高场磁共振仪评估新生儿和婴儿的正常脑髓鞘

目的：应用高场ＭＲ仪研究正常小儿不同月龄段的脑髓鞘与对应ＭＲＩ信号特征。方法：５８例正常小儿在１．５Ｔ ＭＲ仪内行头部扫描。采用自旋回波（ＳＥ０和快速自旋回波（ＴＳＥ）序列,获取Ｔ１和Ｔ２架驻像,结果：（１）髓鞘形成中的ＭＲＩ信号变化,相对于灰质信号,未的髓鞘呈短Ｔ１和长Ｔ２,在Ｔ１ＷＩ上呈高信号与灰质易区别,在Ｔ２ＷＩ上与灰质信号相近;的髓鞘呈短Ｔ１和短Ｔ２;在Ｔ２ＷＩ上呈低信号,与灰质易区别;     

Two-dimensional MRI at 1.5 and 0.5 T versus CT myelography in the diagnosis of cervical radiculopathy

A prospective comparison was made of standard two-dimensional MRI sequences, at both high and midfield strength, with CT myelography in 23 patients with cervical spondylosis. MRI is adequate for assessment of cord compression, where high field strength is superior to midfield strength. MRI using 4-mm sections is inadequate for presurgical assessment of root compression. It remains to be proven whether thin-section white-CSF volume sequences or gadolinium-enhanced volume studies can replace CT myelography.     

同一个体3.0T与1.5T乳腺MR扩散加权成像的图像质量比较

目的比较3.0 T与1.5 T MR正常乳腺组织扩散加权成像(DWI)的图像质量,从而评价3.0 T乳腺MRDWI的可行性。方法对44名女性乳腺受检者分别在3.0 T MR与1.5 T MR上行DWI。3.0 T DWI应用选择性水激励(Water excitation)技术行脂肪抑制,1.5 T DWI应用频率选择脂肪饱和(Fatsat)技术行脂肪抑制,b值均为0,1000 s/mm2,其他参数相同。比较3.0 T及1.5 T乳腺MR DWI图像的主观质量评分,测量并计算3.0 T及1.5 T乳腺MR DWI乳腺组织信噪比(SNR)及表观扩散系数(ADC)值,进行统计学分析。结果 3.0 T乳腺MR DWI的图像质量平均评分为(3.07±0.79),主观质量评分达到3分(可以诊断)及以上者为34名,占总检查例数的77.27%。1.5 T乳腺MR DWI的图像质量平均评分为(3.23±0.52),主观质量评分达到3分及以上者为42例,占总检查例数的95.45%。两者比较差异无统计学意义(P=0.1615,>0.05)。3.0 T乳腺MR DWI的乳腺组织SNR为(52.28±19.34),1.5 T乳腺MR DWI的乳腺组织SNR为(49.97±17.99)。3.0 T乳腺MR DWI图像乳腺组织平均SNR略高于1.5 T,但二者差异无统计学意义(P=0.5500,>0.05)。3.0 T MR DWI的平均ADC值为(1.80±0.44)×10-3mm2/s,1.5 T MR DWI的平均ADC值为(1.73±0.32)×10-3 mm2/s,两者比较差异无统计学意义(P=0.0652,>0.05)。结论 DWI可用于3.0 T MR乳腺成像,图像质量可以达到1.5 T MR DWI的效果,且ADC值与1.5 T的ADC值无明显差异。     

Diffusion weighted fMRI at 1.5 T

Functional magnetic resonance imaging (fMRI) is capable of detecting task-induced blood oxygenation changes using susceptibility sensitive pulse sequences such as gradient-recalled echo-planar imaging (EPI). The local signal increases seen in the time course are believed to be due to an increase in oxygen delivery that is incommensurate with oxygen demands. To help isolate the sources of functional signal changes, the authors have incorporated various forms of diffusion weighting Into EPI pulse sequences to characterize the apparent mobility of the functionally modulated protons. Results suggest that the majority of the functional signal at 1.5 T arises from protons that have apparent diffusion coefficients that are approximately four or five times higher than that of brain tissue. This implies that significant functional signal sources are either protons within the vascular space or protons from the perivascular space that is occupied by cerebro-spinal fluid.     

