DWI在脑部的应用

1、Diffusion weighted MR imaging in non-infarct lesions of the brain DWI在非梗塞性脑病变中的应用在非梗塞性脑病变中的应用林亚南林亚南2012-7- LogoIntroductionv Diffusion weighted imaging (DWI) is based on the sensitivity of MR to microscopic mobility of water molecules within tissues.v DWI基于基于MR对组织内水分子微观运动的敏感性对组织内水分子微观运动的敏感性v DWI con

2、sists of a DW image and an apparent diffusion coefficient (ADC) map.v 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.v 由于由于DWI联合定性及定量

3、的联合定性及定量的ADC图可以鉴别细胞毒性和血管源性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水肿，已广泛地应用在急性脑梗塞的诊断v Edema is a non-specific reaction of brain parenchyme to diffenernt factors ,which can be differentiated by DWI.v DWI可鉴别不同因素导致的脑实质的非特异性反应可鉴别不同因素导致的脑实质的非特异性反应-水肿水肿 LogoIntroductionv Cytotoxic edema characterized by abnormal

4、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. v On the other hand,vasogenic edema, caused by increased pe

5、rmeability of the bloodbrain barrier, and interstitial edema, caused by subependymal water diffusion in acute hydrocephalus have intermediate signal on the DW image with increased ADCv DWI区分水肿的性质：区分水肿的性质： 细胞毒性水肿和和髓鞘性水肿细胞毒性水肿和和髓鞘性水肿由于同向性弥散受限，弥散相呈由于同向性弥散受限，弥散相呈高信号，高信号，ADC值下降；值下降； 血管源性水肿和间质性水肿血管源性水肿和间质

6、性水肿弥散不受限，弥散相呈中等信号，弥散不受限，弥散相呈中等信号，ADC值升高。值升高。 LogoIntroductionvAlthough DWI has been tried for different organ systems, it has been found its primary use in the central nervous system. vThe most widely used clinical application is in the detection of hyperacute infarcts and the differentiation of acu

7、te or subacute infarction from chronic infarctionv尽管尽管DWI已经应用在不同系统的器官，但是主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。要应用在中枢神经系统。v临床最广泛的应用是诊断超急性脑梗塞和鉴别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急性或亚急性脑梗塞与陈旧脑梗塞 LogoIntroductionv Recently DWI has been applied to various other cerebral diseases. v 现在现在DWI被应用在多种脑部疾病被应用在多种脑部疾病v In

8、 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 hypoxicischemic, hypertensive, eclamptic, toxic, metabolic and mitochondrial

9、 encephalopathies leukodystrophies, vasculitis and vasculopathies, hemorrhage and traumav 本课件讲述不同弥散图像高信号的脑部非梗塞性疾病，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、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高血压、子癫、中毒、代谢性和线粒体脑病-脑白质病脑白质病变，血管炎和血管病变、出血及外伤变，血管炎和血管病变、出血及外伤 LogocontentsEncephalopathiesLeuk

10、odystrophiesDemyelinating diseasesVasculitis and vasculopathiesDWINeoplastic lesionsEpilepsyHemorrhageT LogoBrain abscessv Brain abscesses are cystic lesions with a thick, rim-shaped contrast enhancing capsule, surrounded by massive vasogenic edema.v 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脑脓肿是一种壁呈环形强化的囊性病变，伴周围

11、脑组织广泛血管源性水肿。源性水肿。v This appearance on conventional MR images with similar clinical findings can sometimes not be differentiated from cystic necrotic tumors.v 传统的传统的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。变相鉴别。 v On the DW image,brain abscesses show very high signal associated with decr

12、eased 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 cellsv 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），性细胞），DWI弥散受限表现：弥散图呈高信号，弥散受限表现：弥散图呈高信号，ADC值下降。值下降。

13、Logo男性，男性，65yFig.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 Logo单纯疱疹病毒性脑炎单纯疱疹病毒性脑炎(Herpes simplex encephalitis)v Herpes simplex encephalitis is

