PC机辅助MR人脑表观扩散系数图的成像研究

目的 研究PC机辅助MR人脑平均表观扩散系数(ADCav)图的成像软件，探讨其I临床应用价值。资料与方法 在PC机上使用MR脑ADCav图成像软件，对6例正常人和12例亚急性期脑梗死患者扩散加权图像进行后处理，计算出ADCav图。结果 应用MR脑ADCav图成像软件可以在PC机上实现扩散加权图像的后处理，计算出人脑ADCav图，进行ADC值的定量分析，图像以伪彩色显示，能够更加明确病变的范围。结论 PC机辅助MR人脑ADCav图成像软件简单易行，对临床和科研具有重要价值。     

微机辅助CT脑灌注成像以及定量测量

目的：报告微机辅助CT脑灌注成像以及定量测量方法。方法：以PentiumⅡ300MHz微处理器，128MB内存，16MB显存，6G硬盘PC机和Windows98第2版为平台，用VissualC 为开发语言，根据中心容积定理，利用动态CT图像分析并计算脑血流动力学的有关参数，包括脑血流量（cerebral blood flow,CBF)，脑血容量（cerebral blood volume,CBV),平均通过时间（mean transit time,MTT)和峰值时间（time to peak,TTP)等。最后，将脑血流动力学数据根据色阶分别处理成脑血流量图（mapping of CBF)，脑血容量图（mapping of CBV)，平均通过时间图（mapping of MTT)和峰值时间图（mapping of TTP)。结果：动态增强CT图像经软件处理后可以在微机上显示脑组织的CBF，CBV，TTP和MTT灌注原始图像以及分割颅骨，皮下组织和脑室后的图像。急性脑缺血患者在MR T1加权像，T2加权像，平扫CT以及增强CT未显示的责任病灶，脑CT灌注图像可以清楚显示脑血流动力学的异常。结论：微机辅助CT脑灌注成像简单铁行，可显示常规CT和MR无法发现的早期脑缺血区的血流异常。与MR灌注成像相比更适用于急诊检查。     

慢性大脑中动脉狭窄与闭塞的MR灌注成像研究

目的:探讨单侧大脑中动脉(MCA)慢性重度狭窄、闭塞患者的MR脑灌注成像表现及其应用价值.方法:28例单侧MCA慢性重度狭窄或闭塞患者行MR脑灌注成像检查,得出有关脑灌注参数图,包括相对脑血流量(rCBF)、相对脑血容量(rCBV)、相对平均通过时间(rMTT)和达峰时间(TTP)图,对灌注成像表现进行定性和定量分析.结果:28例MCA慢性重度狭窄或闭塞患者,磁共振灌注加权成像(PWI)均发现病变侧灌注异常,病变侧rCBV、rMTT和TTP与对侧比较差异有显著性意义(P＜0.01),rCBF差异无显著性意义(P＞0.05).rMTT和TTP图显示病变侧较对侧明显延迟,24例仅累及MCA供血区,4例同时累及MCA和分水岭区.结论:PWI检查能够显示单侧MCA慢性重度狭窄或闭塞患者脑血流动力学受损情况,对临床诊断和治疗具有重要价值.     

