The physics behind the different angulations in tomosynthesis
Tissue superimposition is a challenge in mammography. Providing 3D images of the breast, Digital Breast Tomosynthesis can relieve this issue. The angle used for Digital Breast Tomosynthesis plays an important role in how strong overlapping tissue can be reduced. We are convinced that a wide-angle system is the best possible solution.
Principles of the wide angle
The figure illustrates that, depending on the position of the X-ray source, the single projections will show the black and white spheres with more or less overlap. The wider the angle, the better the two spheres can be separated.
Delivering a higher depth resolution, a wider angle can better reduce superimposition of breast tissue. This has been proven in many scientific studies, for example1-3, and also by researchers from the FDA4.
How the angle affects the depth resolution
Comparing different angles shows how accurately the location of a hypothetical circular lesion can be determined. A 2D FFDM provides no information on the spatial location of the lesion, meaning the lesion could be at any height. The wider the tomosynthesis angle, the smaller becomes the height-probability area, indicating that the lesion can be located with increased precision.
How the angle affects the image contrast
A wider scan angle also improves the detection of large-area low-contrast lesions like breast masses. From a physics point of view, these masses are low-frequency objects in the Fourier space. The sampling of these low frequencies is much better with a wide angle and will result in a higher image contrast. This improvement in mass detection performance has been confirmed in many studies.2;5-9
About High Definition Breast Tomosynthesis
Increase your diagnostic confidence efficiently and easily with High Definition Breast Tomosynthesis. Already superior with the widest angle, the highest number of projections, and full detector readout, it is now the world’s first tomosynthesis to incorporate EMPIRE Technology.
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2Mertelmeier T, Ludwig J, Zhao B, Zhao W (2008) Optimization of Tomosynthesis Acquisition Parameters: Angular Range and Number of Projections. In: Krupinski EA (ed) Digital Mammography. Springer Berlin Heidelberg. Berlin, Heidelberg, pp 220–227.
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9Endo T, Morita T, Oiwa M, Suda N, Sato Y, Ichihara S et al. (2016) Detectability comparison of modes in dual-mode digital breast tomosynthesis. Breast cancer (Tokyo, Japan). doi:10.1007/s12282-016-0725-0.