Monte Carlo simulation of a neuroimaging acquisition with MAPSSIC, a β + sensitive intracerebral microprobe for awake and freely moving rats

Objective: Establishing robust correlations between molecular neuroimaging and behavioral studies is essential in preclinical research to advance our understanding of brain function and to critically assess the translational relevance of animal models in drug development.Achieving this goal, however, requires imaging animals while they are awake and freely moving -an ongoing challenge, as most preclinical imaging techniques rely on anesthesia. Approach: To overcome the limitations imposed by anesthesia, the MAPSSIC project aims to develop a novel implantable pixelated probe based on Monolithic Active Pixel Sensors (MAPS), designed for use in awake, freely moving rats. By virtue of its direct implantation within the targeted brain regions, the MAPSSIC probe enables the local detection of short-range β + particles emitted by radiotracers, in contrast to conventional micro-PET systems that rely on detecting coincident annihilation γ-rays. In this study, we present Monte Carlo simulations of a typical in vivo brain imaging experiment using [ 11 C]Raclopride, a commonly employed β + -emitting radiotracer, to evaluate the probe’s performance. Main results: Results show that over 93 % of detected events originate from particles emitted within the first 2 mm surrounding the probe while also allowing to quantify variations of 5 % to 30 % of the non-displaceable binding potential (BP ND ) with discrepancy of less than 4 % compared to micro-PET. Significance: This Monte Carlo study demonstrates the device’s ability to capture small variations of BP ND based on spatially localized information, validating its suitability for quantitative kinetic analysis in brain structures such as the striatum.