MRI at 1.5 T of intramedullary ependymoma and classification of pattern of contrast enhancement

We retrospectively reviewed the MRI findings in 28 patients with an intramedullary spinal cord ependymoma who underwent surgical treatment. There were 26 tumours in the cervical and two in the thoracic spine. T1- and T2-weighted and contrast-enhanced images at 1.5 T were obtained in all cases. T1-weighted imaging showed solid tumour as isointense in 13 patients, high-signal in ten and low signal in five. In contrast, T2-weighted imaging showed all tumours as high signal. Contrast enhancement was heterogeneous 13 patients, homogeneous 10, heterogeneous with cyst wall enhancement in three, and a nodule on a cyst wall was seen in two. Cases with these latter patterns require careful differential diagnosis from astrocytoma or haemangioblastoma. Received: 5 August 1999 Accepted: 24 April 2000     

放射性脑损伤的MRI分析

目的：分析放射性脑损伤的MRI表现及MRI诊断的意义。方法：回顾性分析25例放射性脑损伤患者的MRI资料,观察并比较病变的部位、范围及增强表现。结果：急性放射性脑损伤1例,深部脑白质及胼胝体压部对称性长T2信号,脑白质和胼胝体压部肿胀,增强扫描无强化;早期迟发性放射性脑损伤18例,深部脑白质对称性长T2信号,增强扫描无强化;晚期迟发性放射性脑损伤6例,双侧颞叶不均匀长T1长T2信号,增强扫描呈明显花环样强化。结论：放射性脑损伤具有特征性MRI表现,MRI对诊断放射性脑损伤具有重要价值。     

脑干梗死的MRI和MRA征象

目的：探讨脑干梗死的MRI和MRA征象特点。方法：搜集我院1998年～2002年49例经MRI和MRA检查并经临床治疗证实的脑干梗死病例，其中21例行Gd-DTPA增强扫描，对比临床症状进行分析。结果：中脑梗死11例，桥脑梗死32例，延髓梗死6例。病灶直径以6～15mm为主，病灶形态主要因为不规则斑片状。病灶信号为长T1、长T2信号，行Gd—DTPA增强扫描，大部分呈斑片状或环状强化。MRA检查异常发现主要为椎动脉、基底动脉的狭窄或闭塞，基底动脉纡曲扩张。结论：脑干梗死主要因为椎-基底动脉异常，病灶部位可提示其临床意义。     

高场强原发性肝癌MR表现及分析

目的：分析高场强下原发性肝癌的MRI表现。方法：收集经手术或尸检病理证实的原发性肝癌MR资料43例，其中巨块型肝癌32例，其中伴子灶3例，结节型5例，小肝癌6例。设备为GE1．5T超导signa advantage MR。应用SET1WI，FSEPDWI，T2WI进行轴位扫描，所有病均行增强扫描。结果：肝癌在T1WI呈高、等、低信号，在T2WI呈高信号，部分肿瘤内部信号不均，肝癌的强化程度主要取决于肿瘤血供的多少，肝癌的包膜由纤维组织构成，表现为低信号环，无包膜的肿瘤门静脉侵犯发生率高，肿瘤的信号及包膜与其病理分级有一定的相关性。结论：MRI对反映原发性肝癌的病理特征有其独特的优越性。     

MRI demonstration of haemorrhage in the wall of a brain abscess: possible implications for diagnosis and management

Haemorrhage in the wall of a brain abscess is rare and may falsely suggest a neoplasm on MRI. We describe two cases of haemorrhage in the wall of a brain abscess and discuss the role of in vivo proton MRS in the diagnosis and management. Received: 6 February 2000 Accepted: 31 August 2000     

In vivo magnetic resonance elastography of human brain at 7 T and 1.5 T

Purpose:

To investigate the feasibility of quantitative in vivo ultrahigh field magnetic resonance elastography (MRE) of the human brain in a broad range of low‐frequency mechanical vibrations.

Materials and Methods:

Mechanical vibrations were coupled into the brain of a healthy volunteer using a coil‐driven actuator that either oscillated harmonically at single frequencies between 25 and 62.5 Hz or performed a superimposed motion consisting of multiple harmonics. Using a motion sensitive single‐shot spin‐echo echo planar imaging sequence shear wave displacements in the brain were measured at 1.5 and 7 T in whole‐body MR scanners. Spatially averaged complex shear moduli were calculated applying Helmholtz inversion.

