快速FLAIR序列在脑梗塞中的应用

目的:探讨FLAIR技术对脑梗塞的诊断价值。材料与方法:应用0.5T超导MR系统对65例脑梗塞患者分别采用FLAIR技术、快速自旋回波T_2加权像(T_2WI)进行对比分析。结果:FLAIR序列比T_2加权像能更敏感、更清楚地显示梗塞灶。提示:FLAIR序列由于反转时间(TI)较长,可抑制脑脊液信号,回波时间长产生重度T_2图像,从而能增加病变对比度,显示T_2加权像未能发现或可疑病灶。结论:FLAIR技术可作为颅脑MR常规检查方法之一。     

MR增强后液体衰减反转恢复序列对柔脑膜病变的诊断价值

目的评价MR液体衰减反转恢复（FLAIR）序列对柔脑膜病变的诊断价值。方法分析17例柔脑膜病变的MR平扫FLAIR、增强FLAIR和增强T1WI表现并比较三者对病变高信号的显示。结果柔脑膜病变在MR平扫FLAIR、增强FLAIR和T1WI上均呈沿脑沟、脑池弥漫或局部分布的异常脑回样或线样高信号。增强FLAIR与增强T1WI对病变显示的比较：7例只在增强FLAIR显示病变；7例二者均明显显示病变；2例二者均显示病变，但前者优于后者；另有1例结核性脑膜脑炎的双侧大脑半球脑沟弥漫性病变只在增强FLAIR显示，脑池病变二者均显示但前者优于后者。增强与平扫FLAIR对病变显示的比较：9例只在增强FLAIR显示病变；4例二者均明显显示病变；3例二者均显示病变但前者优于后者；另有1例结核性脑膜脑炎的脑池病变只在增强FLAIR显示，双侧大脑半球脑沟弥漫性病变二者均显示但前者优于后者。结论增强FLAIR显示柔脑膜病变优于平扫FLAIR和增强T1WI，对于平扫FLAIR和（或）增强T1WI怀疑柔脑膜病变时，增强FLAIR是必要的检查序列。     

FLAIR序列在脑部疾病中的应用研究

目的　对比脑梗塞、脑出血、脑炎患者颅脑MR平扫时FLAIR序列与SE序列T2 WI的差异。方法　采用液体衰减翻转恢复序列 (FLAIR)和SE序列T1 WI、T2 WI序列MR技术 ,对 36例脑梗塞、1 8例脑出血、1 0例脑炎患者行颅脑MR平扫。观察、统计、测量这三类疾病FLAIR序列与常规T2 WI序列的MR信号强度、病灶面积、数目、分布。结果　早期脑梗塞患者FLAIR序列与常规T2 WI信号强度相同 ,病灶面积显示FLAIR序列小于T2 WI序列。晚期脑梗塞患者尤其在脑软化灶形成后FLAIR序列呈现明显低信号 ,而T2 WI为明显高信号。中期和晚期FLAIR序列发现脑梗塞病灶优于T2 WI序列 ,在近脑表面部FLAIR序列有其明显的优势。各期脑出血患者FLAIR序列的信号强度与T2 WI序列相似。FLAIR序列在脑炎患者的病灶面积显示上要小于T2 WI,显示的病灶边界比T2 WI序列清晰。结论　FLAIR序列在显示脑梗塞尤其是靠近脑表面的梗塞灶、鉴别脑软化灶和脱髓鞘改变以及脑炎病灶面积的显示上优于T2 WI。     

脑弥漫性轴索损伤的MRI诊断价值与序列优化

目的比较MR各序列成像诊断脑弥漫性轴索损伤(DAI)的价值,优化MRI显示DAI的最佳序列组合.材料和方法对23例DAI患者行常规快速自旋回波(FSE)T1WI、T2WI 、液体衰减反转恢复序列(FLAIR)和场回波序列(FE)T2*WI、快速场回波-平面回波(FFE-EPI)T2*WI扫描,比较各种序列对DAI的显示率,分析其信号特征.结果82个病灶中47个为非出血性病灶,FLAIR显示47个,常规序列显示42个,FLAIR序列对非出血性DAI病灶显示多于常规序列.35个为出血性病灶,FE显示35个,常规序列显示21个,FE和FFE-EPI序列对出血性DAI的检出率、对比度明显高于常规序列.结论FLAIR FE或FFE-EPI序列组合可以准确诊断不同类型的DAI.     

