Myocardial SPET imaging with 99Tcm-tetrofosmin in clinical practice: comparison of a 1 day and a 2 day imaging protocol.

99Tcm-tetrofosmin is a new myocardial perfusion agent with the advantage that it can be reconstituted at room temperature. Because two separate injections are required for rest and stress images, a separate-day imaging protocol with one injection each day would be optimal in terms of image quality. From the logistical point of view, a 1 day protocol may be more convenient for the majority of those referred as outpatients. The main aim of this study was to determine whether the detection of myocardial ischaemia would be impeded by the use of a 1 day protocol instead of a 2 day protocol. A secondary aim was to establish the relative diagnostic accuracy of the two imaging strategies. 99Tcm-tetrofosmin SPET imaging was performed in 157 patients. Sixty-nine (44%) patients were administered 250 MBq (7 mCi) 99Tcm-tetrofosmin at rest followed 4 h later by 750 MBq (21 mCi) during stress (the 1 day protocol), whereas 88 (56%) patients had rest and stress imaging studies on two separate days, receiving a 500 MBq (14 mCi) dose of 99Tcm-tetrofosmin on each occasion (the 2 day protocol). With the 1 day protocol, 135 of 621 (22%) abnormal segments (i.e. both reversible and persistent defects) were observed, compared with 195 of 792 (25%) segments with the 2 day protocol. Also, the occurrence of reversible defects only did not differ between the two protocols (both 9%). The sensitivity for the detection of coronary artery disease was 83 and 90% for the 1 and 2 day protocols respectively. We conclude that the 1 and 2 day protocols provide similar scintigraphic information and are equally sensitive and specific for the detection of coronary artery disease. Therefore, the imaging protocol can be adjusted as appropriate for the patient in question.