Results:

Viscoelastic properties of brain tissue could be reliably determined in vivo at 1.5 and 7 T using both single‐frequency and multifrequency wave excitation. The deduced dispersion of the complex modulus was consistent within different experimental settings of this study for the measured frequency range and agreed well with literature data.

Conclusion:

MRE of the human brain is feasible at 7 T. Superposition of multiple harmonics yields consistent results as compared to standard single‐frequency based MRE. As such, MRE is a system‐independent modality for measuring the complex shear modulus of in vivo human brain in a wide dynamic range. J. Magn. Reson. Imaging 2010;32:577–583. © 2010 Wiley‐Liss, Inc.     

Enhancement efficacy of magnetic starch microspheres (MSM) in conventional spin-echo and turbo spin-echo sequences at 0.5 T and 1.5 T

The efficacy of the superparamagnetic contrast agent magnetic starch microspheres (MSM) was evaluated in vitro by NMR relaxometry and in vivo by MR imaging using T2-weighted spin-echo (SE) and turbo spin-echo (TSE) sequences at 0.5 T and 1.5 T in 60 normal rats who received MSM in doses of 10–50 μmol/kg. MR imaging was performed using T2-weighted SE and TSE sequences. The relaxation rates 1/T1 and 1/T2 for liver and spleen increased linearly with MSM concentrations up to 30 μmol/kg body weight, and approached almost constant levels for higher doses. The slopes in the linear part of the 1/T2 diagram were 0.62 Hz ± 0.03 for the liver and 0.51 Hz ± 0.06 × kg/μmol for the spleen. On all T2-weighted sequences at 0.5 T and 1.5 T, liver signal-to-noise ratio (SNR) decreased by a factor of 2-3 already at the lowest dose of 10 μmol/kg. SNR values of TSE sequences exceeded values for SE sequences by 50–80%. The SNR decrease was not significantly different between SE and TSE sequences. Our results show that MSM is well suited as a T2 contrast agent at both magnetic field strengths when using conventional SE and fast TSE sequences.     

Age-related structural changes in the young adult brain shown by magnetic resonance diffusion tensor imaging

RATIONALE AND OBJECTIVE: Structure of the brain is generally thought to remain stationary over the course of young adulthood. However, there is some evidence that microstructural changes of the brain do occur during this period. Magnetic resonance diffusion tensor imaging (DTI) provides quantitative measures of structural changes in the brain. We used DTI to detect possible age-related structural changes in the brains of young adults. MATERIALS AND METHODS: Twenty-five healthy adults in their 20s and 30s were studied using DTI. Maps of mean diffusivity and fractional anisotropy (FA) were created for subsequent histogram and region-of-interest analyses, and the results were correlated with the respective ages of the subjects. RESULTS: The histogram analysis revealed a significant increase in the mean FA value (r = 0.407, P < .05) and a significant decrease in FA peak height (r = -0.578, P < .002) with increasing age. No age-related changes were observed in indices derived from mean diffusivity maps. Region-of-interest analysis showed no focal white matter regions with significant FA change. CONCLUSION: Quantitative DTI revealed age-related structural changes in the brains of young adults. Changes on FA histograms observed in this study were considered to be related to changes in the relative volumes of gray and white matter and may represent maturational changes.     

大鼠活体脑1.5T1H-MRS技术

目的探讨大鼠活体脑1.5T1H-MRS方法及技术参数,并评价其图像质量.方法对25只正常雄性SD大鼠进行单体素1H-MRS采用自制的提高信噪比器具,眼线圈,选用PRESS序列,以大脑胼胝体为中心设定感兴趣区,体素用6mm×6mm×6mm与6mm×10mm×6mm两种,比较NAA、Cho、Cr的信噪比及图像质量.5例大鼠在处死60min后作MRS,观测各谱峰的变化.结果MRS谱图上,脑主要代谢产物NAA、Cho、Cr等谱锋清晰,基线较平.体素6mm×6mm×6mm时主要化合物波谱信噪比显著高于体素6mm×10mm×6mm(P＜0.001),图像质量更好.5例大鼠处死后60min MRS,于1.35ppm处见特征性Lac倒置双峰,NAA、Cho、Cr下降不明显.结论1.5T MR可进行大鼠活体MRS检查,有望用于脑弥漫性病变的实验研究.     

