Dampening of Blood-Flow Pulsatility along the Carotid Siphon: Does Form Follow Function?

T Schubert,F Santini,J Bock,S Wetzel,S Meckel,L Bonati,M Markl,A.F Stalder

doi:10.3174/ajnr.a2426

Abstract

The tortuous distal part of the ICA may have an attenuating effect on pulsatile arterial flow. We investigated local arterial blood flow patterns in the ICA proximal and distal to the carotid siphon to detect quantitative waveform changes. Arterial flow patterns were analyzed by using flow-sensitized 4D PC MR imaging (time-resolved 3D PCMR) at 3T in 17 healthy volunteers. Time-resolved blood flow velocities were extracted from the source data at the C4 and C7 segments of the ICA. PI, RI, and PA were calculated by using time-resolved flow volume. A linear mixed-effects model was applied to compare values at C4 and C7. Furthermore, 3D blood flow visualization was performed for all 34 ICAs. PI, RI, and PA were significantly lower at the distal C7 segment compared with the proximal C4 segment of the ICA (P < .0001). Helical flow patterns were observed in 5 ICAs of 4 subjects. Arterial flow patterns showed a significant reduction in PI, RI, and PA when compared distal to proximal to the carotid siphon. The observed attenuation of flow pulsatility is most likely related to the contorted shape of the distal ICA and may bear a protective effect for downstream cerebral vasculature.

Highlights

MethodsArterial flow patterns were analyzed by using flow-sensitized 4D PC MR imaging (time-resolved 3D PCMR) at 3T in 17 healthy volunteers
AND PURPOSE: The tortuous distal part of the ICA may have an attenuating effect on pulsatile arterial flow
Arterial flow patterns showed a significant reduction in PI, RI, and PA when compared distal to proximal to the carotid siphon

Summary

Methods

Arterial flow patterns were analyzed by using flow-sensitized 4D PC MR imaging (time-resolved 3D PCMR) at 3T in 17 healthy volunteers. Time-resolved blood flow velocities were extracted from the source data at the C4 and C7 segments of the ICA. 3D blood flow visualization was performed for all 34 ICAs. Study Population Thirty-four ICAs of 17 healthy volunteers (10 men, 7 women; median age, 22.5 years; range, 19 –32 years) were investigated. Blood flow patterns were visualized and time-resolved blood flow measurement was performed. Data acquisition resulted in a series of 3D volumes representing 3D blood flow in consecutive timeframes within the cardiac cycle with a temporal resolution of 54.4 –56.0 ms.[18] The total acquisition times ranged between 25 and 30 minutes, depending on the patient’s individual heart rate (13–16 acquired cardiac phases). Images were reconstructed to a matrix of 320 ϫ 256 by using zero-filling, resulting in a reconstructed resolution of 0.7 ϫ 0.7 ϫ 1.2 mm

Results

Discussion

Conclusion