What is the role of breast-specific gamma imaging (BSGI) and positron emission mammography (PEM) in breast cancer imaging?

Updated: Oct 17, 2016
  • Author: Nagwa Dongola, MD, FRCR; Chief Editor: Peter Eby, MD  more...
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Answer

Currently, there are 2 types of nuclear-based imaging for the breast that are FDA approved and used in clinical practice: breast-specific gamma imaging (BSGI) and positron emission mammography (PEM).

Technetium-99m (99m Tc)-sestamibi was the first radiopharmaceutical to be approved by the FDA for use in scintimammography and is used in BSGI. [33] A BSGI exam consists of 4 views that are identical in positioning to a screening mammogram. Each view requires 10 minutes, and the patients must stay still. The total imaging time is 40 minutes. Sestamibi must be injected intravenously, and it delivers a radiation dose to the entire body as it circulates. There is ongoing research into a reduced-dose protocol.

In a retrospective study, the overall sensitivity of99m Tc-sestamibi BSGI in the detection of breast cancer was 95%. BSGI single and dual head devices are available. [34]

18F-Fluorodeoxyglucose (18F-FDG) FDG is used for PEM. PEM produces data that can be displayed as a 12-slice reconstruction. A clinical study reported a sensitivity of 93% and a specificity of 89% in patients with known cancer. [35] There are no data on screening with PEM.

Although not indicated as a screening procedure for the detection of breast cancer for average-risk patients, BSGI and PEM may play a useful role in various specific clinical indications, as in the screening of high-risk patients who cannot undergo an MRI or in evaluating tumor response to chemotherapy.

The disadvantages of BSGI and PEM include the radiation dose that extends to the whole body, the false-positive findings, and the lack of technique and equipment for BSGI-guided tissue sampling. The recommended injection for BSGI is 740–1100 MBq (20–30 mCi) of99m Tc-sestamibi, resulting in an estimated effective whole-body dose of 8.9 to 9.4 mSv. [36] For PEM, 370 MBq of 18F-FDG results in an estimated effective whole-body dose of 6.2 to 7.1 mSV. These are both much higher than the average effective dose to the breast from a mammogram, which is 0.44 mSV to 0.56 mSV. The dose from natural background radiation is 3 mSV per year.


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