Factors Affecting Acquired PET Data

The projection data acquired in the form of sinograms are affected by a number of factors, namely variations in detector efficiencies between detector pairs, random coincidences, scattered coincidences, photon attenuation, dead time, and radial elongation. Each of these factors contributes to the sinogram to a varying degree depending on the 2D or 3D acquisition and needs to be corrected for prior to image reconstruction. These factors and their correction methods are described below. 

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Although PET/CT modality is widely employed for diagnostic purpose, CT data acquired either for fusion of PET and CT images or for photon attenuation correction are affected by several factors that cause artifacts in PET/CT images. The factors include patient positioning, metal objects, CT contrast agents, truncation artifacts, and respiratory movement, which are discussed below. 

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