Association of cerebral infarction with vertebral arterial fenestration using non-Newtonian hemodynamic evaluation.

PURPOSE: Cerebral artery fenestration is a rare vascular anomaly, but its existence has been increasingly documented. The association of cerebral infarction and fenestration is of great clinical interest, and the exact underlying mechanism remains unclear. This study aims to identify risk factors contributing to cerebral infarction by computational hemodynamics analysis. METHODS: Eight patients with image findings of fenestration structure were recruited in this research, in which four suffered fenestration-related cerebral infarction (A series) while the other four (B series) were set as control matched by the fenestration size. Three-dimensional models were reconstructed from the MRA images and computational simulations with non-Newtonian flow model were performed to get interested hemodynamic characteristics. RESULTS: The blood flow pattern was relatively separated along two channels of fenestration in series A compared with series B cases in Group 1-2, however, no significant difference was shown in Group 3-4. Quantitatively, planes were cut in the middle of fenestrations and the ratio of mass flow rate and area was calculated at systolic peak. Results showed that the side of the dominant blood supply was opposite between A and B series, and the dominant side was also opposite between small and large fenestrations. In infarction cases, the basilar top was distributed with larger areas of detrimental hemodynamic indicators and a larger concentrated high viscosity region. CONCLUSION: The flow division condition throughout the fenestration structure has a key impact on further flow redistribution and flow pattern. The blood viscosity has the potential to be a useful tool in identifying the risk factors for cerebral infarction and more emphasis should be placed on the hemodynamic environment at superior cerebellar arteries.

Simulation analysis of aneurysm embolization surgery: Hemorheology of aneurysms with different embolization rates (CTA).

BACKGROUND: Embolization degree acts as an important factor affecting recurrence of aneurysm. OBJECTIVE: To analyze the role of hemodynamics parameters of different degrees of embolization in the occurrence, development and post-treatment of aneurysms, and to determine the specific factors causing the occurrence and recurrence of aneurysms after hemodynamics treatment. Our study provides a theoretical basis for the prevention and treatment of aneurysms. METHODS: Computed tomography angiography data of a patient with cerebral aneurysm was used to model 0%, 24%, 52%, 84% and 100% of endovascular embolization, respectively. The time average wall shear stress, time average wall shear stress, oscillatory shear index, hemodynamics formation index and relative retentive time were used to analyze the changes of hemodynamics indexes in different embolic models. RESULTS: With the increase of embolic rate, the values of time average wall shear stress, time average wall shear stress grade and aneurysm index formation gradually increased, and the values of relative retention time gradually decreased. Oscillatory shear index was higher in patients with incomplete embolization and decreased in patients with complete embolization. CONCLUSIONS: As the degree of embolization increased, the blood flow tended to stabilize, reducing the risk of cerebral aneurysm rupture, and finding that the wall of the vessel junction was susceptible to injury.

[Phase separation characteristics of an anaerobic baffled reactor treating organic wastewater containing sulphate].

Phase separation characteristics of anaerobic baffled reactor (ABR) treating organic wastewater containing sulphate were investigated in a 5-compartment ABR with an effective volume of 32 L. During a start-up experiments of 132 days, the chemical oxygen demand (COD) and sulphate (SO4(2-)) removal efficiency, volatile fatty acid (VFA) and sulfide (S2-) distribution in each compartment were measured. The microbiology communities of granular sludge were also investigated by scanning electronic microscope (SEM). The experimental results showed that low influent loading and low increase are the keys to start-up of ABR. The volumetric loading rates of COD and SO4(2-) increased stage and stage from 1.5 kg x (m3 x d)(-1) to 3.3 kg x (m3 x d)(-1) and from 0.07 kg x (m3 x d)(-1) to 0.18 kg x (m3 x d)(-1) for 132d, and achieved a stable state that resulted in 95% COD and 85% SO4(2-) removal. COD had the trend of decreasing with compartments along flow direction, it's removal rate in compartment 1, 4 and 5 took the large proportion in total COD removal rate, and sulphate removal rate in the initial three compartments took the large proportions in the total sulphate removal rate. The VFA and S2- concentrations were high in the initial three compartments and obviously declined in the final two compartments. With the loading rate increase, the proportion of COD and SO4(2-) removal rates in the final room increased, the highest and the lowest point of VFA and S2- concentrations were gradually moved to hind room. The SEM observation indicated microbiology communities of granular sludge in each compartment were cooperative and specific, it showed that the acidogenic phase and methanogenic phase, sulfate-reducing phase and sulfur-producing phase were separated in the ABR.