DWI在脑部的应用

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单纯疱疹病毒性脑炎(Herpes simplex encephalitis) DW image shows high signal in the lesions with usually decreased ADC values representing cytotoxic edema and rarely higher ADC values representing vasogenic edema. 病变DWI表现为高信号，ADC值降低代表细胞 毒性水肿，少数高ADC值代表血管源性水肿 Areas of cytotoxic edema correspond to a worse outcome compared to areas of vasogenic edema 细胞毒性水肿与血管源性水肿相比，结局较差
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单纯疱疹病毒性脑炎(Herpes simplex encephalitis)
Herpes simplex encephalitis is one of the most common viral infections. T2-hyperintense lesions with typical temporal and frontal localization with petechial hemorrhage are characteristic findings. 单纯疱疹病毒性脑炎是最常见的病毒感染性疾病之一， T2高信号和典型的颞叶、额叶点状出血是其特征表现。 Conventional MR imaging and clinical findings might be non-specific, necessitating the proof of evidence of viral DNA by polymerase chain reaction in the cerebrospinal fluid. 常规MRI和临床表现可能是非特异性的，需要脑脊液中 病毒DNA的PCR试验来验证
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contents
Infection Trauma Hemorrhage DWI Vasculitis and vasculopathies Leukodystrophies
Neoplastic lesions
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Encephalopathies
Epilepsy
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克雅氏病 （ Creutzfeld-Jakob disease ） Creutzfeld-Jakob disease is one of several spongiform encephalopathies. Characteristic findings are rapidly progressive dementia, myoclonus and periodic sharpwave complexes on electroencephalography. 克雅病（皮质-纹状体-脊髓变性 ） 是几种海绵状脑病 之一。典型临床表现为：快速进展的痴呆、肌阵挛，脑 电图表现为周期性的锐波。 MR imaging is helpful in differentiating the two forms of the disease. 磁共振可以帮助鉴别克雅氏病的两种类型。
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Introduction
Although DWI has been tried for different organ systems, it has been found its primary use in the central nervous system. The most widely used clinical application is in the detection of hyperacute infarcts and the differentiation of acute or subacute infarction from chronic infarction 尽管DWI已经应用在不同系统的器官，但是主 要应用在中枢神经系统。 临床最广泛的应用是诊断超急性脑梗塞和鉴别 急性或亚急性脑梗塞与陈旧脑梗塞
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Introduction
Cytotoxic edema – characterized by abnormal cellular uptake of water and myelin edema – characterized by intramyelinic accumulation of vacuolated or free water – have high signal intensity on the diffusion trace, with decreased ADC as a result of isotropically restricted water diffusion. On the other hand,vasogenic edema, caused by increased permeability of the blood–brain barrier, and interstitial edema, caused by subependymal water diffusion in acute hydrocephalus have intermediate signal on the DW image with increased ADC DWI区分水肿的性质： 细胞毒性水肿和和髓鞘性水肿——由于同向性弥散受限，弥散相呈 高信号，ADC值下降； 血管源性水肿和间质性水肿——弥散不受限，弥散相呈中等信号， ADC值升高。
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Introduction
Recently DWI has been applied to various other cerebral diseases. 现在DWI被应用在多种脑部疾病 In this paper，I demonstrate different DWI patterns of non-infarct lesions of the brain which are hyperintense in the diffusion trace image, such as infectious, neoplastic and demyelinating diseases, encephalopathies – including hypoxic–ischemic, hypertensive, eclamptic, toxic, metabolic and mitochondrial encephalopathies – leukodystrophies, vasculitis and vasculopathies, hemorrhage and trauma 本课件讲述不同弥散图像高信号的脑部非梗塞性疾病， 例如炎症、肿瘤、脱髓鞘疾病、脑病变包括缺血缺氧性、 高血压、子癫、中毒、代谢性和线粒体脑病-脑白质病 变，血管炎和血管病变、出血及外伤
Diffusion weighted MR imaging in non-infarct lesions of the brain DWI在非梗塞性脑病变中的应用
林亚南 2012-7-11
Introduction
Diffusion weighted imaging (DWI) is based on the sensitivity of MR to microscopic mobility of water molecules within tissues. DWI基于MR对组织内水分子微观运动的敏感性 DWI consists of a DW image and an apparent diffusion coefficient (ADC) map. DW image, together with qualitative and quantitative assessment of the ADC map has been widely used in the diagnosis of acute cerebral infarction, owing to the reliable distinction of cytotoxic and vasogenic edema. 由于DWI联合定性及定量的ADC图可以鉴别细胞毒性和血管源性 水肿，已广泛地应用在急性脑梗塞的诊断 Edema is a non-specific reaction of brain parenchyme to diffenernt factors ,which can be differentiated by DWI. DWI可鉴别不同因素导致的脑实质的非特异性反应--水肿
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男性，30岁
Fig.2.Herpes simplex encephalitis: 30 years old, male. (a)shows a hyperintense lesion in the left temporal lobe. hipocampal and parahypocampal gyri, (b) the diffusion trace shows high signal with increased ADC (c). Single voxel proton MR spectroscopy shows decreased N-acetyl aspartate with a prominent lactate peak(d).
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Demyelinating diseases
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Brain abscess
Brain abscesses are cystic lesions with a thick, rim-shaped contrast enhancing capsule, surrounded by massive vasogenic edema. 脑脓肿是一种壁呈环形强化的囊性病变，伴周围脑组织广泛血管 源性水肿。 This appearance on conventional MR images with similar clinical findings can sometimes not be differentiated from cystic necrotic tumors. 传统的MRI可能不能使其与临床表现相似的囊性坏死性肿瘤性病 变相鉴别。 On the DW image,brain abscesses show very high signal associated with decreased ADC. The limited diffusion in abscesses are attributed to the high viscosity of the proteinaceous fluid and hypercellularity of the pus consisting of bacteria and inflammatory cells 由于脓肿内含有粘稠的蛋白质液体和大量的细胞成分（细菌和炎 性细胞），DWI弥散受限表现：弥散图呈高信号，ADC值下降。
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男性，65y
Fig.1.Cerebral absecess:65 years old ,male.A right temporal lobe absecess with a thick rim enhancing capsule,surrounded by massive edema.On the DWI,the lesion has high signal with partially deceased ADC.