快速FLAIR技术在脑部疾病诊断中的应用

目的探讨快速液体衰减反转恢复(FAST FLAIR)序列在脑部疾病诊断中的应用价值. 资料与方法对76例脑部疾病患者进行FAST FLAIR序列及常规快速自旋回波(FSE)序列扫描,比较两种序列对病灶的显示情况. 结果在76例脑部疾病中,FLAIR共显示病灶172个,而T2WI只显示123个.FAST FLAIR显示病灶较T2WI清楚明确.在FAST FLAIR上病灶与正常脑组织的对比度更高. 结论 FLAIR技术对颅脑病变的显示优于FSE序列T2WI, 特别是对脑表面或脑室周围病灶的显示, FLAIR有很高的临床使用价值,应成为颅脑常规扫描序列.     

小角度激发快速梯度回波序列在脑内海绵状血管瘤诊断中的价值

目的探讨小角度激发快速梯度回波（fast low angle shot,FLASH）序列成像在脑内海绵状血管瘤诊断中的应用价值。方法搜集并分析14例脑内海绵状血管瘤患者影像资料,MR检查包括进行常规自旋回波T1WI（SE-T1WI）、快速自旋回波T2WI（FSE-T2WI）、液体衰减翻转恢复（FLAIR）序列、FLASH序列及Gd-DTPA增强扫描,将FLASH图像与常规序列图像进行对比。结果 14例海绵状血管瘤中,常规序列显示病灶21个,FLASH显示35个,明显多于常规序列,且显示更清楚。结论 FLASH序列成像对脑内海绵状血管瘤检出有高度敏感性,在脑内海绵状血管瘤的诊断中有重要价值。     

MR各成像序列对脑弥漫性轴索损伤的诊断价值

目的比较MR各序列成像诊断脑弥漫性轴索损伤(DAI)的价值。方法对21例临床诊断DAI的患者行常规自旋回波(SE)T1WI、快速自旋回波(TSE)T2WI、流动衰减反转恢复序列(FLAIR)、扩散加权成像(DWI)和小角度激发快速梯度回波序列(FLASH)扫描,比较各序列脑内病灶的显示率,分析其信号特征。结果FLASH为显示DAI病灶最敏感的序列,能显示常规序列所不能显示的DAI小针尖样大小的出血灶。21例各序列脑内各部位DAI病灶平均检出数依次为:T1WI(0.78±0.58)个、T2WI(1.96±1.30)个、FLAIR(2.98±2.39)个、DWI(3.67±2.75)个、FLASH(6.24±5.46)个。FLASH的DAI病灶检出数最高,与SE T1WI、TSE T2WI的差异有统计学意义(q值分别为3.14、2.47,P值均<0.05)。结论FLASH序列能提高DAI病灶的检出数及早期诊断率,应作为MR诊断DAI的首选序列。     