Prostate cancer detection with 3-T MRI: comparison of diffusion-weighted and T2-weighted imaging

OBJECTIVE: To compare the clinical value of diffusion-weighted (DW) and T2-weighted (T2W) imaging in detecting prostate cancer using a 3-Tesla (3T) magnetic resonance (MR) system. MATERIALS AND METHODS: Thirty-seven patients with suspected prostate cancer underwent T2W and DW imaging at 3T using an 8-channel phased-array coil. These images and apparent diffusion coefficient (ADC) maps were read retrospectively and blindly. The results were compared with histopathologic findings, and receiver operating characteristic (ROC) analysis was used to compare the cancer detection performance of T2W and DW imaging. RESULTS: The areas under the ROC curves for DW imaging and T2W imaging were 0.89 and 0.82, respectively. The performance of DW imaging in prostate cancer detection was significantly better than that of T2W imaging (P=0.0371). CONCLUSION: With a 3T MR system, the performance of DW imaging in detecting prostate cancer was better than that of T2W imaging. DW imaging appears to be a robust and reliable method to examine the whole prostate within an acceptable scan time in clinical settings.     

MRI of acute cerebral infarction: a comparison of FLAIR and T2-weighted fast spin-echo imaging

Fluid-attenuated inversion-recovery (FLAIR) sequences have been reported to provide high sensitivity to a wide range of central nervous system diseases. To our knowledge, however, FLAIR sequences have not been used to study patients with acute cerebral infarcts. We evaluated the usefulness of FLAIR sequences in this context. FLAIR sequences were acquired on a 0.5 T superconducting unit within 8 h of the onset in 19 patients (aged 26–80 years) with a total of 23 ischaemic lesions. The images were reviewed retrospectively by three neuroradiologists, and the FLAIR images were compared with T2-weighted fast spin-echo images. All but one of the ischaemic lesions involving grey matter was clearly demonstrated on FLAIR images as increased signal intensity in cortical or central grey matter. FLAIR images were particularly useful for detecting the hyperacute cortical infarcts within 3 h of onset, which were not readily detected on the spin-echo images. In 9 of 11 patients with complete proximal occlusion, the distal portion of the cerebral artery was visible as an area of high signal intensity on FLAIR images. Received: 5 June 1996 Accepted: 6 September 1996     

Evaluation of turbo spin echo sequences for MRI of focal liver lesions at 0.5 T

To determine whether turbo spin echo (TSE) sequences can replace conventional T2-weighted spin echo (SE) sequences in MRI of the liver, 40 patients with focal liver lesions were imaged at 0.5 T. A T2-weighted SE sequences (TR/TE 1800/90 ms, number of signals averaged [NEX]=2, scan time=7:16 min), a TSE sequence (TR/TE 1800/90 ms, NEX=4, number of echos per excitation=13, echo spacing=12.9 ms, scan time=4:16 min) and a T1-weighted SE sequence (TR/TE 350/15 ms, NEX=2, scan time=4:21 min) were obtained and image quality, lesion detectability and lesion differentiation were evaluated qualitatively by subjective assessment using scores and quantitatively by lesion-liver contrast-to-noise (CNR) and tumour/liver signal intensity (SI) ratios. The image quality of the TSE sequence was substantially better compared with the T2-weighted SE sequence due to a reduction in motion artefacts and better delineation of anatomical details. Of a total of 158 visible lesions the T1-weighted SE, TSE, and T2-weighted SE sequences showed 91%, 81% and 65% of the lesions, respectively. Thus the TSE sequence depicted 24% (P< 0.001) more lesions than the T2-weighted SE sequence. In all types of pathology the lesion-liver CNR of the TSE sequence was significantly (P< 0.001) higher compared to the CNR of the T2-weighted SE sequence (+ 55–65%), indicating superior lesion conspicuity. Lesion characterization was equally good on the two T2-weighted sequences with no difference in the tumour/liver SI ratio. Using a criterion of tumour/liver SI ratio equal to or higher than 2, haemangiomas larger than 1 cm in diameter could be differentiated from other lesions with a sensitivity and specificity of 95% and 96%, respectively. Our results indicate that the TSE sequence is suitable for replacing the conventional T2-weighted SE sequence in MRI of focal liver lesions.This paper was presented at ECR 1993 Correspondence to: B. Kreft     

