磁敏感加权成像与动态磁敏感对比MRI在急性脑缺血患者中的对比研究
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摘要
背景和目的
缺血性脑卒中(脑梗死)是我国的一种常见病、多发病,具有高发病率、高复发率及高致残率等特点,在我国的死因中居首位,严重威胁着人民的健康和生活质量。影像学检查在脑缺血的诊断和预后判定中起着重要作用。虽然常规颅脑磁共振可以对脑缺血作出诊断,但是对于缺血灶局部的血流灌注状态却不能够很好的反映。脑梗死后再灌注损伤(cerebral ischemic reperfusion, CIR)是脑缺血灶局部血流再通的一种继发改变。早期及时的对缺血灶进行溶栓治疗,可以挽救缺血半暗带,减少最终梗死的范围和程度；但是溶栓治疗会引起梗死后再灌注损伤,导致出血的发生。而出血灶的存在,是临床非常重视的问题。因此寻求一种能够简单可靠的评价缺血灶的灌注状态以及再灌注损伤的技术,对脑卒中患者的诊断和治疗非常重要。动态磁敏感对比(dynamic susceptibility contrast, DSC) MRI能够早期发现局部脑组织的灌注异常,因而在脑血管疾病诊断上的应用较为广泛；但DSC需要高压注射器注射对比剂,增加了技术难度和费用,而且对脑卒中伴发微出血及动脉血栓形成的检出不够敏感；磁敏感加权成像(susceptibility weighted imaging, SWI)是基于对脱氧血红蛋白等顺磁性物质超级敏感的特性和血氧水平依赖(blood oxygen level dependent, BOLD)效应成像的一种新的MRI技术,能够清晰的显示脑内小静脉及敏感的检出微出血灶,且具有无创性,在对脑缺血的诊断和评价方面有着潜在的应用价值。本研究的目的是对比分析急性脑缺血在SWI与DSC上的影像表现,探讨SWI在评价急性脑缺血组织的血流动力学状态及梗死再灌注损伤方面的可能的应用价值。
材料和方法
选取2010年1月-2011年1月间在我院经临床及影像确诊的发病3天内的急性脑缺血患者46例,其中男29例,女17例,年龄46-82岁,平均年龄64岁。所有受试者均采用Siemens Trio Tim 3.0T MR行常规MRI (T1WI、T2WI FLAIR和DWI)、高分辨SWI和DSC检查。观察各种MRI技术的表现,根据DSC的表现将其分为四种,即灌注不足、正常灌注、延迟灌注和过度灌注；根据SWI上缺血灶及其周围小静脉显示情况将其分为三种,即静脉增多、静脉减少和正常。采用Mann-Whitney检验对SWI和DSC两种技术结果的一致性进行定性分析。同时,在扩散加权成像显示的病变部位及对侧正常半球的镜像区域分别选取三个感兴趣区(ROI),测量信号强度并计算信号强度比(梗死区／正常对照区),将结果做配对t检验分析。
结果
46例急性脑缺血患者中,有38例在DSC上均表现为灌注不足,其中32例SWI上表现为梗死灶静脉减少或消失,梗死灶周围小静脉增多、增粗,6例梗死灶和灶周小静均显示减少或消失；其余8例患者中DSC显示灌注不足3例、延迟灌注2例、过度灌注3例,而在SWI上均表现正常。定性分析结果显示两种技术间差异无统计学意义(Z=2.361,P>0.05)。定量分析示两种技术的病侧与对照侧信号强度比值DSC为0.83±0.26,SWI为0.91±0.24,两者间差异无统计学意义(t=0.729,P>0.05)。同时,12例患者SWI发现梗死灶区出血,6例检测到梗死灶外的微灶出血,而在常规MRI和DSC上均未见显示。
结论
1.与DSC相比,SWI可无创性地提示缺血脑组织的脑血流动力学状态,为评价缺血脑组织的血流灌注状态提供了一种简单易行的新方法。
2.高分辨率SWI可以很敏感的检测出脑缺血灶中的微灶出血,反映再灌注损伤的程度,为临床选择合理的治疗方案提供影像学依据。
3.SWI可与常规MRI结合,为临床急性脑卒中的诊断、治疗和预后评估提供更多有价值的信息。
Objective
Ischemic cerebral stroke (cerebral infarction) is very common in China, which has high occurrence rate, reoccurence rate and disability rate. It has been one of the main causes of death in our country. Imaging examination plays an important role in the diagnosis and prognostic evaluation in patients with ischemic stroke. Though conventional MRI is very helpful for the diagnosis of cerebral infarction, but it can not provide the hemodynamic information of ischemic tissue. Cerebral ischemic reperfusion (CIR) often occurs after the revascularization under the ischemia condition. Though early thrombolytic therapy could save the ischemic penumbra and reduce the degree and area of infarction, it may lead to hemorrhage which is recognized to be of great importance to clinical treatment. Therefore, to explore a technique that can simply and accurately assess the perfusion status and reperfusion injury in patients with ischemic stroke is very important for the diagnosis and therapy in patients with ischemia. As dynamic susceptibility contrast (DSC) MRI could detect the early perfusion abnormality of ischemic cerebral tissue, it has been widely used in stroke. But DSC has some technical limitations such as high-pressure injector and contrast agents are needed in DSC, which increase the technical difficulty and cost. Furthermore, DSC can not display the intracerebral hemorrhage accompanied with the cerebral stroke and the arterial thrombosis. Susceptibility-weighted imaging (SWI) is a new MR technique which is based on the high sensitivity to paramagnetic substances and blood oxygen level dependent (BOLD) effect. It can noninvasively display cerebral vein and detect microbleeds. Thus SWI has the potential in the diagnosis and therapy of cerebral ischemia. Our aim was to compare SWI and DSC in acute ischemia and investigate the value of SWI in assessing hemodynamic status of ischemic tissue and reperfusion injury.
