3D Mammography – Tomosynthesis
Physicians who care for breast patients know that mammographic screening reduces mortality and saves lives. However, mammography is not perfect. This is particularly evident in women with dense breast. Mammographic screening sensitivity decreases with increasing density of breast tissue. In standard two dimensional mammographic films, dense breast tissue can overlap, potentially hiding cancers.
3D (three-dimensional) mammography, also called breast tomosynthesis, is a digital mammography technique that permits individual sections of the breast to be visualized while lowering the impact from overlapping tissue. Tomosynthesis images are then reconstructed from a series of images from many different angles. During the mammogram, the X-ray tube moves in a semi-circle (or sweeps) around the breast while images are taken. Then the information is assembled to produce three-dimensional images of the breast.
Breast tomosynthesis has several benefits. It has been shown to detect smaller breast cancers that may be hidden on traditional 2D (two-dimensional) mammography. It has a greater likelihood of detecting multiple breast tumors, and provides clearer images of dense breast tissue as seen in a clinical trial which involved many breast imaging centers compared standard 2D mammography and 3D mammography (tomosynthesis). The study found that 3D mammography improved the ability to find breast cancer and reduced recall rates (the need for a patient coming back to the center for more images) for patients who did not have breast cancer.
Because tomosynthesis decreases the superimposition of tissue of the breast, its impact on making lesions more visible is most evident for masses, asymmetries, and areas of architectural distortions. Calcifications appear similar on both modalities and detection improvements are minimal for lesions presenting as calcifications.
There are some potential disadvantages of breast tomosynthesis.
- The radiation dose for women having tomosynthesis is slightly higher than it would be with standard digital mammography; however, the dose remains lower than the maximum allowed with older, analog mammography.
- The time it takes to obtain the images of the breast is slightly longer for tomosynthesis in comparison to 2D mammography. Patients have to hold their breath longer and movement may lead to motion artifact.
- The large number of reconstructed images increases the interpretation time for the radiologist. Radiologists also need additional training to interpret 3D breast tomosynthesis images.
Breast tomosynthesis provides a 3D imaging capability that allows for more accurate evaluation of lesions by enabling better visualization of breast tissue. Lower recall rates and higher cancer detection rates have been observed. Breast tomosynthesis is an advancement in breast imaging.