Feasibility Study of Developing a Brain-Dedicated SPECT Scanner

Due to population aging, early diagnosis of neurodegenerative diseases have been noticed. To fulfill such clinical need, developing a hi-performance SPECT scanner for brain function imaging was raised. In this research, a practical scanner geometry was provided and the resolution performance of imaging detectors for composing the scanner was also studied. Consider the resolution and practicality, a cylindrical scanner design, with a detector ring of 48-cm diameter and a rotatable collimator cylinder of 32-cm diameter was chosen for further development. With 1-mm pinholes placing on the collimator cylinder, a FOV (field-of-view) of 21-cm diameter and 15-cm height, also a magnification factor of 0.48 are formed. In such design, the resolution is derived by the intrinsic resolution of imaging detectors. In the aspect of imaging detector unit, three different pixel size were studied. Three GAGG detector units with pixel size of 1.8, 1.5 and 1.2 mm were built and tested. The resultant 2D crystal maps and pixelated energy spectrum were examined to see how crystal pixels being resolved. The outward appearance of the detector unit showed that no peripheral dead space exhibits and thus allows 2D scalable to achieve the scanner building need. The 2D maps of the three detector units all showed successfully distinguished crystal arrays, therefore 1.3 mm resolution for the imaging detector can be achieved at current stage. It means the best scanner resolution at the FOV center of 2.88 mm is expected. In this study, a practical scanner geometry design is made, also its imaging detector unit is developed. Preliminary results show that the best resolution performance is better than 3 mm. Therefore the following task is to design the pinhole collimator pattern, trying to maximize the scanner sensitivity while keeping the resolution around 3 mm.