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1. Each scintillator block is coupled to 4 photomultipliers which convert the emitted light into electrical charge.

2. The NAI scintillation crystal used in SPECT and planar imaging not suitable for PET as Linear Attenuation Coefficient (LAC) is not enough for the annihilation photons which have a higher energy of 511 keV.

3. Most commonly used scintillator in PET imaging is bismuth germanate (BGO). But the light output and light decay time are inferior to NaI.

4. Detectors can be separated by thin lead septae to reduce cross talk between them.

5. These are retractable on some scanners.

6. Retracting the septae increases sensitivity but also increases the number of false coincidences.


1. Bushberg, J. T. (2012). The essential physics of medical imaging. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins. Find it at Amazon
2. Heggie, J. C., Liddell, N. A., & Maher, K. P. (1997). Applied imaging technology. Melbourne: St. Vincents Hospital.

Ⓒ A. Manickam 2018

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