Speaker
Description
Plastic scintillators primarily consist of a fluorophore—which absorbs and converts the kinetic energy of particles into lower-energy light—dissolved in a polymer matrix, with the frequent addition of a wavelength shifter. Despite the numerous advantages offered by plastic scintillators, including fast scintillation signal, low cost and ease of manipulation and shaping, they are characterized by a low atomic number Z, which negatively affects their ability to detect the photopeak of gamma rays. Attempts at solving this issue have been made by loading the plastic scintillators with high-Z impurities to increase their effective Z. However, the fabrication of samples exhibiting high transparency, homogeneous dopant distribution and light output comparable to that of inorganic crystals is challenging. Not even the leading companies specializing in the fabrication of organic scintillators offer samples exceeding 5% dopant concentration, due to the associated degradation in optical clarity and scintillation efficiency. These limitations prevent applications in nuclear medical imaging, where the ability to detect the gamma-ray photopeaks is crucial to guarantee the required diagnostic efficiency.
Our research line aims at developing loaded plastic scintillators to realize medical imaging detectors that are expected to offer improved time performances at a lower cost, thus broadening the availability of these crucial tools in the fight against cancer. In particular, two projects are ongoing. The first one (reSPECT project) concerns the implementation of a new SPECT (Single-Photon Emission Computed Tomography) detector based on our high-Z doped scintillators polymerized inside the holes of a 3D-printed tungsten collimator, read by CMOS sensors arranged in tiles. The second one (TRONDHEIM project) aims at realizing a compact portable dosimeter for radiopharmaceutical dose customization in 177-Lu-PSMA-617 radio-metabolic therapy.
The first step we accomplished was the synthesis of a new series of organic molecules to serve as fluorophores in the plastic scintillators [Patent: Mattiello L.; Patera V.; Belardini A.; Rocco D.; Marafini M.; Organic Scintillator. Patent WO2023156957A1, 2023]. Through the comparison of light output and time properties of these novel materials [D.Rocco et al., “TOPS fast timing plastic scintillators: Time and light output performances”. NIM A 1052, 168277 (2023); doi: 10.1016/j.nima.2023.168277], we identified the most promising candidates, subsequently employed in the realization of scintillator prototypes enriched with Bismuth in concentrations up to 10%. The results are encouraging in terms of transparency, homogeneity and performances of the final samples.
Moreover we explored different manufacturing techniques, from the polymerization of the PVT-based loaded scintillators inside various molds (PE, PTFE, metal) to the use of 3D-printed resin as scintillator substrate.
