Myocardial scintigraphy and reconstructive tomography positron imaging using nitrogen-13 labelled ammonia

In this paper the use of a short half-life (9.95 minute) positron emitter nitrogen-13 is reviewed. Labelled ammonia (13NH4+) is a cold spot myocardial nuclide that can be imaged using a standard gamma camera. More recently a novel form of positron imaging has been developed to obtain back projection tomographic myocardial images, anatomical localization of uptake defects and to quantitate the information collected. The studies reported here have shown that high-quality, high-count density myocardial scintigrams can be obtained in man using intravenous nitrogen-13 ammonia and a mobile scintillation camera array, the configuration of which is described. This method is reliable and safe even in very ill patients for the detection of myocardial uptake defects. It is especially useful when serial myocardial imaging at short intervals is needed. The motion and 3-dimensional geometry of the heart limit the accuracy of conventional imaging techniques in defining uptake defects anatomically, but positron imaging using a double gamma camera system suitably modified and the development of computer algorithms provides back projection longitudinal tomograms in the coronal plane which largely overcome the geometric and technological problems of routine gamma camera myocardial scintigraphy. The new method furthermore, is capable of quantifying the information obtained and of providing an accurate anatomical assessment of position and extent of myocardial uptake defects. (Auth.)