As new radiopharmaceutical tracers are becoming available for cerebral perfusion and receptor systems in the brain, single photon emission computed tomography (SPECT) promises to have many potential applications in psychiatry. In schizophrenia research, much work is needed in the testing of specific hypotheses about regional abnormalities in cross-correlating findings from anatomic (CT, MRI) and functional (PET, SPECT) imaging techniques. However, the current SPECT imaging systems do not have adequate performance for this type of work. We have recently designed a high performance SPECT system for functional imaging of the brain and are currently evaluating the feasibility of this approach and the potential to achieve our theoretically estimated imaging performance. However, this design is for single slice imaging only. Since each SPECT imaging procedure takes a long time to acquire, multislice imaging capability to reduce imaging time is essential to any practical clinical SPECT system. The current direction in SPECT design holds that the most desirable form of multislice imaging is continuous sampling along the axial direction for volume imaging. This continuous volume sampling may provide multiple slices simultaneously over the brain and also allow the selection of the slices' position flexibly through reconstruction software. To extend our proposed single slice ring SPECT system to the third dimension, we can replace the individual small crystal detector with a position sensitive bar detector with its long axis oriented in the 3rd dimension to obtain information in the axial (Z) direction. Due to cost considerations and the small width of the bar detector, we propose that photomultiplier tubes (PMTs) be shared among several adjacent bar detectors. Conventional Anger position logic or similar digital position sensing schemes can be adapted to derive the energy and position signals. This proposed pilot study is to determine the feasibility of using small bar detectors and medium-size PMTs, arranged in a special pattern and shared by multiple bar detectors, to provide adequate energy and position signal for SPECT volume imaging of the brain.
