Investigation of feline brain anatomy for the detection of cortical spreading depression with magnetic resonance imaging

Cortical spreading depression (CSD) and peri‐infarct depolarisation (PID) are related phenomena that have been associated with the human clinical syndromes of migraine (CSD), head injury and stroke (PID). Nevertheless the existence of CSD in man remains controversial, despite the detection of this phenomenon in the brains of most, if not all, other animal species investigated. This failure to unambiguously detect CSD clinically may be at least partly due to the anatomically complex, gyrencephalic structure of the human brain. This study was designed to establish conditions for the study of CSD in the brain of a gyrencephalic species using the noninvasive technique of magnetic resonance imaging (MRI). The 3‐dimensional (3D) gyrencephalic anatomy of the cat brain was examined to determine the imaging conditions necessary to detect CSD events. Orthogonal transverse, sagittal and horizontal T₁‐weighted image slices showed that the marginal and suprasylvian gyri were the most appropriate cortical structures to study CSD. This was in view of (1) their simple geometry: (2) their lengthy extent of grey matter orientated rostrocaudally in the cortex: (3) their separation by a sulcus across which CSD spread could be studied and (4) the discontinuity in the grey matter in these regions between the right and left hemispheres dorsal to the corpus callosum. The structure suggested by the T₁‐weighted images was corroborated by systematic diffusion tensor imaging to map the fractional anisotropy and diffusion trace. Thus a single horizontal image plane could visualise the neighbouring suprasylvian and marginal gyri of both cerebral hemispheres, whereas its complex shape and position ruled out the ectosylvian gyrus for CSD studies. With the horizontal imaging plane, CSD events were reproducibly detected by animating successive diffusion‐weighted MR images following local KCl stimulation of the cortical surface. In single image frames, CSD detection and characterisation required image subtraction or statistical mapping methods that, nevertheless, yielded concordant results. In repeat experiments, CSD events were qualitatively similar in appearance whether elicited by sustained or transient KCl applications. Our experimental approach thus successfully describes cat brain anatomy in vivo, and elucidates the necessary conditions for the application of MRI methods to detect CSD propagation.     

Enhancing magnetic resonance imaging tumor detection with fluorescence intensity and lifetime imaging

Early detection is important for many solid cancers but the images provided by ultrasound, magnetic resonance imaging (MRI), and computed tomography applied alone or together, are often not sufficient for decisive early screening ∕ diagnosis. We demonstrate that MRI augmented with fluorescence intensity (FI) substantially improves detection. Early stage murine pancreatic tumors that could not be identified by blinded, skilled observers using MRI alone, were easily identified with MRI along with FI images acquired with photomultiplier tube detection and offset laser scanning. Moreover, we show that fluorescence lifetime (FLT) imaging enables positive identification of the labeling fluorophore and discriminates it from surrounding tissue autofluorescence. Our data suggest combined-modality imaging with MRI, FI, and FLT can be used to screen and diagnose early tumors.     

A review on brain structures segmentation in magnetic resonance imaging

Background and objectivesAutomatic brain structures segmentation in magnetic resonance images has been widely investigated in recent years with the goal of helping diagnosis and patient follow-up in different brain diseases. Here, we present a review of the state-of-the-art of automatic methods available in the literature ranging from structure specific segmentation methods to whole brain parcellation approaches.MethodsWe divide first the algorithms according to their target structures and then we propose a general classification based on their segmentation strategy, which includes atlas-based, learning-based, deformable, region-based and hybrid methods. We further discuss each category's strengths and weaknesses and analyze its performance in segmenting different brain structures providing a qualitative and quantitative comparison.ResultsWe compare the results of the analyzed works for the following brain structures: hippocampus, thalamus, caudate nucleus, putamen, pallidum, amygdala, accumbens, lateral ventricles, and brainstem. The structures on which more works have focused on are the hippocampus and the caudate nucleus. In general, the accumbens (0.69 mean DSC) is the most difficult structure to segment whereas the structures that seem to get the best results are the brainstem, closely followed by the thalamus and the putamen with 0.88, 0.87 and 0.86 mean DSC, respectively. Atlas-based approaches achieve good results when segmenting the hippocampus (DSC between 0.75 and 0.90), thalamus (0.88–0.92) and lateral ventricles (0.83–0.93), while deformable methods perform good for caudate nucleus (0.84–0.91) and putamen segmentation (0.86–0.89).ConclusionsThere is not yet a single automatic segmentation approach that can emerge as a standard for the clinical practice, providing accurate brain structures segmentation. Future trends need to focus on combining multi-atlas methods with learning-based or deformable approaches. Employing atlases to provide spatial robustness and modeling the structures appearance with supervised classifiers or Active Appearance Models could lead to improved segmentation results.     