短暂性脑缺血发作的MR脑灌注达峰时间参数研究

目的 :探讨MR脑灌注达峰时间 (timetopeak ,TTP)参数在短暂性脑缺血发作 (TIA)的应用价值。方法 :对 18例临床诊断TIA的病人行常规MR头颅平扫和MR脑灌注加权成像检查 ,9例伴有一侧肢体无力 ,9例不伴有肢体无力。常规MR扫描后应用平面回波序列 (EPI)连续扫描 6 0次 ,在第 10次扫描时 ,经肘静脉快速团注Gd DTPA ,脑灌注图像使用MRPerfusion软件进行后处理 ,获得TTP图和TTP延迟 (timetopeakdelay,TTP D)图 (延迟 >0 ,≥ 2 ,≥ 4 ,≥ 6 ,≥ 8和≥ 10s) ,并测量TTP D图上病变的体积。结果 :TTP图上 18例TIA患者中有 12例发现与临床症状相对应的灌注异常区 ,表现为TTP延迟 ;9例伴有一侧肢体无力的患者TTP图上均发现灌注异常区 ,9例不伴有肢体无力的患者 3例TTP图上发现灌注异常区 ,经 χ2 检验 ,TIA患者症状与TTP图上有无灌注异常区有显著意义 (P <0 .0 1)。 12例TTP图发现灌注异常区的患者 ,病变区TTP较对侧延迟均 >0s和≥ 2s ,10例 (83% )≥ 4s ,6例 (5 0 % )≥ 6s,4例 (33% )≥ 8s,2例 (17% )≥ 10s ;TTP D图上病变的体积随时间延长而减小 ,平均体积分别为 75 .4、6 2 .6、33.4、2 4 .5、10 .2和 2 .6mm3 。结论 :TTP参数是评价TIA患者脑血液动力学损伤的敏感指标 ,能够显示灌注损伤的范围和程度。     

急性缺血性卒中发病第1周内的MR灌注与弥散加权成像

MR灌注加权成像(PWI)与弥散加权成像(DWI)是早期显示脑缺血性改变非常灵敏的手段。两者在显示急性期脑梗塞梗塞灶的大小上常不一致(即PW-DW不一致)。这个不一致可用不同的灌注参数确定,即相对脑血管容量(rCBV)、相对脑血流量(rCBF)和平均通过时间(MTT)。本研究的目的在于:①测量各类图像上病灶体积,并探讨rCBV、rCBF和MTT在预测梗塞灶的扩大及最终梗塞面     

PC平台MR图像后处理工作站的开发与扩散张量参数图的研究

目的　研究并开发适合实验室磁共振图像后处理的PC平台的工作站。讨论图像后处理软件的PC水平的硬件工作环境。分析合成的人脑表观扩散系数 (ADC)参数图图像特点 ,讨论其临床应用价值。方法　对 6例正常人进行常规与功能性MR扩散成像扫描获得的结构与扩散张量参数图像 ,在市售PC机平台上运行Perfect Tech图像后处理软件进行各种ADC参数图的重建。结果　应用Perfect Tech软件在目前市售PC机硬件条件下可以实现MR功能性图像后处理与分析。ADC参数图表现为灰白质界限不清 ,呈等信号 ,白质区的各向异性被均化消除 :脑白质区ADC值平均为(7 5 9± 1 12 )× 10 -4 mm2 /s,灰质区ADC值平均为 (10 5 0± 4 34 )× 10 -4 mm2 /s ,两者间差异无显著性意义 ,脑脊液表现为高信号。在各向异性指数图 (AI)上表现为灰质区与白质区分界明显 ,灰质区表现为低信号 ,白质区的信号强度表现为高信号 ,扩散的各向异性被突出 ,白质区AI为 0 2 0± 0 0 9,灰质区AI为 0 0 9± 0 0 7,之间差异存在显著性意义 (t=4 13,P <0 0 1)。结论　可以在PC机水平上实现磁共振图像后处理以及功能性参数图的运算与显示 ,扩散张量参数图对临床与科研具有重大的实用价值。     

