The PET components mounted on the rear of the support are those of a standard Siemens ECAT® ART scanner  comprising dual arrays of bismuth ger-manate (BGO) block detectors. Each array consists of 11 blocks (transverse) by 3 blocks (axial); the blocks are 54 mm x 54 mm x 20 mm in size, cut into 8 x 8 crystals each of dimension 6.75 mm x 6.75 mm x 20 mm. The transverse field-of-view (FOV) is 60 cm and the axial FOV is 16.2 cm, subdivided into 24 (partial) rings of detectors for a plane spacing of 3.375 mm. Shielding from out-of-field activity is provided by arcs of lead, 2.5 cm thick, mounted on both sides of the detector assembly and projecting 8.5 cm into the FOV beyond the front face of the detectors. The PET scanner has no septa and the detector arrays rotate continuously at 30 rpm to collect the full set of projections required for image reconstruction. Power and serial communications to the rotating assembly are transmitted over mechanical slip rings, while high speed digital data transfer is by optical transmission.
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