title: Comparison of gating methods for the real-time analysis of left ventricular function in nonimaging blood pool studies.
abstract: BACKGROUND
  Gating methods developed for electrocardiographic-triggered radionuclide ventriculography are being used with nonimaging detectors. These methods have not been compared on the basis of their real-time performance or suitability for determination of load-independent indexes of left ventricular function. This work evaluated the relative merits of different gating methods for nonimaging radionuclude ventriculographic studies, with particular emphasis on their suitability for real-time measurements and the determination of pressure-volume loops.
  
  
  RESULTS
  A computer model was used to investigate the relative accuracy of forward gating, backward gating, and phase-mode gating. The durations of simulated left ventricular time-activity curves were randomly varied. Three acquisition parameters were considered: frame rate, acceptance window, and sample size. Twenty-five studies were performed for each combination of acquisition parameters. Hemodynamic and shape parameters from each study were compared with reference parameters derived directly from the random time-activity curves. Backward gating produced the largest errors under all conditions. For both forward gating and phase-mode gating, ejection fraction was underestimated and time to end systole and normalized peak ejection rate were overestimated. For the hemodynamic parameters, forward gating was marginally superior to phase-mode gating. The mean difference in errors between forward and phase-mode gating was 1.47% (SD 2.78%). However, for root mean square shape error, forward gating was several times worse in every case and seven times worse than phase-mode gating on average.
  
  
  CONCLUSIONS
  Both forward and phase-mode gating are suitable for real-time hemodynamic measurements by nonimaging techniques. The small statistical difference between the methods is not clinically significant. The true shape of the time-activity curve is maintained most accurately by phase-mode gating.
authors.affiliation: Department of Biomedical Engineering, School of Medicine, Vanderbilt University, Nashville, Tenn., USA. bbb@vuse.vanderbilt.edu
authors.forename: B B
authors.initials: BB
authors.lastname: Beard
authors.forename: J R
authors.initials: JR
authors.lastname: Stewart
authors.forename: R G
authors.initials: RG
authors.lastname: Shiavi
authors.forename: C H
authors.initials: CH
authors.lastname: Lorenz
mesh_terms: D003198:Computer Simulation; D015637:Gated Blood-Pool Imaging; D006439:Hemodynamics; D006801:Humans; D016277:Ventricular Function, Left