Relationship Of Anterior Cerebral Artery A1Segment Hypoplasia And Anterior Communicating Artery Aneurysm And Establishment Of Patient-specific AComA Aneurysm3D Rigid Wall CFD Model

Part OneA1segment hypoplasia accompanied by AcomA aneurysms assessedwith magnetic resonance angiographyPurpose: This study is to evaluate the use of3-dimensional time-of-flight magneticresonance angiography (3D-TOF MRA) at3.0T for the detection and classification ofA1segment hypoplasia based on a large case series and investigate the potential linkswith AcomA aneurysm occurrence.Methods: Between January2009and June2012,8,013patients underwent MRAexamination at3.0T in our hospital. MRA was performed using3D-TOF withvolume rendering (VR) technique. The presence and location of A1segmenthypoplasia and AcomA aneurysm was reviewed.Results: Among the8013patients examined,138patients were identified withAcomA aneurysms.425patients were defined with A1segment hypoplasia,amongwhom303right-sided A1hypoplasia and122left-sided A1hypoplasia.60of these425patients were confirmed with AcomA aneurysms， among them were49 right-sided A1hypoplasia. The prevalence of AcomA aneurysm with A1segmenthypoplasia was14.1%, which was much higher compared with that (1.0%) of AcomAaneurysm without A1segment hypoplasia (P<0.001).Conclusions: The incidence of right-sided A1segment hypoplasia eitheraccompanied with AcomA aneurysm or not was much greater than that of left-sided.Intracranial AcomA aneurysm development appeared to be associated with A1segment hypoplasia. Part TwoImpact of A1hypoplasia on the rupture rate of anteriorcommunicating artery aneurysmsPurpose: To analyze the impact of anatomical variation of anterior cerebral artery A1segment hypoplasia on the rupture rate of the anterior communicating artery (AcomA)aneurysms.Materials and methods:161AcomA aneurysms in161patients were identified withMRA between January2008and June2012. Parent artery variations at anteriorcerebral artery A1segment were classified as: A1hypoplasia (including aplasia)versus advantageous A1size versus symmetrical A1size. The rupture rate of AcomAaneurysms between each group was compared.Results：The mean size of AcomA aneurysms of three categories were as follows: A1hypoplasia4.18mm, advantageous size3.32mm, symmetric size3.14mm.As for theruptured AcomA aneurysms, there were44(60.3%) in the A1hypoplasia group,14(37.8%) in the advantageous A1group and15(29.4%) in the symmetric A1group.The odds ratio for aneurysm rupture of A1hypoplasia configuration were2.493timesof the advantageous A1group, with the95%CI,1.105–5.621(p=0.026) and3.641 times of the symmetric A1group, with the95%CI,1.697–7.812(p=0.001). Thecorrelation coefficient of aneurysm size and rupture was0.617using Spearman’scorrelation analysis. Multivariate logistic regression analysis also showed that A1configuration and aneurysm size were independent risk predictors for AcomAaneurysm rupture.Conclusion: A1hypoplasia was associated with higher rupure rate of AcomAaneurysms.The higher risk seemed to correlate to the larger size of AcomA aneurysmwith A1hypoplasia configuration. Both A1configuration and aneurysm size shouldbe considered when predicting rupture risk of AcomA aneurysm. Part ThreeEstablishment of patient-specific AcomA aneurysm3D rigid wallCFD model based on3D-TOF-MRA at3.0TPurpose: Through the source image data from3-dimensional time-of-flight magneticresonance angiography (3D-TOF-MRA) at3.0T, patient-specific AcomA aneurysm3D rigid wall CFD model was to established to analyze aneurysm hemodynamiccharacteristics.Materials and methods: Two cases of AcomA aneurysms with A1hypoplasiadetected by3D-TOF-MRA were reconstructed. The CFD software gambit andFluent12.1were used to do the numerical simulation adopting finite element method.One case was an unruptured aneurysm and the other was a ruptured one. Calulate anddescribe the aneurysm flow field and their hemodynamic characteristics. Select thesame cases to simulate and compare the influence of different inlet speed on theaneurysm hemodynamic characteristics such as WSS and static pressure. Results: Two cases of AcomA aneurysm models were simulated and the flow lines,flow velocity and WSS and static pressure of the models were calculated anddescribed. The two models showed distinctive difference of the hemodynamiccharacteristics. Adopting different inlet speed had great impact on the CFD simulationparameter outcome though the models showed almost the same distribution ofhemodynamic characteristics.Conclusion: Patient-specific AcomA aneurysm3D rigid wall CFD modelsreconstructed by3D-TOF-MRA have high resolution and can describe thehemodynamic features of the AcomA aneurysm and surrounding parent artery.Patient-specific model based on3D-TOF-MRA showed its potential for CFDsimulation and rupture risk evaluation of intracranial aneurysms in the future. Part FourInfluence of Hemodynamic Factors on Rupture of IntracranialAcomA Aneurysms: Patient-Specific3D Aneurysms ModelComputational Fluid Dynamics Simulation based on3D-TOF MRABackground and purpose: Hemodynamic factors especially WSS play an importantrole in the rupture of cerebral aneurysms. The purpose of this study was to evaluatethe impact of hemodynamic factors on the rupture of AcomA Aneurysms with3Dreconstruction model CFD simulation based on3D-TOF MRA.Materials and methods: MRA was performed in14intracranial AcomA Aneurysmsand these aneurysms were divided into ruptured and unruptured groups, each groupwith7aneurysms. The hemodynamic factor WSS of the aneurysms and their domevertex were compared. Results: There was a significant difference in the WSS at peak systole at the regionsof aneurysm dome vertex between the ruptured and unruptured group (ie,0.68±0.32Pa versus3.82±2.94Pa, P=0.003) but not at the entire aneurysm regions (ie,7.24±3.90Pa versus10.87±4.39Pa, P=0.085). The proportion of the low WSS area to thewhole area of the aneurysms was23.07±17.75%in the ruptured group and5.86±5.80%in the unruptured group; the difference between the2groups was statisticallysignificant (P=0.013).Conclusion: Patient-Specific3D aneurysm model computational fluid dynamicssimulation based on3D-TOF MRA may be a useful model to investigate thoseaneurysms with higher rupturing prospect. The ruptured AcomA aneurysmsmanifested lower WSS at the regions of aneurysm dome vertex, a higher proportion ofthe low WSS area to the whole area of aneurysm compared with the unrupturedaneurysms.