基于18F-NaF PET/MR评价颅内动脉粥样硬化斑块微钙化及其稳定性的机制研究

颅内动脉粥样硬化易损斑块破裂是引发缺血性脑卒中的主要原因，微钙化是增加斑块易损性、促使斑块发生破裂的重要因素。传统影像学方法不能评价斑块内微钙化，18F-NaF PET能够检测出斑块中新陈代谢活跃的微钙化，但无法辨别解剖学特征，高分辨率MR能够提供斑块解剖学信息及斑块内出血、新生血管等易损特征，一体化PET/MR能够实现颅内动脉斑块微钙化的无创评估，为研究微钙化在颅内动脉粥样硬化斑块破裂中的作用提供了可能。我们前期研究证实，颈动脉斑块的18F-NaF摄取值与组织病理学上微钙化的程度呈正相关，因此，本项目应用18F-NaF PET/MR，分析比较症状性和无症状颅内动脉粥样硬化患者的斑块微钙化特征，探索微钙化与MR斑块易损特征的相关性，并进行纵向观察，揭示斑块内微钙化演变规律及与颅内动脉粥样硬化患者预后的关系，阐明微钙化在颅内动脉不稳定斑块中的作用机制，进行早期影像学预警，降低脑卒中的发生。

Rupture of vulnerable intracranial atherosclerotic plaques is the main cause of ischemic stroke. Microcalcification is a key factor that can increase plaque vulnerability and promote plaque rupture. Traditional imaging methods can not evaluate microcalcification within the plaque. 18F-sodium fluoride (18F-NaF) PET can be used to identify active microcalcification within the plaque. PET is the lack of anatomical landmarks to confirm that the observed hot spots are indeed derived from plaques. High-resolution MR can be able to provide anatomical information of plaques and vulnerable features (eg, intraplaque hemorrhage and neovascularization, etc). Hybrid PET/MR allows evaluating the microcalcification within the intracranial plaque, which makes it possible to explore the mechanism of microcalcification in the rupture of intracranial atherosclerotic plaque. Our preliminary study demonstrated that there was a significant correlation between tracer activity in the carotid plaques and the microcalcification in the corresponding histological sections. In this study, microcalcification was assessed and compared in symptomatic and asymptomatic plaques by 18F-NaF PET/MR. We will then analyze the correlations between microcalcification and MR imaging features. Through longitudinal follow-up, we aim to reveal the evolution of plaque microcalcification, and clarify the relationship between microcalcification and the prognosis of patients with intracranial atherosclerosis. We also aim to clarify the pathophysiological mechanism of microcalcification in the intracranial plaque stability. Finally, early identification of vulnerable plaque is expected to reduce the incidence of ischemic stroke.