Digital breast tomosynthesis, commonly known as 3D mammography, is an advanced X-ray imaging technology used for breast screening and diagnostics. This technique moves beyond the traditional flat image to create a three-dimensional representation of the breast tissue. The primary function of tomosynthesis is to improve the visibility of potential abnormalities by minimizing the confusion caused by overlapping structures within the breast. It is used for annual screening in asymptomatic individuals and for diagnostic evaluation when a symptom or concerning finding requires a closer look.
The method was approved by the U.S. Food and Drug Administration (FDA) in 2011 and is quickly becoming a preferred method for breast cancer detection. By providing a clearer, layered view of the breast anatomy, tomosynthesis aids healthcare providers in identifying small lesions and subtle changes that might be obscured in a standard image. This enhanced imaging capability helps in the early detection of breast cancer, which is associated with improved treatment outcomes.
The Core Technology Behind 3D Imaging
The process begins while the breast is compressed, similar to a standard mammogram. Instead of a single static exposure, the X-ray tube mounted on the imaging machine begins an arc-like sweep over the breast. This movement covers a defined angle, capturing a series of projection images, typically between 11 and 25, during its short motion.
Each image is taken at a unique angle using a very low dose of radiation, creating raw data points. These low-dose exposures are transmitted to a sophisticated computer system, which utilizes advanced mathematical algorithms to reconstruct the data.
This reconstruction process synthesizes the multiple two-dimensional captures into a volumetric dataset. The resulting images are presented to the radiologist as thin, distinct “slices” of the breast tissue, often measuring about one millimeter thick. The total number of slices created depends directly on the compressed thickness of the individual breast being examined.
This layered imaging allows the radiologist to scroll through the entire volume of the breast tissue, akin to flipping through a book. This layered format defines the technology as “3D,” providing detail unavailable in older imaging methods.
Distinguishing Tomosynthesis from 2D Mammography
The difference between tomosynthesis and conventional 2D mammography lies in how each handles breast anatomy. A standard 2D mammogram captures all the tissue in the breast within a single image, similar to a photograph. This single-shot approach inevitably leads to the superimposition of structures, creating the problem of “tissue overlap”.
Dense, normal breast tissue, which appears white on an X-ray, can overlap in the 2D image and obscure a small cancer, which also appears white. Conversely, this tissue overlap can sometimes create the appearance of an abnormal mass when none exists, leading to a false-positive result. Tomosynthesis directly addresses this limitation by separating the overlapping layers of tissue into individual slices.
By examining the breast in one-millimeter sections, the radiologist can see past dense tissue that might have hidden a tumor in a single flat image. This clarity improves clinical outcomes by enhancing cancer detection rates. Studies have shown that tomosynthesis can detect a higher percentage of invasive breast cancers compared to 2D mammography alone, with reported increases ranging from 20% to 65%.
The technology is beneficial for individuals with dense breast tissue, where the risk of a missed cancer is greater with 2D imaging. Another advantage is the reduction in false positives, resulting in fewer patient callbacks for unnecessary follow-up imaging. The rate of callbacks for additional testing has been reported to decrease by up to 40% when tomosynthesis is used for screening. This reduction alleviates patient anxiety and decreases the overall cost and time associated with screening programs.
The Patient Experience and Safety Profile
Undergoing a tomosynthesis examination is very similar to having a traditional 2D mammogram. The patient stands in front of the machine, and the breast is compressed by a plastic paddle. The duration of the compression remains comparable to the standard procedure, which is important for image quality and patient comfort.
The primary difference is the slightly longer overall time the examination takes. While compression time is similar, the X-ray tube’s arc motion adds a few seconds to each view to capture multiple images. The entire procedure takes approximately 10 to 20 minutes.
A common concern is the radiation dose, as it involves capturing more images than a standard mammogram. Although the procedure involves more exposures, each uses a very low dose of X-ray energy. The total radiation dose is generally comparable to or only slightly higher than that of a standard 2D mammogram, remaining within FDA safety guidelines.
Modern systems often incorporate technology to generate a “synthetic 2D image” from the 3D data, which eliminates the need to perform a separate, full-dose 2D image. This approach significantly reduces the total radiation exposure, bringing it closer to the level of a 2D mammogram while retaining the benefits of the layered, three-dimensional view. The medical consensus is that the increased accuracy and improved detection rates offered by tomosynthesis outweigh the small difference in radiation exposure.