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(Department of Radiology, Xuanwu Hospital of Capital Medical University, Beijing Key Laboratory ofMagnetic Resonance Imaging and Brain Informatics, Beijing 100053, China)

Progresses of hybrid PET/MR in quantificative evaluation of cerebral blood flow

SHANYi，LUJie*，LIKuncheng

(DepartmentofRadiology,XuanwuHospitalofCapitalMedicalUniversity,BeijingKeyLaboratoryofMagneticResonanceImagingandBrainInformatics,Beijing100053,China)

The hybrid PET/MR has a unique advantage of simultaneous scanning of both PET and MRI images, which has been gradually applied in clinical practice. In the clinical studies of severe brain diseases (such as cerebrovascular disease, brain tumor and epilepsy), accurate quantification of cerebral blood flow (CBF) can help to understand the etiology, pathogenesis, and to make early diagnosis as well as therapeutic solutions. The hybrid PET/MR can implement a noninvasive, convenient and accurate method of arterial input function for quantification of CBF. The application of the hybrid PET/MR in quantification of cerebral blood flow were reviewed in this article.

Magnetic resonance imaging; Positron-emission tomography; Cerebral blood flow

脑血流量(cerebral blood flow, CBF)对维持脑组织功能和代谢水平起决定性作用，精准定量CBF对脑部重大疾病的早期诊断、评估病情、制定诊疗方案及评价疗效具有重要价值。一体化PET/MR具有同步扫描的独特优势，一次扫描可同时获得PET和MRI图像，并可实现图像的精确配准、融合，为定量评估CBF提供了新方法。本文对一体化PET/MR评估CBF的研究进展进行综述。

1 CBF的概念及其临床意义

1.1CBF的概念 CBF指每100 g脑组织单位时间内通过的血流量，是脑灌注成像最常用的参数之一。脑灌注成像可评价血流通过毛细血管网、将携带的氧气及营养物质输送至脑组织并加以利用的过程，反映特定脑区的血流动力学状态及功能。CBF的升高或降低直接反映脑组织功能代谢水平。

1.2定量CBF的临床意义 脑部重大疾病如缺血性脑卒中、阿尔茨海默病(Alzheimer disease, AD)、癫痫、脑肿瘤等，均可因局部血脑屏障被破坏等病理生理学改变导致CBF异常。对于急性缺血性脑卒中患者，准确定量CBF能区分脑内不可逆的中心梗死区及可挽救的缺血半暗带，有利于临床及时进行溶栓治疗；对于慢性脑动脉硬化性狭窄或闭塞患者，CBF异常提示血管自我调节能力失代偿，发生脑梗死的概率增高；评估无症状高危人群的CBF，可有助于进行恰当的临床干预[1]。CBF是AD早期诊断、判断预后的重要生物学标志，研究[2]发现，AD患者额叶、颞叶及海马等部位的脑灌注下降，并与其病理改变密切相关。对于癫痫患者于发作期和发作间期联合评估CBF有助于定位致痫灶，对显示致痫灶向功能脑区的播散具有高敏感度[3]。……