Breast Positron Emission Tomography

Updated: Sep 01, 2014
  • Author: Thomas F Heston, MD, FAAFP, FASNC, FACNM; Chief Editor: Gowthaman Gunabushanam, MD, FRCR  more...
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Overview

Background

Breast positron emission tomography (PET) is an organ-specific high-resolution technology that is used to visualize the metabolism of the breast. PET scanning is a nuclear medicine technique that images the flow of molecules in the body. This is made possible by attaching a radionuclide to a molecule that enters into metabolic pathways; the photons emitted when the radionuclide decays are then imaged. While anatomic imaging allows visualization of body structures, PET molecular imaging allows visualization of molecular flow and metabolic processes within the body.

The primary benefit of PET imaging is that diseases such as cancer often first manifest as disordered metabolism before anatomic changes can be seen. [1, 2] In addition, dense breast tissue or scarring may cause anatomic techniques (mammography, MRI, ultrasonography) to be indeterminate. In such cases, knowing whether an anatomic structure is glucose hypermetabolic can be critical in the determination of proper medical management. [3, 4]

Breast PET typically utilizes the radiotracer F-18 fluorodeoxyglucose (F-18 FDG) to image glucose metabolism [5] ; however, other radiotracers are under development.

Whole-body PET cameras are typically combined with a CT scanner to allow acquisition of anatomic and molecular information from a single procedure. These hybrid PET/CT cameras are donut-shaped. During the procedure, the patient is passed through the central hole of the camera. PET/CT cameras have the detector several centimeters away from the body surface, which limits scan resolution.

While PET/CT cameras are useful for whole-body imaging, breast-specific PET imaging, known as positron emission mammography (PEM), requires the PET camera to be configured like a mammography machine. Current PEM cameras utilize two small movable flat detectors that are pressed directly against the breast.

The camera technology utilized by PEM has been shown to be more sensitive than whole-body PET/CT imaging in the detection of breast tumors. [6]

Grade III multifocal infiltrating ductal carcinoma Grade III multifocal infiltrating ductal carcinoma as seen on F-18 fluorodeoxyglucose positron emission tomography . This organ specific positron imaging technique results in a much higher resolution (down to 1 to 2 mm) compared to whole body PET/CT imaging.
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Indications

PEM is a relatively new technology, and the clinical indications are evolving rapidly. PEM is particularly useful when other imaging scan results are indeterminate. It has a useful complementary role to mammography, ultrasonography, and MRI.

PEM can assist in presurgical planning in breast cancer, monitoring response to therapy, and evaluating for tumor recurrence. In some cases, it may be useful in breast cancer staging and in helping guide breast biopsies.

This image demonstrates the ability of positron em This image demonstrates the ability of positron emission tomography to quickly assess response to chemotherapy, as early as 1 week after the first cycle. (Images courtesy of Mary K. Hayes, MD, Memorial Healthcare System, Hollywood, FL)
This image shows the ability of positron emission This image shows the ability of positron emission mammography to help ensure a breast biopsy is taken in the best location. The most metabolically active tissue needs to be evaluated for malignancy. The top image is obtained right before performance of the biopsy. The bottom image shows the biopsy needle to be properly positioned.

PEM has a sensitivity and specificity of over 90% in the detection of primary breast cancer. [7]

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Complication Prevention

Because F-18 FDG releases radiation, caution is urged when using in pregnant women or in nursing mothers. [8] Women who are pregnant or breastfeeding will only rarely undergo a nuclear medicine procedure such as F-18 FDG PEM. Although F-18 FDG PEM has not been shown to cause any harm to the fetus or breastfeeding infant, caution is urged.

For pregnant women in whom the benefits of PEM are thought to greatly outweigh any potential risks, the physician may modify the dose of the radiotracer.

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Outcomes

When required, a PET-guided breast biopsy has been found to be safe, effective, and associated with only minimal to mild discomfort. [9]

The camera technology utilized by PEM has been shown to be more sensitive than whole-body PET/CT imaging in the detection of breast tumors. [6]

PEM has a sensitivity and specificity of over 90% in the detection of primary breast cancer. [7]

In a retrospective study, Satoh et al determined that whole-body total lesion glycolysis (WTLG) on FDG PET/CT images is an independent prognostic factor for survival in breast cancer patients who have metastases on initial presentation. [10]

Although very rare, hypersensitivity allergic reactions to the radiotracer can occur.

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