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。     

CT灌注成像在短暂性脑缺血发作的临床应用价值

目的:探讨CT脑灌注成像在短暂性脑缺血发作(TIA)的应用价值。方法:对15例临床诊断TIA的病人行CT灌注成像,在常规轴面CT扫描后根据临床症状选取4个相邻的兴趣层面,团注对比剂4s后开始持续50s的连续动态扫描,重建的200幅动态图像使用脑灌注软件包进行处理,获得灌注图像。测量脑内感兴趣区的到达峰值时间、血流量和血容量,对这些图像进行定量分析。结果:TIA患者中有8例发现与临床症状相对应的灌注异常区,表现为达峰时间延迟和/或血流量下降;另外7例未发现灌注异常区。15例患者患侧与对侧的平均达峰时间分别为(12.01±3.53)s和(10.31±2.68)s,经配对t检验:t=3.68,P<0.01,两者间差异具有显著性意义;两侧平均血容量间的差异无统计学意义。结论:CT脑灌注成像能够为TIA患者提供有价值的脑血流动力学信息,显示灌注异常的范围。     

磁共振灌注成像参数图在小乳腺癌诊断中的初步应用

目的:研究小乳腺癌在各种MR灌注参数图像上的影像表现及其灌注特征,评价磁共振灌注成像参数图的临床应用价值.方法:29例女性小乳腺癌[共46个经病理证实的病灶(最大径≤2cm)]被纳入研究范畴.采用快速小角度激发(FLASH)序列行双侧乳腺动态高分辨对比增强MR成像(DCE MRI),共连续6个回合成像,绘制时间一信号强度曲线(TIC),并选取3个时间点,通过软件获得Washin、Washout、MIPt及PEI等4种乳腺灌注伪彩参数图像,分别测定整个病灶、病灶周边及中心以及对侧正常乳腺组织的各灌注参数值,分析小乳腺癌的灌注特点.结果:Washin、Washout、MIPt及PEI等4种灌注参数图像分别可以显示41个、19个、44个及45个小乳腺癌灶,检出率分别为89.1%、41.3%、95.7%及97.8%.Washin图不能检出的5个病灶中4个(80.0%)TIC为Ⅰ型曲线,Washout图检出的19个病灶中,15个(78.9%)为Ⅲ型曲线.46个小乳腺癌中,35个(76.1%)呈现明显不均匀异常灌注增强,其中26个周边灌注更明显.对各参数值的测定及分析结果显示小乳腺癌灶与正常乳腺组织之间、乳癌周边部分与中心部分间的各灌注参数值差异有统计学意义(P<0.05).结论:乳腺动态高分辨对比增强MR灌注成像参数图对乳腺癌病灶的检出率较高,大部分小乳腺癌呈明显不均匀灌注增强,且增强早期即出现异常灌注,周边部分灌注更显著.乳腺MR灌注参数图像可为小乳腺癌的诊断和鉴别提供重要的补充信息.     

TIA患者脑动态CT峰值时间灌注成像的初步研究

目的:探讨脑动态CT峰值时间（TTP）灌注成像对短暂性脑局部缺血发作（TIA）的诊断价值。材料和方法:对17例临床诊断为TIA的患者进行脑动态CT扫描TTP灌注成像检查。感兴趣区层厚10mm,扫描矩阵512×512,曝光电压和功率与常规扫描相同。动态CT检查为在启动高压注射器经肘静脉快速注入对比剂的同时对感兴趣层面进行连续快速扫描。曝光时间为1s,连续扫描40s,共40层。碘对比剂为300mg碘海醇,流量为8ml/s,总量为40ml。CT检查结束后,用自编软件进行动态增强CT数据处理。用手工画线方式将脑实质与颅骨、皮下组织、脑室和图像背景分割,最后仅留下脑实质的彩色TTP灌注图像。结果:17例常规CT检查（包括增强检查）和12例常规MR检查均未发现脑内有与TIA发作临床表现相符合的新鲜病灶。脑动态CT扫描TTP灌注成像显示脑内有与TIA发作临床表现相符合的病灶14例（82.35％）。其余3例脑TTP灌注成像未见异常。结论:虽然动态CT峰值时间脑灌注成像只能进行单一层面的检查,但其方法简单、易行,可显示常规CT和MR无法发现的早期脑缺血区的血流异常,对TIA的研究具有重要临床实用价值。该方法优于CBF和CBV灌注成像。     

