Hemodynamic Significance of Internal Carotid or Middle Cerebral Artery Stenosis Detected on Magnetic Resonance Angiography

Purpose

We evaluated hemodynamic significance of stenosis on magnetic resonance angiography (MRA) using acetazolamide perfusion single photon emission computed tomography (SPECT).

Materials and Methods

Of 171 patients, stenosis in internal carotid artery (ICA) and middle cerebral artery (MCA) (ICA-MCA) on MRA and cerebrovascular reserve (CVR) of MCA territory on SPECT was measured using quantification and a 3-grade system. Stenosis and CVR grades were compared with each other, and their prognostic value for subsequent stroke was evaluated.

Results

Of 342 ICA-MCA, 151 (44%) presented stenosis on MRA; grade 1 in 69 (20%) and grade 2 in 82 (24%) cases. Decreased CVR was observed in 9% of grade 0 stenosis, 25% of grade 1, and 35% of grade 2. The average CVR of grade 0 was significantly different from grade 1 (p<0.001) and grade 2 stenosis (p=0.007). In quantitative analysis, average CVR index was -0.56±7.91 in grade 0, -1.81±6.66 in grade 1 and -1.18±5.88 in grade 2 stenosis. Agreement between stenosis and CVR grades was fair in patients with lateralizing and non-lateralizing symptoms (κ=0.230 and 0.346). Of the factors tested, both MRA and CVR were not significant prognostic factors (p=0.104 and 0.988, respectively), whereas hypertension and renal disease were significant factors (p<0.05, respectively).

Conclusion

A considerable proportion of ICA-MCA stenosis detected on MRA does not cause CVR impairment despite a fair correlation between them. Thus, hemodynamic state needs to be assessed for evaluating significance of stenosis, particularly in asymptomatic patients.     

三维对比增强磁共振血管造影中的透视触发技术研究

三维对比增强磁共振血管造影(M RA)检查中,正确估计或测算扫描延时时间是检查成败的关键。目前临床应用中普遍使用的定时技术是试验性团注技术,但其存在着局限性,如缺乏完善性、空间分辨率有限及技术复杂等。本文提出一种技术,通过使用M R透视法实时检测靶血管内对比度的变化,当检测到对比度增强时,开启带有椭圆中心视图命令的三维M RA序列采集数据。结果表明这种技术可获得静脉抑制,消除运动伪影,极大提高空间分辨率,在团注检测中的可靠性高达95%以上。这种技术为众多血管区域提供了高质量的对比增强M R血管造影。     

The Action Sites of Propofol in the Normal Human Brain Revealed by Functional Magnetic Resonance Imaging

Propofol has been used for many years but its functional target in the intact brain remains unclear. In the present study, we used functional magnetic resonance imaging to demonstrate blood oxygen level dependence signal changes in the normal human brain during propofol anesthesia and explored the possible action targets of propofol. Ten healthy subjects were enrolled in two experimental sessions. In session 1, the Observer's Assessment of Alertness/Sedation Scale was performed to evaluate asleep to awake/alert status. In session 2, images with blood oxygen level dependence contrast were obtained with echo‐planar imaging on a 1.5‐T Philips Gyroscan Magnetic Resonance System and analyzed. In both sessions, subjects were intravenously administered with saline (for 3 min) and then propofol (for 1.5 min) and saline again (for 10.5 min) with a constant speed infusion pump. Observer's Assessment of Alertness/Sedation Scale scoring showed that the subjects experienced conscious–sedative–unconscious–analepsia, which correlated well with the signal decreases in the anesthesia states. Propofol induced significant signal decreases in hypothalamus (18.2% ± 3.6%), frontal lobe (68.5% ± 11.2%), and temporal lobe (34.7% ± 6.1%). Additionally, the signals at these three sites were fulminant and changed synchronously. While in the thalamus, the signal decrease was observed in 5 of 10 of the subjects and the magnitude of decrease was 3.9% ± 1.6%. These results suggest that there is most significant inhibition in hypothalamus, frontal lobe, and temporal in propofol anesthesia and moderate inhibition in thalamus. These brain regions might be the targets of propofol anesthesia in human brain. Anat Rec, 2010. © 2010 Wiley‐Liss, Inc.     

急性脑梗死的脑循环与磁共振血管成像的临床探讨

目的：观察急性脑梗死脑循环动力学改变与MRA的临床相关性。方法：54例急性脑梗死病人进行了脑循环动力学检查,同时做正常人38例对照,另外34例行MRA的检测。结果：54例病人的脑循环动力学结果中493例有不同程度异常改变,而MRA的34例中仅23例为异常。结论：脑循环动力学的改变阳性率高于MRA,而且脑循环动力学监测简便,费用低,操作简单,可以在临床推广使用。若两者结合应用则效果更好。     

非人灵长类动物超高场磁共振脑成像技术进展

非人类灵长类动物是神经科学研究中的重要动物模型,可以兼容多种侵入式和非侵入式神经信号探测和神经活动调控方法.结合侵入式和非侵入式方法的非人灵长类动物的神经科学研究,有助于将大量基于动物模型的基础研究成果进行临床转化.其中磁共振脑成像技术是目前最主要的非侵入式大脑神经信号探测手段.非人灵长类动物磁共振脑成像研究,对于深入...     

