Breast imaging has seen significant advancements, moving beyond traditional two-dimensional (2D) mammography to more sophisticated techniques. One such advancement is tomosynthesis, also known as three-dimensional (3D) mammography, which provides a layered view of breast tissue. To further enhance the accuracy of these detailed images, Computer-Aided Detection (CAD) systems are increasingly integrated. CAD refers to software programs that analyze medical images to highlight areas that may warrant a radiologist’s closer inspection. This combination aims to improve the detection of breast abnormalities and offers a more comprehensive approach to breast screening and diagnosis.
Understanding Digital Breast Tomosynthesis
Digital Breast Tomosynthesis (DBT) evolves from standard 2D mammography. Unlike conventional mammography, which captures a single flat image where overlapping tissue can obscure abnormalities, DBT acquires multiple low-dose X-ray images from various angles as the X-ray tube moves in an arc over the compressed breast. These images are then digitally processed and reconstructed into a series of thin, high-resolution “slices” or layers, typically 1 millimeter thick.
This layered approach allows radiologists to scroll through the breast tissue slice by slice, similar to flipping through the pages of a book. The ability to view the breast in these thin sections helps to minimize the effect of overlapping breast tissue, which can either hide a true abnormality or create a false appearance of one in a 2D image. By separating overlapping structures, DBT can reveal cancers that might otherwise be hidden and can also help distinguish normal tissue from suspicious findings, thereby reducing the likelihood of false positives.
The Purpose of Computer-Aided Detection
Computer-Aided Detection (CAD) serves as an analytical tool that works in conjunction with tomosynthesis images. This software program is designed to scrutinize the detailed 3D breast images and identify regions that exhibit characteristics potentially associated with suspicious findings. These characteristics often include subtle masses, distortions in tissue architecture, or microcalcifications, which are tiny calcium deposits that can sometimes indicate early cancer.
The CAD system functions as a supplementary aid for the radiologist, akin to a “second pair of eyes.” After the tomosynthesis images are acquired, the CAD software processes them, highlighting areas of concern with markers such as boxes or circles. It is important to understand that CAD does not make a diagnosis itself; rather, it directs the radiologist’s attention to specific areas for further evaluation. This assistance can help improve detection rates and potentially reduce the chances of subtle findings being overlooked during the radiologist’s interpretation, particularly as it can identify features that might be imperceptible to the human eye.
Combined Advantages and the Examination Process
The combined application of Digital Breast Tomosynthesis (DBT) and Computer-Aided Detection (CAD) offers synergistic advantages in breast imaging. Using DBT with CAD can lead to improved accuracy in breast cancer detection, as the 3D imaging capability reduces tissue overlap, and the CAD system provides an additional layer of analysis to highlight subtle abnormalities. This combined approach can significantly reduce the rate of unnecessary patient callbacks for additional imaging, which often occur when ambiguous findings are seen on 2D mammograms. Studies have indicated that DBT in combination with full-field digital mammography (FFDM) can detect approximately 30% more cancers and result in about 15% fewer false positives compared to FFDM alone.
During a tomosynthesis with CAD examination, the patient experience is largely similar to a traditional mammogram, typically taking about 10-15 minutes for the entire procedure, though the scanning portion itself is usually a few seconds per view. The patient’s breast is positioned and gently compressed between two plates. It is important for the patient to remain very still during this process, and they might be asked to hold their breath for a few seconds to ensure clear, unblurred images. After the images are acquired, the CAD software analyzes them, and the radiologist reviews both the 3D slices and the CAD-highlighted areas for a comprehensive assessment.