著者

礒田 治夫

出版者

日本磁気共鳴医学会

雑誌

日本磁気共鳴医学会雑誌 (ISSN:09149457)

巻号頁・発行日

vol.39, no.4, pp.126-136, 2019-11-15 (Released:2019-12-05)

参考文献数

29

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For larger blood vessels, such as cervical arteries and aortic arteries, 4D-Flow imaging with high signal to noise ratio (SNR) can be used to collect accurate measurements. When the SNR is sufficient and the voxel size is less than 30% of the vessel diameter, the error rate for the cross-sectional average flow velocity obtained by 4D-Flow is less than 10%. When the SNR is sufficient and the voxel size is less than 10% of the vessel diameter, error rate for the maximum flow velocity is also less than 10%. However, for smaller vessels, such as intracranial arteries, 4D-Flow imaging underestimates the flow velocities owing to the low spatial resolution or low SNR. Meanwhile, because of the partial volume phenomenon, the velocity of each voxel is underestimated within the vessel and overestimated near the vessel wall. Thus, the spatial resolution affects the velocity profile in the blood vessels. Higher spatial resolution leads to more accurate velocity profile and more accurate wall shear stress (WSS). However, it should be noted that the WSS determined by 4D-Flow is smaller compared to the true value. We can obtain the 3D velocity vector fields, maximum flow velocity, spatially averaged flow velocity, volume flow rate, streamlines, pathlines, streak lines, and WSS and its derivatives using a flow analysis software. The spatial resolution and SNR of 4D-Flow affects the accuracy of each voxel, velocity profile in blood vessels, and ultimately, the calculated WSS. However, there is a trade-off between the spatial resolution and SNR and hence there are limitations to increase the spatial resolution. Artificial intelligence (AI) may be able to interpolate lower spatial resolution data, and therefore, address this problem in the future. AI may also help us to obtain flow related biomarkers like WSS and its derivatives more easily and quickly in clinical practice. Development of the magnetic resonance fluid dynamics is ongoing and can provide a promising solution.