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Objective To construct an individualized fluid-solid coupling model, calculate and analyze the influence of different blood characteristics on hemodynamics in the aneurysm cavity, and further explore the influence on rupture of the cerebral aneurysm. Methods First, three-dimensional (3D) digital silhouette images were collected to construct an aneurysm model, and the influence of different blood flow characteristics on dynamic parameters of the carotid aneurysm was analyzed by computational fluid dynamic (CFD) method under the same boundary conditions. Finally, particle image velocimetry (PIV) experiment was performed on the simplified carotid aneurysm experimental model to verify reliability of the blood flow calculation method. Results For the fluid-structure coupling model with different blood flow characteristics, within a cardiac cycle, at the same time, obvious differences were found in the low velocity area of tumor cavity, the streamline distributions of tumor cavity, the wall shear stress (WSS) and deformation of the aneurysm wall. Through PIV experiments, it was found that the vortex position in tumor cavity changed with the velocity, which was consistent with flow trend of the simulation analysis results. Conclusions The two kinds of blood characteristics have small differences, but the non-Newtonian fluid is closer to true state of the blood, and the numerical results will be closer to true flow state.
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Objective To explore the value of intravoxel incoherent motion (IVIM) imaging in evaluating diffusion and perfusion variations in subacute brain infarction.Methods MRI data of 35 patients with subacute brain infarction were analyzed retrospectively,including routine DWI,IVIM imaging and three-dimensional arterial spin labeling (3D-ASL) sequence.The ADC maps were obtained by routine DWI sequence.Pure molecular-based diffusion coefficient (D) maps,pseudo diffusion coefficient of perfusion (D*) maps and perfusion fraction (f) maps were obtained by IVIM sequence.Cerebral blood flow (CBF) maps were obtained by 3D-ASL sequence.ADC,D,D*,f,CBF values and the relative values (rADC,rD,rD*,rf,rCBF) of brain infarction lesion and contralateral mirror area were calculated.All the parameters between brain infarction lesion and contralateral mirror area were compared.The correlations were analyzed between rADC value and rD,rD*,rf values respectively,as well as between rCBF value and rD,rD*,rf values respectively.Results Quantitative analysis showed significant decreases of ADC,D,D*,f and CBF values in the brain infarction lesion compared with those in the contralateral mirror area (all P＜0.05).There were positive correlations between rADC value and rD,rf values (r=0.687,0.601,P=0.005,0.018).And the positive correlation was found between rCBF value and rf value (r=0.581,P=0.022).Conclusion IVIM imaging can concurrently provide the perfusion and diffusion informations of subacute brain infarction patients,which is helpful to further elucidate the mechanisms of subacute brain infarction.
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Objective To study the value of three-dimensional pseudo-continuous arterial spin labeling(3D pCASL) for estimating collateral flow after middle cerebral artery(MCA) stenosis.Methods 3D pCASL was performed in 28 cases of negative diffusion weighted imaging(DWI) patients with MCA stenosis for estimating collateral vessels formation.The post-labeling delay(PLD) of 3D pCASL was set to 1.5 s and 2.5 s.The cerebral blood flow (CBF) of 3D pCASL with two PLD was calculated by AW workstation respectively.Nineteen normal persons were regarded as the control group.The 95% confidence interval of the ratio of left/right side of CBF of control group was set as reference value.The characteristic of the ratio of stenosed/contralateral side of CBF was analyzed.The characteristics of collateral flow was investigated with digital subtraction angiography(DSA).Results Abnormal perfusion was found in 28 patiens.Two types of abnormal perfusion were found, including typeⅠ: rCBF(PLD=1.5 s) decreased,rCBF(PLD=2.5 s) was normal (n=16);typeⅡ:rCBF(PLD=1.5 s) decreased,rCBF(PLD=2.5s) decreased (n=12).On brain DSA, abundant of collateral flow supply was found in 16 patients with typeⅠabnormal perfusion,whereas deficiency of collateral flow supply was found in 12 patients with typeⅡ.Conclusion 3D pCASL with two PLDs may provide important reference value for estimating collateral flow after middle cerebral artery stenosis.