SINGLE-PHOTON EMISSION TOMOGRAPHY STUDIES OF RB-81 IN THE DETECTION OF ISCHEMIC-HEART-DISEASE, USING A STRESS-REINJECTION PROTOCOL

The present study was designed to determine the feasibility of using s ingle-photon emission tomography (SPET) imaging with rubidium-81 (T-1/ 2 = 4.54 h) to detect ischaemic heart disease, using a stress-reinject ion protocol and a specially constructed 511-keV hexagonal hole collim ator for a standard gamma camera. The diagnostic performance of Rb-81 SPET in detecting coronary artery disease (CAD) was investigated in 52 patients with a high prevalence of CAD. Coronary arteriography was pe rformed in 34 patients, 25 of whom were classified as having significa nt stenosis (greater than or equal to 50%). At peak exercise (Cornell protocol), 111-222 MBq Rb-81 was injected i.v. for stress imaging, and after 3 h of rest, 74-111 MBq was reinjected for rest imaging. The di splayed short- and long-axis slices and the polar map images were inte rpreted qualitatively. In comparison to coronary arteriography, which served as the gold standard, the performance of Rb-81 SPET revealed a sensitivity of 95% for the detection of CAD, Images of diagnostic qual ity were obtained in all patients, these being comparable to thallium- 201 SPET images. In conclusion, these results indicate that the descri bed method can be routinely used for the positron emitter Rb-81 with a conventional gamma camera and special shielding. Rb-81 has the well-k nown advantages of a potassium analogue and Rb-81 SPET permits better visualization, particularly of the posterior wall of the myocardium, d ue to the higher photon energy. Considering the typical dose of (201)T 1 used for SPET (74-148 MBq), a Rb-81 SPET Scan imposes a significantl y lower radiation burden on the patient.