1.5T 1H-MRS在正常胰腺中的应用

目的:探讨1.5T氢质子磁共振波谱成像(MRS)在活体正常胰腺中的应用价值及影响因素.方法:采用单体素点分辨波谱(PRESS)序列采集20例健康志愿者的正常胰腺波谱,分析脂质峰高(Lip)、峰下面积、脂质峰下面积(Lip)/组织内水峰下面积(InW)比值与年龄、身高体重指数(BMI)的相关性,分析胆固醇和不饱和脂肪酸的混合峰下面积(Chol+UnSat)/脂质峰下面积(Lip)比值与年龄、BMI的相关性.结果:1.5T活体胰腺MRS扫描成功率为90％(18/20).Lip峰、TMA峰和Chol+ UnSat混合峰显示率分别为100.0％(18/18)、89％(16/18)和100％(18/18).Lip峰高与年龄、BMI呈正相关(r=0.715、0.356),有统计学意义(P=0.01、0.047),峰下面积与年龄、BMI呈正相关(r=0.503、0.135),与年龄有统计学意义(P=0.033),与BMI无统计学意义(P=0.593).Lip/InW比值与年龄、BMI呈正相关(r=0.718、0.563),有统计学意义(P=0.01、0.015).(Chol+ Unsat)/Lip比值与年龄、BMI呈正相关(r=0.762、0.520),有统计学意义(P=0.000、0.027).Chol+ Unsat峰下面积与年龄、BMI呈正相关(r=0.519、0.466),有统计学意义(P=0.004、0.000).结论:1.5T磁共振波谱成像能够用于检测正常活体胰腺的主要代谢物并分析其谱线形态.     

常规MRI用于总成熟度评分量化早产儿脑成熟度及其预后的价值

87)分,差异均有统计学意义(t值分别为2.26、2.50、2.04,P值均<0.05).胚胎生发基质评分分别为(1.00 ±0.01)、(1.14±0.36)分,神经胶质细胞移行带评分分别为(1.11±0.46)、(1.29±0.78)分,差异均无统计学意义(t值分别为1.83、0.88,P值均0.05).结论 常规MRI借助TMS评分能半定量评价早产儿脑成熟度,预测早产儿的WMD.     

磁共振成像和磁共振血管造影对脑动静脉畸形的诊断评价

目的 探讨MRI和MRA,尤其后者对脑动静脉畸形（AVM）诊断价值和限度。材料与方法,对16例AVM者行MRI和MRA检查并与DSA进行对照研究,分别观察供血动脉,血管巢和引流静脉情况。结果 与DSA对照,显示供血动脉,MRA与其无显著差异（P＞0．05）,MRI有其极显著差异（P＜0．001）;血管巢大小,MRI,MRA与其均无显著差异（P＞0．05）,引流静脉,MRI与其有显著差异（P＜0．001）。结论 MRA与MRI联合应用可准确显示供血动脉,血管巢和部分引流静脉,是一种评价AVM血管内治疗,手术切除或立体定向放疗及效果观察的有效无创性检查方法。随着MRA新技术的不断开发,完善,将部分取代有创性DSA检查。     

Diffusion-weighted MRI of myelination in the rat brain following treatment with gonadal hormones

Previous studies have demonstrated the ability of high-resolution diffusion-weighted MRI to show maturation of white-matter structures in the developing rat brain. The purpose of this study was to investigate the influence of gonadal steroid hormones on the rate of this development. Starting from their second postnatal day, 16 rat-pups of either sex were repeatedly treated with subcutaneous implants containing 17-beta estradiol or delta-androstene 3,17 dione, respectively. Serial T1-, T2- and diffusion-weighted MRI was performed weekly for 8 weeks using a 4.7 T unit. Maturation of anterior optic pathways and hemisphere commissures was assessed. Diffusion-weighted images were processed to produce “anisotropy index maps”, previously shown to be sensitive to white-matter maturation. Compared with untreated rat-pups, estrogen-treated animals showed accelerated, and testosterone-treated animals delayed maturation on anisotropy index maps and histological sections. In all animals, maturational changes appeared earlie on anisotropy index maps than on other MRI sequences or on myelin-sensitive stained sections. Diffusion-weighted imaging, and the construction of spatial maps sensitive to diffusion anisotropy, seem to be the most sensitive approach for the detection of maturational white-matter changes, and thus may hold potential for early diagnosis of temporary delay or permanent disturbances of white-matter development. Received: 1 September, 1995 Accepted: 27 February, 1996