颅内夹层动脉瘤动态变化的影像学基础和血流动力学机制研究

Intracranial dissecting aneurysm (IDA) is one of the most intractable cerebral vascular diseases. Although the evolution of imaging has led to an increased diagnosis of IDA in recent decades, optimal management of this disorder is still unclear and somewhat controversial. IDAs differ from intracranial saccular aneurysms in a number of ways and are progressive lesions. It is found that the lumen wall pathology features are the cause of morphological changes by autopsy. Understanding the pathological status of a dissecting aneurysm may be important for speculating its possible outcome and choosing rational treatment strategies. However, evaluation of the underlying pathological status of such lesions is challenging during clinical work due to the difficulty in obtaining in vivo pathological species of IDA. Digital subtraction angiograph (DSA), which shows geometric shapes of the affected artery instead of imaging features of the lumen wall, has long been the criterion standard for the diagnosis and follow-up. It hampered to comprehensive assess the dynamic changes of intracranial dissecting aneurysm due to lack of observation combined arterial wall structure with lumen. Recently 3T high-resolution magnetic resonance imaging (HR-MRI) is a noninvasive imaging technique that provides a delineation of the arterial wall. We have investigated vessel wall imaging features combined with the luminal shapes of IDAs by 3T HR-MRI and DSA. Our research team testified that 3T HR-MRI combined with DSA offered clear visualization of vessel wall features and accurate assessment of the lumen in IDAs. This combined approach would be highly useful for understanding the underlying pathological status of IDAs. Because IDAs have a characteristic of dynamic changes, quantitative analysis and follow-up studies is important to objectively assess the dynamic changes of IDAs. We also testified that hemodynamic factors play an important role in aneurysm growth and outcome after treatment. On the basis of the preliminary work of our research teams, we suppose that imaging characteristics of IDAs and corresponding the possible mechanism of progressive lesions could help determine treatment strategies. We are planning to carry out quantitative and qualitative analysis and follow-up researches of the dynamics changes of IDA by 3T MRI and DSA and make computational fluid dynamics research. The conclusion made by our researches will be contributive to profoundly understand the dynamic changes of IDAs and predict the outcomes of the lesions. It is also beneficial to understand pathological status of such lesions, identify high-risk patients and guide treatment strategies.

颅内夹层动脉瘤是难治性脑血管病，其病理过程与颅内囊状动脉瘤不同,呈动态变化。尸检发现管壁结构的变化是管腔形态多样性的原因，但临床难以获得病理标本，无法根据病理类型选择治疗方案。脑血管造影(DSA)是影像学诊断和随访的金标准，但仅显示管腔的形态学改变，缺乏结合管壁结构的观察研究，不利于认识颅内夹层动脉瘤的病理特征和动态变化。课题组前期应用3T核磁共振(MR)和DSA综合评价颅内夹层动脉瘤管壁和管腔的特征，发现3T MR能显示管壁结构特点，有助理解不同管腔形态变化的病理特征；前期证实血流动力学因素在脑动脉瘤的发展和转归中的重要作用。本研究拟应用多模式3T MR结合DSA获得颅内夹层动脉瘤管壁和管腔影像，行定性、定量分析及随访研究，建立动态变化的影像学特征和病理变化的关联；并利用血流动力学分析其动态变化的机制。本研究对于全面认识颅内夹层动脉瘤动态变化机制和相应影像学特征，指导临床决策有重大意义。

颅内夹层动脉瘤是难治性脑血管病，其病理过程与颅内囊状动脉瘤不同，呈动态变化。脑血管造影(DSA)是影像学诊断和随访的金标准，但仅显示管腔的形态学改变，缺乏结合管壁结构的观察研究，不利于认识颅内夹层动脉瘤的病理特征和动态变化。前期研究发现3T 核磁共振(MR)能显示管壁结构特点，可以有助理解不同管腔形态变化的病理特征；并且血流动力学因素在脑动脉瘤的发展和转归中的重要作用。因此，本研究主要是基于高分辨核磁影像及血流动力学分析，探索颅内夹层动脉瘤动态变化过程及其发生机制。本项目利用多中心大样本数据库的独特优势，与国内各中心进行合作交流，优化了3T 高分辨核磁共振成像的扫描序列方法，采用先进的颅内动脉瘤血流模拟方法和丰富的临床资源，开展了多项回顾性颅内夹层动脉瘤预后的临床及血流动力学分析。其中临床分析代表性研究结果有：1.收集多个中心数据并分析颅内夹层动脉瘤复发危险因素，发现动脉瘤直径及支架在瘤颈处的金属覆盖率是复发的独立预测因素。2.回顾性分析数据库内经血管内治疗重建的未破裂夹层动脉瘤的手术前后的高分辩核磁影像，发现动脉瘤的最大直径以及动脉瘤壁的强化是动脉瘤治疗后复发的独立危险因素。3. 在建立的数据库基础上，我们参与制订了颅内动脉夹层的影像学诊断标准，参与了《颅内动脉夹层的影像学诊断中国专家共识》的拟定。另外，我们开展多项回顾性颅内夹层动脉瘤术后转归的血流动力学分析。主要结果发现：1.使用虚拟支架的方法分析了颅内夹层动脉瘤复发的血流动力学特征，发现高血流冲击以及不充分的流速下降是复发的危险因素。2. 探讨了支架血流导向能力在颅内夹层动脉瘤预后过程中的作用及其对分支血流的作用，发现支架的血流导向能力在改变瘤内血流冲击起到重要作用，然而对分支血流影响较小。以上研究成果提示对颅内夹层动脉瘤进行高分辨核磁以及血流动力学分析，可有助于全面了解颅内夹层动脉瘤动态变化及其机制，具有重要临床实际意义。