正常兔脑多层螺旋CT灌注及MR灌注成像

目的：探讨多层螺旋CT及MR在正常兔脑血流动力学测量中的应用。材料和方法：健康新西兰种大白兔15只，行CT平扫后，选择基底节层面及相邻层面，经耳缘静脉途径以0．5ml／s速率注入CT造影剂，同时开始连续50s多层动态扫描；CT造影剂排空后，经耳缘静脉途径快速团注MR造影剂，同时开始连续43s多层动态扫描，经后处理获得CT及MR灌注图像。对感兴趣区测量血流量、血容量及平均通过时间等血流动力学参数，并与小脑的相应值相比进行分析。结果：应用CT灌注可以获得较好图像质量，MR灌注可反映出全兔脑组织的血流动力学状态，CT灌注及MR灌注获得的血流动力学参数相对值之间比较无显著性差异（P〉0．05）。结论：多层螺旋CT灌注及MR灌注成像为兔脑血流动力学研究提供了新的无创性手段。     

MR perfusion imaging in a case of cerebral proliferative angiopathy

Proliferative angiopathy is an uncommon type of cerebral arteriovenous shunt characterized by an extensive capillary network with normal brain intermingled and few clinical symptoms (mostly seizures and headaches). This case report depicts an extensive proliferative angiopathy located in the right hemisphere. Its hemodynamic disturbances were studied with MR perfusion imaging (local or remote areas of increased time to peak, decrease ratio of signal, and relative regional cerebral blood volume values). Electronic Publication     

Hyperacute stroke: simultaneous measurement of relative cerebral blood volume, relative cerebral blood flow, and mean tissue transit time

PURPOSE: To investigate additional information provided by maps of relative cerebral blood flow in functional magnetic resonance (MR) imaging of human hyperacute cerebral ischemic stroke. MATERIALS AND METHODS: Diffusion-weighted and hemodynamic MR imaging were performed in 23 patients less than 12 hours after the onset of symptoms. Maps of relative cerebral blood flow and tracer mean tissue transit time were computed, as were maps of apparent diffusion and relative cerebral blood volume. Acute lesion volumes on the maps were compared with follow-up imaging findings. RESULTS: In 15 of 23 subjects (65%), blood flow maps revealed hemodynamic abnormalities not visible on blood volume maps. A mismatch between initial blood flow and diffusion findings predicted growth of infarct more often (12 of 15 subjects with infarcts that grew) than did a mismatch between initial blood volume and diffusion findings (eight of 15). However, lesion volumes on blood volume and diffusion maps correlated better with eventual infarct volumes (r > 0.90) than did those on blood flow and tracer mean transit time maps (r approximately 0.6), likely as a result of threshold effects. In eight patients, blood volume was elevated around the diffusion abnormality, suggesting a compensatory hemodynamic response. CONCLUSION: MR imaging can delineate areas of altered blood flow, blood volume, and water mobility in hyperacute human stroke. Predictive models of tissue outcome may benefit by including computation of both relative cerebral blood flow and blood volume.     

磁共振灌注加权成像在脑梗死诊断中的初步应用研究

目的：探讨脑梗死的磁共振灌注加权成像（ＰＷＩ）表现并评价ＰＷＩ在不同时期脑梗死诊断中的应用价值。材料和方法：应用梯度回波ＥＰＩ（平面回波）序列对１９例脑梗死患者进行了２６例次注射造影剂后的ＰＷＩ。通过工作站重建相对局部脑血容量（ｒＣＢＶ）图。计算脑梗死中心区和边缘区与对侧相应部位的ｒＣＢＶ比值和ＭＴＴ比值,并分析ＰＷＩ表现与ＭＲＡ（１９例次）表现之间的关系。结果：除恢复期以外,脑梗死病社中心多数表现为ｒＣＢＶ减少和ＭＴＴ增加;ＭＲＡ显示有血管闭塞或严重狭窄的脑梗死较ＭＲＡ未见血管异常的脑梗死之病灶中心ｒＣＢＶ减少和ＭＴＴ增加更为显著。结论：ＰＷＩ可以反映脑梗死区的血流动力学改变信息,与常规ＭＲＩ相结合,可同时反映脑梗死的形态和功能变化。     

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.     

