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. Author manuscript; available in PMC: 2010 Oct 21.
Published in final edited form as: Nucl Instrum Methods Phys Res A. 2009 Oct 21;610(1):11–15. doi: 10.1016/j.nima.2009.05.032

Figure 1.

Figure 1

a) Diagram of a gamma camera used for SPECT, known as an Anger camera. Scintillation light from gamma ray interactions is detected by multiple photomultiplier tubes. The interaction position is determined by the ratio of the analog signals, and the energy by the analog sum of the signals. b) Diagram of a PET detector module. A block of scintillator crystal is sawed into 64 segments, each 6 mm × 6 mm × 30 mm deep. When a 511 keV photon interacts in any of the segments, the scintillation light is distributed across the back face of the BGO crystal, where it is simultaneously measured by four 1” square PMTs. The sum of the four output signals is used to derive both a timing signal and a signal proportional to the energy deposit. Anger logic (i.e. the ratio of the light observed in each of the four PMTs) is then used to determine the segment of interaction.