TABLE OF CONTENTS In recent years there has been a growing interest in developing compact gamma cameras to improve gamma ray imaging. Conventional full size gamma cameras using NaI(T1) scintillator block coupled to a bulky array of photomultiplier tubes are precluded from use in all applications where light weight, small size, easy handling and positioning is required. Furthermore the limit of the standard Anger camera is the poor intrinsic spatial and energy resolution. This has led to the design and testing of new gamma cameras which generally fall into three types:
semiconductor imagers (like Ge, CdTe or CdZnTe) in which the gamma rays interact directly in a position sensitive solid state detector [1], [2];
scintillation crystals coupled to an array of solid state photodetectors (photodiode) [3] [7];
scintillation crystals coupled to a Position Sensitive Photo-Multiplier Tube.
Other interesting detectors are currently under investigation, such as Avalanche PhotoDiode (APD) [8] and Silicon Drift Detector (SDD) [9], [10] but suitable detection area are not jet available.
The gamma cameras based on position sensitive photomultipliers could be the best chance to obtain a realistic and low cost compact gamma camera.
Over the last 15 years, starting from first generation PSPMT built by traditional PMT manufacturing, the technological enhancement allow to achieve very compact size (25 25 20 mm 3) by a novel charge multiplication system (see Fig. 9.1).