液体衰减反转恢复序列MR成像在颅脑创伤诊断中价值的研究

目的评价MR液体衰减反转恢复序列(fluid-attenuated inversion recovery,FLAIR)诊断各种颅脑创伤病变的价值.方法22例颅脑创伤病例均进行了CT和MR T1WI、T2WI及FLAIR序列检查,CT与MR检查的时间间隔为4.6±3.7天.观察CT与三种MR序列上各种病变病灶的显示数,将FLAIR所见的结果分别与CT、T1WI及T2WI结果作统计学分析(t检验).结果22例共有100个颅内创伤病灶,CT检出率为25%,T1WI为49%,T2WI为71%,FLAIR检出率为100%,差异显著(P<0.0005).其中FLAIR对非出血性脑挫伤的显示效果最佳,优于其它三种技术(P<0.0005);对于出血性挫伤,FLAIR优于CT(P<0.0025),但与T1WI及T2WI无明显差别;FLAIR对硬膜下/硬膜外血肿的发现能力与其它三种技术相似,对硬膜下积液的显示优于CT(P<0.0025),与T1WI及T2WI则无显著差异;FLAIR对亚急性期的蛛网膜下腔出血(SAH)的显示能力超过CT和T2WI(P<0.05),但CT与FLAIR对急性SAH的显示能力一致.结论FLAIR序列能明显地改善颅脑创伤性病变的显示,优于CT和常规MRI技术,其中以非出血性挫伤和亚急性期的SAH效果最佳.FLAIR序列可作为颅脑创伤检查的常规手段.     

膝关节软骨缺损性病变的MR成像序列研究

目的　评价各种临床常用MR扫描序列诊断关节软骨病变的价值。方法　实验猪膝关节 5只 ,在股骨内外髁关节面软骨上制成缺损模型 ,分别采用各种常用序列扫描 ,测量各种扫描序列上关节软骨的信噪比 (SNR)、软骨相对周围组织的对比噪声比 (CNR) ,采用一致性评价指标 (ICC)评价软骨缺损MRI测量值与实际测量值的一致性。采用实验中优选的MR序列对 2 3例膝关节病变患者进行检查 ,并与关节镜分级诊断结果比较。结果　实验膝关节软骨SNR良好者有质子和T2 WI快速自旋双回波 (FSEPD/T2 WI)、附加脂肪抑制的三维快速扰相梯度回波 (FS 3DFSPGR)和附加脂肪抑制的质子和T2 WI快速自旋双回波 (FSFSEPD/T2 WI)。CNR表现“极佳”者 ,对骨皮质 :FS 3DFSPGR、FSFSEPD/T2 WI;对关节液 :脂肪抑制快速自旋回波 (FSFSE)T2 WI、FS 3DFSPGR ;对半月板和韧带 :FS 3DFSPGR、FSFSEPD/T2 WI、SET1WI、反转时间为 70 0ms的T1WI反转恢复 (IRTI70 0 )序列 ;对脂肪 :FS 3DFSPGR、SET1WI。ICC只有IRTI70 0序列有统计学上的意义 (P <0 .0 5 ) ,且一致性评价为“极佳”。对2 3例膝关节病变患者MR检查结果 :FS 3DFSPGR序列的敏感性为 86 %、特异性为 96 %、表示准确度的Kappa值为 0 .8;IRTI70 0序列的敏感性为 6 8%、特异性为 99%、Kappa值为 0     

059肝脏的单次屏气MR T2WI:单次激发快速自旋回波(SSFSE)和多次激发自旋回波(MSFSE)EPI的价值

在肝脏MR成像中T2WI具有重要作用.常规自旋回波序列(CSE)T2WI对于肝局灶性病变的检出和定性非常有用,但该序列成像时间长,且由于运动伪影较大造成图像质量差.为减少由呼吸运动造成的图像质量下降,在T2WI中应用呼吸触发快速自旋回波(RTFSE)或屏气快速自旋回波(BHFSE).     

颅脑MRI快速液体衰减反转回复技术探讨

目的：探讨快速液体衰减反转回复（ＦＬＡＩＲ）技术原理及其在颅脑的临床应用。材料与方法：对４０例健康志愿者及１２４例颅脑疾患患者前瞻性地进行快速ＦＬＡＩＲ及Ｔ２加权序列ＭＲ检查，并比较了快速ＦＬＡＩＲ上不同ＴＲ、ＴＩ（间隔时间）、ＴＥ组合所得图像质量。结果：ＴＲ／ＴＩ／ＴＥ为８０００／２０００／２００毫秒的组合能较好地抑制脑脊液信号。ＦＬＡＩＲ与快速自旋回波Ｔ２加权序列比较，能增加病灶的对比度，从而     

