Tomosynthesis in X-ray: proven additional value?

Abstract

Digital breast tomosynthesis (DBT) is a new promising modality for breast imaging. Breast tomosynthesis is based on a full-field digital mammography (FFDM) platforms, and the DBT images are obtained in the same standard projections (cranio-caudal and mediolateral oblique views) as for conventional mammography [1,2]. The tomographic images or “slices” are usually reconstructed at 1mm intervals and presented in the default setting as thin “slices” on the dedicated work-station. The images may, however, also be displayed as a volume consisting of several slices (“slabs”). The idea of using DBT is that the shape and margins of breast masses may be more clearly delineated by reducing or eliminating overlapping tissue, and the ability to distinguish superimposed tissue from breast lesions would be improved. Thus, it is suggested that this new technology may improve the specificity as compared with conventional mammography. Furthermore, the elimination of superimposed breast tissue should theoretically improve the detection of lesions otherwise hidden by dense breast parenchyma. The ability of DBT to reduce or eliminate the interpretation problems caused by overlapping breast tissue may be particularly valuable in women with dense breasts. Furthermore, it is suggested that digital breast tomosynthesis may improve the detection of architectural distortion especially in women with heterogeneous dense breasts. Theoretically, the very thin spiculations seen in architectural distortion would be expected to be more easily identified on 1mm thin slices as compared with a conventional projection mammogram. There has been a lot of concern regarding the perception (detection) and analysis (characterization) of calcifications on digital breast tomosynthesis. Theoretically, micro-calcifications may represent a challenge for DBT due to the so-called “thin-sliceeffect” since only few or microcalcifications might be seen on each slice and not all calcifications of cluster as is the case on conventional FFDM projection images. Viewing the microcalcifications in a “slab”-mode may resolve some of these problems, and a larger study comparing sharpness, contrast, and diagnostic quality of microcalcifications concluded that calcifications can be demonstrated with equal or even greater clarity on DBT than on mammography [3]. Analysis of microcalcification clusters on DBT may have a learning curve effect. There have been only few publications on DBT in a clinical setting so far, and consequently the future role of tomosynthesis, whether its implementation will be in mammography screening or in clinical (i.e., “diagnostic”) imaging, or in both settings, is still not clear.