Motion compensation in histogram-mode and list-mode EM reconstructions: Beyond the event-driven approach

Arman Rahmim, Peter Bloomfield, Sylvain Houle, Mark Lenox, Christian Michel, Kenneth R. Buckley, Thomas J. Ruth, Vesna Sossi

Research output: Contribution to journalArticlepeer-review

100 Scopus citations


With continuous improvements in spatial resolution of positron emission tomography (PET) scanners, small patient movements during PET imaging become a significant source of resolution degradation. This work explores incorporation of motion information into expectation-maximization (EM) reconstruction algorithms. An important issue addressed is the existence of lines-of-response (LORs) corresponding to no actual pairs of detectors and their motion-induced "interaction" with the detectable LORs. An example of this is a scanner design with gaps existing in between the detector beads. It is shown that to properly account for such LORs in histogram-mode and list-mode EM reconstructions, in addition to motion correction of the events, the algorithms themselves must be modified. This modification is implemented by including motion-compensated sensitivity correction factors. We are able to demonstrate experimentally that the proposed approach resolves image artifacts that can appear when the conventional purely event-driven motion correction technique is used. An alternate image-space-based method for calculation of motion-compensated sensitivity factors is also derived, applicable in both histogram-mode and list-mode reconstruction tasks, which has the potential of being considerably faster in presence of frequent motion, especially in high-resolution tomographs.

Original languageEnglish (US)
Pages (from-to)2588-2596
Number of pages9
JournalIEEE Transactions on Nuclear Science
Issue number5 II
StatePublished - Oct 2004
Externally publishedYes


  • Expectation-maximization (EM) algorithm
  • Histogram-mode
  • List-mode
  • Motion compensation
  • Positron emission tomography (PET) reconstruction

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Nuclear Energy and Engineering
  • Electrical and Electronic Engineering


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