A high-throughput whole-body PET scanner using flat panel PS-PMTs

A new positron emission tomography (PET) scanner for whole-body studies has been developed. The scanner has 720 block detectors, each of which consists of a flat panel position-sensitive photomultiplier and a 16×8 BGO crystal array. The detector system is composed of 12 layers of block detector rings stacked axially, and each ring consists of a circular array of 60 block detectors. Since each block detector ring contains 8 crystal rings, the total number of detector rings is 96 and the axial field of view (FOV) is 685 mm, which is sufficient to measure a whole-body with two steps of scan. The detector ring diameter is 1,020 mm and the transaxial FOV is 600 mm in diameter. Coarse slice septa are placed between the block detector rings, which are effective to reduce scattered coincidence events while keeping a high detection sensitivity. Parallel 16 personal computers are used for the data acquisition and processing to deal with a large amount of event data. The acquired data in 3D manner are converted to 2D data set with Fourier rebinning algorithm and reconstructed with a fast iterative algorithm "DRAMA". The reconstructed images for the whole body are obtained within 5 min after the scan. By using the coarse septa, the scatter fraction measured with NEMA NU2-2001 standard was 31.4% whose value was significantly lower than that of 3D PET without septa. The system sensitivity was 9.72 cps/kBq, and the peak counts of the noise equivalent count rate used with direct random-subtraction was 113.6 kcps at 10.5 kBq/ml.