TC-99M TETROFOSMIN MYOCARDIAL DISTRIBUTION 4 HOURS POST INJECTION

The recommended protocol for Tc99m tetrofosmin myocardial imaging sugg ests either a one- or two day imaging protocol so that stress and rest studies are sufficiently separated in time to allow optimum myocardiu m to background uptake ratios to differentiate between myocardial isch aemia and/or infarction. The biokinetic data for tetrofosmin suggest t hat no significant changes occur in myocardial distribution up to 180 minutes post injection. It is, therefore, necessary for two doses of t he radiopharmaceutical and two separate studies to evaluate the myocar dial status during stress and rest. This study assessed the difference s between the 1 and 4 hour post injection SPET images obtained followi ng peak exercise in 20 consecutively chosen patients. In addition, the se images were compared to the rest images obtained on the following d ay after a second dose of the radiopharmaceutical was administered. In 4 patients, a one and four hour post injection study was also done du ring the rest phase. The results demonstrate significant changes in Tc -99m tetrofosmin distribution between the one hour and four hour post injection images. These differences are present during the stress as w ell as rest studies.