Manganese-enhanced magnetic resonance imaging (MEMRI) of brain activity and applications to early detection of brain ischemia

Divalent manganese ion (Mn2+) has been reported to be a useful contrast agent for functional MRI, through a technique named activity-induced manganese-dependent MRI (AIM). In AIM, signal enhancement is related to functional increases in calcium influx, and therefore AIM is, thus far, the only MRI method able to map brain activation in vivo independently of the surrogate hemodynamic changes used in functional MRI. Because of its high signal-to-noise ratio (SNR) and high sensitivity, AIM allows the use of multi-slice or three-dimensional MRI techniques to map functional activity at high spatial resolution. In the present review, we define AIM as a functional MRI tool based on the administration of divalent ionized manganese through an open or disrupted blood-brain barrier (BBB). The adequacy and efficacy of AIM in detecting neural activation is described in light of supporting experiments on inhibition of calcium channels, FOS expression, and on direct comparison to BOLD- and perfusion-based functional MRI. Two main applications of AIM, mapping brain activation in rat somatosensory cortex, as well stroke research based on the well-established middle cerebral artery occlusion model, are described in detail. Methodological problems associated with a strong dependence on anesthetic conditions, potential corruption due to disruption of the BBB, and unspecific increase of the baseline signal due to acoustical noise are discussed. Finally, recommended preparation methods and experimental protocols for AIM are introduced.     

Use of postmortem brain magnetic resonance imaging at autopsy

The study was undertaken to define the possibilities of using postmortem MRI for examining the brain. A complex study was made to explore 21 neutral formalin-fixed gross brain specimens from patients with neurosurgical pathology. Macroscopic and target histological studies of the changed signal areas detected by MRI were performed using histochemical stains. The significance of the results obtained by MRI in vitro has been defined, which furnish considerable opportunities to use the technique for the postmortem diagnosis of various diseases, to detect macroscopically undetectable changes (perifocal changes, metastases), to make a complex of intractable diagnostic problems, and to study the histological substrate of changed MR signal areas.     

咀嚼时局部脑活动的功能性核磁共振成像

目的：应用功能性核磁共振成像（fMRI）探测人吸嚼时的大脑功能活动。方法：要求人在无任何其它躯体活动条件下咀嚼肌以10s运动20s休息的频率进行。选用8例成人冠状切面和横轴面的头部磁共振片,观察脑功能活动情况。结果：①在咀嚼时脑的广泛区域是激活的;②在相对应的咀嚼活动中有优势半球的激活区;③第I躯体感觉区激活的方式远较第I躯体运动区多样化;④在额叶中4例年轻观察对象出现了广泛的神经元激活区,但在老年人很少出现这样的激活区。结论：咀嚼活动除了它本身的功能运动外,在维持脑的活动方面具有重要的作用。同时也说明fMRI在研究活体人脑功能活动方面是一个相当有效的方法。     

Nerves on magnetic resonance imaging

Nerves are often visualized on magnetic resonance imaging (MRI) studies of the soft tissues on the chest and shoulder girdle. To learn the reasons for the contrast between the nerves and adjacent tissues, the authors obtained a fresh specimen containing part of the brachial plexus nerves from the left axilla and compared MRI with x-ray projections and photomicrographs of histologic sections. The results suggest that the high signals from the nerves stand out in contrast to the low signals from their rich vascular supply.     

Trifluoromethoxy-benzylated ligands improve amyloid detection in the brain using (19)F magnetic resonance imaging

The chemical properties of probes that improve amyloid detection by non-invasive (19)F magnetic resonance imaging (MRI) are of interest. We synthesized benzoxazole compounds with trifluoromethoxy groups, and found that these compounds displayed sharp (19)F nuclear magnetic resonance (NMR) signals in an assay buffer. However, the intensities of the (19)F NMR signals were dramatically reduced in mouse brain lysates. Our results indicate that the inhibitory effect of brain tissue on the (19)F NMR signals from these probes can be attributed to the hydrophobicity of the tissue. These results highlight the importance of using hydrophilic (19)F-MRI agents to avoid the inhibitory effects of brain tissues on (19)F NMR signals.     

