Direct Assessment of Wall Shear Stress by Signal Intensity Gradient from Time-of-Flight Magnetic Resonance Angiography

Abstract

The aim of the study was to calculate the arterial wall signal intensity gradient (SIG) from time-of-flight MR angiography (TOF-MRA) and represent arterial wall shear stress. We developed a new algorithm that uses signal intensity (SI) of a TOF-MRA to directly calculate the signal intensity gradient (SIG). The results from our phantom study showed that the TOF-MRA SIG could be used to distinguish the magnitude of blood flow rate as high (mean SIG ± SD, 2.2 ± 0.4 SI/mm for 12.5 ± 2.3 L/min) and low (0.9 ± 0.3 SI/mm for 8.5 ± 2.6 L/min) in vessels (p < 0.001). Additionally, we found that the TOF-MRA SIG values were highly correlated with various flow rates (β = 0.96, p < 0.001). Remarkably, the correlation coefficient between the WSS obtained from the computational fluid dynamics (CFD) analysis and the TOF-MRA SIG was greater than 0.8 in each section at the carotid artery (p < 0.001 for all β values). This new technique using TOF-MRA could enable the rapid calculation of the TOF-MRA SIG and thereby the WSS. Thus, the TOF-MRA SIG can provide clinicians with an accurate and efficient screening method for making rapid decisions on the risk of vascular disease for a patient in clinical practice.

Comparison of Hemodynamic Visualization in Cerebral Arteries: Can Magnetic Resonance Imaging Replace Computational Fluid Dynamics?

“…With a workflow that takes less than 5 min, the present study suggests that TOF-MRA SIG could provide specific hemodynamic information for each subject. Thus, it can help clinicians make rapid decisions by offering an effective screening process regarding the risk of cardiovascular disease for a patient and in deciding whether or not further examination is required [ 15 ].…”

“…4D flow MRI, which is based on dynamic phase display of the flow, can provide the arterial WSS distribution [ 7 ], but previous studies have reported that it is not appropriate for analyzing arterial WSS [ 29 , 39 ]. In clinical practice, the use of 4D flow MRI for estimating WSS remains limited due to the unclear relevance of WSS and concerns about its accuracy due to poor spatial resolution along the arterial wall [ 15 ].…”

“…The workflow of TOF-MRA SIG analysis was described in previous publications [ 15 , 23 ]. The 2D source TOF-MRA images was imputed into the in-house-developed software (VINT64).…”

“…Computational fluid dynamics (CFD) with image-based vasculature geometry extraction was used to obtain detailed knowledge of 3D fluid flow fields [ 10 , 11 ], but there was insufficient evidence that the results of the CFD simulation were physiologically true [ 12 , 13 , 14 ]. Han et al [ 15 ] conducted a series of validation experiments on time-of-flight magnetic resonance angiography (TOF-MRA) signal intensity gradient (SIG) and showed that this approach is feasible to rapidly assess the arterial WSS. However, studies on the validation of this new method are rare.…”

Association of Carotid Artery Endothelial Signal Intensity Gradient with Unilateral Large Artery Ischemic Stroke

“…In the previous study, carotid artery endothelial signal intensity gradient (SIG) from time-of-flight magnetic resonance angiography (TOF-MRA) was reported to represent the relative ESS, showing strong positive correlations with wall shear stress from computational fluid dynamics [11]. TOF-MRA, which is based on the physiologic feature of flow enhancement in the construction of vascular imaging, is one of the most commonly used angiographies [12,13].…”