Minimum wall shear stress points and their underlying intra-aneurysmal flow structures of unruptured cerebral aneurysms on 4D flow MRI - 14/09/22

Doi : 10.1016/j.neurad.2022.09.001

Kazuya Futami ^a,^{^{1
Co-authors},}^⁎ , Kouichi Misaki ^b,^{^{1
Co-authors}} , Takehiro Uno ^b,^{^{1
Co-authors}} , Iku Nambu ^b,^{^{1
Co-authors}} , Taishi Tsutsui ^b,^{^{1
Co-authors}} , Tomoya Kamide ^b,^{^{1
Co-authors}} , Mitsutoshi Nakada ^b,^{^{1
Co-authors}}
^a Department of Neurosurgery, Hokuriku Central Hospital, 123 Nodera, Oyabe, 932-8503 Toyama, Japan
^b Department of Neurosurgery, Graduate School of Medicine, Kanazawa University, 13-1 Takara-machi, Kanazawa, 920-8641 Ishikawa, Japan

^⁎Corresponding author at: Department of Neurosurgery, Hokuriku Central Hospital, 123 Nodera, Oyabe, 932-8503 Toyama, Japan.Department of NeurosurgeryHokuriku Central Hospital123 NoderaOyabeToyama932-8503Japan

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Highlights

•	This study first identified minimum wall shear stress (Min-WSS) points and their underlying intra-aneurysmal flow structure patterns in unruptured cerebral aneurysms using four-dimensional flow magnetic resonance imaging.
•	The location of Min-WSS point corresponded with the location of the vortex core or center in 76% of all aneurysms.
•	The Min-WSS points were located not only on the apex, but also on the neck.
•	The location of the Min-WSS point and underlying intra-aneurysmal flow structure affected the Min-WSS value.

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Abstract

Background and purpose

Minimum wall shear stress (Min-WSS) points may be associated with wall instability of unruptured cerebral aneurysms. We aimed to investigate the relationship between the locations of Min-WSS points and their underlying intra-aneurysmal flow structure patterns in unruptured cerebral aneurysms using four-dimensional (4D) flow magnetic resonance imaging (MRI).

Materials and methods

Min-WSS points and the intra-aneurysmal flow structure patterns were identified in 50 unruptured aneurysms by 4D flow MRI.

Results

The Min-WSS points were located around a vortex core tip in 31 (62.0%) aneurysms and on an intra-bleb vortex center in 7 (14.0%). Sixteen (32.0%) aneurysms had the Min-WSS points on the aneurysmal apex, and in 24 (48.0%) were on the neck. The Min-WSS values of aneurysms with the Min-WSS points on an intra-bleb flow were significantly lower than those of the other groups (P = 0.030). Aneurysms with the Min-WSS points on the neck had significantly higher Min-WSS values than the other aneurysms (P = 0.008).

Conclusions

The location of the Min-WSS point was corresponding to the vortex core or center in 76% of all aneurysms. The underlying intra-aneurysmal flow structure and location of the Min-WSS point affect the Min-WSS value. Further studies are needed to characterize Min-WSS points to identify aneurysms with a higher risk of wall instability.

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Keywords : Wall instability, Unruptured cerebral aneurysm, Wall shear stress, Vortex, 4D flow MRI

Abbreviation : CFD, 4D, MRI, Min-WSS, WSS