Design of a variable field prototype PET camera

A prototype PET camera has been designed and is being constructed to test the concept, and develop the engineering design and production methodology for a variable field PET camera. The long term goal of the design is to develop a lower cost, high resolution PET camera. The camera has eight detector heads which form a closely packed octagon detector ring with an average diameter of 44 cm for brain/breast and animal model imaging. The heads can be translated radially to a maximum ring diameter of 70 cm for whole body imaging. In the larger diameter modes, the camera rotates 45/spl deg/ during imaging. The camera heads can be set to intermediate positions to fit the camera to the subject size to maximize detection sensitivity and sampling uniformity. Special design features for imaging the breast and the axillary metastases have been incorporated. The detector design implemented is the quadrant sharing photomultiplier (PMT) design using circular 19 mm PMT. The BGO detector pitch size is 2.7/spl times/2.7 mm. The prototype camera images 27 slices simultaneously with an axial field of view (FOV) of 39 mm. The prototype's limited axial FOV, which is appropriate for testing the camera concept, would be expanded in a next-generation clinical camera implementation. Preliminary simulation studies have been performed to evaluate the resolution, sensitivity, and sampling uniformity.