Tomosynthesis, also known as  tomosynthesis (DTS), or 3D mammography, is a method for performing high-resolution limited-angle tomography at radiation dose levels comparable with projectional radiography.

Tomosynthesis reconstruction algorithms are similar to CT reconstructions, in that they are based on performing an inverse radon transform. 

Digital tomosynthesis combines digital imaging and processing with simple tube/detector motion as used in computed tomography (CT). 

In modern CT, the source/detector makes at least a complete 180-degree rotation about the subject obtaining a complete set of data from which images may be reconstructed. 

Digital tomosynthesis, on the other hand, only uses a limited rotation angle (e.g., 15-60 degrees) with a lower number of discrete exposures (7-51degrees) than CT. 

This incomplete set of projections is digitally processed yielding images similar to conventional tomography with a limited depth of field. 

The digital imaging process a series of slices at different depths and with different thicknesses can be reconstructed from the same acquisition.

Since  fewer projections are needed than CT to perform the reconstruction, radiation exposure and cost are both reduced.

Digital breast tomosynthesis (DBT)is Food and Drug Administration (FDA) approved for use in breast cancer screening.

The data acquired are 85 – 160 micron typical resolution, much higher than CT, so DBT is unable to offer the narrow slice widths that CT offers (typically 1-1.5 mm). 

DBT has higher resolution detectors permitting a  very high in-plane resolution.

Tomosynthesis has a much more limited depth of field than does CT, and it is likely will not be able to replace CT for the evaluation of the deeper organs of the body. 

With wrist fractures, digital tomosynthesis was shown to enable detection of more fractures than radiography while simultaneously providing lower metal artifact than radiography.

Evaluation of erosions in rheumatoid arthritis: 

Tomosynthesis shows sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of 80%, 75%, 78%, 76%, and 80%, compared to digital radiography were 66%, 81%, 74%, 77%, and 71%.

Tomosynthesis is usually used where a CT slice is required at high magnification, where conventional CT would not allow the sample to be located close enough to the x-ray source.

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