SINGLE-PHOTON EMISSION IMAGING BY POSITION-SENSITIVE PMT

Position Sensitive Photo Multiplier Tube (PSPMT) represents a strong t echnological improvement for Nuclear Medicine imaging. Over the: last 10 years Hamamatsu has developed a number of PSPMTs with different sha pes and sizes, from 1 in. square up to more recent prototype of 8 in. diameter. The position is continuously detected by centroid method and spatial resolution represents its statistical uncertainty. By couplin g PSPMTs to scintillating arrays it was possible to push PMTs near the ir intrinsic limit. A number of scintillating crystals arranged in a m atrix were tested such as: YAP:Ce, NaI(Tl), CsI(TI) and CsI(Na) with d ifferent pixel size (from 0.3 x 0.3 mm(2) to 2 x 2 mm(2)) with overall dimension from 4 x 4 cm(2) up to 11 cm diameter. A number of applicat ions in Nuclear Medicine were performed, such as miniature gamma camer as for radiopharmaceutical investigations on little animals where sub- millimeter spatial resolution values were carried out. More recently, the first prototype of dedicated gamma camera for scintimammography ha s been developed for small cancer detection in the breast. (C) 1998 El sevier Science B.V, All rights reserved.