Experimental evaluation of a high resolution CdTe-based PET system

Small animal PET imaging requires both high resolution and high sensitivity in order to detect small amounts of radiopharmaceutical with precision. Semiconductor detector such as cadmium telluride (CdTe) makes it possible to localize gamma ray interactions in 3D at submillimetric scale, enabling the design of PET system architectures with innovative geometries. Indeed, thank to a good knowledge of the depth of interaction (DOI) inside the detection unit, it becomes achievable to obtain a homogeneous spatial resolution in the whole field of view (FOV) and then to maximize the solid angle coverage, and then the line-of-response (LOR) coverage. We are developing a CdTe PET detection module, based on the stacking of individual detectors, associated with read-out ASICs. To validate experimentally this design, a small test bench featuring two detection heads was built. A dedicated electronics associating the readout ASIC and FPGA-based processing boards was developed. Experiments were carried out with point sources (using 200 micrometer capillary tubes) phantoms. Results show the potential of this technology to achieve homogeneous spatial resolution in the whole field of view.