Comparison of MR sequences in early cerebral infarction at 0.5 T

Purpose: To compare the diagnostic values of fluid-attenuated inversion recovery (FLAIR) and gradient spin-echo (GRASE) with those of conventional spin-echo (SE) and fast SE T2-weighted sequences in the evaluation of acute cerebrovascular lesions at 0.5 T.Material and Methods: Twenty-two consecutive patients with the clinical diagnosis of acute cerebrovascular accident were examined by MR imaging within the first 48 h of ictus. MR examination included 5-mm axial conventional SE and turbo SE (TSE) T2-weighted, dual-echo GRASE and FLAIR sequences. The patients also had pre- and postcontrast T1-weighted axial images. Two examiners evaluated the images and scored the conspicuity of the acute lesions.Results: Regardless of location, FLAIR provided the best lesion conspicuity in the detection of acute infarcts, followed by the GRASE sequence. In the posterior fossa, TSE and SE demonstrated the lesions better than GRASE and FLAIR techniques. In the detection of hemorrhagic elements within the ischemic region, TSE demonstrated statistically significant superiority over other sequences.Conclusion: In the detection of acute ischemic lesions in locations other than the posterior fossa, FLAIR provided the best lesion conspicuity among four T2-weighted sequences, including SE, TSE, GRASE and FLAIR. However, for the posterior fossa examination, preference of SE or TSE T2-weighted sequences is suggested.     

Exclusion of brain lesions: is MR contrast medium required after a negative fluid-attenuated inversion recovery sequence?

We hypothesized that in patients with negative fluid-attenuated inversion recovery (FLAIR) images T(2) weighted fast spin-echo (FSE) images and T(1) weighted spin-echo (SE) images before and after intravenous administration of gadolinium-based contrast medium display no pathology either. Thus, we assessed the negative predictive value of FLAIR images to rule out MR-detectable brain lesions. 1026 consecutive cranial MR examinations were reviewed. Routine MRI of the brain included T(1) weighted coronal imaging before and after administration of gadopentetate dimeglumine, axial T(2) weighted FSE and fast-FLAIR imaging. The FLAIR images were rated by two radiologists into categories of 0 (without pathologic changes) and 1 (with pathologic changes). Two other radiologists analysed the complete examination. In 284 MR examinations of the brain no abnormalities were found (28%). FLAIR-ratings were false-negative in four cases and false-positive in 30 cases. Sensitivity and specificity of the FLAIR sequence for MR-detectable brain lesions were 99.5% and 89.4%. The unselective application of gadolinium avoided one false-negative MR-reading and improved the sensitivity of the MR-examination from 99.5% to 99.6%. Positive and negative predictive values were 96.1% and 98.4%, respectively. The interobserver reliability was kappa=0.93 for the FLAIR-readers and 0.89 for the readers who rated the complete examination. In conclusion, negative FLAIR images provide a high negative predictive value for MR-detectable brain lesions. Thus, in patients with negative FLAIR images the unselective application of gadolinium seems to be unnecessary.     

Fluid-attenuated inversion recovery intraarterial signal: an early sign of hyperacute cerebral ischemia.

