全脑CT灌注成像在烟雾病血管重建术中的应用价值

目的探讨全脑CT灌注成像在烟雾病血管重建术中的应用价值。方法 18例烟雾病患者实施血管重建术前、术后分别行全脑CT灌注成像,对手术前后脑血流量(CBF)、脑血容量(CBV)、平均通过时间(MTT)和达峰时间(TTP)进行定性和定量分析,采用配对t检验比较手术前后CT灌注参数值的差异。结果 18例患者术后CTA均显示搭桥血管通畅。血管重建术后1周手术侧异常灌注明显改善,TTP和MTT较术前减低,CBF和CBV较术前增高,手术前后灌注参数绝对值的差异有统计学意义。结论全脑CT灌注成像能评价烟雾病血管重建术前和术后的脑血流动力学变化,同时还可评估桥血管再通情况,具有较高的临床应用价值。     

CT脑灌注与血管造影在急性脑梗死中的临床应用

目的:探讨64层螺旋CT脑灌注成像和脑血管造影技术在急性期脑梗死中的应用价值。方法:应用PhilipsBrilliance CT 64,对30例发病12h内急性脑缺血患者行CT平扫、CT脑灌注成像(CTP)和CT血管造影(CTA)检查。分析平扫及灌注成像表现,计算出缺血区脑血流参数,包括:脑血容量图(CBV)、血流量图(CBF)、对比剂平均通过时间(MTT)和对比剂峰值时间(TTP),与对侧相应区灌注参数进行比较,并重建颈段和脑内动脉CTA图像。所有病例在发病后3~14天复查CT平扫。结果:30例患者中16例头颅平扫发现早期脑梗死征象,14例常规平扫未发现异常,而CTP均发现灌注异常区。CTP表现为CBF及CBV减低、MTT及TTP延迟;患侧CBF、MTT、TTP与对侧差异有显著性意义(P<0.01),患侧CBV与对侧差异无显著性意义(P>0.01)。重建CTA图像显示16例一侧颈内动脉狭窄,8例一侧大脑中动脉狭窄(其中1例伴大脑后动脉狭窄、左侧后交通动脉闭塞);4例左侧大脑中动脉闭塞,2例左侧颈内动脉闭塞。结论:CTP能够早期、及时、准确地反映缺血部位及程度,预测半暗带;CTA可以显示病变血管的部位和程度;联合应用两者,对早期诊断急性脑缺血和指导治疗有重要价值。     

CT脑灌注评估颈动脉狭窄的血流动力学改变

目的 评价CT脑灌注在评估颈动脉狭窄患者的脑血流动力学改变中的应用价值.方法 对50例临床诊断为可疑颈动脉狭窄的患者进行常规头颅CT平扫,CT灌注扫描(CT perfusion,CTP)及CT血管成像扫描(CT angiography,CTA).CTP可获得脑血流量(CBF),脑血容量(CBV),平均通过时间(MTT)及达峰时间(TTP)等灌注参数图,CTA采用CPR,MPR及VR等重建方式重建头颈部血管.观察CTA所示的颈动脉狭窄率与CTP灌注参数变化间的关系.结果 38例单侧颈动脉狭窄患者中,10例轻度狭窄者,患侧各灌注参数变化与健侧各参数无统计学差异,9例中度狭窄与19例重度狭窄及闭塞患者中,患侧MTT与TTP较健侧显著延长,而CBF与CBV无明显变化.结论 灌注参数MTT与TTP能敏感地显示颈动脉中重度狭窄或闭塞患者的血流动力学改变,是诊断脑缺血最敏感的指标,为临床早期治疗提供可靠的依据,从而预防脑卒中的发生.     

