title: The effect of energy window on cardiac ejection fraction.
abstract: ECG gated gamma-ray energy spectra from the left ventricle were created each 50 msec during the cardiac cycle. Nine of ten subjects were studied with a nonimaging Nal probe, and the tenth with a high-resolution Germanium detector. Placing multiple energy windows over the energy spectra, EF was found to vary with the energy window selected. Moving a 20% window across the photopeak produced a roughly linear increase in EF with energy (2.3 EF units per 10 keV increase in energy) in eight of the ten subjects. Dividing the photopeak into a low (126-140 keV) and high-energy (140-154 keV) portion gave significantly different EFs (high energy exceeding low energy by 17%). Increasing the width of a narrow window centered about the photopeak produced negligible change in EF. Examining the energy spectra showed that the small-angle scattered radiation (126-139 keV) was proportionately greater at end systole than at end diastole, after normalizing the spectra to the same photopeak area.
authors.affiliation: Nuclear Medicine Dept., National Institutes of Health, Bethesda, MD 20892.
authors.forename: S L
authors.initials: SL
authors.lastname: Bacharach
authors.forename: M V
authors.initials: MV
authors.lastname: Green
authors.forename: R O
authors.initials: RO
authors.lastname: Bonow
authors.forename: S L
authors.initials: SL
authors.lastname: Findley
authors.forename: M E
authors.initials: ME
authors.lastname: Daube-Witherspoon
authors.forename: S M
authors.initials: SM
authors.lastname: Larson
mesh_terms: D004562:Electrocardiography; D004912:Erythrocytes; D006321:Heart / Q000000981:diagnostic imaging / Q000502:physiology*; D006801:Humans; D011877:Radionuclide Imaging; D013318:Stroke Volume; D013667:Technetium
chemical_list: D013667:Technetium