Positron Emission Tomographic Imaging of the Myocardium with 81Rb

An approach to the assessment of regional myocardial perfusion has been developed utilizing positron emission tomographic imaging of the heart after intravenous administration of 81Rb (T1/2=4.6 hr) and a multicrystal positron camera. In five intact anesthetized dogs, 1.0 to 2.0 mCi of 81 RbCl was administered and imaging begun 5 min later. A total of 7 to 9 transverse section images of the heart (1 cm thick) were obtained by the computer reconstruction of 208 images taken at uniformly spaced angles as the camera was rotated 180 degrees around the animal. Collection time was 18 min. Emission images of 81Rb activity were corrected for attenuation by first obtaining transmission data using a planar positron-emitting source. Transverse section images through the apex of the heart showed uniform uptake of 81Rb+ activity below the left ventricular (LV) cavity. Tomographic images through the midventricular level showed myocardial 81Rb+ distribution in an annular pattern around the LV cavity, and tomographic cuts through the base of the heart showed a horseshoe appearance of activity anteriorly and diminished tracer uptake posteriorly in the region of the left atrial wall. These studies demonstrate the feasibility of three-dimensional myocardial imaging by using the 33% positron emission of 81Rb+ and a positron camera.