冠状动脉周围脂肪衰减指数的成像原理、临床证据与应用边界

Pericoronary Fat Attenuation Index: Imaging Principles, Clinical Evidence, and Boundaries of Application

摘要: 局部免疫炎症贯穿冠状动脉粥样硬化进展及斑块破裂过程，而危险因素、血液指标和狭窄程度对炎症发生部位与活动状态的描述均不充分。冠状动脉周围脂肪衰减指数(fat attenuation index, FAI)从既有冠状动脉CT血管成像(coronary computed tomography angiography, CCTA)数据中读取血管外信息：冠状动脉壁释放的炎症信号可改变邻近脂肪细胞成熟及组织内脂质、水分构成，继而引起CT衰减分布和径向梯度改变。FAI据此形成对局部炎症相关表型的间接量化。研究表明，FAI与急性冠状动脉综合征罪犯病变、危险斑块征象和后续心血管事件存在关联，在无阻塞性冠状动脉疾病患者中亦可能补充传统风险评估。本文围绕其病理生理依据、测量流程、主要临床研究、可能用途和现实限制展开讨论。综合现有证据，FAI可拓展CCTA的功能信息，但数值会受到管电压、重建方式、解剖差异和算法校正的共同影响，既往研究截点不能脱离方法学背景使用。FAI进入常规决策之前，仍需统一采集与分析规范，并通过跨中心验证和前瞻性干预研究证明临床效用。

Abstract: Local immune activity contributes to the progression and rupture of coronary atherosclerotic plaques, but conventional risk factors, blood biomarkers, and stenosis grading provide limited information about where that activity is occurring. The pericoronary fat attenuation index (FAI) extracts additional information from existing coronary computed tomography angiography (CCTA). Inflammatory signals released by the arterial wall influence adipocyte maturation and the lipid-water composition of adjacent fat, producing measurable shifts in CT attenuation and its radial distribution. FAI therefore represents an imaging readout of an inflammation-related local phenotype rather than direct visualization of inflammatory cells. Published studies associate FAI with culprit lesions in acute coronary syndromes, adverse plaque characteristics, and subsequent cardiovascular events; the metric may also refine assessment in patients without obstructive coronary disease. This review examines the pathophysiological rationale, measurement workflow, principal clinical evidence, possible uses, and practical limitations of FAI. Although FAI broadens the functional information available from CCTA, its value is affected by tube voltage, reconstruction technique, anatomy, and algorithmic correction. Study-specific thresholds should consequently not be transferred between platforms without validation. Harmonized acquisition and analysis, external testing across centres and populations, and prospective evidence that FAI-informed care improves outcomes are needed before routine adoption.