Dark matter search application for the medical physics: the 3D$\Pi$ project.

3D$\Pi$ will be the first total-body scanner for Positron Emission Tomography (PET) using liquid Argon as a scintillator medium. The project is an application in medical physics of the ongoing R&D of the DarkSide collaboration, whose main aim is the direct detection of dark matter particles via liquid Argon targets. Utilizing liquid Argon as a scintillator will allow for a competitive and cost-effective total-body PET scanner to be built, thanks to the high availability of atmospheric Argon that can be isotopically distilled as needed, along with potential for the availability of underground Argon. The preliminary results here demonstrate that, while the spatial resolution is comparable to that of commercial scanners, the 3D$\Pi$ scanner is expected to show outstanding detection sensitivity, allowing for a reduction of the PET scanning time or a reduction of the patient dose.