Quantitative Measurements of Blood Flow Velocity in Basal Cerebral Arteries with Transcranial Duplex Color‐Flow Imaging: A Comparative Study with Conventional Transcranial Doppler Sonography

Abstract

Transcranial duplex color-flow imaging is a new diagnostic method that allows visual display of blood flow in the basal cerebral arteries. This method allows determination of and correction for the Doppler angle of insonation. Conventional transcranial Doppler sonography has no imaging component and assumes a 0-degree Doppler angle for the calculation of flow velocities. The magnitude of the angle of insonation and the effect on flow velocity estimates have not been clearly defined. In order to evaluate the angle of insonation and the effect of angle correction on velocity readings, 50 patients referred for evaluation of cerebrovascular disease were studied. The mean age was 45 years (range, 24-62 yr). All were examined with conventional transcranial Doppler and transcranial duplex color-flow imaging. Specific vessels of the circle of Willis were identified by location, course, and direction of flow on color-flow images and by depth, direction of flow, and transducer orientation with conventional Doppler sonography. Visually controlled measurements of the Doppler angle of insonation were made by color-flow imaging. The data show that the mean angle of insonation was 33 degrees (+/- 15) in the middle cerebral artery, 35 degrees (+/- 17) in the anterior cerebral artery, 45 degrees (+/- 18) in the posterior cerebral artery, and 15 degrees (+/- 14) in the basilar artery. Angle-corrected peak systolic flow velocities were higher in all vessel segments (middle cerebral = 15%, anterior cerebral = 18%, posterior cerebral = 30%, and basilar = 3%), compared to uncorrected velocity readings by conventional Doppler sonography.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment: Transcranial Doppler ultrasonography: [RETIRED]

“…Depending on the vessel, the uncorrected insonation angle may be as high as 73°. 120,121,124 As a result, angle-corrected flow velocities may be as much as 25 to 30% higher than nonangle-corrected flow velocities. [120][121][122]124 Age-specific normative data have been published.…”

“…120,121,124 As a result, angle-corrected flow velocities may be as much as 25 to 30% higher than nonangle-corrected flow velocities. [120][121][122]124 Age-specific normative data have been published. 124,126,127 In Caucasian atherosclerotic patients over age 60, vessel detection rates are lower and blood flow velocities are higher in women.…”

“…However, errors in flow velocity measurement in two dimensions may still occur because of the three-dimensional course of intracranial arteries and the possibility of large insonation angles. 121 Use of the lateral frontal bone window may help with detection of posterior communicating artery flow and flow direction. 128 As with conventional TCD, a major limitation of TCCS is insufficient transtemporal ultrasound beam penetration due to hyperostosis of the skull.…”

“…TCCS is a relatively new, bedside noninvasive technique that shows a real-time two-dimensional depiction of cerebral parenchymal and intracranial vascular structures. [119][120][121][122][123][124][125] Compared with conventional TCD, there is more accurate demonstration of vascular anatomy, because imaging of smaller arterial branches and venous structures is feasible. Depending on the vessel, the uncorrected insonation angle may be as high as 73°.…”

“…128 As with conventional TCD, a major limitation of TCCS is insufficient transtemporal ultrasound beam penetration due to hyperostosis of the skull. [119][120][121][122][123][124][125][126] Transpulmonary echocontrast agents (ECA) increase the Doppler signal intensity and improve the signalto-noise ratio for transcranial insonation. 129 The use of an ECA enhances the ability of TCCS to visualize the number and length of basal cerebral arteries and second-or third-order branches of major cerebral arteries, 126 particularly in patients with poor transtemporal windows.…”