14、one of the most common viral infections. T2-hyperintense lesions with typical temporal and frontal localization with petechial hemorrhage are characteristic findings.v 单纯疱疹病毒性脑炎是最常见的病毒感染性疾病之一，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。高信号和典型的颞叶、额叶点状出血是其特征表现。v Conventional MR imaging and clinic

15、al findings might be non-specific, necessitating the proof of evidence of viral DNA by polymerase chain reaction in the cerebrospinal fluid.v 常规常规MRI和临床表现可能是非特异性的，需要脑脊液中和临床表现可能是非特异性的，需要脑脊液中病毒病毒DNA的的PCR试验来验证试验来验证 Logo单纯疱疹病毒性脑炎单纯疱疹病毒性脑炎(Herpes simplex encephalitis)vDW image shows high signal in the le

16、sions with usually decreased ADC values representing cytotoxic edema and rarely higher ADC values representing vasogenic edema.v病变病变DWI表现为高信号，表现为高信号，ADC值降低代表细胞值降低代表细胞毒性水肿，少数高毒性水肿，少数高ADC值代表血管源性水肿值代表血管源性水肿vAreas of cytotoxic edema correspond to a worse outcome compared to areas of vasogenic edema v细胞毒

17、性水肿与血管源性水肿相比，结局较差细胞毒性水肿与血管源性水肿相比，结局较差 Logo男性，男性，30岁岁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 spectrosco

18、py shows decreased N-acetyl aspartate with a prominent lactate peak(d) Logo克雅氏病克雅氏病 （ Creutzfeld-Jakob disease ）v Creutzfeld-Jakob disease is one of several spongiform encephalopathies. Characteristic findings are rapidly progressive dementia, myoclonus and periodic sharp-wave complexes on electroen

19、cephalography.v 克雅病（皮质克雅病（皮质-纹状体纹状体-脊髓变性脊髓变性 ） 是几种海绵状脑病之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。图表现为周期性的锐波。v MR imaging is helpful in differentiating the two forms of the disease.v 磁共振可以帮助鉴别克雅氏病的两种类型。磁共振可以帮助鉴别克雅氏病的两种类型。 Logo克雅氏病克雅氏病 （ Creutzfeld-Jakob disease ）v The spora

20、dic type is characterized by bilateral symmetric hyperintensity in the putamen and head of caudate nucleus on T2-weighted and FLAIR images are characteristic, sometimes associated with bilateral thalamic or cerebral cortical involvement.v Symmetrical high signal of the pulvinar thalami, known as “th

21、e pulvinar sign” is characteristic for the variant type.v 偶发型偶发型双侧壳核及尾状核头在双侧壳核及尾状核头在T2加权和加权和FLAIR像对像对称性的高信号是典型表现。丘脑及大脑皮层有时也可累称性的高信号是典型表现。丘脑及大脑皮层有时也可累及及 变异型变异型“丘脑后结节征丘脑后结节征”即双侧丘脑后结节对称性高信即双侧丘脑后结节对称性高信号。号。 Logo克雅氏病克雅氏病 （ Creutzfeld-Jakob disease ） Although thalamic high signal may be seen in both types

22、, it is less pronounced than in the caudate and putamen in the sporadic type, whereas it is the most prominent sign in the variant type 尽管两种类型均可见丘脑的高信号，但是在偶发型中，丘脑没有壳尽管两种类型均可见丘脑的高信号，但是在偶发型中，丘脑没有壳核和尾状核的高信号显著，而在变异型中丘脑的高信号是一个显核和尾状核的高信号显著，而在变异型中丘脑的高信号是一个显著的特征著的特征v Diffusion trace image shows high signal

23、with decreased ADC .v The restricted diffusion can be attributed to the compartmentalization of water molecules within the clustered vacuoles in the gray matter. DWI表现为弥散受限伴表现为弥散受限伴ADC值下降。这与灰质中簇状分布的液泡值下降。这与灰质中簇状分布的液泡中的水分子有关。中的水分子有关。v Persistence of high signal on the DW image is helpful in different