Glial neoplasms: dynamic contrast-enhanced T2*-weighted MR imaging.

PURPOSE: To evaluate the role of T2*-weighted echo-planar perfusion imaging by using a first-pass gadopentetate dimeglumine technique to determine the association of magnetic resonance (MR) imaging-derived cerebral blood volume (CBV) maps with histopathologic grading of astrocytomas and to improve the accuracy of targeting of stereotactic biopsy. MATERIALS AND METHODS: MR imaging was performed in 29 patients by using a first-pass gadopentetate dimeglumine T2*-weighted echo-planar perfusion sequence followed by conventional imaging. The perfusion data were processed to obtain a color map of relative regional CBV. This information formed the basis for targeting the stereotactic biopsy. Relative CBV values were computed with a nondiffusible tracer model. The relative CBV of lesions was expressed as a percentage of the relative CBV of normal white matter. The maximum relative CBV of each lesion was correlated with the histopathologic grading of astrocytomas obtained from samples from stereotactic biopsy or volumetric resection. RESULTS: The maximum relative CBV in high-grade astrocytomas (n = 26) varied from 1.73 to 13.7, with a mean of 5.07 +/- 2.79 (+/- SD), and in the low-grade cohort (n = 3) varied from 0.92 to 2.19, with a mean of 1.44 +/- 0.68. This difference in relative CBV was statistically significant (P < .001; Student t test). CONCLUSION: Echo-planar perfusion imaging is useful in the preoperative assessment of tumor grade and in providing diagnostic information not available with conventional MR imaging. The areas of perfusion abnormality are invaluable in the precise targeting of the stereotactic biopsy.     

Brain perfusion imaging in asymptomatic patients receiving cyclosporin.

BACKGROUND AND PURPOSE: Cyclosporin has neurotoxic effects in a significant number of transplant patients that are associated with characteristic findings on MR images. Focal abnormalities in cerebral perfusion have been implicated in the pathophysiology of cyclosporin neurotoxicity. In the clinically asymptomatic patient, however, it is not known whether any imaging evidence of cyclosporin's effect on the brain is demonstrable. Our hypothesis was that conventional MR imaging, perfusion MR imaging, and single-photon emission CT (SPECT) could enable detection of subclinical lesions in asymptomatic patients. The ability to detect such lesions might aid in the identification of persons most at risk for clinical neurotoxicity. METHODS: Ten posttransplant patients being treated with cyclosporin were recruited prospectively. Imaging studies were performed within 3 weeks of transplantation. Patients were examined with MR imaging, using standard spin-echo and dynamic contrast-enhanced perfusion techniques, and SPECT scanning. Postprocessing of MR perfusion data was performed to obtain pixel-by-pixel maps of regional cerebral blood volume, peak height, and time-to-peak parameters. RESULTS: The mean age of the patients was 45 +/- 11 years. At the time of imaging, three patients had minor neurologic manifestations commonly associated with cyclosporin (ie, mild tremor, headache), but no patient had clinical neurotoxicity. Findings on conventional MR images, MR perfusion maps, and SPECT perfusion scans were normal in all patients. CONCLUSION: Conventional MR imaging, dynamic perfusion MR imaging, and SPECT do not depict any lesions in asymptomatic patients on cyclosporin. Therefore, it may not be possible for imaging methods to aid in the identification of patients at risk for neurotoxicity. Our findings support previously published conclusions that the lesions visible in patients with clinical neurotoxicity are due to cyclosporin effects and not to preexisting coincidental abnormalities.     

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