Duplex ultrasonography: its expanding role in noninvasive vascular diagnosis.

Duplex scanning is only beginning to achieve widespread acceptance. On the positive side, it offers anatomic and physiologic information that cannot be obtained by any other method. The examination is totally noninvasive and is well accepted by both patients and referring physicians. The accuracy in the carotid bifurcation, the only area adequately investigated thus far, is quite good in comparison with arteriography, but the exact relationship between arteriography and duplex scanning in the carotid system demands further investigation. Duplex scanning is also cost-effective, and judicious use of the modality may considerably lessen the cost of a frequently expensive cerebrovascular evaluation. On the negative side, duplex scanning is extremely operator-dependent and is difficult to master effectively. At this time, few institutions or companies even offer the novice a place to learn and make their early mistakes out of sight. Limitations of the technique also exist. This is particularly problematic in the head, where the cerebral vasculature is not generally accessible to the ultrasound beam. Areas of stenosis contained within dense calcific plaque may also be completely hidden, and as already discussed, the deep abdominal vessels, particularly the iliac arteries, are not visible in an unacceptable number of patients. These technical limitations, however, may be circumvented; authors are already seeking sonic portals into the brain. Scanning from multiple vantage points usually overcomes the problem of acoustic shadowing from calcific plaque, and newer ultrasound technology may facilitate penetration of the sound beam deep into the abdomen. Overall, duplex sonography holds great promise for the future and may be destined to completely change the face of noninvasive vascular diagnosis.