Correlation Between Changes in Arterial Wall Shear Stress and Prognosis Following Acute Major Intracranial Artery Occlusion and Recanalization

1. Background The prognosis for ischemic stroke patients experiencing acute major intracranial artery occlusion is determined by a variety of factors. The status of arterial recanalization and the time taken to achieve recanalization play pivotal roles in determining patient outcomes. Even under similar conditions, short or long-term outcomes significantly differ among patients, making it challenging to solely explain with traditional risk factors. An acute occlusion in a major intracranial artery results in significant alterations in cerebral blood flow, enhancing flow through the Circle of Willis and collateral circulation to make up for the reduced blood supply to the affected area. After thrombectomy, the patterns of intracranial blood flow. changes again.

Wall Shear Stress (WSS) is the frictional resistance force exerted by blood flow as it directly interacts with the vascular walls, and it serves as a critical indicator of vascular health. WSS is well-known for its correlation with atherosclerotic changes. Studies have shown that WSS in the internal carotid artery of ischemic stroke patients is lower compared to healthy individuals. Additionally, WSS was found to be reduced in the carotid artery of patients with lacunar infarctions. WSS in large artery strokes was lower than in the cardioembolic group. There have also been reports linking WSS to the progression of Moyamoya disease, suggesting that WSS may be associated with various vascular pathophysiologies, not just atherosclerotic changes.

Time-of-Flight Magnetic Resonance Angiography (TOF-MRA) is a commonly used brain MRI technique, often utilized in conjunction with CT angiography to assess the course and condition of intracranial arteries. The signal intensity from MRA-TOF presents diverse distributions across different subjects and arteries. Based on this, the concept of Signal Intensity Gradient (SIG) has been derived. SIG has shown a strong correlation (correlation coefficient >0.8) with Computational Fluid Dynamics (CFD), a well-known method for assessing blood shear stress. In patients with the large artery atherosclerosis subtype of stroke, the SIG in the ipsilateral internal carotid artery was significantly lower than that on the contralateral side. These findings suggest a potential association between SIG, vascular shear stress, and the related pathophysiology.

There is no need for additional imaging beyond TOF, and it is possible to measure even arteries of relatively small diameter. Therefore, SIG enables the analysis of shear stress pattern in major cerebral arteries before and after recanalization. 2. Aims We aim to investigate the blood flow patterns and characteristics in the periods of pre and post-recanalization using SIG. 3. Target number of participants A total of 160 participants (20 individuals from each center, total 8 centers) 4. Sample size assessment Although there haven't been many similar studies in the past, a study (PLoS One. 2020 Sep 21;15(9):e0238620) conducted a hemodynamic evaluation before and after major vessel recanalization, analyzing 11 patients. Sample size estimation using G*Power indicated that registration of approximately 144 patients would be necessary. Taking into account factors such as image quality, we anticipate an additional recruitment of about 10%, resulting in a final target of 160 cases. 5. Data Acquisition This study is a retrospective cohort study that involves the collection of electronic medical records and imaging data.

Imaging Data to be Collected: (All images will be collected as DICOM files)

• Brain MRI (Specific imaging conditions: Fluid Attenuated Inversion Recovery, Susceptibility Weighted Imaging, T1-Weighted Imaging, T2-Weighted Imaging, Diffusion Weighted Imaging, Apparent Diffusion Coefficient)
• Brain MRA (Specific imaging conditions: source images from both extra and intracranial TOF-MRA, and 3D TOF-MRA)

6. Derivation of Intravascular Shear Stress (SIG) Through Image Analysis The transferred DICOM files are reconstructed into 3D vasculature using a separate software (VINT).