Solid-State Detectors for Small-Animal Imaging - Molecular Imaging of Small Animals

Semiconductor detector technology, initially developed for high energy physics applications, has found a distinctive role in high performance systems for X-ray and gamma-ray medical imaging applications, including small animal imaging. Single-Photon Emission Computed Tomography (SPECT) small animal imaging requires the development of compact detectors with intrinsically ultrahigh spatial resolution, high energy resolution and good detection efficiency, in addition to suitable radiation collimation strategies. This overall performance can only partly be guaranteed by scintillator based systems with photomultiplier tube readout, the most used technology at present for small animal SPECT scanners. On the other hand, with respect to scintillator based detectors, semiconductor detectors can offer a gain by approximately a factor two in energy resolution at typical radionuclide energies, a factor greater than two in intrinsic spatial resolution, and a comparable intrinsic detection efficiency, though usually at a reduced field of view. Moreover, their compactness could be crucial in devising animal “personalized” miniature scanners. An additional interesting feature of semiconductor based small animal SPECT scanners is that the detector technology can be used both for gamma-ray imaging and for X-ray imaging, when coupling the SPECT scanner to a low resolution X-ray CT scanner for anatomical registration. The requirement of high spatial resolution, coupled to high sensitivity, becomes also stringent in microPET systems, where semiconductor detectors could be the technology of choice for future high performance PET scanners