脑MR灌注成像的技术与应用

MR成像常用于对在脑解剖的评价。近来在MR灌注成像新技术中，通过测量不同的血液动力学参数，如脑血容量（CBV）、脑血流速度（CBF）、平均通过时间（MTT）等，拓展了MR成像技术的应用领域，本综述了MR灌注成像对大脑局部血液动力学评估这一新技术及其在脑疾病的诊断和治疗等方面的临床应用价值和前景。     

低剂量CT血流灌注成像对阿尔茨海默病的诊断价值

目的 评价低剂量CT血流灌注成像对阿尔茨海默病(Alzheimer's disease,AD)的诊断价值.方法 根据临床诊断标准随机选择52例AD和30例健康对照组.对他们进行低剂量血流灌注扫描(CTPI),并在工作站上进行处理,生成伪彩图及进行灌注参数测量,灌注参数包括脑血容量(cerebral blood volume,CBV)、脑血流量(cerebral blood flow,CBF)、平均通过时间(mean transit time,MTT)和达峰时间(time to peak,TTP).选择双侧额叶皮质、双侧颞叶皮质、双侧海马、双侧基底节区域进行测量.结果 健康对照组的双侧额叶、颞叶、基底节和海马CBV、CBF值明显高于AD组,而AD组上述部位的MTT和TTP明显大于健康对照组,有统计学意义(P＜0.05).结论 AD患者伴有微循环障碍和缺血改变.低剂量CT灌注对AD的诊断有一定意义.     

脑MR灌注成像的技术与应用

MR成像常用于对大脑解剖的评价。近来在MR灌注成像新技术中，通过测量不同的血液动力学参数，如脑血容量(CBV)、脑血流速度(CBF)、平均通过时间(MTT)等，拓展了MR成像技术的应用领域。本文综述了MR灌注成像时大脑局部血液动力学评估这一新技术及其在脑疾病的诊断和治疗等方面的临床应用价值和前景。     

颅内巨大动脉瘤行载瘤动脉闭塞术的CT灌注评估

目的利用CT灌注成像(CTP)评估颅内巨大动脉瘤(GIA)患者行载瘤动脉闭塞术(PAO)的脑血流动力学改变。方法 2例GIA患者,经球囊闭塞实验阴性,行PAO手术前后分别接受CTP检查,通过手术侧与对侧大脑半球的脑血流量(CBF)、血容量(CBV)及达峰时间(TTP)对比,评价疗效。结果第一例患者的动脉瘤腔内涡流形成,阻碍了远端血管充盈,术前CTP显示CBF和CBV明显下降,PAO手术解除了涡流,Willis环代偿良好,术后CTP显示脑血流灌注明显好转。第二例患者的术前CTP正常,术后CTP提示TTP轻度延长,CBF和CBV正常。结论 CTP能够有效的评估GIA患者行PAO手术的疗效。     

颈内动脉中重度狭窄支架置入血管成形术后局部脑灌注的变化及意义

目的 探讨颈内动脉支架置入血管成形术后脑血流动力学的变化情况.方法 对38例颈内动脉中重度狭窄患者行支架置入血管成形术,在手术前后对患者行脑CT灌注成像检查,观察患侧和对侧局部脑血流量(CBF)、脑血容量(CBV)及造影剂平均通过时间(MTT)的变化.结果 在支架置入血管成形术前,与对侧比较,患者患侧CBF、CBV降低...     

多层CT脑灌注成像与CT血管成像诊断颈动脉狭窄性短暂性脑缺血发作

目的 研究脑CT灌注成像对诊断颈动脉狭窄所致短暂性脑缺血发作(TIA)的价值.方法 对20例临床诊断为TIA的病人行常规CT,CT灌注和CT血管成像.评价CT灌注成像的峰值时间(TTP)、血流量(CBF)、血容量(CBV)以及颈动脉的狭窄程度.结果 15例TIA病人在TTP图上发现与临床症状相对应的灌注异常区,TTP较对侧延迟.CT灌注显示异常灌注病灶的数目及范围多于平扫.患侧TTP延长及对侧的TTP分别为(13.0±3.8) s和(8.3±1.7) s,P＜0.01,而CBF无显著性差异.20例病人40支颈动脉CTA观察到4支血管闭塞,31支血管狭窄,颈动脉狭窄程度同TTP之间的差异无统计学意义(P>0.05).结论 CT脑灌注成像结合CTA,可同时观察颈内动脉的血管形态变化及脑组织的血流动力学变化.     