Methods
46 patients (27 males,19 females, mean age 64 year) with acute ischemic stroke within 3 days of symptom onset were enrolled in this study. The conventional brain MRI (T1WI, T2WI, FLAIR and DWI), high-resolution SWI and DSC were performed on all subjects by using SIEMENS Trio Tim 3.0T MR scanner. The MR findings of the SWI and DSC were observed and compared. For qualitative analysis, MR findings of DSC were grouped into four categories (hypoperfusion, normal perfusion, delayed perfusion or hyperperfusion), while SWI findings were categorized into three types according to the changes of vein numbers (increased veins, decreased veins, normal veins) and signal intensity of the ischemic lesion. Mann-Whitney test was used for qualitative analysis. Three regions of interest (ROI) were defined in the diffusion-weighted imaging abnormalities and mirror regions in the contralateral normal brain tissues, respectively. Signal intensity ratios of infracted region to the normal contralateral region were calculated and compared by using a paired t test.
Results
In 38 out of 46 patients, all DSC showed hypoperfusion, while SWI demonstrated veins reduction or disappearance in infarcted area and veins dilatation in peri-infarcted region in 32 patients, and vein reduction or disappearance in both infracted and peri-infarcted area in 6 patients; in the other 8 patients, DSC showed perfusion deficitin 3 cases, delayed perfusion in 2 and hyperfusion in 3 cases, while SWI showed normal in all the 8 cases. Qualitative analysis demonstrated there was no significant difference between the two techniques (Z=2.361, P>0.05). The mean signal intensity ratio infracted region to the normal contralateral region on DSC was 0.83±0.26, while SWI was 0.91±0.24, and no significant difference was revealed between the two techniques (t=0.729, P> 0.05). In addition, SWI detected hemorrhage in infracted region in 12 patients, and in peri-infarcted area in 6 patients, while conventional MRI and DSC didn't demonstrate the hemorrhage in all these patients.
Conclusion
1. Compared to DSC, SWI can noninvasively demonstrate the hemodynamic status of ischemic tissue and provide a new simple technique for evaluating brain perfusion status.
2. The high-resolution SWI is sensitive in detecting hemorrhage in cerebral ischemic lesions, which is helpful for evaluating the degree of CIR and provides imaging evidence for reasonable treatment.
3. SWI can be combined with routine MRI and provide more valuable information in the diagnosis, therapy and progronostic evaluation of acute cerebral ischemic stroke.
缺血性脑卒中(脑梗死)是我国的一种常见病、多发病,具有高发病率、高复发率及高致残率等特点,在我国的死因中居首位,严重威胁着人民的健康和生活质量。影像学检查在脑缺血的诊断和预后判定中起着重要作用。虽然常规颅脑磁共振可以对脑缺血作出诊断,但是对于缺血灶局部的血流灌注状态却不能够很好的反映。脑梗死后再灌注损伤(cerebral ischemic reperfusion, CIR)是脑缺血灶局部血流再通的一种继发改变。早期及时的对缺血灶进行溶栓治疗,可以挽救缺血半暗带,减少最终梗死的范围和程度；但是溶栓治疗会引起梗死后再灌注损伤,导致出血的发生。而出血灶的存在,是临床非常重视的问题。因此寻求一种能够简单可靠的评价缺血灶的灌注状态以及再灌注损伤的技术,对脑卒中患者的诊断和治疗非常重要。动态磁敏感对比(dynamic susceptibility contrast, DSC) MRI能够早期发现局部脑组织的灌注异常,因而在脑血管疾病诊断上的应用较为广泛；但DSC需要高压注射器注射对比剂,增加了技术难度和费用,而且对脑卒中伴发微出血及动脉血栓形成的检出不够敏感；磁敏感加权成像(susceptibility weighted imaging, SWI)是基于对脱氧血红蛋白等顺磁性物质超级敏感的特性和血氧水平依赖(blood oxygen level dependent, BOLD)效应成像的一种新的MRI技术,能够清晰的显示脑内小静脉及敏感的检出微出血灶,且具有无创性,在对脑缺血的诊断和评价方面有着潜在的应用价值。本研究的目的是对比分析急性脑缺血在SWI与DSC上的影像表现,探讨SWI在评价急性脑缺血组织的血流动力学状态及梗死再灌注损伤方面的可能的应用价值。
材料和方法
选取2010年1月-2011年1月间在我院经临床及影像确诊的发病3天内的急性脑缺血患者46例,其中男29例,女17例,年龄46-82岁,平均年龄64岁。所有受试者均采用Siemens Trio Tim 3.0T MR行常规MRI (T1WI、T2WI FLAIR和DWI)、高分辨SWI和DSC检查。观察各种MRI技术的表现,根据DSC的表现将其分为四种,即灌注不足、正常灌注、延迟灌注和过度灌注；根据SWI上缺血灶及其周围小静脉显示情况将其分为三种,即静脉增多、静脉减少和正常。采用Mann-Whitney检验对SWI和DSC两种技术结果的一致性进行定性分析。同时,在扩散加权成像显示的病变部位及对侧正常半球的镜像区域分别选取三个感兴趣区(ROI),测量信号强度并计算信号强度比(梗死区／正常对照区),将结果做配对t检验分析。
