Assessment of Cerebral Blood Flow Pulsatility and Cerebral Arterial Compliance With 4D Flow MRI

Abstract

Background: Four-dimensional flow magnetic resonance imaging (4D flow MRI) enables efficient investigation of cerebral blood flow pulsatility in the cerebral arteries. This is important for exploring hemodynamic mechanisms behind vascular diseases associated with arterial pulsations. Purpose: To investigate the feasibility of pulsatility assessments with 4D flow MRI, its agreement with reference twodimensional phase-contrast MRI (2D PC-MRI) measurements, and to demonstrate how 4D flow MRI can be used to assess cerebral arterial compliance and cerebrovascular resistance in major cerebral arteries. Study Type: Prospective. Subjects: Thirty-five subjects (20 women, 79 AE 5 years, range 70-91 years). Field Strength/Sequence: 4D flow MRI (PC-VIPR) and 2D PC-MRI acquired with a 3T scanner. Assessment: Time-resolved flow was assessed in nine cerebral arteries. From the pulsatile flow waveform in each artery, amplitude (ΔQ), volume load (ΔV), and pulsatility index (PI) were calculated. To reduce high-frequency noise in the 4D flow MRI data, the flow waveforms were low-pass filtered. From the total cerebral blood flow, total PI (PI tot ), total volume load (ΔV tot ), cerebral arterial compliance (C), and cerebrovascular resistance (R) were calculated. Statistical Tests: Two-tailed paired t-test, intraclass correlation (ICC). Results: There was no difference in ΔQ between 4D flow MRI and the reference (0.00 AE 0.022 ml/s, mean AE SEM, P = 0.97, ICC = 0.95, n = 310) with a cutoff frequency of 1.9 Hz and 15 cut plane long arterial segments. For ΔV, the difference was -0.006 AE 0.003 ml (mean AE SEM, P = 0.07, ICC = 0.93, n = 310) without filtering. Total R was 11.4 AE 2.41 mmHg/(ml/s) (mean AE SD) and C was 0.021 AE 0.009 ml/mmHg (mean AE SD). ΔV tot was 1.21 AE 0.29 ml (mean AE SD) with an ICC of 0.82 compared with the reference. PI tot was 1.08 AE 0.21 (mean AE SD). Data Conclusion: We successfully assessed 4D flow MRI cerebral arterial pulsatility, cerebral arterial compliance, and cerebrovascular resistance. Averaging of multiple cut planes and low-pass filtering was necessary to assess accurate peak-topeak features in the flow rate waveforms. Level of Evidence: 2 Technical Efficacy Stage: 2 J. MAGN. RESON. IMAGING 2020;51:1516-1525.View this article online at wileyonlinelibrary.com.

Middle cerebral artery pressure laterality in patients with symptomatic ICA stenosis

“…However, we assumed that the effect of these profiles was small and that the inlets, functioning as flow extensions, reduced the boundary effects. A limitation for the time-resolved simulations was the assumption about rigid walls, which excluded dampening effects from the arterial walls [ 19 ]. The main advantage of the stationary simulation was that it was performed on a standard PC in less than an hour, while the time-resolved results required up to four days of computational time.…”

“…From the data in Table 1 , we found that the MCA flow laterality was about 12% of the mean MCA flow. For the corresponding average perfusion pressure, we used the approximate MAP of 93 mmHg and assumed an intracranial pressure of 11.6 mmHg [ 19 ]. The mean pressure laterality found in our paper was about 8% of this approximated cerebral perfusion pressure.…”

“…Flow rate quantification was performed according to a previously developed post-processing method [ 19 ]. Pulsatile blood flow rates were measured in the left and right ICA, proximal middle cerebral artery (MCA1), ACA1 and the ACA2.…”

“…There was no measurable flow in three ACA1 and four ICA on the ipsilateral side. Flow rates were obtained by averaging the flow waveforms from 15 consecutive cut planes [ 19 ].…”

4D flow MRI for non-invasive measurement of blood flow in the brain: A systematic review

“…Several studies were found to have used 4D flow to assess the role of vessel stiffness (manifest as pulsatility) in cerebrovascular health. Holmgren et al 34 demonstrated the technique's ability to measure arterial pulsatility and compliance, and cerebrovascular resistance, across a range of cerebral arteries in a population of elderly subjects (mean 79 AE 5 years). Birnefeld et al 16 examined the ICAs and MCAs (M1, M3) of 89 patients with acute ischaemic stroke or transient ischaemic attack (divided into two groups based on clinical assessment: those with associated cerebral small vessel disease (SVD) and those without).…”