64层螺旋CT脑灌注成像评价急性脑梗死溶栓前后脑血流动力学改变

目的探讨64层螺旋CT脑灌注成像(CTP)在评价急性脑梗死溶栓疗效中的应用价值。资料与方法20例急性脑梗死患者于发病3~10h行常规CT平扫和CTP检查,其中16例行静脉溶栓、4例行动脉溶栓治疗。溶栓后2~7天复查CT平扫和CTP。对溶栓治疗前后病变区的脑血流量(CBF)、脑血容量(CBV)和达峰时间(TTP)进行定性和定量比较分析。结果20例中5例头颅CT平扫发现早期脑梗死征象,15例常规CT平扫未发现异常,CTP均发现与临床症状对应的脑灌注异常区,表现为CBF、CBV降低,TTP延迟。溶栓后15例脑灌注异常范围缩小,CBF和CBV增加,TTP缩短;3例脑灌注异常区范围扩大,CBF、CBV进一步降低,TTP延迟更加显著;2例出现局部过度灌注。统计学分析结果显示溶栓治疗后多数患者脑灌注情况明显改善,缺血边缘区CBF和TTP与溶栓前差异有统计学意义(P<0.05),缺血中心区CBF和CBV与溶栓前差异无统计学意义(P>0.05)。结论脑CTP检查能够观察溶栓治疗前后脑血流动力学指标的变化,为评价急性脑梗死患者的溶栓疗效提供重要依据。     

CT perfusion parameter values in regions of diffusion abnormalities

BACKGROUND AND PURPOSE: Dynamic CT perfusion imaging is a rapid and widely available method for assessing cerebral hemodynamics in the setting of ischemia. Nevertheless, little is known about perfusion parameters within regions of diffusion abnormality. Since MR diffusion-weighted (DW) imaging is widely considered the most sensitive and specific technique to examine the ischemic core, new knowledge about CT perfusion findings in areas of abnormal diffusion would likely provide valuable information. The purpose of our study was to measure the CT-derived perfusion values within acute ischemic lesions characterized by 1) increased signal intensity on DW images and 2) decreased apparent diffusion coefficient (ADC) and compare these values with those measured in contralateral, normal brain tissue. METHODS: Analysis was performed in 10 patients with acute middle cerebral artery territory stroke of symptom onset less than 8 hours before imaging who had undergone both CT perfusion and DW imaging within 2 hours. After registration of CT perfusion and DW images, measurements were made on a pixel-by-pixel basis in regions of abnormal hyperintensity on DW images and in areas of decreased ADC. RESULTS: Significant decreases in cerebral blood flow and cerebral blood volume with elevated mean transit times were observed in regions of infarct as defined by increased signal intensity on DW images and decreased ADC. Comparison of perfusion parameters in regions of core infarct differed significantly from those measured in contralateral normal brain. CONCLUSION: CT perfusion findings of decreased cerebral blood flow, mean transit time, and cerebrovascular volume correlate with areas of abnormal hyperintensity on DW images and regions of decreased ADC. These findings provide important information about perfusion changes in acute ischemia in areas of diffusion abnormality.     

PC机辅助MR脑灌注成像初步研究

目的:研究PC机辅助MR脑灌注成像软件,探讨其临床应用价值。方法:在PC机上使用MR脑灌注成像软件,对5例健康人和18例脑缺血患者的灌注图像进行后处理,计算出有关脑灌注参数图,包括相对脑血流量(rrCBF)图、相对脑血容量(rrCBV)图、局部灌注达峰时间(TTP)图和团注平均通过时间(bMTT)图。结果:应用MR脑灌注成像软件可以在PC机上实现灌注图像的后处理,脑灌注参数图能够为脑缺血患者提供有价值的脑血液动力学信息,显示灌注异常的范围。结论:PC机辅助MR脑灌注成像软件简单易行,可显示常规MR无法显示的血流动力学异常,对临床和科研具有重要价值。     