以磁共振成像诊断早产儿脑损伤相关危险因素的回顾性分析

目的探讨以MRI诊断的早产儿脑损伤的相关危险因素。方法回顾性分析中国医科大学盛京医院2年中早产儿脑损伤相关危险因素,以MRI（T1WI-T2WI）和弥散加权成像诊断早产儿脑损伤,详细统计临床资料,进行单因素分析,对单因素分析有统计学意义的因素行早产儿脑损伤主要危险因素的Logistic回归分析。结果358例早产儿中,无脑损伤177例,有脑损伤181例,其中缺血性脑损伤占70.7%（128/181）;单纯出血性脑损伤占53.0%（96/181）;缺血伴出血性脑损伤占23.7%（43/181）。对21种危险因素进行分析。单因素分析：急产、双胎妊娠、母孕期感染、循环障碍、产道分娩、代谢性酸中毒、低钠血症、低钙血症与早产儿出血性脑损伤有统计学意义;母孕期感染、母孕期糖尿病、产前使用硫酸镁、复苏抢救史、循环障碍、产道分娩、代谢性酸中毒、低钠血症、低钙血症与早产儿缺血性脑损伤有统计学意义。Logistic分析示：母孕期感染（OR=4.738,95%CI：1.201～18.685,P〈0.05）、产道分娩（OR=9.191,95%CI：4.699～17.979,P〈0.05）、低钠血症（OR=3.244,95%CI：1.173～8.969,P〈0.05）和低钙血症（OR=3.162,95%CI：1.325～7.545,P〈0.05）是早产儿出血性脑损伤的危险因素;母孕期糖尿病（OR=5.211,95%CI：1.272～21.341,P〈0.05）、产道分娩（OR=3.078,95%CI：1.824～5.194,P〈0.05）、低钠血症（OR=3.331,95%CI：1.506～7.366,P〈0.05）和低钙血症（OR=4.713,95%CI：2.412～9.209,P〈0.05）是早产儿缺血性脑损伤的危险因素,产前使用硫酸镁（OR=0.375,95%CI：0.183～0.766,P〈0.05）是其保护因素。结论母孕期感染、母孕期糖尿病等宫内暴露因素,分娩过程及出生后内环境紊乱均为早产儿脑损伤的危险因素,因此早产儿脑损伤是多种因素相互作用的复杂结果。在围生期的诊断治疗工作中应当尽量避免这些因素,减少神经系统并发症及降低其严重程度。     

Ultrahigh field brain magnetic resonance imaging using semiadiabatic radiofrequency pulses

Great attention is being paid to solving, or mitigating, the technical problems associated with MRI at ultrahigh field strengths of 7 T and higher. This paper explores the use of the semiadiabatic spin-echo (SA-SE) pulse sequence, which uses semiadiabatic radiofrequency (RF) pulses to remove and/or mitigate the effects of the nonuniform B₁ excitation field and B₀ inhomogeneity associated with the electromagnetic properties of the human brain. A semiadiabatic RF pulse version of the recently published serial transmit excitation pulse (STEP) RF pulse sequence is also presented that now incorporates semiadiabatic pulses, henceforth is called SA-STEP. As demonstrated by computer simulation, and confirmed using head imaging, both techniques can produce multislice SE MR imaging at 7 T. These new methods use relatively low RF power and achieve good coverage of the human brain in a single scan.     

磁共振评价躯体病变的定位研究与应用

背景：以往的医学影像检查手段只限于检查病变,对病变影像定位、定性等,而不能做到直观表面定位,为了更好的帮助临床准确定位就需要一种装置,在检查病变同时做到准确定位。 目的：分析磁共振检查躯体骨骼及软组织病变定位器准确性。 方法：检索磁共振检查躯体骨骼及软组织病变的定位研究与应用的相关研究文献,检索词为“磁共振(magnetic resonance imaging, MRI),定位(location),诊断(diagnosis),躯体病变(body lesions),占位性病变(space-occupying lesions),定位器(locator),神经系统疾病(nervous system disease),神经外科(neurosurgery)”,语言分别设定为中文和英文。 结果与结论：磁共振扫描前将定位器固定于可疑病变部位,透过该定位器进行扫描,扫描完成后做好表面定位,患者在定位下分别实施穿刺、手术、放疗。使用磁共振检查躯体病变定位器均能快速定位,准确性高,且能避开大血管、神经及韧带等重要功能区;对手术或穿刺治疗起到重要指导作用。磁共振检查肢体病变定位器操作简单、使用灵活,固定方便、使用安全,结构合理,技术创新,能确定病变的精确空间位置,克服了手术中寻找病灶难的问题,有利于查找微小的病变,或者是在某个序列不能很好显示的病变。     

Improving CT-guided transthoracic biopsy of mediastinal lesions by diffusion-weighted magnetic resonance imaging

OBJECTIVES:

To evaluate the preliminary results obtained using diffusion-weighted magnetic resonance imaging and the apparent diffusion coefficient for planning computed tomography-guided biopsies of selected mediastinal lesions.