结果
46例急性脑缺血患者中,有38例在DSC上均表现为灌注不足,其中32例SWI上表现为梗死灶静脉减少或消失,梗死灶周围小静脉增多、增粗,6例梗死灶和灶周小静均显示减少或消失；其余8例患者中DSC显示灌注不足3例、延迟灌注2例、过度灌注3例,而在SWI上均表现正常。定性分析结果显示两种技术间差异无统计学意义(Z=2.361,P>0.05)。定量分析示两种技术的病侧与对照侧信号强度比值DSC为0.83±0.26,SWI为0.91±0.24,两者间差异无统计学意义(t=0.729,P>0.05)。同时,12例患者SWI发现梗死灶区出血,6例检测到梗死灶外的微灶出血,而在常规MRI和DSC上均未见显示。
结论
1.与DSC相比,SWI可无创性地提示缺血脑组织的脑血流动力学状态,为评价缺血脑组织的血流灌注状态提供了一种简单易行的新方法。
2.高分辨率SWI可以很敏感的检测出脑缺血灶中的微灶出血,反映再灌注损伤的程度,为临床选择合理的治疗方案提供影像学依据。
3.SWI可与常规MRI结合,为临床急性脑卒中的诊断、治疗和预后评估提供更多有价值的信息。
Objective
Ischemic cerebral stroke (cerebral infarction) is very common in China, which has high occurrence rate, reoccurence rate and disability rate. It has been one of the main causes of death in our country. Imaging examination plays an important role in the diagnosis and prognostic evaluation in patients with ischemic stroke. Though conventional MRI is very helpful for the diagnosis of cerebral infarction, but it can not provide the hemodynamic information of ischemic tissue. Cerebral ischemic reperfusion (CIR) often occurs after the revascularization under the ischemia condition. Though early thrombolytic therapy could save the ischemic penumbra and reduce the degree and area of infarction, it may lead to hemorrhage which is recognized to be of great importance to clinical treatment. Therefore, to explore a technique that can simply and accurately assess the perfusion status and reperfusion injury in patients with ischemic stroke is very important for the diagnosis and therapy in patients with ischemia. As dynamic susceptibility contrast (DSC) MRI could detect the early perfusion abnormality of ischemic cerebral tissue, it has been widely used in stroke. But DSC has some technical limitations such as high-pressure injector and contrast agents are needed in DSC, which increase the technical difficulty and cost. Furthermore, DSC can not display the intracerebral hemorrhage accompanied with the cerebral stroke and the arterial thrombosis. Susceptibility-weighted imaging (SWI) is a new MR technique which is based on the high sensitivity to paramagnetic substances and blood oxygen level dependent (BOLD) effect. It can noninvasively display cerebral vein and detect microbleeds. Thus SWI has the potential in the diagnosis and therapy of cerebral ischemia. Our aim was to compare SWI and DSC in acute ischemia and investigate the value of SWI in assessing hemodynamic status of ischemic tissue and reperfusion injury.
Methods
46 patients (27 males,19 females, mean age 64 year) with acute ischemic stroke within 3 days of symptom onset were enrolled in this study. The conventional brain MRI (T1WI, T2WI, FLAIR and DWI), high-resolution SWI and DSC were performed on all subjects by using SIEMENS Trio Tim 3.0T MR scanner. The MR findings of the SWI and DSC were observed and compared. For qualitative analysis, MR findings of DSC were grouped into four categories (hypoperfusion, normal perfusion, delayed perfusion or hyperperfusion), while SWI findings were categorized into three types according to the changes of vein numbers (increased veins, decreased veins, normal veins) and signal intensity of the ischemic lesion. Mann-Whitney test was used for qualitative analysis. Three regions of interest (ROI) were defined in the diffusion-weighted imaging abnormalities and mirror regions in the contralateral normal brain tissues, respectively. Signal intensity ratios of infracted region to the normal contralateral region were calculated and compared by using a paired t test.
