Implantable CMOS pixel sensor for positron imaging in rat brain

IMIC is a Monolithic Active Pixel Sensor prototype designed for the MAPSSIC project, which aims at developing wireless intracerebral probes dedicated to image positron-emitting source activity in the brain of awake and freely moving rats. Former experiments with the PIXSIC positron probe based on a passive sensor have validated the proof of concept, but have also shown limitations with regards to the probe robustness and to its transparency to annihilation photons. The IMIC circuit features a matrix of 16 × 128 active pixels of 30 × 50 µm2 size and targets to overcome the PIXSIC probe drawbacks by exploiting a thin sensitive layer of 18 µm, still featuring an overall thickness close to 300 µm. Additionally, by using a low power (55 nW/pixel) in-pixel front-end architecture providing binary output, IMIC solves the challenge of implanting an active sensor in tissues where overheating is forbidden.