METHODS:

Eight patients with mediastinal lesions suspicious for malignancy were referred for computed tomography-guided biopsy. Diffusion-weighted magnetic resonance imaging and apparent diffusion coefficient measurement were performed to assist in biopsy planning with diffusion/computed tomography fused images. We selected mediastinal lesions that could provide discordant diagnoses depending on the biopsy site, including large heterogeneous masses, lesions associated with lung atelectasis or consolidation, lesions involving large mediastinal vessels and lesions for which the results of biopsy using other methods and histopathological examination were divergent from the clinical and radiological suspicion.

RESULTS:

In all cases, the biopsy needle was successfully directed to areas of higher signal intensity on diffusion-weighted sequences and the lowest apparent diffusion coefficient within the lesion (mean, 0.8 [range, 0.6–1.1]×10^-3 mm²/s), suggesting high cellularity. All biopsies provided adequate material for specific histopathological diagnoses of four lymphomas, two sarcomas and two thymomas.

CONCLUSION:

Functional imaging tools, such as diffusion-weighted imaging and the apparent diffusion coefficient, are promising for implementation in noninvasive and imaging-guided procedures. However, additional studies are needed to confirm that mediastinal biopsy can be improved with these techniques.     

Estimation of the brain stem volume by stereological method on magnetic resonance imaging

Neuron loss that occurs in some neurodegenerative diseases can lead to volume alterations by causing atrophy in the brain stem. The aim of this study was to determine the brain stem volume and the volume ratio of the brain stem to total brain volume related to gender and age using new Stereo Investigator system in normal subjects. For this purpose, MR images of 72 individuals who have no pathologic condition were evaluated. The total brain volumes of female and male were calculated as 966.81?±?77.44 and 1,074.06?±?111.75?cm³, respectively. Brain stem volumes of female and male were determined as 18.99?±?2.36 and 22.05?±?4.01?cm³, respectively. The ratios of brain stem volume to total brain volume were 1.96?±?0.17 in female and 2.05?±?0.29 in male. The total brain and brain stem volumes were observed smaller in female and it is statistically significant. Among the individuals whose ages are between 20 and 40, total brain and brain stem volume measurements with aging were not statistically significant. As a result, we believe that the measurement of brain stem volume with an objective and efficient calculation method will contribute to the early diagnosis of neurodegenerative diseases, as well as to determine the rate of disease progression, and the outcomes of treatment.     

Robust image registration for functional magnetic resonance imaging of the brain

Motion-related artifacts are still a major problem in data analysis of functional magnetic resonance imaging (FMRI) studies of brain activation. However, the traditional image registration algorithm is prone to inaccuracy when there are residual variations owing to counting statistics, partial volume effects or biological variation. In particular, susceptibility artifacts usually result in remarkable signal intensity variance, and they can mislead the estimation of motion parameters. In this study, Two robust estimation algorithms for the registration of FMRI images are described. The first estimation algorithm was based on the Newton method and used Tukey's biweight objective function. The second estimation algorithm was based on the Levenberg-Marquardt technique and used a skipped mean objective function. The robust M-estimators can suppress the effects of the outliers by scaling down their error magnitudes or completely rejecting outliers using a weighting function. The proposed registration methods consisted of the following steps: fast segmentation of the brain region from noisy background as a preprocessing step; pre-registration of the volume centroids to provide a good initial estimation; and two robust estimation algorithms and a voxel sampling technique to find the affine transformation parameters. The accuracy of the algorithms was within 0.5 mm in translation and within 0.5° in rotation. For the FMRI data sets, the performance of the algorithms was visually compared with the AIR 2.0 software, which is a software for image registration, using colour-coded statistical mapping by the Kolmogorov-Smirov method. Experimental results showed, that the algorithms provided significant improvement in correcting motion-related artifacts and can enhance the detection of real brain activation.     

Manganese-enhanced magnetic resonance imaging (MEMRI) of mouse brain development

Given the importance of genetically modified mice in studies of mammalian brain development and human congenital brain diseases, MRI has the potential to provide an efficient in vivo approach for analyzing mutant phenotypes in the early postnatal mouse brain. The combination of reduced tissue contrast at the high magnetic fields required for mice, and the changing cellular composition of the developing mouse brain make it difficult to optimize MRI contrast in neonatal mouse imaging. We have explored an easily implemented approach for contrast-enhanced imaging, using systemically administered manganese (Mn) to reveal fine anatomical detail in T1-weighted MR images of neonatal mouse brains. In particular, we demonstrate the utility of this Mn-enhanced MRI (MEMRI) method for analyzing early postnatal patterning of the mouse cerebellum. Through comparisons with matched histological sections, we further show that MEMRI enhancement correlates qualitatively with granule cell density in the developing cerebellum, suggesting that the cerebellar enhancement is due to uptake of Mn in the granule neurons. Finally, variable cerebellar defects in mice with a conditional mutation in the Gbx2 gene were analyzed with MEMRI to demonstrate the utility of this method for mutant mouse phenotyping. Taken together, our results indicate that MEMRI provides an efficient and powerful in vivo method for analyzing neonatal brain development in normal and genetically engineered mice.     

