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.
Our findings indicated that nh-WSS and nh-SWSSG were good biomarkers for aneurysm initiation in the paraclinoid ICA.
Vasoconstrictor effects of endothelin-1 (ET) were investigated in endothelium-denuded strips of cerebral (basilar and posterior cerebral) and mesenteric arteries of the dog. ET produced a concentration-dependent contraction in these arteries. Contractile responses to lower concentrations (below 3 x 10(-10) M) of ET were significantly greater in the cerebral arteries than in the mesenteric artery. Inhibition by nifedipine of the contractile responses to ET was greater in the basilar artery than in the mesenteric artery. After the inhibition by 10(-7) M in the mesenteric artery. After the inhibition by 10(-7) M nifedipine, the remaining responses to ET were similar in the two arteries. Cerebral arteries, but not the mesenteric artery, relaxed significantly from the resting level when placed in a Ca2(+)-free solution containing 0.1 mM EGTA (0-Ca solution). Readdition of Ca2+ to the cerebral arteries placed in the 0-Ca solution caused a biphasic contraction that was sensitive to nifedipine. When 10(-9) M ET was introduced before the Ca2(+)-induced contraction, this peptide produced only a very small contraction, but enhanced the Ca2(+)-induced contraction. The extent of the enhancement induced by ET was much greater in the cerebral arteries than in the mesenteric artery. These results indicate that the enhanced responses to ET in the cerebral arteries were dependent to a large extent on Ca2+ influx through voltage-dependent Ca2+ channels (VDCs). It is likely that the VDCs in these arteries are more activated in the resting state than those in the mesenteric artery.
Demonstration of the exact site of dural fistulas in cases of cerebrospinal fluid rhinorrhea is difficult. Previous reports have described the use of metrizamide cisternography combined with either hypocycloidal tomography or computerized tomography; however, direct, dynamic, real-time visualization of the fistula is difficult with instillation of a minimal dose of metrizamide using those methods. A digital video subtraction fluoroscopy system can visualize the actual site of the fistula directly and dynamically using only a small amount of metrizamide.
We performed 3-dimensional cine phase-contrast magnetic resonance-based computational fluid dynamics for a basilar artery that developed a sidewall aneurysm over a 25-month period. There was an area with high gradient oscillatory number in the location of the future aneurysm ostium and an area with high wall shear stress (WSS) and high spatial WSS gradient at the distal edge of the future aneurysm. These could be biomarkers for development of intracranial aneurysms.Keywords: computational fluid dynamics, hemodynamics, intracranial aneurysms, magnetic resonance fluid dynamics, wall shear stress (WSS) IntroductionHemodynamics is thought to play very important roles in the initiation, progression, and rupture of intracranial aneurysms. The formation and regression of a flow-related cerebral aneurysm has been reported. 1 Although an area of relatively low and rotating wall shear stress (WSS) may cause an aneurysm to form, 2 high WSS is a more likely cause.3 Recently proposed initiating causes of intracranial aneurysms include high WSS and high spatial WSS gradient (SWSSG) 4 -6 or high gradient oscillatory number (GON), 6,7 the index for the temporal fluctuation of the SWSSG over the cardiac cycle.We performed 3-dimensional (3D) cine phasecontrast (PC) magnetic resonance (MR)-based computational fluid dynamics (CFD) with patient-specific boundary conditions for a basilar artery that developed a sidewall aneurysm at the ventral aspect of its distal portion over a 25-month period, and we investigated whether an area with high WSS and SWSSG or an area with high GON was present in and around the location of the aneurysm before it formed to predict future development of intracranial aneurysms. Case ReportOur institutional review board approved this study, and we obtained informed consent from the subject.An 88-year-old woman with heaviness of the head underwent MR examination including 3D time-of-flight (TOF) MR angiography (MRA) using *Corresponding author, Phone: +81-52-719-3154, Fax: +81-52-719-1509, E-mail: isoda@met.nagoya-u.ac.jp Magn Reson Med Sci, Vol. 14, No. 2, pp. 139-144, 2015 ©2015 (0.37 © 1 © 0.5 mm 3 with ZIP); bandwidth, 41.67 kHz; and imaging time, 5 min 29 s. Three-dimensional TOF MRA showed a 4-mm aneurysm at the bifurcation of the right middle cerebellar artery (MCA), a 3-mm aneurysm at the M1 segment of the left MCA, and ventral curving of the basilar artery without a distinct aneurysm (Fig. 1A, B). Because of the patient's age, her doctors determined that she should be followed closely without therapy.She underwent follow-up MR examination including 3D TOF MRA and 3D cine PC MR imaging 25 months after the initial examination. Imaging parameters for 3D TOF MRA were the same as those used previously; parameters for 3D cine PC MR imaging 8 were: TR/TE/NEX, 5.3 ms/2.3 ms/ 1; FA, 12 degrees; slab orientation, transaxial; FOV, 160 © 160 © 30 mm 3 ; matrix, 160 © 160 © 30 (160 © 160 © 60 with ZIP); voxel size, 1 © 1 © 1 mm 3 (1 © 1 © 0.5 mm 3 with ZIP); bandwidth, 62.5 kHz; number of phases, 20; velocit...
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