Positron emission mammography

PEM is not recommended for routine use or for breast cancer screening, in part due to higher radiation dose compared to other modalities. Compared to breast MRI, PEM offers higher specificity. Specific indications can include "high-risk patients with masses > 2 cm or aggressive malignancy and serum tumor marker elevation". ¹⁸F-FDG is the most common radiopharmaceutical used for PEM.

Equipment

PEM uses a specialised scanning system. Though some systems resemble a small PET scanner with a ring of detectors, others consist of a pair of gamma radiation detectors placed above and below the breast. On these systems, mild breast compression is applied to spread the breast and reduce its thickness. The detection process is identical to standard PET scanners. Positrons emitted by the injected ¹⁸F-FDG annihilate on interaction with electrons in tissue, leading to the emission of a pair of photons travelling in opposite directions. The detection of two simultaneous photons indicates the emission of a positron at a point on the line linking the two detection events. An image is the reconstructed from the collected emission data.