CRYSP: a Total-Body PET based on cryogenic cesium iodide crystals

Total Body PET (TBPET) scanners have recently demonstrated the ability to significantly reduce both acquisition time and the administered radioactive dose, thanks to their increased sensitivity. However, their widespread adoption is limited by the high costs associated with the current available systems. In this context, pure cesium iodide (CsI) monolithic crystals, given their much lower cost compared with currently used rare-earth crystals, offer a promising solution to improve accessibility. When operated at cryogenic temperatures (approximately 100 K), CsI crystals exhibit one of the highest light outputs among inorganic crystals, around $10^5$ photons/MeV. This results in energy resolution below 7%, millimeter-scale spatial resolution (including accurate depth-of-interaction determination), and coincidence time resolution at the nanosecond level, despite their relatively slow scintillation decay time. This study demonstrates that a TBPET scanner based on cryogenic CsI monolithic crystals might have the potential to deliver high-performance imaging at a reduced cost compared with conventional systems, paving the way for broader deployment and accessibility.