Results
In 38 out of 46 patients, all DSC showed hypoperfusion, while SWI demonstrated veins reduction or disappearance in infarcted area and veins dilatation in peri-infarcted region in 32 patients, and vein reduction or disappearance in both infracted and peri-infarcted area in 6 patients; in the other 8 patients, DSC showed perfusion deficitin 3 cases, delayed perfusion in 2 and hyperfusion in 3 cases, while SWI showed normal in all the 8 cases. Qualitative analysis demonstrated there was no significant difference between the two techniques (Z=2.361, P>0.05). The mean signal intensity ratio infracted region to the normal contralateral region on DSC was 0.83±0.26, while SWI was 0.91±0.24, and no significant difference was revealed between the two techniques (t=0.729, P> 0.05). In addition, SWI detected hemorrhage in infracted region in 12 patients, and in peri-infarcted area in 6 patients, while conventional MRI and DSC didn't demonstrate the hemorrhage in all these patients.
Conclusion
1. Compared to DSC, SWI can noninvasively demonstrate the hemodynamic status of ischemic tissue and provide a new simple technique for evaluating brain perfusion status.
2. The high-resolution SWI is sensitive in detecting hemorrhage in cerebral ischemic lesions, which is helpful for evaluating the degree of CIR and provides imaging evidence for reasonable treatment.
3. SWI can be combined with routine MRI and provide more valuable information in the diagnosis, therapy and progronostic evaluation of acute cerebral ischemic stroke.
引文
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[40]Kidwell CS, Alger JR, Saver JL, et al. Beyond mismatch:evolving paradiagms in imaging the ischemic penumbra with multimodal magnetic resonance imaging [J]. Stroke,2003, 34:2729-2735.
[1]吴桂贤,吴兆苏,刘静等.北京部分地区15年脑卒中事件变化趋势[J].中国慢性疾病预防与控制,2001,9：106-108.
[2]Warach S, Baron JC. Advances in stroke 2003:neuroimaging [J]. Stroke,2004, 35:351-352.
[3]Haacke EM, Mittal S, Wu Z, Neelavalli J, Cheng YC. Susceptibility-weighted imaging: Technical aspects and clinical applications, part 1 [J]. AJNR Am J Neuroradiol,2009, 30(1):19-30.
[4]Haacke EM, Xu Y, Cheng YC, et al. Susceptibility weighted imaging (SWI) [J]. Magn Reson Med,2004,52(3):612-618.
[5]Hermier M, Nighoghossian N. Contribution of Susceptibility-Weighted Imaging to Acute Stroke Assessment [J]. Stroke,2004,35:1989-1994.
[6]Tong KA, Ashwal S, Holshouser BA, et al. Hemorrhagic shearing lesions in children and adolescents with posttraumatic diffuse axonal injury:improved detection and initial results [J]. Radiology,2003,227:332-339.
[7]Thamburaj K, Radhakrishnan VV, Thomas B, et al. Intratumoral microhemorrhages on T2*-weighted gradient-echo imaging helps differentiate vestibular schwannoma from meningioma [J]. AJNR Am J Neuroradiol,2008,29(3):552-557.
[8]Thomas B, Somasundaram S, Thamburaj K, et al. Clinical applications of susceptibiity weighted MR imaging of the brain—a pictorial review [J]. Neuroradiology,2008, 50:105-116.
[9]Tan IL, van Schijndel RA, Pouwels PJ, et al. MR venography of multiple sclerosis [J]. AJNR Am J Neuroradiol,2000,21:1039-1042.
[10]Schaller B, Craf R. Cerebral ischemia and reperfusion:the pathophysiologic concept as a basis for clinical therapy [J]. J Cereb Blood Flow Metab,2004,24(2):351-371.
[11]Pan J, Konstas AA, Bateman B, et al. Reperfusion injury following cerebral ischemia: pathophysiology, MR imaging and potential therapies [J]. Neuroradiology,2007,49 (2):93-102.
[12]Schwamm LH, Koroshetz WJ, Sorensen AG, et al. Time course of lesion with acute st-roke:serial diffusion-and hemodynamic-weighted magnetic resonance imaging [J]. Stroke, 1998,29:2268-2276.
[13]Zheng Z, Yenari MA.Post-ischemic inflammation:molecular mechanisms and therapeutic implications [J].Neurol Res,2004,12,26(8):884-92.
[14]全冠民,袁涛,刘怀军.急性脑梗死出血性转化及MRI评估[J].国外医学临床放射学分册,2006,29(5)：311-314.
[15]Kidwell CS, Saver JL, Villablanca JP, et al. Magnetic resonance imaging detection of microbleeds before thrombolysis:an emerging application[J]. Stroke,2002,33(1):95-98.
[16]吴凌峰,张昆南,高幼奇等.青、老年脑梗死患者的危险因素及病因分析[J].中华脑血管病杂志(电子版),2010,4(4)：6-8.
[17]Schellinger PD, Jansen O, Fiebach JB, et al. A standardized MRI stroke protocol, comparison with CT in hyperacute intracerebral hemorrhage[J]. Stroke,1999, 30(4):765-768.
[18]Greer DM, Koroshetz WJ, Cullwn S, et al. Magnetic resonance imaging improves detection of intracerebral hemorrhage over computed tomography after intra-arterial thrombolysis [J]. Stroke,2004,35(2):491-495.
