Contrast enhanced and dual energy mammography

Occasionally, a lesion is missed on mammography either because it lies within a region of dense surrounding breast tissue or because its X-ray absorption appears to be almost identical to that of the adjacent tissue. In breast magnetic resonance imaging, images acquired pre and post administration of an intravenous contrast agent (Gd DTPA) are subtracted to reveal pooling and washout of this agent in the presence of tumour angiogenesis, which occurs as a growing tumour recruits the development of new blood vessels. Breast magnetic resonance imaging has been shown to be much more sensitive than mammography in certain groups of young, high-risk women. It is possible to exploit this phenomenon using a much less costly and more accessible approach through contrast-enhanced digital mammography. Here, a nonionic iodine contrast agent is injected between pre and post contrast image acquisitions in which the X-ray beam is produced at a relatively high energy, above the K-edge of iodine. The images are subtracted, cancelling the soft-tissue contrast that is common to the two images and isolating the iodine signal in the region of angiogenesis. A series of post-contrast images can be obtained to track the kinetics of the uptake and washout. These images and the morphology of the lesion can reveal the presence, characteristics and extent of disease. Dual-energy approaches to improve speed or a combination of contrast imaging with tomosynthesis to provide three-dimensional images are also possible. The concept of this technique will be presented and some clinical cases will be shown.