COMPARISON OF THALLIUM SCINTIGRAPHY AND POSITRON-EMISSION-TOMOGRAPHY

Assessment of tissue viability has become an important issue in recent years. Scintigraphic measurements have provided important diagnostic, therapeutic, and prognostic information in patients with myocardial d ysfunction, who may improve in left ventricular function after revascu larization. For detection of regional myocardial ischemia and viabilit y, thallium 201 (Tl-201) has been the most widely used tracer in singl e-photon scintigraphy. However, Tl-201 scintigraphy may underestimate regional viability, especially after myocardial infarction. Positron e mission tomography (PET) provides an advanced imaging technology that permits the accurate definition of regional tracer distribution. In co mbination with nitrogen (N-13) ammonia, PET allows for the sensitive a nd specific detection of coronary artery disease. Several studies indi cate the superiority of this approach in comparison with standard Tl-2 01 tomographic (SPECT) imaging. In addition, regional blood flow can b e accurately measured with N-13 ammonia PET, and this approach can be employed in conjunction with pharmacologic stress imaging to quantify regional flow reserve. In combination with metabolic markers, such as fluorine 18 (F-18) deoxyglucose, an indicator of glucose uptake, PET i s capable of assessing myocardial viability. Furthermore, the PET appr oach may differentiate between various forms of cardiomyopathy. More s tudies are needed to define the cost-benefit ratio of both the Tl-201 reinjection and the PET technique for the management of patients with coronary artery disease or cardiomyopathy.