[19]Linfante I, Llinas RH, Caplan LR, et al. MRI features of intracerebral hemorrhage within 2 hours from symptom onset [J]. Stroke,1999,30:2263-7.
[20]Chalela JA, Kidwell CS, Nentwich LM, et al. Magnetic resonance imaging and computed tomography in emergency assessment of patients with suspected acute stroke:a prospective comparison [J]. Lancet,2007,369:293-8.
[21]Moulin T, Crepin Leblond T, Chopard JL, et al. Hemorrhagic infarcts [J]. Eur Neurol 1993, 34:64-77.
[22]Nighoghossuan N, Hermier M, Adeline P, et al. Old microbleeds are a potential riskfactor for cerebral bleeding after ischemic stroke. A gradient-echo T2*-weighted brain MRI study [J]. Stroke,2002,33:735-742.
[23]Sehgal V, Delproposto Z, Haacke EM. Clinical applications of neuroimaging with susceptibility-weighted imaging[J]. J Magn Reson Imaging,2005,22(4):439-450.
[24]王彩云,张强,薛敏.磁化率加权成像：一种对颅内血管疾病敏感的MRI技术[J].国外医学(临床放射学分册),2007,30(2)：135-140.
[25]Derex L, Nighoghossian N, Hermier M, et al. Thrombolysis for ischemic stroke in patients with old microbleeds on pretreatment MRI [J]. Cerebrovasc Dis,2004,17(2-3):238-241.
[26]Koennecke HC. Cerebral microbleeds on MRI:Prevalence, associations, and potential clinical implications [J]. Neurology,2006,66(2):165-171.
[27]Wahlgret N, Ahmed N, Davalos A, et al. Symptomatic intracerebral hemorrhgge, mortality and independence at 3 months for patients treated 3-4.5h after stroke onset in the sits thrombolysis register (SITS-ISTR) [J]. Cerebrovasc Dis,2008,25(Suppl 2):3.
[28]Rovia A, Orellana P, Alvarez-Sabin J,et al. Hyperacute ischemic stroke:middle cerebral artery susceptibility sign at echo-planar gradient-echo MR imaging[J]. Radiology,2004, 232:466-473.
[29]Chalela JA, Haymore JB, Ezzeddine MA, et al. The hypointense MCA sign [J]. Neurology, 2002,58:1470.
[30]Flacke S, Urbach H, Keller E, et al. Middle cerebral artery (MCA) susceptibility sign at susceptibility-based perfusion MR imaging:clinical importance and comparison with hyperdense MCA sign at CT[J]. Radiology,2000,215(2):476-482.
[31]刘梅丽,崔世民,张蕾莉等.磁共振扩散加权成像和灌注成像对超急性脑梗死影像半暗带的研究[J].中华放射学杂志,2002,12,36(12)：1095-1100.
[32]Rohl L, Ostergaard L, Simonsen CZ, et al. Viability threholds of ischemic penumbra of hyperacute stroke defined by perfusion-weighted MR1 and apparent diffusion coefficient[J]. Stroke,2001,32:1140-1146.
[33]韩鸿宾,谢敬霞.MR扩散与灌注成像在脑缺血诊断中的应用[J].中华放射学杂志,1998,6,32(6)：364-369.
[34]张芳,谢敬霞.早期脑梗死缺血半暗带MR扩散、灌注成像的研究进展[J].临床放射学杂志,2002,21(11)：907-909.
[35]Kidwell CS, Alger JR, Saver JL, et al. Beyond mismatch:evolving paradiagms in imaging the ischemic penumbra with multimodal magnetic resonance imaging [J]. Stroke,2003, 34:2729-2735.
[36]Lee JM, Vo K D, An H, et al. Magnetic resonance cerebral metabolic rate of oxygen utilization in hyperacute stroke patients [J]. Ann Neurol,2003,53(2):227-232.
[37]Geisler BS, Brandhoff F, Fiehler J, et al. Blood-oxygen-level-dependent MRI allows metabolic description of tissue at risk in acute stroke patients [J]. Stroke,2006,37:1778-1784.
[38]An H, Lin W. Quantitative measurements of cerebral blood oxygen saturation using magnetic resonance imaging [J]. J Cereb Blood Flow Metab,2000,20(8):1225-1236.
[39]Kettunen MI, Grohn OH, Silvennoinen MJ, et al. Quantitative assessment of the balance between oxygen delivery and consumption in the rat brain after transient ischemia with T2-BOLD magnetic resonance imaging [J]. J Cereb Blood FlowMetab,2002,22(3):262-270.
[40]Tamura H, Hatazawa J, Toyoshima H, et al. Detection of deoxygenation-related signal change in acute ischemic stroke patients by T2*-weighted magnetic resonance imaging [J]. Stroke,2002,33(4):967-971.
[41]Liebeskind DS, Ances BM, Welgele JB, et al. Intravascular deoxygenation of leptomeningeal collaterals detected with gradient-echo MRI [J]. Stroke,2004,35(1):266-270.
