PET-CT

PET-CT fuses two scans into one. The CT half supplies a detailed anatomical map — where everything is — while the PET half adds a functional layer showing how active the tissue is. Before the scan the patient is given a small dose of radioactive sugar (FDG). Because hungry, fast-growing cells gobble up glucose, the tracer pools in metabolically busy spots, which the PET camera detects and the computer overlays onto the CT picture.

In lung cancer this combination is powerful for staging — working out how far a cancer has spread. A primary tumour usually lights up brightly, and so do involved lymph nodes and distant metastases that look unremarkable on size alone. A single scan from skull base to thighs can therefore reveal disease in lymph nodes, bones, adrenal glands or elsewhere that would change whether surgery is appropriate.

PET is informative but not perfect. Inflammation and infection also consume glucose and can light up falsely (false positives), while slow-growing or very small tumours may take up little tracer (false negatives). For this reason a suspicious PET finding that would change treatment — particularly mediastinal lymph nodes — is often confirmed by tissue sampling rather than acted on from the image alone.