Identification of diffuse and focal brain lesions by clinical magnetic resonance spectroscopy

The purpose of this paper is to facilitate the comparison of magnetic resonance (MR) spectra acquired from unknown brain lesions with published spectra in order to help identify unknown lesions in clinical settings. The paper includes lists of references for published MR spectra of various brain diseases, including pyogenic abscesses, encephalitis (herpes simplex, Rasmussen's and subacute sclerosing panencephalitis), neurocysticercosis, tuberculoma, cysts (arachnoid, epidermoid and hydatid), acute disseminated encephalomyelitis (ADEM), adrenoleukodystrophy (ALD), Alexander disease, Canavan's disease, Krabbe disease (globoid cell leukodystrophy), Leigh's disease, megalencephalic leukoencephalopathy with cysts, metachromatic leukodystrophy (MLD), Pelizaeus-Merzbacher disease, Zellweger syndrome, HIV-associated lesions [cryptococcus, lymphoma, toxoplasmosis and progressive multifocal leukoencephalopathy (PML)], hydrocephalus and tuberous sclerosis. Each list includes information on the echo time(s) (TE) of the published spectra, whether a control spectrum is shown, whether the corresponding image and voxel position are shown and the patient ages if known. The references are listed in the approximate order of usefulness, based on spectral quality, number of spectra, range of echo times and whether the voxel positions are shown. Spectra of Zellweger syndrome, cryptococcal infection, toxoplasmosis and lymphoma are included, along with a spectrum showing propanediol (propylene glycol).     

Neuroprotective effect of lamotrigine and MK-801 on rat brain lesions induced by 3-nitropropionic acid: evaluation by magnetic resonance imaging and in vivo proton magnetic resonance spectroscopy

Magnetic resonance imaging and in vivo proton magnetic resonance spectroscopy were used to evaluate the therapeutic effect of lamotrigine and MK-801 on rat brain lesions induced by 3-nitropropionic acid. Systemic administration of 3-nitropropionic acid (15 mg/kg per day) to two-month-old Sprague-Dawley rats (n = 10 for each group) for five consecutive days induced selective striatal and hippocampal lesions and specific behavioral change. Pretreatment with lamotrigine (10 mg/kg or 20 mg/kg per day) or MK-801 (2 mg/kg per day) attenuated the lesions and behavioral change. There were no significant differences in T2 values of the striatum and hippocampus among rats pretreated with MK-801, lamotrigine (20 mg/kg) and sham controls. Significant elevations of succinate/creatine and lactate/creatine ratios and decreases of N-acetylaspartate/creatine and choline/creatine ratios were observed after 3-nitropropionic acid injections (P < 0.001). The changes were nearly prevented after pretreatment with lamotrigine (20 mg/kg). However, the N-acetylaspartate/creatine in rats pretreated with lamotrigine (10 mg/kg) (P < 0.01) and MK-801 (P < 0.05) still showed significant reduction as compared with sham controls. Thus we conclude that both lamotrigine and MK-801 are effective in attenuation of brain lesions induced by 3-nitropropionic acid. A higher dose of lamotrigine provides a better neuroprotective effect than MK-801. With a better therapeutic effect and fewer side effects, lamotrigine is more promising for potential clinical application.     

Course of cerebral lesions in a patient with periarteritis nodosa studied by magnetic resonance imaging

Summary The course is reported of a patient with periarteritis nodosa who initially presented with neurological symptoms. Multiple cerebral lesions were documented by the first magnetic resonance imaging (MRI) investigation. The majority of these had disappeared completely in the follow-up MRI studies. In contrast to neurological improvement the patient eventually died due to multiorgan failure. Postmortem histological examination revealed no pathological findings in the brain except one single necrotic area already known from MRI. Remissions of histological and angiographic alterations in periarteritis nodosa have been described as local healing leading to fibrosis and scarring. Our findings suggest that restitutio ad integrum may occur, at least in cerebral lesions.Abbreviations PAN panarteritis nodosa - MRI magnetic resonance imaging - CT computerized tomography - CNS central nervous system