24、iating from infarctv 克雅病克雅病DWI长期表现为弥散受限，可与脑梗塞相鉴别。长期表现为弥散受限，可与脑梗塞相鉴别。 Logo女性，女性，55岁岁Fig. 3. CreutzfeldtJacob disease: 55 years old, female. (a) FLAIR imaging shows diffuse high signal in both cerebral cortices sparing the sensorimotor cortices, with high signal on the DW image (b) LogocontentsEncepha

25、lopathiesLeukodystrophiesDemyelinating diseasesVasculitis and vasculopathiesDWINeoplastic lesionsEpilepsyHemorrhageT LogoTumorsTumorsPrimary tumors M Logo Primary tumors（原发肿瘤）v Brain neoplasms show variable signal on the DW image and the ADC map. Tumors with higher cellularity or higher grade show i

26、ncreased signal on the DW image and a marked reduction in ADC values.v原发性脑肿瘤的原发性脑肿瘤的DWI表现多变，细胞成分多或表现多变，细胞成分多或者是高级别肿瘤通常表现为弥散图高信号伴者是高级别肿瘤通常表现为弥散图高信号伴ADC值明显降低值明显降低v In addition to the hypercellularity which causes increased intracellular water, the low ADC values are also related to the decreased extra

27、cellular fluidv除了细胞增殖所致的细胞内水增多，低除了细胞增殖所致的细胞内水增多，低ADC值值也与细胞外水减少有关也与细胞外水减少有关 Logo Primary tumors（原发肿瘤）vLow grade gliomas, because of their low cellularity, have a significantly higher ADC values compared to high grade gliomas and lymphomasv而低级别胶质瘤因为细胞成分少，其而低级别胶质瘤因为细胞成分少，其ADC值明值明显高于高级别胶质瘤和淋巴瘤显高于高级别胶质瘤和

28、淋巴瘤vConjoint evaluation of conventional MR sequences and DWI are of great importance in atypical casesv有些研究表明传统有些研究表明传统MR序列与序列与DWI相结合对非相结合对非典型肿瘤病例的诊断有重要意义典型肿瘤病例的诊断有重要意义 Logo Primary tumors（原发肿瘤）v Lymphomas are highly cellular tumors.DWI of which is controversial. Typical MR findings are slightly hyp

29、erintense lesions compared to normal brain tissue on T2-weighted images usually in the cerebral hemispheres, basal ganglia and thalamus, with ring-shaped or diffuse enhancement.v 淋巴瘤富含细胞，其淋巴瘤富含细胞，其DWI表现有争议。常规表现有争议。常规MRI表现为表现为大脑半球、基底节区及丘脑大脑半球、基底节区及丘脑T2WI稍微高信号，边缘或稍微高信号，边缘或弥漫性增强弥漫性增强v Cerebral lymphoma

30、s without contrast enhancement are regarded as cerebral manifestation of a systemic disease, namely angiotropic large cell lymphoma or intravascular lymphomatosisv 没有增强的脑淋巴瘤病是系统性疾病的脑部表现，称作没有增强的脑淋巴瘤病是系统性疾病的脑部表现，称作噬血管性大细胞淋巴瘤或血管内淋巴瘤病噬血管性大细胞淋巴瘤或血管内淋巴瘤病 Logo Primary tumors（原发肿瘤）v K uker et al have found

31、that DWI was helpful in differentiating primary central nervous system lymphomas from angiotropic large cell lymphoma which is frequently accompanied by diffusion abnormalities due to brain ischemia. v K等发现等发现DWI有助于鉴别原发性中枢神经系统淋巴瘤与噬血管性大有助于鉴别原发性中枢神经系统淋巴瘤与噬血管性大细胞淋巴瘤（伴随脑缺血所致的扩散异常）细胞淋巴瘤（伴随脑缺血所致的扩散异常）v In

