What is digital subtraction and contrast-enhanced digital mammography?

Updated: Oct 17, 2016
  • Author: Nagwa Dongola, MD, FRCR; Chief Editor: Peter Eby, MD  more...
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Answer

Contrast enhanced digital mammography (CEDM) was invented to address the decreased sensitivity of mammography in dense breasts and the high cost of MRI. It was approved by the FDA in 2011. It is not being used for screening but is being used sparsely for cancer staging or neoadjuvant follow-up in places where MRI may not be available. Contrast resolution of CEDM is lower than that of CT or MRI. Subtraction can be performed by temporal or dual-energy techniques. [17]

Temporal subtraction requires immobilization and compression for both pre- and post-contrast images taken minutes apart. Compression can prevent blood flow and contrast enhancement. For these reasons, temporal subtraction has largely been abandoned. Dual-energy acquires 2 identical images after contrast injection in full compression a few seconds apart. Dual-energy takes advantage of the difference in the atomic density of tissue, as compared to the contrast. [18]

Two images are acquired, and the low-density breast tissue is subtracted; however, the high energy of contrast persists, allowing any enhancing abnormality to be more visible. In a recent study comparing CEDM to MRI, the results indicated very high sensitivity for the index lesion with both modalities, but MRI detected more satellite tumors and CEDM had fewer false positives. [19]


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