Development Of A Prototype 3d Pet Scanner Using Semiconductor Detectors And Depth Of Interaction Information

A prototype brain positron emission tomography (PET) scanner using semiconductor detectors and depth of interaction (DOI) information has been developed to achieve high spatial resolution and reduced scatter fraction. At the first step of the development, we created a two-dimensional prototype PET scanner composed of a single-slice full-ring detector unit to confirm the feasibility of the basic technologies that are necessary to realize a semiconductor PET scanner. Through phantom and small-animal studies, the feasibility of the semiconductor PET was confirmed and the results showed that the semiconductor PET could produce quantitative imaging with high spatial resolution. Based on these achievements, a prototype brain PET scanner was developed to demonstrate the high spatial resolution and quantitative imaging capability required in human imaging.The prototype brain PET scanner has a patient port diameter of 350 mm and an axial field of view of 250 mm without interplane septa. It consists of 18 detector units arranged around the patient port. Each detector unit has 22 detector boards arranged along an axial field of view. The detector board has cadmium telluride (CdTe) detectors on each side. Signals are read by three-layer DOI. The total number of detector channels is about 80 000, and signals from each detector are processed with "individual channel readout" technology. Physical performance indicators, such as spatial resolution, sensitivity, and noise equivalent count rates (NECRS) were measured with National Electrical Manufacturers Association (NEMA) standards.The transverse and axial resolutions near the center are 2.3 mm and 5.1 mm, respectively. The absolute sensitivity and the scatter fraction of the scanner evaluated with the NEMA NU2-1994 phantom are 650 kcps/mu Ci/cc and 23%, respectively. These estimates are for a lower energy threshold of 450 keV. The NECR is 41 kcps at 0.2 mu Ci/cc.These results show that the PET scanner based on semiconductor detectors is feasible for clinical use, with high spatial resolution, and with good potential for providing the high spatial resolution and quantitative imaging capability required in the brain and the head-and-neck region.