[42]Schaffer CB, Friedman B, Nishimura N et al. Two-photon imaging of cortical surface microvessels reveals a robust redistribution in blood flow after vascular occlusion [J]. PLoS Biol,2006,4(2):258-270.
[43]Kucinski T, Koch C, Eckert B, et al. Collateral circulation is an independent radiological predictor of outcome after thrombolysis in acute ischemic stroke [J]. Neuroradiology,2003, 45(1):11-18.
[44]Pantano P, Toni D, Caramia F, et al. Relationship between vascular enhancement, cerebral hemodynamics, and MR angiography in cases of acute stroke [J]. Am J Neuroradiol,2001, 22(2):255-260.
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[2]Warach S, Baron JC. Advances in stroke 2003:neuroimaging [J]. Stroke,2004, 35:351-352.
[3]Rempp KA, Brix G, Wenz F, et al. Quantification of regional cerebral blood flow and volume with dynamic susceptibility contrast-enhanced MR imaging [J]. Radiology,1994, 193:637-641.
[4]Haacke EM, Mittal S, Wu Z, Neelavalli J, Cheng YC. Susceptibility-weighted imaging: Technical aspects and clinical applications, part 1 [J]. AJNR Am J Neuroradiol,2009, 30(l):19-30.
[5]Haacke EM, Xu Y, Cheng YC, et al. Susceptibility weighted imaging (SWI) [J]. Magn Reson Med,2004,52(3):612-618.
[6]Ostergaard L, Sorensen AG, Chesler DA, et al. Combined diffusion-weighted and perfusion-weighted flow heterogeneity magnetic resonance imaging in acute stroke [J]. Stroke,2000,31:1097-1103.
[7]Wu O, Koroshetz WJ, Ostergaard L, et al. Predicting tissue outcome in acute human cerebral ischemia using combined diffusion and perfusion weighted MR imaging[J]. Stroke 2001,32:933-942.
[8]Igarashi H, Hamamoto M, Yamaguchi H, et al. Cerebral blood flow index:dynamic perfusion MRI delivers a simple and good predictor for the outcome of acute-stage ischemia lesion [J]. Comput Assist Tomogr,2003,27:874-881.
[9]Grandin GB, Duprez TP, Smith AM, et al. Usefulness of magnetic resonance-derived quantitatived measurements of cerebral blood flow and volume in predication of infarct growth in hyperacute stroke [J]. Stroke,2001,32:1147.
[10]Haacke EM, Hu C, Parrish T, et al. Whole brain stress test using caffeine:effects on fMRI and SWI at 3T. Proceedings of the 11th annual meeting of ISMRM[C].Toronto:International Society for Magnetic Resonance in Medicine,2003:1731.
[11]陈家祥,宋桂芳,马岩等.MR磁敏感成像诊断缺血性中风的应用价值[J].上海医学影像,2008,17(2)：110-112.
[12]Geisler BS, Brandhoff F, Fiehler J, et al. Blood-oxygen-level-dependent MRI allows metabolic description of tissue at risk in acute stroke patients [J]. Stroke,2006,37:1778-1784.
[13]Kettunen MI, Grohn OH, Silvennoinen MJ, et al. Quantitative assessment of the balance between oxygen delivery and consumption in the rat brain after transient ischemia with T2-BOLD magnetic resonance imaging [J]. J Cereb Blood FlowMetab,2002,22(3):262-270.
[14]Pantano P, Toni D, Caramia F, et al. Relationship between vascular enhancement, cerebral hemodynamics, and MR angiography in cases of acute stroke [J]. Am J Neuroradiol,2001, 22(2):255-260.
[15]杨志宏,苗延巍,伍建林等.磁敏感加权成像在脑梗死再灌注损伤中的临床应用价值[J].中国临床医学影像杂志,2010,21(1)：38-40.
[16]Kucinski T, Koch C, Eckert B, et al. Collateral circulation is an independent radiological predictor of outcome after thrombolysis in acute ischemic stroke [J]. Neuroradiology,2003, 45(1):11-18.
[17]Schaffer CB, Friedman B, Nishimura N et al. Two-photon imaging of cortical surface microvessels reveals a robust redistribution in blood flow after vascular occlusion [J]. PLoS Biol,2006,4(2):258-270.
[18]Chalela JA, Alsop DC, Gonzalez-Atavales JB, et al. Magnetic resonance perfusion imaging in acute ischemic stroke using continuous arterial spin labeling [J]. Stroke,2000,31(3): 680-687.
[19]Moulin T, Crepin Leblond T, Chopard JL, et al. Hemorrhagic infarcts [J]. Eur Neurol 1993, 34:64-77.
[20]Pan J, Konstas AA, Bateman B, et al. Reperfusion injury following cerebral ischemia: pathophysiology, MR imaging, and potential therapies. Neuroradiology,2007, 49(2):93-102.
[21]Greer DM, Koroshetz WJ, Cullwn S, et al. Magnetic resonance imaging improves detection of intracerebral hemorrhage over computed tomography after intra-arterial thrombolysis [J]. Stroke,2004,35(2):491-495.
