cancer diagnoses—more than any other specialist, it may be worth the additional workflow impact or fiscal cost if the use of CAD reduces the likelihood of capricious judgments. If a radiologist and a CAD system both fail to detect an abnormal mammographic finding, then it becomes less likely that the missed cancer can be successfully argued to be due to negligence on the part of the interpreting radiologist.

Magnetic Resonance Imaging (MRI)

[In its current state,] MRI has nothing to do with the average woman undergoing screening for breast cancer. It’s a promising technology, but right now it’s overreaching to say it’s useful for the average woman.84

William J. Gradishar, M.D.

Northwestern University

Researchers have been exploring the use of MRI in breast cancer detection for more than 15 years.104 In 1991, the FDA cleared MRI for use as a diagnostic tool to evaluate breast tissue abnormalities found in other exams—but not as a screening tool. It has been suggested that MRI is useful in a number of clinical indications such as finding small breast lesions that are sometimes missed in mammograms, generating better images of dense or augmented breast tissue, revealing multifocality of breast cancer, and aiding in treatment staging and follow-up.103 There is also growing agreement in the clinical community that MRI could be a valuable tool in screening protocols for women at higher risk for breast cancer.

Results of the largest prospective, multicenter study of MRI screening to date were presented at the 2003 meeting of the American Society of Clinical Oncology. The study compared the findings of yearly x-ray mammography and MRI breast exams in more than 1,000 women at higher than average breast cancer risk. Over 2 years, 40 breast cancers were found. Sixteen percent of the cancers were identified by clinical exam, 36 percent by mammography exams, and 71 percent by MRI.67 However, MRI was less specific than mammography (88 versus 95 percent). In another 2003 study, researchers found that, for use as a tool in screening women with breast cancer gene mutations and helping diagnose disease earlier, MRI appeared to be superior to mammography and sonography (ultrasound).92

Likewise, mammography is also the primary technique for detecting ductal carcinoma in situ (DCIS). Recent research indicates that contrast-enhanced MRI might help detect otherwise occult foci (such as those that occur in DCIS), or in patients with small or dense breasts for whom mammography can be less reliable (Figure 3-5).53,121 A gadolinium-based con-



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