32、 a study with seven central nervous system T-cell lymphomas,three patients showed hyperintensity and four patients showed isointensity in the DW image and ADC maps.v 有研究，有研究，7例中枢神经系统例中枢神经系统T细胞淋巴瘤中，细胞淋巴瘤中，3例呈高信号，例呈高信号，4例呈例呈等信号等信号v In some other studies it has been reported that ADC values of the prim

33、ary central nervous system lymphomas were lower than other intracerebral tumors, close to acute infarctv 其他的研究报道原发中枢神经系统淋巴瘤比其他脑内肿瘤的其他的研究报道原发中枢神经系统淋巴瘤比其他脑内肿瘤的ADC值低，与急性脑梗塞相近值低，与急性脑梗塞相近 Logo Primary tumors（原发肿瘤）v Epidermoid cysts are rare congenital lesions arising from the inclusion of ectodermal tiss

34、ue into the neural tube. Cere-bellopontine angle is the most common location. v 表皮样囊肿是少见的起源于外胚层组织的先天性疾病，桥小脑角表皮样囊肿是少见的起源于外胚层组织的先天性疾病，桥小脑角区是最常见的发病部位区是最常见的发病部位v Typical MR imaging findings are well-defined, lobulated masses, slightly hyperintense or isointense to the cerebrospinal fluid on T1-and T2-we

35、ighted images with no internal contrast enhancement.v 典型的典型的MRI表现是轮廓清楚、分叶状肿块、表现是轮廓清楚、分叶状肿块、T1和和T2加权成像与脑加权成像与脑脊液相比，呈轻度高或等信号，内部没有强化脊液相比，呈轻度高或等信号，内部没有强化v On proton density and FLAIR images, the lesions are slightly hyperintense to the cerebrospinal fluid. The lesions show high signal on the DW image wi

36、th mixed signal on the ADC mapv 在质子密度和在质子密度和FLAIR成像，病变与脑脊液相比呈轻度高信号。病成像，病变与脑脊液相比呈轻度高信号。病变在变在DWI上呈高信号，上呈高信号，ADC图呈混杂信号图呈混杂信号 Logo Primary tumors（原发肿瘤）v Initial studies have attributed the high signal in DWI to the increased cellularity and restricted diffusion of water molecules due to high viscosity o

37、f the fluid containing keratohyalin and cholesterol crystals. v 最初的研究把最初的研究把DWI高信号归因于细胞增殖和限制水分子高信号归因于细胞增殖和限制水分子的扩散归因于透明角质蛋白与胆固醇结晶的高粘度的扩散归因于透明角质蛋白与胆固醇结晶的高粘度v However, recent reports suggest that this is due to the T2 shine through effect.v 但是，最近的报道称这归因于但是，最近的报道称这归因于T2的透过效应的透过效应v DWI is not only helpf

38、ul in differentiating epidermoids from arachnoid cysts, but also differentiating residual or recurrent tumor from cerebrospinal fluid-filled cavities in the postoperative patient v DWI不仅有助于鉴别表皮样囊肿与蛛网膜囊肿，还可以不仅有助于鉴别表皮样囊肿与蛛网膜囊肿，还可以鉴别残余或复发肿瘤与脑脊液填充的空腔鉴别残余或复发肿瘤与脑脊液填充的空腔 Logo Metastases(转移瘤)v Metastases sh

39、ow variable signal (generally iso- or hypointense, occasionally hyperintense) in the DWI .v Rarely high signal intensity in the DW image with decreased ADC may be seen, due to mostly the hypercellularity of the lesion，extracelular methemoglobin or sometimes increased protein concentration in the for

40、m of highly viscous mucin in cystic metastases v 转移瘤转移瘤DWI表现也多变，弥散相多为等或低信号，少数表现也多变，弥散相多为等或低信号，少数高信号（源于细胞丰富、血管外正铁血红蛋白或囊性转高信号（源于细胞丰富、血管外正铁血红蛋白或囊性转移瘤中高粘度蛋白移瘤中高粘度蛋白) Logo Metastases(转移瘤)v In case of multiple lesions in the setting of a known primary malignancy, metastatic tumors are not a diagnostic challenge.