磁共振脑血流灌注的影像及定量分析

目的 应用对比增强磁共振脑血流灌注成像,研究不同病理状态下脑组织的血液动力学变化。方法 采用对Ｔ２＾＊敏感的平面回波自由衰减序列（ＥＰＩ－ＦＩＤ）,对４５例因性因管病、１１例其他脑血管病、４例脑肿瘤和４例脑炎患者进行了注射对比剂后的血流灌注加权成像（ＰＷＩ）,分析脑血流灌注图,并定量地研究脑组织的血液动力学变化。结果 磁共振脑血流灌注图和定量分析发现５４个病例的脑组织有异常的血液动力学变化;ＰＷＩ     

Correlation of early dynamic CT perfusion imaging with whole-brain MR diffusion and perfusion imaging in acute hemispheric stroke

BACKGROUND AND PURPOSE: Compared with MR imaging, dynamic CT perfusion imaging covers only a fraction of the whole brain. An important assumption is that CT perfusion abnormalities correlate with total ischemic volume. The purpose of our study was to measure the degree of correlation between abnormalities seen on CT perfusion scans and the volumes of abnormality seen on MR diffusion and perfusion images in patients with acute large-vessel stroke. METHODS: Fourteen patients with acute hemispheric stroke symptoms less than 12 hours in duration were studied with single-slice CT perfusion imaging and multislice MR diffusion and perfusion imaging. CT and MR perfusion studies were completed within 2.5 hours of one another (mean, 77 minutes) and were reviewed independently by two neuroradiologists. Hemodynamic parameters included cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). Extents of abnormality on images were compared by using Kendall correlation. RESULTS: Statistically significant correlation was found between CT-CBF and MR-CBF abnormalities (tau = 0.60, P =.003) and CT-MTT and MR-MTT abnormalities (tau = 0.65, P =.001). Correlation of CT-CBV with MR-CBV approached significance (tau = 0.39, P =.06). Extent of initial hyperintensity on diffusion-weighted images correlated best with extent of MR-CBV abnormality (tau = 0.69, P =.001), extent of MR-MTT abnormality (tau = 0.67, P =.002), and extent of CT-CBV abnormality (tau = 0.47, P =.02). CONCLUSION: Good correlation was seen between CT and MR for CBF and MTT abnormalities. It remains uncertain whether CT perfusion CBV abnormalities correspond well to whole-brain abnormalities.     

Dynamic Angiography and Perfusion Imaging Using Flat Detector CT in the Angiography Suite: A Pilot Study in Patients with Acute Middle Cerebral Artery Occlusions

BACKGROUND AND PURPOSE:Perfusion and angiographic imaging using intravenous contrast application to evaluate stroke patients is now technically feasible by flat detector CT performed by the angiographic system. The aim of this pilot study was to show the feasibility and qualitative comparability of a novel flat detector CT dynamic perfusion and angiographic imaging protocol in comparison with a multimodal stroke MR imaging protocol.MATERIALS AND METHODS:In 12 patients with acute stroke, MR imaging and the novel flat detector CT protocol were performed before endovascular treatment. Perfusion parameter maps (MTT, TTP, CBV, CBF) and MIP/volume-rendering technique images obtained by using both modalities (MR imaging and flat detector CT) were compared.RESULTS:Comparison of MIP/volume-rendering technique images demonstrated equivalent visibility of the occlusion site. Qualitative comparison of perfusion parameter maps by using ASPECTS revealed high Pearson correlation coefficients for parameters CBF, MTT, and TTP (0.95–0.98), while for CBV, the coefficient was lower (0.49).CONCLUSIONS:We have shown the feasibility of a novel dynamic flat detector CT perfusion and angiographic protocol for the diagnosis and triage of patients with acute ischemic stroke. In a qualitative comparison, the parameter maps and MIP/volume-rendering technique images compared well with MR imaging. In our opinion, this flat detector CT application may substitute for multisection CT imaging in selected patients with acute stroke so that in the future, patients with acute stroke may be directly referred to the angiography suite, thereby avoiding transportation and saving time.

