What is it?

MBI is a nuclear medicine imaging modality that uses a radiotracer to identify metabolically active breast lesions. It improves lesion detection in women with dense breast tissue by highlighting areas of increased cellular activity that may not be visible on mammography.

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How Does it Work?

A small amount of a radioactive tracer—typically technetium-99m sestamibi—is injected intravenously. Tumor cells, which have higher metabolic activity, uptake the tracer at significantly higher levels than normal tissue. Gamma cameras then capture high-contrast images, where suspicious areas appear bright against a dark background, minimizing the masking effect of dense tissue.

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Best for:

MBI is most effective as a supplemental screening tool for:

• Women with heterogeneously or extremely dense breasts

• Patients with elevated breast cancer risk where MRI is contraindicated or unavailable

• Further evaluation of equivocal mammogram findings

 

Clinical Performance:

• MBI identifies an additional 6 cancers per 1,000 women screened when added to digital mammography, compared to 3 additional cancers per 1,000 with 3D mammography alone.¹

• Offers higher sensitivity in dense tissue compared to standard 2D or 3D mammography

• Demonstrates improved cancer detection with lower recall rates in some studies

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Limitations:

Availability is currently limited to select centers with nuclear medicine capability

• The radiation dose is modest (~2.4 mSv), but higher than that of mammography. Recent advancements have reduced the dose while maintaining image quality.

• Tracer-related risks are minimal but include rare allergic reactions

• Not yet standardized as a routine screening tool in national guidelines

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Regulatory Status:

• FDA-approved for breast imaging; not included in USPSTF or ACR recommendations for routine screening at this time. Consideration is case-by-case, based on individual risk and imaging context.