How can PET scans help distinguish lung cancer from scar tissue?

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Medical illustration of the human chest showing the lungs, diaphragm, ribs, trachea, bronchus, and bronchioles, with one lung cut away to reveal internal structures. — respiratory disease The bronchioles of the lungs are the site where oxygen is exchanged for carbon dioxide during the process of respiration. Inflammation, infection, or obstruction of the bronchioles is often associated with acute or chronic respiratory disease, including bronchiectasis, pneumonia, and lung abscesses.

Positron emission tomography (PET) is a diagnostic imaging technique that functions by tracking the metabolic activity of tissues within the body.1

In the context of distinguishing lung cancer from scar tissue, PET scans are effective because they measure biochemical processes, such as glucose metabolism. Malignant cancer cells typically exhibit a significantly higher rate of glucose consumption compared to healthy tissue or inactive scar tissue. By injecting a radiopharmaceutical—often a glucose analog—into the patient, the PET scanner can detect areas of increased metabolic activity, which appear as "hot spots" on the resulting images.1

While scar tissue is generally metabolically inactive and shows low uptake of the radiotracer, cancerous lesions usually show high uptake, allowing clinicians to differentiate between the two. This capability makes PET a valuable tool for detecting cancer and monitoring the spread of the disease, known as metastasis.1