Solid Scintillation Detectors in PET

Basics of PET Imaging Physics, Chemistry, and Regulations, 19 

Although many scintillation detectors have been investigated, only a few have been widely used in PET technology. The characteristics of different detectors that have application in PET technology are listed in Table 2.1. The choice of a detector is based on several characteristics, namely  

The stopping power of the detector determines the mean distance the photon travels until complete deposition of its energy and depends on the density and effective atomic number (ZeU) of the detector material. The scintillation 

The detection efficiency of a detector is another important property in PET technology. Since it is desirable to have shorter scan times and low tracer activity for administration, the detector must detect as many of the emitted photons as possible. The 511-keV photons interact with detector material by either photoelectric absorption or Compton scattering, as discussed in Chap. 1. Thus, the photons are attenuated (absorbed and scattered) by these two processes in the detector, and the fraction of incident 7 rays that are attenuated is determined by the linear attenuation coefficient (/x) given in Chap. 1 and gives the detection efficiency. At 511 keV, /x = 0.92 cm-1 for bismuth germanate (BGO), 0.87 cur1 for lutetium oxyorthosilicate (LSO), and 0.34 cm-1 for Nal(Tl) (Melcher, 2000). Consequently, to have similar detection efficiency, Nal(Tl) detectors must be more than twice as thick as BGO and LSO detectors. 

BGO detectors are used in most of the PET systems because of its highest stopping power (highest density and linear attenuation coefficient). However, it suffers from its longer scintillation decay time 0-300 ns) and poor light output. The longer decay time increases the dead time of the detector and limits 

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