Positron Emission Tomography (PET)

Positron Emission Tomography (PET) is a medical imaging technique that shows how tissues are functioning, rather than just their structure.

The patient is injected with a radioactive tracer, most commonly FDG (a form of glucose), which builds up in areas with high metabolic activity, like many cancers. The tracer emits positrons, and the scanner detects the resulting gamma rays to build a 3D image. It's often combined with a CT scan (PET/CT).

For breast cancer, it's mostly used for staging and checking whether cancer has spread, rather than for screening. See also Mammography and Magnetic Resonance Imaging (MRI).