Three-dimensional mammography

The contribution of screening mammography to reducing mortality due to breast cancer in women over 40 years old has been clearly demonstrated. Nevertheless, film mammography has several technical limitations that diminish its performance in women with dense breasts. Digital mammography goes part of the way to overcoming these limitations, but its diagnostic accuracy can still be impaired by superposition of fibroglandular structures at different levels within the breast. It may be possible to improve sensitivity and specificity further by producing tomographic images of the breast through one of two new techniques, tomosynthesis or breast computed tomography. Tomosynthesis can be carried out on a modified digital mammography system in which the X-ray tube can be rotated about the breast to obtain a number of projection views over a range of different angles. The images are obtained from these projections by mathematical reconstruction. Computed tomography requires a dedicated gantry that allows a full rotation of the X-ray beam about the pendant breast as the woman lies prone on a table. Each of these imaging methods isolates structures within the breast, potentially making tumours and microcalcifications more conspicuous. Each technique has its strengths and weaknesses with respect to radiation dose and various aspects of image quality, and these will be discussed in the current presentation. In addition, trials underway to evaluate the techniques' performance will be described.