Optimal 4DFlow MR sequence parameters for the assessment of internal carotid artery stenosis: a simulation study
In patients with ICA stenosis, increased peak systolic velocity is a marker of stenosis at risk of ischemic stroke. 4DFlow MRI is a reproducible technique to evaluate velocities in ICA stenosis, although it seems to underestimate velocities as compared with Doppler ultrasonography. The purpose of our study was to confirm that velocities were underestimated on a new set of data acquired with a clinical 4DFlow sequence, and to devise optimal acquisition parameters for ICA stenosis exploration based on a numerical simulation.
After review board approval, 15 healthy controls and 12 patients presenting ICA stenosis were explored with Doppler ultrasonography and 4DFlow MRI. We created a 2-dimensional simulation of ICA stenosis and its corresponding 4DFlow acquisition, and compared its mean peak systolic velocity underestimation to real MRI and Doppler. We then simulated the acquisition for voxel size ranging from 0.5 to 1.25 mm and number of phases per cardiac cycle ranging from 10 to 25.
On acquired data, 4DFlow MR underestimated peak systolic velocities (mean difference between Doppler and 4DFlow: − 35 cm/s), especially high velocities. With spatial and temporal resolutions equivalent to MR acquisition, our simulation yielded similar underestimation (mean difference: − 31 cm/s, P = 0.30). Simulations showed that 0.7-mm resolution and 20 phases per cardiac cycle would be necessary to record peak systolic velocities up to 250 cm/s.
Higher spatial resolution can provide accurate peak systolic velocities measurement with 4DFlow MRI, thus allowing better ICA stenosis assessment. Further studies are needed to validate the proposed parameters.
KeywordsMagnetic resonance angiography Carotid artery Carotid stenosis Stroke
Autocalibrating parallel imaging with k-space and temporal undersampling
Peak systolic velocity
The study was partially supported by GE Healthcare. GE Healthcare employees were involved in the setup and configuration of the 4DFlow sequence but did not interfere during examination or analysis of the data.
Compliance with ethical standards
Conflict of Interest
VC-M, engineer at GE Healthcare, was involved in the setup of the 4DFlow sequence as well as in article proofreading for intellectual content, but did not interfere in data analysis.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
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