Lutetium oxyorthosilicate

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. 

A recently introduced detector, yttrium-activated lutetium oxyorthosilicate (LYSO), has the physical properties similar to LSO and has been used in PET scanners by a commercial vendor. 

Bushberg JT, Seibert JA, Leidholdt Sr EM, Boone JM (2002). The essential physics of medical imaging, 2nd ed. Lippincott, Williams and Wilkins, Philadelphia Chatziioannou AF, Cherry SR, Shao Y et al (1999). Performance evaluation of microPET a high-resolution lutetium oxyorthosilicate PET scanner for animal imaging. J Nucl Med 40 1164... 

Bartram RH, Hamilton DS, Kappers LA, Lempicki A, Glodo J, Schweitzer JS et al (1999) Electron traps and transfer efficiency in cerium-doped lutetium oxyorthosilicate sdntillatms. 

Differences between PET-CT systems apply to the number of detector rows with which the CT component is equipped. Currently, up to 64 detector rows have been integrated in PET-CT. For the PET component, different detector materials have been available. The three most common detector materials are bismuth ger-manate (BGO), lutetium oxyorthosilicate (LSO), and gadolinium oxyorthosilicate (GSO). All available PET-GT systems are equipped with a full-ring PET detector (360° coverage). The size of each detector crystal defines the spatial resolution of the tomograph, which may range from 2 to 5 mm. 

Melcher CL, Schweitzer IS. Cerium-doped lutetium oxyorthosilicate a fast, efficient new scintillator. IEEE Trans Nucl Sci 1992 39 502-505. 

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