Another imaging modality complementary to breast tomosynthesis, contrast enhanced mammography, involves injecting a contrast agent intravenously while the patient is imaged with a sequence of digital mammograms that show the flow of the contrast agent over time. The contrast agents employed in the study are the same iodine pharmaceuticals commonly used in CT imaging, such as Isovue or Omnipaque.
Contrast enhanced mammography is based on the principle that rapidly growing tumors require an increased supply of blood to support their growth. The contrast agent preferentially accumulates in such areas, and contrast enhanced mammography offers a method of imaging the distribution of the agent in the breast tissue. The clinical protocol consists of administering the contrast agent through a venous injection in the arm. As the contrast agent distributes throughout the body, a sequence of digital mammograms are taken. The mammograms identify areas with increased contrast agent concentrations.
There are two ways that the images are evaluated. One is to look for the image where the iodine concentration peaks, typically around one minute post injection. Regions having high uptake reflect active tissue growth and may be indicative of malignant tissues. Another method is known as kinetic analysis. In this method, the flow of the iodine into and out of a tissue area is analyzed. Studies have shown that malignant cancers often exhibit a rapid washin and washout of iodine, while benign tissues will have a slow uptake of the iodine over the five-minute study duration.
