Investigation of the block effect in positron emission tomography

Sara St James, Christopher J. Thompson, Nada Tomic, Brad Kemp

Research output: Contribution to journalConference articlepeer-review


Spatial resolution in PET depends on a number of factors. Among these is the block effect, which has been introduced to account for the degradation in spatial resolution observed in imaging systems which use block detectors and which is not observed in systems with one-to-one coupling of scintillation crystals to photomultiplier tubes. The origin of the block effect is not well understood. We present a comparison of the block effect for two commercially available block detectors: CTI HR+ and GE Advance. We find that the block effect contributes 1.2 mm and 1.3 mm, added in quadrature to the spatial resolution, for the CTI HR+ and GE Advance detectors respectively. Both of these values are considerably lower than the value of 2 nun cited in the literature. We also perform a study of the effect of multiple interactions of gamma rays within the crystal array, which is one factor which is thought to contribute to the block effect We find only a marginal change in the spatial resolution when multiple photon interactions are minimized. Finally we study the effect of contributions to the summed image from events at different crystal depths and show that the event location depends on the depth of interaction.

Original languageEnglish (US)
Article numberM9-31
Pages (from-to)3370-3374
Number of pages5
JournalIEEE Nuclear Science Symposium Conference Record
StatePublished - Dec 1 2004
Event2004 Nuclear Science Symposium, Medical Imaging Conference, Symposium on Nuclear Power Systems and the 14th International Workshop on Room Temperature Semiconductor X- and Gamma- Ray Detectors - Rome, Italy
Duration: Oct 16 2004Oct 22 2004

ASJC Scopus subject areas

  • Radiation
  • Nuclear and High Energy Physics
  • Radiology Nuclear Medicine and imaging


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