Diffusion-weighted magnetic resonance imaging detects early neuropathology following four vessel occlusion ischemia in the rat

Early neuropathology following a prolonged duration of four-vessel occlusion (4 VO) ischemia in the rat was charted using magnetic resonance imaging (MRI). Animals received either 30 minutes of 4 VO (N = 6) or sham operation (N = 6) prior to in vivo assessment. Proton density and T(2) and combined T(2)/diffusion-weighted (T(2)/DW) MRI were performed at 6, 24, and 72 hours postocclusion. T(2)/DW imaging was the most effective sequence for delineating between injured and intact tissues, indicating neuropathology in the dorsolateral striatum at 24 hours and in the CA1/CA2 subfields of the hippocampus at 72 hours following ischemia. Apparent diffusion coefficient values were significantly reduced in the striatum (P = 0.03) and hippocampus (P = 0.005) at 24 and 72 hours, respectively. This is the first report, to our knowledge, of T(2)/DW imaging detecting lesions following 4 VO in accord with the known temporal evolution of ischemic brain damage.     

Visualization of brain infarction with nuclear magnetic resonance imaging

Summary Nine patients with cerebral or cerebellar hemispheric infarction and two patients with brain stem lesions were studied with NMR imaging in order to examine the lesion with different weightings on the various NMR parameters. The time interval between examination and the acute onset of the stroke varied from one day to six months. The lesions were clearly detected by the T₁ weighted inversion recovery sequence but the tissue contrast was better using the spin echo sequence with a long repetition rate and a long echo delay (SE_2000/100). In two patients the brain stem lesions were invisible with CT, but were easily depicted with NMR. In one of them the further progress of the lesion was also confirmed and visualized with the follow-up NMR study.     

Automatic quality assessment in structural brain magnetic resonance imaging

MRI has evolved into an important diagnostic technique in medical imaging. However, reliability of the derived diagnosis can be degraded by artifacts, which challenge both radiologists and automatic computer‐aided diagnosis. This work proposes a fully‐automatic method for measuring image quality of three‐dimensional (3D) structural MRI. Quality measures are derived by analyzing the air background of magnitude images and are capable of detecting image degradation from several sources, including bulk motion, residual magnetization from incomplete spoiling, blurring, and ghosting. The method has been validated on 749 3D T₁‐weighted 1.5T and 3T head scans acquired at 36 Alzheimer's Disease Neuroimaging Initiative (ADNI) study sites operating with various software and hardware combinations. Results are compared against qualitative grades assigned by the ADNI quality control center (taken as the reference standard). The derived quality indices are independent of the MRI system used and agree with the reference standard quality ratings with high sensitivity and specificity (>85%). The proposed procedures for quality assessment could be of great value for both research and routine clinical imaging. It could greatly improve workflow through its ability to rule out the need for a repeat scan while the patient is still in the magnet bore. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Metabolic characterization of distinct neuroanatomical regions in rats by magic angle spinning 1H nuclear magnetic resonance spectroscopy.

High-resolution magic angle spinning (HRMAS) (1)H NMR spectroscopy has been applied to the biochemical characterization of specific brain regions in rats in order to establish baseline levels of tissue metabolite profiles with which to compare models of neuropathology or toxic lesion. Cores of tissue (20 mg) from the brain stem, cerebellum, frontal cortex, and hippocampus were obtained from histologically defined coronal slices of brain from 18 male Sprague-Dawley rats. HRMAS (1)H NMR spectra were acquired for each of the regions sampled and the degree of intersample variability, as assessed by principal components analysis and discriminant analysis by projection to latent structure was found to be low. Clear region-specific differences in the biochemical profiles were observed using both comparison of metabolite ratios and/or pattern recognition methods. Relatively low concentrations of GABA in the cerebellum, high concentrations of taurine and N-acetylaspartate in the cortex, and high levels of choline, glycerophosphocholine, and phosphocholine in the hippocampus predominantly influenced the classification of the different brain regions. Additionally, N-acetylaspartylglutamate was detected in the brain stem, but was largely absent from the other regions examined. Such analyses provide a baseline reference for further HRMAS NMR spectroscopic studies to monitor disease and pharmacological insults in specific regions of the brain.     

