A Preliminary Study On Hemodynamics Of Intracranial Venous System With 4D Flow MRI

Objective:The purpose of this study is to preliminarily investigate the hemodynamic characteristics of normal physiological intracranial venous system and pathological conditions with venous sinus thrombosis(CVST)and idiopathic intracranial hypertension(IIH)by using four-dimensional flow magnetic resonance imaging(4D Flow MRI).As a screening and complementary imaging tool,4D Flow MRI further explores the potential for application in neurological diseases by combining with traditional imaging methods and associating with clinical indicators,and predicts future clinical outcomes based on hemodynamic parameters,thus improving the understanding of the pathophysiology of venous system diseases.Methods:According to strict inclusion and exclusion criteria,CVST and IIH patients with elevated intracranial pressure admitted to the Department of Neurology of the First Hospital of Jilin University from October 2022 to February 2023 were collected in this study.A total of 17 patients were included,including 9 CVST patients and 8 IIH patients.MRV and 3D T1 VISTA examinations were performed at the same time.Among them,1 CVST patient was reexamined 3 months later,and the remaining 16 patients were first-time patients with lumbar puncture evidence.4D Flow MRI data of13 patients(7 CVST+6 IIH patients)were valid because that the vessels were too narrow to capture blood flow signals.At the same time,a total of 14 healthy volunteers were included and underwent MRV,3D T1 VISTA and 4D Flow MRI examinations.In this study,the relationship between the expansion of the optic nerve sheath diameter(ONSD)and intracranial pressure was clarified.4D Flow MRI was used to analyze the visual blood flow pattern of the intracranial venous system under physiological conditions and increased intracranial pressure(CVST+IIH),and the comparison analysis of hemodynamic parameter data within the group and the correlation analysis with intracranial pressure were obtained.SPSS22.0 and Graph Pad Prism 9 were used for statistical analysis and plotting of data.p < 0.05 was considered statistically significant.Results:1、4D Flow MRI was used to observe the laminar flow blood flow pattern of the intracranial venous system under physiological conditions in healthy volunteers.0cases(0%)showed disordered blood flow,and only a few vortices were observed at the junction of the sinuses with relatively complex anatomy.The blood flow velocity increased gradually along the superior sagittal sinus,and the hemodynamic parameters of the right vessel were higher than those of the left.2 、 There was a linear relationship between ONSD and cerebrospinal fluid opening pressure(p < 0.05).AUC value was 0.8728,sensitivity was 0.75,specificity was 0.929.3、Complex blood Flow patterns were observed in CVST patients using 4D Flow MRI,including non-laminar flow,eddy current display,stagnant blood flow,and disordered blood flow direction.Hemodynamic parameters,including blood flow velocity,flow volume,wall shear stress and maximum pressure gradient,changed with the level of open pressure of cerebrospinal fluid.Although there was no clear linear relationship between the two,they were negatively correlated,and all of them were lower than normal people.After vascular recanalization,laminar blood flow similar to that of normal people could be observed in patients with CVST reexamination,and blood flow parameters were significantly increased compared with those before reexamination.4、4D Flow MRI was performed on patients with IIH.Since the peak velocity and maximum pressure gradient at the stenosis were greater than those at the upstream,high-speed red streamlines were usually visible at the stenosis.In the downstream of IIH stenosis,blood flow parameters are all higher,so fluidic flow can be seen in the downstream,and concentric-circle turbulent eddies can be seen near the stenosis.Compared with the healthy control group,the parameters in the IIH patient group were higher than those in the normal group,and the peak velocity and maximum pressure gradient across the stenosis were statistically different between the two groups(p < 0.05).Although there was no linear relationship between the above indexes and cerebrospinal fluid pressure,they were negatively correlated.Conclusions:1、The blood flow pattern of the normal intracranial venous system is laminar flow,aiming to maintain normal vascular endothelial function.The blood flow parameter values of the right blood vessel are higher than those of the left side,indicating a higher rate of dysplasia of the left transverse sinus due to superior drainage.2、ONSD can be used as supporting imaging evidence of elevated intracranial pressure.3 、 The visual blood flow pattern of patients with CVST is complex,and the hemodynamic parameters are lower than those of normal people,and is negatively correlated with intracranial pressure.After vascular recanalization,the blood flow pattern can be approximately restored to normal,and the complex blood flow including turbulence stimulates the further development of CVST lesions to a certain extent.4、Jet-like blood flow can be seen at the stenosis and downstream of the stenosis in patients with IIH,and eddy currents can be seen near the stenosis.The abnormal blood flow pattern may be to maintain the local blood supply to the brain tissue under pathological conditions as much as possible.In IIH patients with pathological pressure gradient,the peak velocity and maximum pressure gradient values across the stenosis were higher than those of normal people,and were negatively correlated with intracranial pressure,which is helpful to provide more information for the selection of treatment methods for patients.