Journal of Nuclear Medicine Technology, Vol 26, Issue 3 186-190, Copyright © 1998 by Society of Nuclear Medicine
Effect of time on liver clearance of technetium-99m-tetrofosmin in patients with acute chest pain: when should imaging begin?
A Mann, AW Ahlberg, MP White, DM Cross, J Piriz, RS Morris and GV Heller
Nuclear Cardiology Laboratory, Hartford Hospital, CT 06102, USA.
OBJECTIVE: Due to stable myocardial retention and technetium imaging
characteristics, 99mTc-tetrofosmin has been considered potentially useful
for acute chest pain imaging. Tetrofosmin also has favorable biokinetics
with reported rapid liver clearance, 5 min poststress and 30-45 min
post-rest injection. Since comparable data are not available, the effect of
time on liver clearance was evaluated in patients with acute chest pain.
METHODS: One hundred six patients received an intravenous injection of
25-30 mCi 99mTc-tetrofosmin to evaluate acute chest pain. SPECT imaging was
performed 15-120 min after injection of the tracer. Patient images were
grouped according to the time of acquisition after acute injection: 15-30
min, 31-45 min, 46-60 min, 61-90 min and > 90 min. Quantitative analysis
was performed of a similar anterior projection for each patient consisting
of 6 X 6-pixel region of interest over the myocardium and adjacent liver.
Average counts per pixel were determined and a heart/liver (H/Li) ratio was
calculated. RESULTS: The mean H/Li ratio was < 1.0 for patient images
acquired 15-45 min after injection, and > 1.0 for patient images
acquired after 45 min. The difference was statistically significant (p <
0.05). CONCLUSION: Quantitative analysis suggests that the optimal imaging
time should be at least 45 min after the injection of 99mTc-tetrofosmin to
allow adequate liver clearance before image acquisition of acute chest pain
syndromes.
