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Transcranial Doppler Ultrasonography (TCD) is now commonly used to evaluate the cerebral hemodynamics. However, the blood velocity measured with TCD is not always accurate, because as a rule the direction of the blood flow does not completely coincide with that of the ultrasonic beam. The error in the measurement could be as large as 15%. This could be eliminated by calculating pulsatility index (PI) from the Doppler ultrasonography. This study evaluates the reliability of the PI as an index of cerebral hemodynamics. In total, 164 measurements were made in patients with various cerebrovascular diseases (CVD), including 14 of brain death patients (group B) and 14 of inpending herniation patients (group I). Of CVD, 46 were persistent vegetative state patients (group V), and 43 were in relatively good conditions (group A). Other including 15 of hydrocephalus patients (group H) and 19 of cerebral vasospasm after subarachnoid hemorrhages (group S) were also investigated. Nineteen normal young volunteers (group N) were used as controls. The mean level of PI in group N shows 0.82. PI in group A was increased to 1.04, and in group V, 1.27. Furthermore in the brain death group, the mean level of PI was increased to 3.86, which was statistically significant. It was concluded that measurement of PI was very useful to evaluate the changes of cerebral hemodynamics, and the levels of PI was affected more with the changes in diastolic than in systolic flow velocity.

A study of cerebral hemodynamics using transcranial Doppler ultrasonography with special reference to clinical evaluation of pulsatility index.