Evaluation of Cerebral Hemodynamics with Color-Coded Duplex Sonography: Normative Values with Correction of Insonation Angles.

Background: Transcranial color-coded sonography (TCCS) allows direct observation of arteries and the possibility of correcting the insonation angle for reliable evaluation of hemodynamics. We obtained TCCS reference values of the cerebral hemodynamics after correction of insonation angles.

Methods: We studied 195 healthy adults equally allocated into 3 age groups: 18-40, 41-60, and greater than or equal to 61 years. The middle (MCA), anterior (ACA), and posterior cerebral arteries (PCA) were evaluated through the temporal acoustic window using conventional pulsed transcranial Doppler and TCCS. Peak systolic, end diastolic, and mean blood flow velocities were registered, as well as pulsatility and resistance indices at 0° and with correction by alignment of insonation angle parallel to the blood flow vector. We derived normative values assuming both the parametric and nonparametric distributions.

Results: We excluded 33 participants due to inadequate acoustic window (10.3%), carotid disease (2.1%), and embryonic variants (4.6%), leaving out 162 for final analysis (50% female, median age 48 years). The 2.5th-97.5th percentiles of the corrected angle for MCA was 0°-60°, ACA 0°-44°, and PCA 30°-60°. After angle correction, 2.5th-97.5th percentiles for flow velocity of MCA, ACA, and PCA were 37.7-112.5 cm/s, 25.6-71.2 cm/s, and 29.2-80.8 cm/s, respectively. There were wide discrepancies between hemodynamics values obtained with insonation angles at 0° and after angle correction. No differences were found between ultrasound methods at exactly 0° or between hemispheres, however, there were differences according to age and sex.

Conclusions: Specific normative tables should be used in TCCS when the corrected angle is greater than 0° since the hemodynamics values greatly differ after correction of the insonation angle. Further studies are necessary to determine critical cutoffs indicating disease.