D and 3D PET Data Acquisition

Most state-of-the-art full-ring PET scanners can be operated in both 2D and 3D data collection modes whereas newer tomographs operate essentially in fully 3D acquisition geometries. In the 2D mode, PET scanners have septa between detector planes to limit the detection of scattered photons, improve count rate performance and reduce random coincidence events. The use of septa also simplifies the tomographic algorithm needed to reconstruct the data by requiring a technique that needs to account only for lines of response that are contained within one or a few slices in a 2D geometry, rather than in multiple slices as is needed for a 3D geometry. Figure 8 illustrates the conceptual difference between conventional 2D acquisition and volume data acquisition. In 2D PET, data acquisition is limited to coincidences detected within the same detector or adjacent detector rings: each 2D transverse section of the tracer distribution is reconstructed independently of adjacent sections. With the information obtained from detectors belonging to the same detector ring, images representing the tracer distribution in the planes of the detector rings (direct planes) are obtained. With the information obtained from detectors belonging to adjacent detector rings, we reconstruct

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