A laboratory PET scanner with silicon detectors segmented to 1 mm3 detection cells

A high resolution PET detectors are useful in imaging small animals and certain types of human cancer. In the presented approach, high-resolution can be achieved by using finely segmented silicon sensors to record impact position of one or both photons from the annihilation pair. As the high-resolution detector is expected to capture a relatively small portion of emitted radiation, a combination of the high-resolution device with a standard PET scanner is envisaged. In this way a standard PET image can be locally improved in areas where there is a substantial probability that at least one of the photon pair will interact in a high-resolution detector. A setup to test the approach was built at University of Michigan, offering possibilities to test a variety of high-resolution detectors. Previously, tests with silicon detectors segmented to square pads with 1.4 mm side were performed, demonstrating radical improvement in system resolution in combined detector operation relative to the standard ring only. The performance prediction shows resolution gain for even finer segmented detectors. This motivated a replacement of 1.4 mm segmented detectors with 1 mm segmented detectors. A detector module is built of a pair of 1 mm thick silicon sensors measuring 40 by 26 mm² segmented to 1040 independent pads each. The module is read out by a set of 16 VATAGP7 ASICs made by IDEAS. A pair of modules were placed in an edge-on geometry to image a single, lead collimator compressed slice of a high-resolution Derenzo phantom (rod diameters of 1.2 mm to 4.8 mm) filled with ¹⁸F-FDG. The performance of the combined device matched the predicted performance.