MAPSSIC, a beta+ implantable microprobe for neuroimaging of awake and freely moving rats: first sensor characterization and in vivo imaging simulations

The correlation of molecular neuroimaging and behavior studies in the preclinical field is of major interest to unlock progress in the understanding of brain processes and assess the validity of preclinical studies in drug development. However, fully achieving this ambition requires to perform molecular images of awake and freely moving animals, whereas most of the preclinical imaging procedures are currently performed under anesthesia. To achieve such a combination, the MAPSSIC project aims to develop a pixelated intracerebral probe based on the MAPS technology to be implanted on awake freely moving rats. Thanks to its in situ position, the probe is able to directly detect short range positrons of β
⁺
radioisotopes whereas micro-PET devices use the coincident γ-rays from annihilation as a relevant signal. In this paper, we discuss the first characterization of the new probe’s sensors and present the results from Monte Carlo simulations of a typical animal experiment using a commonly used β
⁺
radiotracer to confirm the relevance of this imaging device. First measurements show an energy threshold lower than 1 keV allowing the detection of β
⁺
particles as well as a background sensitivity of 1.7 × 10
⁻³
cps. Simulations confirm the ability of the probe to record a local information, with more than 93 % of the detected particles being emitted within the first 2 mm surrounding the probe, that allows to perform kinetic studies on brain structures such as the striatum.