Digital breast tomosynthesis: The King’s College Hospital experience

Classic tomography is a well-known technique for imaging in sections and has been used by radiologists for almost 100 years. Technical advances in digital mammography have allowed the development of digital breast tomosynthesis (DBT), which has now become a significant addition to standard breast imaging.

DBT is performed with the breast compressed as in standard mammography. The x-ray tube moves across the breast in a limited arc during which multiple low dose exposures are made. The resulting digital data is then reconstructed into thin, typically 1mm, slices in the orientation in which they have been acquired and can be viewed individually or in cine mode. The arc of acquisition and number of projections acquired differ for the different manufacturers. Depending on the manufacturer these acquisitions are taken over a continuous arc or using a ‘stop and shoot’ system. The Hologic Dimensions system used at King’s acquires 11 low dose projection images over an arc of 15 degrees. A 4cm compressed breast will have 40 reconstructed slices and a 6cm compressed breast will have 60 reconstructed slices, all from 11 low dose angled exposures. If DBT were used for all four standard views (bilateral MLO and CCs) there would be 240 images to read if both breasts had a compressed thickness of 6cm. The acquisition time and mean glandular dose are comparable to that for standard digital mammography (one view 2D FFDM = 1.20mGy, one view DBT = 1.45mGy UK dose calculation (Dance method standard UK breast 4.5cm PMMA/5.3cm breast) for the Hologic Dimensions system.

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