BACKGROUND AND PURPOSE: Early detection of arterial occlusion and perfusion abnormality is necessary for effective therapy of hyperacute cerebral ischemia. We attempted to assess the utility of the fast fluid-attenuated inversion recovery (fast-FLAIR) sequence in detecting occluded arteries as high signal (referred to as intraarterial signal) and to establish the role of fast-FLAIR in detecting ischemic penumbra of hyperacute stroke within 24 hours after ictus. METHODS: We studied 60 patients with hyperacute cerebral ischemia caused by occlusion of intracranial major arteries. We compared intraarterial signal on FLAIR images with time of flight (TOF) on MR angiograms, flow voids on T2-weighted images, hyperintense lesions on diffusion-weighted images, and results of follow-up CT or MR scans. RESULTS: In 58 (96.7%) patients, FLAIR detected intraarterial signals as early as 35 minutes after stroke onset. In 48 (80.0%) patients, intraarterial signal on FLAIR images coincided with lack of TOF on MR angiograms. In 41 (74.5%) of 55 patients, the intraarterial signals of fast T2-weighted imaging depicted occlusion better than did deficient flow void on T2-weighted images. In 25 (41.7%) of 60 patients, the area of intraarterial signal distribution was larger than the hyperintense lesion measured on diffusion-weighted images. Areas of final infarction had sizes between those of intraarterial signal distribution on FLAIR images and lesions measured on diffusion-weighted images. In 35 (87.5%) of 40 patients, areas of intraarterial signal distribution were equal to regions of abnormal perfusion. CONCLUSION: Intraarterial signal on FLAIR images is an early sign of occlusion of major arteries. FLAIR combined with diffusion-weighted imaging can be helpful to predict an area at risk for infarction (ischemic penumbra). FLAIR plays an important role for determining whether a patient should undergo perfusion study.     

MRI of arachnoid granulations within the dural sinuses using a FLAIR pulse sequence

The purpose of the study was to assess the signal intensities of arachnoid granulations within the dural sinuses using the FLAIR sequence for differentiation of space-occupying lesions in and adjacent to the dural sinuses. We retrospectively reviewed MR images of the brain of 1118 consecutive subjects, ranging in age from 0 to 93 years (mean 57.2 years). Nodules within the dural sinuses with signal intensities similar to that of cerebrospinal fluid (CSF) on both T1 and T2 weighted images were defined as arachnoid granulations. The location, signal intensity on T1 weighted spin echo (SE), T2 weighted fast SE and FLAIR images, the impression on the inner table of the skull, and the size of the lesion were assessed. 112 subjects (10.0%), age range 4-89 years old (mean 58.9 years), were found to have 134 arachnoid granulations. The commonest location was the transverse sinus, with 115 granulations (85.8%). The prevalence of the granulations showed a peak in the sixth decade of age. All granulations were isointense relative to CSF on T2 weighted images and almost all lesions were isointense relative to CSF on T1 weighted images. On FLAIR images, 90.3% of the granulations were isointense relative to CSF and the other 9.7% granulations were slightly hyperintense compared with the CSF. 21 (15.7%) subjects showed impressions on the inner table; one case involved the outer table. In conclusion, arachnoid granulations were isointense or slightly hyperintense relative to CSF on FLAIR. FLAIR images are helpful in differentiating arachnoid granulations from other dural sinus lesions or skull lesions which have an intensity similar to that of CSF on T1 weighted and T2 weighted images.     

Isotropic 3D fast FLAIR imaging of the brain in multiple sclerosis patients: initial experience

The application of image registration and subtraction to detect change in multiple sclerosis (MS) disease burden on serial MR scans benefits from the use of isotropic voxels. An optimised 3D fast fluid-attenuated inversion recovery (FLAIR) sequence with 1.2- and 1.8-mm cubic voxels was compared with a 2D T2 SE sequence using standard 3-mm slices. Three-dimensional fast FLAIR and T2 SE series were obtained in 20 MS patients and 15 controls. Whole brain acquisition times for the 1.2- and 1.8-mm FLAIR were 21 and 10.5 min, respectively, for the interleaved T2 SE 16 min. Brain lesions were marked in consensus by two radiologists and the CNR was calculated in ten lesions. The mean number of lesions detected with the 1.2-mm FLAIR sequence was 115 +/- 76, compared with 85 +/- 59 for the T2 SE series ( p<0.001). The 1.8-mm FLAIR detected only 73 +/- 46 lesions. The CNR of the 1.2-mm FLAIR was significantly better than the T2 SE ( p<0.01), but not as good as the 1.8-mm FLAIR. In conclusion, isotropic 3D fast FLAIR using 1.2-mm cubic voxels is superior to the 2D T2 SE in the detection of brain lesions in MS patients. The isotropic 1.8-mm FLAIR is faster and has better contrast characteristics but lacks sensitivity.     

