The effect of energy window on cardiac ejection fraction.
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.
Bacharach
S L
SL
Nuclear Medicine Dept., National Institutes of Health, Bethesda, MD 20892.
Green
M V
MV
Bonow
R O
RO
Findley
S L
SL
Daube-Witherspoon
M E
ME
Larson
S M
SM
D004562:Electrocardiography; D004912:Erythrocytes; D006321:Heart / Q000000981:diagnostic imaging / Q000502:physiology*; D006801:Humans; D011877:Radionuclide Imaging; D013318:Stroke Volume; D013667:Technetium
D013667:Technetium