[22]Kidwell CS, Saver JL, Villablanca JP, et al. Magnetic resonance imaging detection of microbleeds before thrombolysis:an emerging application[J]. Stroke,2002,33(1):95-98.
[23]Schellinger PD, Jansen O, Fiebach JB, et al. A standardized MRI stroke protocol, comparison with CT in hyperacute intracerebral hemorrhage[J]. Stroke,1999, 30(4):765-768.
[24]Nighoghossuan N, Hermier M, Adeline P, et al. Old microbleeds are a potential riskfactor for cerebral bleeding after ischemic stroke. A gradient-echo T2*-weighted brain MRI study [J]. Stroke,2002,33:735-742.
[25]Tamura H, Hatazawa J, Toyoshima H, et al. Detection of deoxygenation-related signal change in acute ischemic stroke patients by T2*-weighted magnetic resonance imaging [J]. Stroke,2002,33(4):967-971.
[26]Chalela JA, Kidwell CS, Nentwich LM, et al. Magnetic resonance imaging and computed tomography in emergency assessment of patients with suspected acute stroke:a prospective comparison [J]. Lancet,2007,369:293-8.
[27]Sehgal V, Delproposto Z, Haacke EM. Clinical applications of neuroimaging with susceptibility-weighted imaging[J]. J Magn Reson Imaging,2005,22(4):439-450.
[28]Hermier M, Nighoghossian N. Contribution of Susceptibility-Weighted Imaging to Acute Stroke Assessment [J]. Stroke,2004,35:1989-1994.
[29]Linfante I, Llinas RH, Caplan LR, et al. MRI features of intracerebral hemorrhage within 2 hours from symptom onset [J]. Stroke,1999,30:2263-7.
[30]王彩云,张强,薛敏.磁化率加权成像：一种对颅内血管疾病敏感的MRI技术[J].国外医学(临床放射学分册),2007,30(2)：135-140.
[31]Derex L, Nighoghossian N, Hermier M, et al. Thrombolysis for ischemic stroke in patients with old microbleeds on pretreatment MRI [J]. Cerebrovasc Dis,2004,17(2-3):238-241.
[32]Koennecke HC. Cerebral microbleeds on MRI:Prevalence, associations, and potential clinical implications [J]. Neurology,2006,66(2):165-171.
[33]Flacke S, Urbach H, Keller E, et al. Middle cerebral artery (MCA) susceptibility sign at susceptibility-based perfusion MR imaging:clinical importance and comparison with hyperdense MCA sign at CT[J]. Radiology,2000,215(2):476-482.
[34]Rovia A, Orellana P, Alvarez-Sabin J,et al. Hyperacute ischemic stroke:middle cerebral artery susceptibility sign at echo-planar gradient-echo MR imaging[J]. Radiology,2004, 232:466-473.
[35]Chalela JA, Haymore JB, Ezzeddine MA, et al. The hypointense MCA sign [J]. Neurology, 2002,58:1470.
[36]刘梅丽,崔世民,张蕾莉等.磁共振扩散加权成像和灌注成像对超急性脑梗死影像半暗带的研究[J].中华放射学杂志,2002,12,36(12)：1095-1100.
[37]张芳,谢敬霞.早期脑梗死缺血半暗带MR扩散、灌注成像的研究进展[J].临床放射学杂志,2002,21(11)：907-909.
[38]Rohl L, Ostergaard L, Simonsen CZ, et al. Viability threholds of ischemic penumbra of hyperacute stroke defined by perfusion-weighted MRI and apparent diffusion coefficient[J]. Stroke,2001,32:1140-1146.
[39]韩鸿宾,谢敬霞.MR扩散与灌注成像在脑缺血诊断中的应用[J].中华放射学杂志,1998,6,32(6)：364-369.
[40]Kidwell CS, Alger JR, Saver JL, et al. Beyond mismatch:evolving paradiagms in imaging the ischemic penumbra with multimodal magnetic resonance imaging [J]. Stroke,2003, 34:2729-2735.
[1]吴桂贤,吴兆苏,刘静等.北京部分地区15年脑卒中事件变化趋势[J].中国慢性疾病预防与控制,2001,9：106-108.
[2]Warach S, Baron JC. Advances in stroke 2003:neuroimaging [J]. Stroke,2004, 35:351-352.
[3]Haacke EM, Mittal S, Wu Z, Neelavalli J, Cheng YC. Susceptibility-weighted imaging: Technical aspects and clinical applications, part 1 [J]. AJNR Am J Neuroradiol,2009, 30(1):19-30.
[4]Haacke EM, Xu Y, Cheng YC, et al. Susceptibility weighted imaging (SWI) [J]. Magn Reson Med,2004,52(3):612-618.
[5]Hermier M, Nighoghossian N. Contribution of Susceptibility-Weighted Imaging to Acute Stroke Assessment [J]. Stroke,2004,35:1989-1994.
[6]Tong KA, Ashwal S, Holshouser BA, et al. Hemorrhagic shearing lesions in children and adolescents with posttraumatic diffuse axonal injury:improved detection and initial results [J]. Radiology,2003,227:332-339.