In vivo structural imaging of the rat brain with a 3-T clinical human scanner

PURPOSE: To examine the feasibility of using product acquisition software on a 3-T human MRI system to acquire high-resolution structural brain images in the rat. MATERIALS AND METHODS: Three sets of dual spin-echo, high-resolution (0.234 x 0.234 mm in-plane, 0.5 mm thick) images covering the entire rat brain were collected and averaged in 66 min. The images had sufficient signal-to-noise ratio (SNR) and resolution for visual identification and manual outlining of exemplary structures, including the lateral ventricles and dorsal and ventral portions of the hippocampus. Further, the data were adequate for unsupervised, automated segmentation, permitting quantification of the dorsolateral ventricles. The images compared favorably with those collected on a 7-T system. RESULTS: Interrater reliabilities (intraclass correlations) of manual ventricular scoring were greater than 0.97, and manual vs. automated correlations were 0.97. The variability of lateral ventricular size across animals was substantially higher than that of the hippocampus. CONCLUSION: The large variability of some brain structures that can exist across even a highly selected strain of rats can readily be detected with the use of human 3-T systems for the study of small animals.     

Visualization of cortical spreading depression using manganese-enhanced magnetic resonance imaging.

Cortical spreading depression (CSD) was visualized using manganese-enhanced MRI (MEMRI) following topical application of KCl to the exposed rat cortex. MEMRI signal increase in the ipsilateral cortex relative to the contralateral control region was 60 +/- 30% following two KCl applications. MEMRI signal increase for a single (40%) versus double (80%) KCl application suggests an integration effect over successive CSD episodes. CSD-induced MEMRI enhancement involved cortical layers containing dense regions of apical dendrites, supporting the contention that these neuronal structures are necessary for propagation of CSDs. Subcortical enhancement was present in hippocampal and thalamic regions, most likely a result of neuronal connections with cortical layers 4 and 5. These results are consistent with previous studies of CSD using diffusion-weighted MRI and T(2) (*)-weighted MRI and should be useful for investigating CSD itself and its role in other neurologic disorders.     

大鼠C6胶质瘤模型的磁共振成像及1H波谱研究

目的 :评价磁共振成像及其波谱技术在大鼠胶质瘤模型研究中的应用价值。方法 :大鼠C6脑胶质瘤细胞体外培养 ,应用立体定向架将肿瘤细胞注入大鼠脑尾状核区域 ,接种后 12～ 18d分别行磁共振成像及其波谱检查 ,观察大鼠脑C6胶质瘤的磁共振成像及其波谱表现 ,并与病理学变化进行对照分析。结果 :2 4只接种大鼠脑内有 16只胶质瘤生长良好 ,磁共振成像表现为长T1、长T2 信号 ,增强后肿瘤强化明显 ,呈均匀强化或环状强化 ;磁共振波谱表现为NAA峰明显下降甚至消失 ,Cho升高为第一高峰 ,NAA/Cr比值明显下降、Cho/Cr比值明显上升 ,部分肿瘤出现乳酸峰 (Lac)或脂质峰(Lip)。病理学显示肿瘤呈浸润性生长 ,边界不清。随着肿瘤增大 ,肿瘤内部坏死明显 ,乳酸峰 (Lac)或脂质峰 (Lip)出现率增加。结论 :大鼠脑C6胶质瘤模型是一种生长稳定、较为理想的脑胶质瘤模型 ;磁共振成像 (MRI)可以准确提供胶质瘤模型的病理形态学信息 ,磁共振波谱 (MRS)则可以提供胶质瘤的代谢及生化信息。     

Fast method for brain image segmentation: application to proton magnetic resonance spectroscopic imaging.

The interpretation of brain metabolite concentrations measured by quantitative proton magnetic resonance spectroscopic imaging (MRSI) is assisted by knowledge of the percentage of gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF) within each MRSI voxel. Usually, this information is determined from T(1)-weighted magnetic resonance images (MRI) that have a much higher spatial resolution than the MRSI data. While this approach works well, it is time-consuming. In this article, a rapid data acquisition and analysis procedure for image segmentation is described, which is based on collection of several, thick slice, fast spin echo images (FSE) of different contrast. Tissue segmentation is performed with linear "Eigenimage" filtering and normalization. The method was compared to standard segmentation techniques using high-resolution 3D T(1)-weighted MRI in five subjects. Excellent correlation between the two techniques was obtained, with voxel-wise regression analysis giving GM: R2 = 0.893 +/- 0.098, WM: R2 = 0.892 +/- 0.089, ln(CSF): R2 = 0.831 +/- 0.082). Test-retest analysis in one individual yielded an excellent agreement of measurements with R2 higher than 0.926 in all three tissue classes. Application of FSE/EI segmentation to a sample proton MRSI dataset yielded results similar to prior publications. It is concluded that FSE imaging in conjunction with Eigenimage analysis is a rapid and reliable way of segmenting brain tissue for application to proton MRSI.     

