Cardiac stress-rest single-photon emission computed tomography with technetium 99m-labeled tetrofosmin: influence of washout kinetics on regional myocardial uptake values of the rest study with a 1-day protocol.
BACKGROUND
The purpose of this study was to evaluate (1) the washout kinetics of 99mTc-labeled tetrofosmin, separately for myocardium with normal and reduced perfusion, and (2) its influence on quantitative analysis in a 1-day stress-rest protocol.


RESULTS
Twenty-five patients with angiographically proved coronary artery disease underwent bicycle exercise stress testing with injection of 200 MBq 99mTc-labeled tetrofosmin and first single-photon emission computed tomographic (SPECT) imaging 40 minutes after injection. A second SPECT was acquired 2.3 +/- 0.4 hours after the first one immediately before rest injection of 800 MBq 99mTc-labeled tetrofosmin. The rest (third) SPECT was acquired 15 minutes thereafter. The relative washout fraction per time (WOFt) was calculated assuming linear washout kinetics. Thirty-three regional uptake values per study were calculated, normalized to the perfusion maximum (100%) in either the postexercise SPECT and the rest SPECT, for the latter with and without correction of remaining counts from stress injection. In regions with normal perfusion, WOFt was 11.5% +/- 3.5% per hour. In regions with markedly reduced perfusion (relative uptake < 50%, WOFt was 8.3% +/- 9.9% per hour. The highest variation of the relative uptake values between rest SPECT with and without correction of remaining counts from stress injection was 5.4% +/- 3.5% in regions with stress-induced ischemia.


CONCLUSIONS
To use a 1-day protocol with a stress-rest radioactivity ratio of 1:4 and an interval of more than 2 hours between the examinations, a correction for remaining counts from stress injection seems not to be necessary for the quantitative analysis of rest SPECT.
Schulz
G
G
Department of Nuclear Medicine, Aachen University of Technology, Germany.
Ostwald
E
E
Kaiser
H J
HJ
vom Dahl
J
J
Kleinhans
E
E
Buell
U
U
D000328:Adult; D000368:Aged; D003327:Coronary Disease / Q000000981:diagnostic imaging*; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; D015899:Tomography, Emission-Computed, Single-Photon
D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; C078700:technetium tc-99m tetrofosmin