 – 1350 nm). However, this approach presents some drawbacks: the signal monitoring is difficult since excitation and emission lights are close in frequency, and more importantly, the laser power needed is very high and may lead to skin damage and to autofluorescence. The LUMINANCE project aims at the improvement of the scintillation properties of rare-earth doped garnets designed to help the medical community in overcoming two specific needs in bioimaging. Firstly, a new approach in optical bioimaging will be explored by using YAG (Y3Al5O12) nanoparticles doped with near infrared emitting rare earths (Yb, Nd, or Er). This enables the use of low dose x-rays as excitation source instead of lasers, thus eliminating autofluorescence, tissue damages, and detector overexposure. Secondly, we will deepen the structure-property relationships of bulk GGAG (Gd3(Ga,Al)5O12) mixed garnet doped with Ce with the aim of obtaining fast and performing scintillators for TOF-PET detectors. The major strength of the project is the use of rare-earth doped garnet optical ceramics. They can be easily produced with the desired size and shape, not achievable by their single crystal counterparts, but with comparable optical quality, and more affordable costs. Therefore, for the development of YAG nanophosphors, we will use optical ceramics as a transparent testing platform to identify the best doping level and type; on the other hand, we will get performing bulk GGAG as high-quality optical ceramic, also investigating the differences in using nanoparticles or mixed powders as starting materials. Finally, the two proposed solutions will be validated in proof-of-concept experiments.