Time-course imaging of rat embryos in utero with magnetic resonance microscopy

Magnetic resonance (MR) microscopy was used to noninvasively investigate the development of live rat embryos in utero. The difficulty in making sequential observations of a developing mammalian embryo has frustrated developmental biologists for many years. Most current technologies analyze normal and abnormal development by observing end point phenotypes (in fixed specimens) rather than investigating the live embryo. MR microscopy was adapted to allow rat litters to be scanned three times each (at 1- to 3-day intervals) and has produced images of live developing embryos. It was demonstrated that repeated anesthesia and imaging protocols produced no gross malformations in the rat pups that were subsequently delivered and observed. Three-dimensional projection encoding with phase re-winders produced isotropic (256³) image data sets in about 30 minutes with excellent tissue contrast arising from steady-state effects in the amniotic fluid.     

Automatic volumetric measurement of segmented brain structures on magnetic resonance imaging

Purpose The purpose of this study was to produce a fully automatic volumetric segmented brain image system (AVSIS) and to evaluate its utility for measuring hippocampal volumes and total intracranial volume (TIV). Materials and methods We developed a combination technique comprising an anatomical standardization technique to measure TIV, whole brain volume (WBV), and hippocampal volume obtained by magnetic resonance (MR) imaging. Altogether, 15 healthy volunteers and 15 patients with Alzheimer's disease (AD) underwent three-dimensional spoiled gradient echo (3D-SPGR) imaging. Three measurements were performed by manual volumetry as the gold standard, a previous semiautomatic method, and our new method, AVSIS. Results WBV and hippocampal volume in the AD group were significantly smaller than those in the healthy volunteer group measured by the semiautomatic method, manual method, and AVSIS. Each volume measured by AVSIS or semiautomatic method correlated with that measured by the manual method. The correlation coefficients between TIVs, WBVs, or hippocampal volumes measured by AVSIS and the manual method were 0.910, 0.902, and 0.918, respectively; the correlation coefficients between TIVs, or WBVs, measured by the previous semiautomatic method and the manual method were 0.875, and 0.886, respectively. Conclusion We developed a system for a fully automatic measurement of segmented brain structures and obtained good results. This article was presented at the 33rd annual meeting of the Japanese Society for Magnetic Resonance in Medicine, Tokyo, Japan in 2005.     

Role of magnetic resonance imaging in distinguishing fungal from nonfungal multiple brain abscesses

Cladophialophora bantiana is a neurotropic dematiaceous fungus known for affecting immunocompromised and immunocompetent hosts. We report a case of 24 year old immunocompetent male presenting with headache, fever and vomiting. MRI was suggestive of multiple fungal brain abscesses. He underwent total excision of abscesses. Pus culture was suggestive of brain abscess caused by C. bantiana. We report a culture proven case of C. bantiana emphasizing on specific MRI features which are critical in differentiating fungal from nonfungal brain abscesses.     

进食障碍脑结构MRI研究进展

进食障碍（ED）谱系疾病是一组严重的精神类疾病,常见类型为神经性厌食症（AN）、神经性贪食症（BN）、暴食障碍（BED）。ED与脑结构重塑有关,结构MRI包括基于体素的形态学分析（VBM）、基于表面的形态学分析（SBM）和扩散张量成像（DTI）,可用于观察脑灰质形态学和白质微观改变。综述多种结构MRI技术在AN、BN、BED中的研究进展,以期揭示ED的神经病理学机制,为治疗提供新思路。     

Proton magnetic resonance spectroscopic imaging to differentiate between nonneoplastic lesions and brain tumors in children

