Positron emission tomography has the ability to measure chemical changes that occur in the body as a result of many disease processes. The most widely used application of PET in heart patients involves the analysis and location of heart muscle viability. Analysis of the viability of the muscle tissue is very important information when a doctor is in the process of determining the best treatment for a patient with heart muscle damage, after a heart attack. Attempting to increase blood circulation (via angioplasty or bypass surgery) to a portion of the heart muscle that is dead (not viable) is useless. PET therefore provides the information necessary to determine which areas of the heart muscle would benefit from this type of intervention.