Breast cancer is the second leading cause of cancer death for American women today. The key to increasing the survival rate is early detection and treatment. Medical imaging is essential to breast cancer screening and diagnosis. Currently, x-ray mammography is the primary screening modality for breast cancer. Mammography is a radiographic examination technique that uses x rays to image breast tissue to detect breast pathology. Denser tissue absorbs more x rays and results in a bright region on the image. Mammography attempts to identify structural or morphological differences that can indicate presence of cancer, such as masses, microcalcifications, and architectural distortions. Traditionally, the image has been recorded on film. Recently, digital mammography techniques have been adopted that record the image in digital format.
Mammography is a well-developed technology that offers high-quality images at low radiation doses for the majority of patients. Unfortunately, 10â30% breast cancers are not detected on mammography and the positive predictive value (PPV) of mammography is less than 35%. Consequently, other imaging modalities are used in conjunction with x-ray mammography for detection and diagnosis. Moreover, following the diagnosis of cancer, medical imaging is used for treatment planning, monitoring treatment progress, and surveillance for disease recurrence.
The most widely used adjunctive modality for breast imaging is ultrasound. Ultrasound is routinely used to further evaluate suspicious abnormalities identified on screening mammography or a clinical exam. Ultrasound is particularly valuable for distinguishing between cysts and solid lesions and for examining younger women with dense breasts. The roles of other imaging modalities in breast cancer detection and diagnosis are rapidly evolving. Tomosynthesis, newer ultrasound methods such as 3D ultrasound, nuclear medicine methods such as sestamibi breast scintigraphy and positron emission tomography (PET), and magnetic resonance imaging (MRI) are all exciting areas of development in breast cancer care. Each of these alternatives are being sought in order to overcome at least one of the two major inherent limitations of x-ray mammography: the information loss of visualizing a 3D structure in 2D projections and the lack of functional insight regarding the biological processes of the breast tissue imaged.
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