What is the primary use of a positron emission tomography (PET) scan?

The primary use of a positron emission tomography (PET) scan is to assess for myocardial ischemia and viability. PET scans utilize radioactive tracers to evaluate the metabolic processes in the heart muscle. By assessing how well blood flow reaches various areas of the heart, clinicians can determine if certain heart tissues are alive and functioning properly or if they have been damaged due to ischemia, which is a reduction in blood flow.

This technique is particularly valuable in evaluating patients who may have coronary artery disease, as it provides crucial information regarding the viability of the heart muscle, guiding treatment decisions. For example, if a PET scan shows that a portion of the heart is still viable despite poor blood flow, it may influence a clinician's approach to potential revascularization procedures, such as angioplasty or bypass surgery.

The other options present different diagnostic uses that don't accurately reflect the core function of a PET scan. Respiratory diseases and lung blood flow assessments are typically evaluated using other imaging modalities like CT or chest X-rays. Measuring heart rhythm abnormalities generally relies on electrocardiograms (ECGs) or Holter monitors, which are designed to capture electrical activity rather than metabolic processes.