A comparison of MR imaging with fast-FLAIR, HASTE-FLAIR, and EPI-FLAIR sequences in the assessment of patients with multiple sclerosis

BACKGROUND AND PURPOSE: Fast fluid-attenuated inversion-recovery (FLAIR) sequences are sensitive for detecting lesions in patients with multiple sclerosis (MS). More rapid fast-FLAIR imaging of the brain can be achieved by the concomitant use of half-Fourier acquisition single-shot turbo spin-echo (HASTE-FLAIR) and echo-planar imaging (EPI-FLAIR). The present study was performed in a large cohort of subjects to assess and compare the number and volume of brain lesions detected by the fast-FLAIR, HASTE-FLAIR, and EPI-FLAIR sequences in patients with MS. METHODS: Fast-FLAIR, HASTE-FLAIR, and EPI-FLAIR sequences were obtained from 46 consecutive MS patients. Lesions seen on each type of sequence were counted and classified by consensus by two observers. Lesion volumes were measured using a semiautomated segmentation technique based on local thresholding. RESULTS: The quality of the fast-FLAIR images was significantly better than that of HASTE-FLAIR and EPI-FLAIR images. Fast-FLAIR revealed significantly more lesions and higher lesion volumes than did HASTE-FLAIR and EPI-FLAIR. A similar number of large lesions was detected by the three sequences, but HASTE-FLAIR and EPI-FLAIR showed significantly fewer small and intermediate lesions than did fast-FLAIR. The number of lesions seen on HASTE-FLAIR and EPI-FLAIR images was similar. CONCLUSION: HASTE-FLAIR and EPI-FLAIR sequences revealed as many large MS lesions as fast-FLAIR. Because their acquisition times are only a fraction of that needed for fast-FLAIR sequences, they may be useful for making a rapid diagnosis of MS in uncooperative patients. Their reduced ability to detect smaller lesions indicates that they should not be used as a routine approach to imaging patients with MS.     

低场磁共振FLAIR序列对脑脊液内钆剂浓度检出的实验研究

 目的 探讨低场磁共振液体衰减反转恢复序列T2WI对人工脑脊液(cerebral spinal fluid,CSF)内钆浓度的识别水平,为临床应用提供依据.方法 采用浓度0～8 mmol/L的Gd-DTPA人工CSF溶液模拟CSF内不同的强化水平,新鲜熟蛋清模拟正常脑实质.使用0.35T机型,对样本分别行SE序列T1WI和快速FLAIR序列T2WI扫描,测算出各被检样本与参照样本间的对比噪声比(contrast-to-noise ratios,CNR),比较两种成像序列所能检出的最低钆剂浓度.结果 FLAIR序列T2WI所能识别的最低钆剂浓度为0.0078 mmol/L,比SE序列T1WI约低10倍;当样本内钆剂浓度超过0. 8 mmol/L时,FLAIR序列T2WI的检出能力不及SE序列T1WI.结论 低场磁共振FLAIR序列T2WI对人工CSF内低浓度钆剂的检出能力明显优于其SE序列T1WI.     

低场MR FLAIR序列在脑白质疏松症诊断中的应用价值

目的：探讨低场MRI液体衰减反转恢复（fluid liquid attenuated inversion recovery,简称FLAIR） 序列在脑白质疏松症（LA）影像诊断中的应用价值。方法：采用0．3T低场MRI扫描仪对70例LA进行自旋回波（SE）序列和FLAIR序列成像，分析LA在SE及FLAIR序列中的影像表现，比较两种成像序列对LA病变的显示效果。结果：LA MRI表现为侧脑室周围和／或深部脑白质形态不规则、边缘模糊的斑点及点片状异常信号影，SE序列呈等T1或长T1、长T2信号改变，FLAIR呈略高或高信号改变；FLAIR序列成像与SE序列T2WI对LA病灶显示的满意程度及对病变的分级诊断均无明显差异。结论：在低场条件下采用FLAIR序列诊断LA，其成像效果并不比常规SE序列优越。