DEDICATED BREAST PET (POSITRON EMISSION MAMMOGRAPHY, PEM):
What is it? Breast PET uses an injection of a short-lived radioactive sugar (18FDG) into the body to detect metabolically active lesions such as cancer.
How it works: The radioactive sugar accumulates in the cancerous tissue in the breast and emits high-energy positron radiation that is detected and analyzed. For one such system, the breast is gently stabilized with positioning otherwise like mammography. (Figure 17)
Figure 17. Dedicated breast PET (PEM)
Imaging takes 10 minutes per view (total of 40 minutes for a standard 4-view examination) and usually starts at least one hour after injection of the radiotracer. Twelve “slice” images are reconstructed from each view (Fig. 18). The patient must be fasting for 4-6 hours prior to the test.
Figure. 18. Digital Mammogram and breast PET images of ductal carcinoma in situ (DCIS). Vague asymmetry (arrow, left image) is seen on the MLO (an image taken from a side angle) mammogram of this 48-year-old woman with heterogeneously dense breasts. Stereotactic biopsy showed DCIS (early breast cancer). Breast PET was performed one hour after i.v. injection of 10 mCi 18F-fluorodeoxyglucose (FDG), showing more extensive disease than was suspected on the mammogram with segmental uptake of the radiotracer on CC (middle) and MLO (right) breast PET 6-mm thick slice images (arrows).
Benefits: Breast PET is generally considered a diagnostic tool used to determine the extent of cancer once it is found, or to assess for possible recurrence of cancer vs. scar. In women with newly diagnosed breast cancer being treated with chemotherapy prior to surgery, breast PET can help monitor response to treatment. It can be utilized for patients who are unable to have breast MRI. It is a relatively new modality and not widely available.
Considerations: Breast PET exposes the patient to a moderately high whole body radiation dose and is not used for screening.