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We evaluated the ability of transcranial Doppler ultrasonography (TCD) of the middle cerebral artery to detect internal carotid artery luminal area stenosis of 70% or greater by comparing TCD with cerebral angiography in 79 subjects, including 22 with normal cerebral arteriograms and 57 with 30% to 100% internal carotid artery stenosis on at least one side. Of six TCD measurements assessed, the flow acceleration provided the greatest sensitivity (82%) and specificity (73%) in distinguishing 70% to 100% carotid stenosis from lesser degrees of stenosis. The overall accuracy of the flow acceleration was 78%, and the positive predictive value was 79%. A flow acceleration of 351.6 cm/sec2 or less was useful for detecting high-grade stenosis, but there was difficulty in distinguishing unilateral from bilateral high-grade stenosis. TCD measurement of the flow acceleration allows for fairly reliable detection of high-grade stenosis and can thus serve as a useful indirect component of a carotid noninvasive battery.

Cerebral blood flow (CBF) was determined in the rat under 70% nitrous oxide anesthesia and pentobarbital anesthesia. The application of the Fick principle technique of Kety et al. was modified utilizing 123 Xe infused intravenously steadily for 30 seconds, at which time the animal was decapitated and the head frozen in liquid nitrogen. A prior femoral artery to femoral vein shunt was led through a polyethylene catheter of 0.13 ml volume. This catheter passed as a coil in a Nal crystal well-counter with the arterial 133 Xe concentration curve recorded by a ratemeter-recordcr system. The results of the hemispheric blood flow (HBF) were: under 70% nitrous oxide anesthesia in normocapnia (Paco, 38 mm Hg), 86 ± 15 ml/100 gm per minute; with hypocapnia (Paco, 20 mm Hg), 40 ± 5 ml/100 gm per minute; with hypercapnia (Paco, 63 mm Hg), 187 ± 10 ml/100 gm per minute; and with pentobarbital anesthesia (Paco, 38 mm Hg), 41 ± 8 ml/100 gm per minute.

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