[7]Thamburaj K, Radhakrishnan VV, Thomas B, et al. Intratumoral microhemorrhages on T2*-weighted gradient-echo imaging helps differentiate vestibular schwannoma from meningioma [J]. AJNR Am J Neuroradiol,2008,29(3):552-557.
[8]Thomas B, Somasundaram S, Thamburaj K, et al. Clinical applications of susceptibiity weighted MR imaging of the brain—a pictorial review [J]. Neuroradiology,2008, 50:105-116.
[9]Tan IL, van Schijndel RA, Pouwels PJ, et al. MR venography of multiple sclerosis [J]. AJNR Am J Neuroradiol,2000,21:1039-1042.
[10]Schaller B, Craf R. Cerebral ischemia and reperfusion:the pathophysiologic concept as a basis for clinical therapy [J]. J Cereb Blood Flow Metab,2004,24(2):351-371.
[11]Pan J, Konstas AA, Bateman B, et al. Reperfusion injury following cerebral ischemia: pathophysiology, MR imaging and potential therapies [J]. Neuroradiology,2007,49 (2):93-102.
[12]Schwamm LH, Koroshetz WJ, Sorensen AG, et al. Time course of lesion with acute st-roke:serial diffusion-and hemodynamic-weighted magnetic resonance imaging [J]. Stroke, 1998,29:2268-2276.
[13]Zheng Z, Yenari MA.Post-ischemic inflammation:molecular mechanisms and therapeutic implications [J].Neurol Res,2004,12,26(8):884-92.
[14]全冠民,袁涛,刘怀军.急性脑梗死出血性转化及MRI评估[J].国外医学临床放射学分册,2006,29(5)：311-314.
[15]Kidwell CS, Saver JL, Villablanca JP, et al. Magnetic resonance imaging detection of microbleeds before thrombolysis:an emerging application[J]. Stroke,2002,33(1):95-98.
[16]吴凌峰,张昆南,高幼奇等.青、老年脑梗死患者的危险因素及病因分析[J].中华脑血管病杂志(电子版),2010,4(4)：6-8.
[17]Schellinger PD, Jansen O, Fiebach JB, et al. A standardized MRI stroke protocol, comparison with CT in hyperacute intracerebral hemorrhage[J]. Stroke,1999, 30(4):765-768.
[18]Greer DM, Koroshetz WJ, Cullwn S, et al. Magnetic resonance imaging improves detection of intracerebral hemorrhage over computed tomography after intra-arterial thrombolysis [J]. Stroke,2004,35(2):491-495.
[19]Linfante I, Llinas RH, Caplan LR, et al. MRI features of intracerebral hemorrhage within 2 hours from symptom onset [J]. Stroke,1999,30:2263-7.
[20]Chalela JA, Kidwell CS, Nentwich LM, et al. Magnetic resonance imaging and computed tomography in emergency assessment of patients with suspected acute stroke:a prospective comparison [J]. Lancet,2007,369:293-8.
[21]Moulin T, Crepin Leblond T, Chopard JL, et al. Hemorrhagic infarcts [J]. Eur Neurol 1993, 34:64-77.
[22]Nighoghossuan N, Hermier M, Adeline P, et al. Old microbleeds are a potential riskfactor for cerebral bleeding after ischemic stroke. A gradient-echo T2*-weighted brain MRI study [J]. Stroke,2002,33:735-742.
[23]Sehgal V, Delproposto Z, Haacke EM. Clinical applications of neuroimaging with susceptibility-weighted imaging[J]. J Magn Reson Imaging,2005,22(4):439-450.
[24]王彩云,张强,薛敏.磁化率加权成像：一种对颅内血管疾病敏感的MRI技术[J].国外医学(临床放射学分册),2007,30(2)：135-140.
[25]Derex L, Nighoghossian N, Hermier M, et al. Thrombolysis for ischemic stroke in patients with old microbleeds on pretreatment MRI [J]. Cerebrovasc Dis,2004,17(2-3):238-241.
[26]Koennecke HC. Cerebral microbleeds on MRI:Prevalence, associations, and potential clinical implications [J]. Neurology,2006,66(2):165-171.
[27]Wahlgret N, Ahmed N, Davalos A, et al. Symptomatic intracerebral hemorrhgge, mortality and independence at 3 months for patients treated 3-4.5h after stroke onset in the sits thrombolysis register (SITS-ISTR) [J]. Cerebrovasc Dis,2008,25(Suppl 2):3.
[28]Rovia A, Orellana P, Alvarez-Sabin J,et al. Hyperacute ischemic stroke:middle cerebral artery susceptibility sign at echo-planar gradient-echo MR imaging[J]. Radiology,2004, 232:466-473.
[29]Chalela JA, Haymore JB, Ezzeddine MA, et al. The hypointense MCA sign [J]. Neurology, 2002,58:1470.
[30]Flacke S, Urbach H, Keller E, et al. Middle cerebral artery (MCA) susceptibility sign at susceptibility-based perfusion MR imaging:clinical importance and comparison with hyperdense MCA sign at CT[J]. Radiology,2000,215(2):476-482.
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