PURPOSE: To investigate whether in vivo proton magnetic resonance spectroscopic imaging (MRSI) can differentiate between 1) tumors and nonneoplastic brain lesions, and 2) high- and low-grade tumors in children. MATERIALS AND METHODS: Thirty-two children (20 males and 12 females, mean age = 10 +/- 5 years) with primary brain lesions were evaluated retrospectively. Nineteen patients had a neuropathologically confirmed brain tumor, and 13 patients had a benign lesion. Multislice proton MRSI was performed at TE = 280 msec. Ratios of N-acetyl aspartate/choline (NAA/Cho), NAA/creatine (Cr), and Cho/Cr were evaluated in the lesion and the contralateral hemisphere. Normalized lesion peak areas (Cho(norm), Cr(norm), and NAA(norm)) expressed relative to the contralateral hemisphere were also calculated. Discriminant function analysis was used for statistical evaluation. RESULTS: Considering all possible combinations of metabolite ratios, the best discriminant function to differentiate between nonneoplastic lesions and brain tumors was found to include only the ratio of Cho/Cr (Wilks' lambda, P = 0.012; 78.1% of original grouped cases correctly classified). The best discriminant function to differentiate between high- and low-grade tumors included the ratios of NAA/Cr and Cho(norm) (Wilks' lambda, P = 0.001; 89.5% of original grouped cases correctly classified). Cr levels in low-grade tumors were slightly lower than or comparable to control regions and ranged from 53% to 165% of the control values in high-grade tumors. CONCLUSION: Proton MRSI may have a promising role in differentiating pediatric brain lesions, and an important diagnostic value, particularly for inoperable or inaccessible lesions.     

不同肾ROI勾画法对肾积水患者GFR测定影响的研究

目的：探讨不同肾ROI勾画法对肾积水患者肾小球滤过率（GFR）测定的影响。方法：对31例（39只积水肾）血清肌酐（SCr）升高的不同程度肾积水患者行肾动态显像,用Gates法分别按全肾ROI及肾皮质ROI计算GFR,并与同期检测的SCr进行相关性分析。结果：轻、重度肾积水患者,由两种ROI计算的GFR值均与SCr呈显著负相关,但全肾ROI的相关系数低于肾皮质ROI的相关系数;中度肾积水患者,全肾ROI测定的GFR与SCr无相关性,而肾皮质ROI测定的GFR则与SCr呈显著负相关。结论：肾皮质ROI勾画法更灵敏而准确的反映肾积水患者肾功能的变化。     

Automatic registration of brain magnetic resonance images based on Talairach reference system

PURPOSE: To demonstrate a robust registration method of brain magnetic resonance (MR) images based on the Talairach reference system with automatic determinations of the fiducial points. MATERIALS AND METHODS: Eight specified landmark points of the Talairach reference system are determined after successfully extracting the midsagittal plane from three-dimensional MR imaging (MRI) data. Projection information of the image intensity is used to determine the midline of the cerebrum in axial and coronal view images, which is a necessary step for extraction of the midsagittal plane. To find the landmarks of anterior commissure (AC) and posterior commissure (PC) in the midsagittal plane, we adopt two-step shape matching that properly finds locations of the corpus callosum (CC), and then AC and PC, respectively. The shape matching is performed on the edge-enhanced midsagittal plane image to minimize dependency on image intensity variation. Other landmark points of the Talairach reference system are determined by fitting the intensity curve of the cutview with the Gaussian model. RESULTS: The proposed method automatically determines seven landmark points, except the inferior point (IP), and the brain MR images can be successfully registered with the Talairach reference system. CONCLUSION: The suggested registration method can be applied to any MR images for functional studies. It can also be applied to patients unless their brains are highly deformed or have a highly deformed CC.     

A reproducible repositioning method for serial magnetic resonance imaging studies of the brain in treatment trials for multiple sclerosis

Serial MRI is an important measure of disease progression in evaluating the treatment of multiple sclerosis (MS). Accurate comparisons of scans for lesion activity and lesion volume require precise repositioning of patients. A simple, reproducible repositioning method is described. In a multicenter treatment trial of MS using β-interferon-1b, this method has been successful, with only 1.1% of scans being rejected because of poor repositioning.     

Dissociation of brain edema induced by cold injury in rat model: MR imaging and perfusion studies with 14C-iodo-antipyrine

The purpose of this study is to confirm whether T2-weighted imaging and perfusion imaging, i.e. autoradiogram of 14C-iodoantipyrine, on the course of brain edema correspond to each other or not. Cold injured rat brains were used as a model and were sequentially examined by both methods and compared with each other and with histological specimens. Special focus relies on the time changes in the lesions. High SI of T2-weighted images were observed and the percentages in the high SI area to the total brain area in the same slice were 4.7 +/- 0.31, 5.6 +/- 0.46 and 3.4 +/- 0.42 for 6, 24 and 48 hours, respectively. By contrast, low perfusion areas were indicated in the perfusion study and their percentages were 4.6 +/- 0.55, 5.6 +/- 0.86 and 2.4 +/- 0.35 for 6, 24 and 48 hours, respectively. At 48 hours after cold injury, low perfusion areas were smaller than hi