Flat detector CT (FD-CT) equipped angiographic systems are now widely used in neurointerventional institutions. Recently, an application to perform imaging of the brain parenchyma (FD-CT), cerebral vasculature (flat detector CT dynamic perfusion and angiographic imaging [FD-CTA]), and cerebral blood volume has been described and was evaluated in patients with acute middle cerebral artery occlusions.^1–3 However, this application was limited due to the inferior FD-CT soft-tissue resolution of the brain parenchyma in comparison with multisection CT (MS-CT) or MR imaging. Additionally, there was a lack of temporal resolution so that calculation of dynamic (time-dependent) perfusion parameters was not possible.Assessment of the impact of an ischemic stroke is best performed with physiologic criteria because especially in the acute phase, morphologic changes are only minimal and may be difficult to recognize by using MS-CT imaging.⁴ The use of perfusion and angiographic imaging increases the sensitivity of MS-CT and MR imaging in the acute phase of ischemic stroke. Thus, MS-CT angiography and MS-CT perfusion imaging are used to assess patients within a 0- to 4.5-hour time window of ischemic stroke. On the basis of the mismatch concept beyond 4.5 hours, multimodal MR imaging by using FLAIR, MR angiography, diffusion-weighted, and MR perfusion imaging (MRP) is used in many centers to identify patients eligible for recanalization therapies.⁵ MS-CT and MR imaging applications allow visualization of brain parenchyma and vessel occlusion (MS-CT angiography, MRA); and calculation of the dynamic perfusion parameter maps (time-to-peak, mean transit time, cerebral blood flow, and cerebral blood volume) to assess the viability of the brain.^6–9 The ability to obtain dynamic perfusion maps (FD-CTP) and angiographic images by using an intravenous contrast application within the angiography suite would seem to create a single ideal venue for both diagnosis and treatment of patients with an acute ischemic stroke. A FD-CT application replacing MS-CT or MR imaging would optimize the work flow, avoid transportation of the patient from one imaging location to the other, save time, and may allow periodic monitoring of brain viability during the endovascular treatment.To date, dynamic perfusion imaging with the C-arm angiographic system has been limited by the slow gantry rotation time. However, recent studies in canines and swine models have now demonstrated the feasibility of dynamic perfusion imaging with the use of a flat detector angiographic system.^10–12 The aim of this pilot study was to test the feasibility of this novel application by comparing FD-CTP and FD-CTA with a multimodal MR imaging protocol in patients with acute ischemic stroke. Additionally, the effective patient dose was evaluated.     

Functional MR of brain activity and perfusion in patients with chronic cortical stroke.

PURPOSE(1) To determine whether functional MR can reliably map functional deficits in patients with stroke in the primary visual cortex; (2) to determine whether functional MR can reliably map perfusion deficits; and (3) to determine whether functional MR can give any additional diagnostic information beyond conventional MR.METHODSSeven patients who had had a stroke in their primary visual system were examined using two functional MR techniques: (1) dynamic susceptibility contrast imaging, and (2) cortical activation mapping during full-field visual stimulation. Maps of relative cerebral blood volume and activation were created and compared with visual field examinations and conventional T2-weighted images on a quadrant-by-quadrant basis in five of these patients.RESULTSVisual field mapping matched with both T2-weighted conventional images and activation mapping of 16 of 18 quadrants. In two quadrants, the activation maps detected abnormalities that were present on the visual field examination but not present on the T2-weighted images nor on the relative cerebral blood volume maps, which may indicate abnormal function without frank infarction. In addition, the activation maps demonstrated decreased activation in extrastriate cortex and had normal T2 signal and relative cerebral blood volume but was adjacent to infarcted primary cortex, mapping in vivo how stroke in one location can affect the function of distant tissue.CONCLUSIONFunctional MR techniques can accurately map functional and perfusion deficits and thereby provide additional clinically useful information. Additional studies will be needed to determine the prognostic utility of functional MR in stroke patients.     

