Noninvasive diagnosis of extracranial cerebrovascular disease.

Noninvasive methods for diagnosis of carotid and vertebrobasilar disease may be divided into passive techniques and those in which the body is interrogated by the introduction of some sort of signal such as an ultrasound beam. Older techniques have been of limited value, whereas newer noninvasive methods can give specific, accurate, and quantitative information as to the location and extent of arterial stenosis.