title: Optimizing imaging time for improved performance in oncology PET studies.
abstract: OBJECTIVE
  The potential for improving the diagnostic performance of static positron imaging tomography (PET) by judiciously choosing optimum post-injection imaging times is investigated.
  
  
  METHODS
  Dynamic and whole-body scan data, from 2-deoxy-2-[18F]fluoro-D-glucose (FDG) oncological studies, are analyzed for changing standardized uptake value (SUV) behavior with increasing post-injection times at either single- or multiple-bed positions. Model-based interpretations address d(SUV)/dt, shown to correlate with SUV, and the contrast ratio for a tumor and its surroundings. A method for correcting measurements to a standardized time is given.
  
  
  RESULTS
  Both data and model-based equations suggest that starting data acquisition later than the average 55 +/- 15 (SD) minutes post-injection reported in the FDG literature can improve contrast ratios. Considerations for choosing an optimum time from a clinical standpoint are listed.
  
  
  CONCLUSIONS
  It is concluded that the appropriate time for each particular protocol can be found with the aid of the information presented here. True optimization, however, remains a complex issue.
authors.affiliation: Biomedical Imaging Center, Department of Radiology, The University of Tennessee Medical Center at Knoxville, Knoxville, TN, USA.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Thie
authors.forename: Karl F
authors.initials: KF
authors.lastname: Hubner
authors.forename: Gary T
authors.initials: GT
authors.lastname: Smith