【作者】 任远；

【导师】 李志勇；

【作者基本信息】 东南大学 ， 生物医学工程， 2015， 硕士

【摘要】 Willis环是脑动脉最重要的侧支循环,其在维持大脑两侧血供平衡、预防脑卒中发生,改善预后等方面具有重要的意义。然而,在正常人群中,拥有完整Willis环结构的只有不到50%。本论文的首要目的是评估Willis环后循环的不同变异类型在应对单侧颈内动脉狭窄时所表现出的代偿能力大小。除此之外,在血流动力学的研究中,个体化模型的建立是基于不同的医学影像技术。因此,本文的另一个目的是从方法学上对比了不同成像技术(3DRA, CTA, MRA)在颅内动脉瘤模型重建中的差异。在对比性的研究中,我们以3DRA数据所建模型(DM)为“标准模型”,CTA模型(CM)和MRA模型(MM)分别与之在形态学参数、血流动力学参数以及流动特性方面进行对比。结果表明,与DM相比,CM与MM在表征颅内动脉瘤形态方面并无显著差异,但在血流动力学方面则有较大差异。而对三类模型瘤内血流流动特性的评估结果显示,不同影像技术并没有显著影响其流动特性。因材料所限,不同变异类型Willis环代偿能力的研究是基于理想模型进行的。首先,基于Willis环后循环的解剖形态变异,本文构建了8种不同Willis环结构三维理想模型。随后,在各模型右侧颈内动脉施以不同程度的狭窄度,分别为24%、43%、64%以及79%。最后,对这40个理想模型进行计算流体力学的模拟分析,所有模型的边界条件以及其它设置均保持一致。通过观察和对比各出口动脉流量的变化,我们发现对于大脑中动脉(MCA)和大脑前动脉(ACA)而言,过渡型Willis环结构(TansT)的代偿能力是最好的。对于大脑后动脉(PCA)而言,单侧颈内动脉狭窄对单侧后交通动脉缺失型Willis环结构(uabPCoA)影响最小。同时,研究结果表明完全胚胎型Willis环结构(fuFTP)的代偿能力是最差的,在临床中应予以高度重视。本文首先从技术层面对比了不同影像数据在个体模型建立中的差异,这对于血流动力学研究中影像材料的选择具有一定的参考价值。随后,本文研究了后循环变异型Willis环在应对单侧颈内动脉狭窄时所体现的代偿能力大小,这有助于临床医生选择最佳的治疗方案以及对手术风险进行评估。更多还原

【Abstract】 The Circle of Willis (CoW) is the most important collateral pathway of the cerebral artery, which has the fundamental significance in balancing blood supply between the two cerebral hemispheres, preventing stroke and improving prognosis. Unfortunately, no more than 50% of the general population has a complete CoW. The primary purpose of this paper is to assess the collateral capacity of CoW with anatomical variation in the posterior circulation when unilateral internal carotid artery (ICA) is occluded. Besides, the reconstruction of patient-specific model is based on different imaging modalities when studying the hemodynamics. Therefore, another purpose of this paper is to compare the models derived from different medical imaging technology in modelling of the intracranial aneurysm.In the comparative research,3DRA based model (DM) were treated as the "standard models", CTA based models (CM) and MRA based models (MM) were compared with the "standard model" in morphology, hemodynamics and flow characteristics, respectively. The results demonstrated that both CM and MM had no obvious difference in reproducing the aneurysmal geometry when comparing DM. However, the difference of hemodynamic parameters are relative large. Besides, compared with DM, both of CM and MM have a good agreement in assessing the flow characteristics.Due to the limitation of materials, the study of the collateral capacity was based on idealized models. First of all, eight 3D models were reconstructed based on different anatomical variation in the posterior circulation of CoW. Subsequently, a stenosis with different degrees was simulated in the right ICA, namely 24%,43%,640 and 79%, respectively. Finally, a total of 40 models were performed with computational fluid dynamics simulations. All of the simulations shared the same boundary conditions with static pressure and the volume flow rate (VFR) which were obtained to evaluate their collateral capacity. As for the middle cerebral artery (MCA) and the anterior cerebral artery (ACA), the transitional-type model possessed the best collateral capacity. But for the posterior cerebral artery (PCA), unilateral stenosis of ICA had the weakest influence on the unilateral posterior communicating artery (PCoA) absent model. We also found that the full fetal-type posterior circle of Willis was an utmost dangerous variation which should be paid more attention.The comparison of the patient-specific models derived from different imaging modalities may help the researchers choose medical imaging in the study of hemodynamics. Moreover, this study of the collateral capacity of CoW with anatomical variation in the posterior circulation in coping with unilateral ICA occluded may help neurosurgeons select the best treatment strategy and assess operation risk.更多还原