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Related Experiment Videos

Angle correction in transcranial Doppler sonography

B M Eicke1, C H Tegeler, G Dalley

  • 1Department of Neurology, Bowman Gray School of Medicine, Winston-Salem, NC 27157-1078.

Journal of Neuroimaging : Official Journal of the American Society of Neuroimaging
|January 1, 1994
PubMed
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Transcranial Doppler sonography often uses an assumed 0-30 degree angle for flow velocity estimates. However, actual insonation angles vary widely, leading to significant underestimations in about one-fourth of cerebral arteries studied.

Area of Science:

  • Neurology
  • Medical Imaging
  • Ultrasound Technology

Background:

  • Transcranial Doppler (TCD) sonography traditionally assumes a 0-30 degree angle of insonation for flow velocity estimation.
  • This assumption, based on limited anatomical data, may introduce errors due to the Doppler formula's cosine function.
  • Advancements in transcranial color duplex sonography (TCD-CS) enable direct assessment of insonation angles and their impact on velocity measurements.

Purpose of the Study:

  • To evaluate the accuracy of the assumed 0-30 degree insonation angle in TCD sonography.
  • To determine the effect of actual insonation angles on cerebral artery flow velocity measurements.
  • To assess the discrepancies between angle-corrected and uncorrected flow velocities in healthy volunteers.

Main Methods:

Related Experiment Videos

  • Fifteen healthy volunteers underwent bilateral TCD-CS using a unilateral transtemporal approach.
  • Velocity measurements were taken from the middle, anterior, and posterior cerebral arteries.
  • Flow velocities were recorded with and without angle correction, and compared with conventional Doppler findings.

Main Results:

  • The average insonation angle was approximately 30 degrees, but individual angles showed wide variability (0-70 degrees).
  • Angle-corrected velocities exceeded uncorrected velocities by over 25% in approximately 25% of the studied vessels.
  • In 10.8% of vessels, angle-corrected velocities were more than 50% higher than uncorrected values.

Conclusions:

  • The actual angle of insonation in TCD sonography is unpredictable and frequently exceeds the traditionally assumed range.
  • Significant underestimation of flow velocities can occur when relying on uncorrected or assumed angles.
  • Further research is needed to understand the clinical implications of these angle-dependent velocity variations.