Benefits of perfusion MR imaging relative to diffusion MR imaging in the diagnosis and treatment of hyperacute stroke

BACKGROUND AND PURPOSE: The development of thrombolytic agents for use with compromised cerebral blood flow has made it critical to quickly identify those patients to best treat. We hypothesized that combined diffusion and perfusion MR imaging adds vital diagnostic value for patients for whom the greatest potential benefits exist and far exceeds the diagnostic value of diffusion MR imaging alone. METHODS: The cases of patients with neurologic symptoms of acute ischemic stroke who underwent ultra-fast emergent MR imaging within 6 hours were reviewed. In all cases, automatic processing yielded isotropic diffusion images and perfusion time-to-peak maps. Images with large vessel distribution ischemia and with mismatched perfusion abnormalities were correlated with patient records. All follow-up images were reviewed and compared with outcomes resulting from hyperacute therapies. RESULTS: For 16 (26%) of 62 patients, hypoperfusion was the best MR imaging evidence of disease distribution, and for 15 of the 16, hypoperfusion (not abnormal diffusion) comprised the only imaging evidence for disease involving large vessels. For seven patients, diffusion imaging findings were entirely normal, and for nine, diffusion imaging delineated abnormal signal in either small vessel distributions or in a notably smaller cortical branch in one case. In all cases, perfusion maps were predictive of eventual lesions, as confirmed by angiography, CT, or subsequent MR imaging. CONCLUSION: If only diffusion MR imaging is used in assessing patients with hyperacute stroke, nearly one quarter of the cases may be incorrectly categorized with respect to the distribution of ischemic at-risk tissue. Addition of perfusion information further enables better categorizing of vascular distribution to allow the best selection among therapeutic options and to improve patient outcomes.     

Intracranial mass lesions: dynamic contrast-enhanced susceptibility-weighted echo-planar perfusion MR imaging

Dynamic contrast agent-enhanced perfusion magnetic resonance (MR) imaging provides physiologic information that complements the anatomic information available with conventional MR imaging. Analysis of dynamic data from perfusion MR imaging, based on tracer kinetic theory, yields quantitative estimates of cerebral blood volume that reflect the underlying microvasculature and angiogenesis. Perfusion MR imaging is a fast and robust imaging technique that is increasingly used as a research tool to help evaluate and understand intracranial disease processes and as a clinical tool to help diagnose, manage, and understand intracranial mass lesions. With the increasing number of applications of perfusion MR imaging, it is important to understand the principles underlying the technique. In this review, the essential underlying physics and methods of dynamic contrast-enhanced susceptibility-weighted echo-planar perfusion MR imaging are described. The clinical applications of cerebral blood volume maps obtained with perfusion MR imaging in the differential diagnosis of intracranial mass lesions, as well as the pitfalls and limitations of the technique, are discussed. Emphasis is on the clinical role of perfusion MR imaging in providing insight into the underlying pathophysiology of cerebral microcirculation.     

Cerebral blood flow mapping using stable Xenon-enhanced CT in sickle cell cerebrovascular disease

Summary The cerebral blood flow (CBF) of 25 patients with sickle cell cerebrovascular disease (SCCVD) was examined using a Xenon-CT flow mapping method. Brain CT and MR findings were correlated with those of the Xenon-CT flow studies. CBF defects on Xenon-CT correlated reasonably well with the areas of cortical infarctions on the MR images, but in 27% of the cases, flow defects were slightly larger than the areas of infarctions on the MR images. In deep watershed or basal ganglia infarctions, abnormal CBF was noted about the cerebral cortex near infarctions in 72% of the patients, regardless of infarction sizes on the MR images. However, decreased CBF was recognized in 4 of the 9 children whose MR images were virtually normal. Thus, the extent of flow depletion cannot be predicted accurately by MR imaging alone. Xenon-CT flow mapping proved a safe and reliable procedure for evaluation of the CBF of patients with SCCVD. Although this study is preliminary, it may have a potential in selecting patients for hypertransfusion therapy, as a noninvasive test and for following children with SCCVD during their therapy. Careful correlation of results of CBF with those of MR imaging or of CT is important for objective interpretations of flow mapping images.