Count-rate dependent event mispositioning and NEC in PET

R. D. Badawi, P. Domigan, O. Johnson, B. Kemp, H. Kudrolli, T. Rempel, R. Rohatgi, L. V. Romanov, S. Surti, W. A. Worstell, R. E. Zimmerman

Research output: Contribution to conferencePaperpeer-review

5 Scopus citations


Most current PET detector designs suffer from event mispositioning at high count rates, as scintillation light from nearby and nearly simultaneous gamma ray conversions becomes mixed. We have used the NEMA NU 2-2001 70 cm test phantom and a Na-22 point source to quantify this effect as a function of activity on two block-detector tomographs (the Siemens/CTI HR+ and the General Electric Discovery LS), and two Anger-type PET tomographs (the Siemens ECAM DUET and the Philips CPET+). After accounting for event losses due to dead time, we find that the number of counts on LORs passing through a cylinder of diameter and height equal to the point-source full width at tenth-maximum measured at low rate surrounding the point source decreases by between 9% (HR+) and 35% (CPET+) at the activity giving rise to peak Noise Equivalent Count (NEC) rate. Mispositioned events act to reduce signal-to-noise ratio, both by reducing apparent activity at the originating location and by increasing the signal background. We have reformulated the conventional expression for NEC rate to account for this phenomenon. The new formulation of NEC, which we call NEC*, results in a lower peak value which in turn occurs at a lower activity concentration than for the conventional formulation.

Original languageEnglish (US)
Number of pages6
StatePublished - Dec 1 2002
Event2002 IEEE Nuclear Science Symposium Conference Record - Norfolk, VA, United States
Duration: Nov 10 2002Nov 16 2002


Other2002 IEEE Nuclear Science Symposium Conference Record
Country/TerritoryUnited States
CityNorfolk, VA

ASJC Scopus subject areas

  • Computer Vision and Pattern Recognition
  • Industrial and Manufacturing Engineering


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