Assessing the Risk of Intracranial Aneurysm Rupture Using Morphological and Hemodynamic Biomarkers Evaluated from Magnetic Resonance Fluid Dynamics and Computational Fluid Dynamics

Abstract

Purpose: Evaluate in vivo hemodynamic and morphological biomarkers of intracranial aneurysms, using magnetic resonance fluid dynamics (MRFD) and MR-based patient specific computational fluid dynamics (CFD) in order to assess the risk of rupture. Methods: Forty-eight intracranial aneurysms (10 ruptured, 38 unruptured) were scrutinized for six morphological and 10 hemodynamic biomarkers. Morphological biomarkers were calculated based on 3D time-offlight magnetic resonance angiography (3D TOF MRA) in MRFD analysis. Hemodynamic biomarkers were assessed using both MRFD and CFD analyses. MRFD was performed using 3D TOF MRA and 3D cine phase-contrast magnetic resonance imaging (3D cine PC MRI). CFD was performed utilizing patient specific inflow-outflow boundary conditions derived from 3D cine PC MRI. Univariate analysis was carried out to identify statistically significant biomarkers for aneurysm rupture and receiver operating characteristic (ROC) analysis was performed for the significant biomarkers. Binary logistic regression was performed to identify independent predictive biomarkers. Results: Morphological biomarker analysis revealed that aneurysm size [P = 0.021], volume [P = 0.035] and size ratio [P = 0.039] were statistically significantly different between the two groups. In hemodynamic biomarker analysis, MRFD results indicated that ruptured aneurysms had higher oscillatory shear index (OSI) [OSI.max, P = 0.037] and higher relative residence time (RRT) [RRT.ave, P = 0.035] compared with unruptured aneurysms. Correspondingly CFD analysis demonstrated significant differences for both average and maximum OSI [OSI.ave, P = 0.008; OSI.max, P = 0.01] and maximum RRT [RRT.max, P = 0.045]. ROC analysis revealed AUC values greater than 0.7 for all significant biomarkers. Aneurysm volume [AUC, 0.718; 95% CI, 0.491-0.946] and average OSI obtained from CFD [AUC, 0.774; 95% CI, 0.586-0.961] were retained in the respective logistic regression models.

From2Dto4DPhase‐ContrastMRIin the Neurovascular System: Will It Be a Quantum Jump or a Fancy Decoration?

“…92,[113][114][115][116][117] Compared with unruptured aneurysms, aneurysms immediately before the rupture had lower aneurysm-averaged WSS 94 as well as an irregular aneurysm shape, and a higher aspect ratio. Ruptured aneurysms had more area under lower WSS and above higher oscillatory shear index (OSI) compared with unruptured aneurysms, 103,105,110,117 and the rupture point was located in a low WSS region of the aneurysm wall. 118 OSI indicates a directional change of fluctuated WSS during the cardiac cycle, calculated based on the WSS vector.…”

“…4 Depending on either the 1.5T or 3T machines used, the scan times were 7-26 minutes using parallel imaging ARC 2 or GRAPPA 2 in clinical studies that enrolled 203 cerebral aneurysm patients. 117 The scan times for 4D flow MRI was further shortened to 6-10 minutes using k-t acceleration (kat-ARC) with variable density random k-t sampling in 10 healthy volunteers, 15 and to 5 minutes using pseudorandom variabledensity Cartesian undersampling strategy (CIRCUS 4) with the combination of k-t, parallel imaging, and compressed sensing image reconstruction techniques (k-t SPARSE-SENSE) in clinical studies that enrolled five healthy volunteers and eight patients with cerebral aneurysms. 43 In the undersampled 3D radial acquisition technique, centrally located data points in k-space radial trajectory are read out first to ensure good image contrast.…”

“…94 Accelerated 4D flow MRI visualizes complex flow patterns within the aneurysm sac, with improved resolution in a clinically feasible time and estimates the objective hemodynamic parameter for the evaluation of cerebral aneurysm (Table 3). 7,9,11,43,[115][116][117] Flow visualization strategies include velocity vector fields, shearing velocity, streamlines, and pathlines. The analysis of complex and vortical flow patterns seen within the aneurysm can be classified and help stratify the rupture risk of cerebral aneurysms.…”

4D flow MRI hemodynamic biomarkers for cerebrovascular diseases

“…An important challenge is to predict the risk of aneurysm rupture to decide which asymptomatic patients should undergo surgery. 4D flow MRI hemodynamic biomarkers with potential for such aneurysm classification include estimated intra-aneurysmal pressure [85], aneurysm wall shear stress [86][87][88], inflow jet patterns [89], and oscillatory shear index that describes the cardiac-cycle dynaimcs of wall shear stress [90][91][92].…”

“…Aneurysm Static [86][87][88] and dynamic [90][91][92] measures of wall shear stress for rupture risk stratification. Arteriovenous shunts Characterize hemodynamic changes and identify main feeding arteries [93], evaluation of treatment response [94].…”