Magnetic Resonance (MR) Metabolic Imaging in Glioma

This review is focused on describing the use of magnetic resonance (MR) spectroscopy for metabolic imaging of brain tumors. We will first review the MR metabolic imaging findings generated from preclinical models, focusing primarily on in vivo studies, and will then describe the use of metabolic imaging in the clinical setting. We will address relatively well‐established ¹H MRS approaches, as well as ³¹P MRS, ¹³C MRS and emerging hyperpolarized ¹³C MRS methodologies, and will describe the use of metabolic imaging for understanding the basic biology of glioma as well as for improving the characterization and monitoring of brain tumors in the clinic.     

线扫描磁共振成像方法

目的：在磁共振成像领域，线扫描是最早的一种傅立叶成像方法，后逐渐被二维傅立叶成像方法取代，近年来线扫描方法又重新引起了人们的兴趣，本文介绍磁共振线扫描方法，并分析其优缺点；方法：从线扫描与二维傅立叶成像方法的原理人手，在多个方面比较两种方法的差异；结果：线扫描方法在成像速度及图像信噪比方面不如二维傅立叶成像方法。但在克服运动伪影、金属伪影及手术过程中实时磁共振检查等方面优于二维傅立叶成像方法；结论：线扫描方法是一种适用于中低场永磁型磁共振设备的成像方法，在术中磁共振成像方面有广泛的应用前景。     

Localization of the Motor and Speech Zones of the Cerebral Cortex by Functional Magnetic Resonance Tomography

Functional magnetic resonance tomography provides a non-invasive method for mapping the cerebral cortex. The aim of the present work was to assess the potential and suitability of this method in a series of brain disorders. Studies were performed on 32 volunteers (mean age 37.8 +/- 20.9 years) and 16 patients with tumors of the cerebral cortex (mean age 36.2 +/- 24.2 years). Initial functional images were processed by statistical methods. Computed activation maps were superimposed on anatomical images. In 89% of cases, functional magnetic resonance tomography allowed the motor cortex and Broca's area to be localized; in almost 69%, the method impinged on the therapeutic tactics used in patients with cerebral cortex lesions. Thus, functional magnetic resonance tomography can be used in clinical conditions to obtain information not yielded by other diagnostic methods and which can be used to plan the neurosurgical treatment of patients with supratentorial brain tumors with maximum preservation of cerebral cortex function. Assessments of the state of the motor and speech areas by this tomographic method has potential applications in neurosurgery and neurophysiology.     

磁共振弥散张量成像的脑白质纤维优化重建

磁共振弥散张量成像(DTI)可对大脑白质纤维束的三维几何结构进行无创研究,其主要方法为DTI纤维追踪成像.研究打破现有DTI纤维追踪成像从初始种子区域逐步追踪增长的框架,提出脑白质的纤维优化重建方法,从全局角度描述追踪纤维,通过其对弥散倾向和几何结构的优化估计,重构最优纤维路径.结果表明,该方法可提供连接两个感兴趣区域(ROI)的有效和对称连接,同时通过全局优化手段消除累积噪声及局部随机噪声,提高长距离成像的可靠性;在人工合成数据集和真实人体数据集中均能较好成像,较之现有纤维追踪成像具有更高的可靠性和可重复性.     

磁共振成像研究进展

经过20多年的发展,磁共振成像已经成为临床医学影像学检查的重要手段之一,它对各种严重疾病具有早期诊断和疗效监控能力,因此,磁共振成像技术是现代医学的新领域,代表着影像医学的发展方向。本文阐述了磁共振成像的最新发展和临床应用的各种方法,并展望了磁共振成像的发展前景。     

Neurovascular Relations of the Trigeminal Nerve in Asymptomatic Individuals Studied with High-Resolution Three-Dimensional Magnetic Resonance Imaging

Neurovascular compression (NVC) is considered the main cause of classic trigeminal neuralgia (TN) and may be surgically addressed with microvascular decompression (MVD). Preoperative high-resolution three-dimensional magnetic resonance has proven a reliable tool to diagnose NVC in patients with refractory TN undergoing MVD. However, there is still scarce data regarding the rate, degree, and characteristics of neurovascular compression in asymptomatic individuals. This article describes the vascular relations of the trigeminal nerve in the cerebellopontine angle (CPA) in 100 subjects without known TN studied with 3.0T FIESTA (Fast Imaging Employing Steady-state Acquisition) MRI sequence. A NVC was observed in 142 (71%) of the 200 nerves with a 75% rate of bilateral NVC. Of the nerves with NVC, 92.3% showed a mere contact (Grade 1) without distortion and 78% occurred at the cisternal segment. This most common vessel causing the NVC was a vein (66%) followed by the superior cerebellar artery (28%). No significant reduction in diameter suggesting atrophy was seen in the nerves with NVC. The results indicate a high rate of mild, distal and predominantly venous vascular contact with the trigeminal nerve at the CPA in asymptomatic individuals. This clearly contrasts with the usual pattern of NVC observed in TN that is generally a severe, proximal, and arterial compression. Knowledge about the frequent NVC in asymptomatic individuals and its features is essential for interpreting preoperative MRI in patients with refractory classical TN considered for surgery. Anat Rec, 302:639–645, 2019. © 2018 Wiley Periodicals, Inc.     

采用偏微分方程的磁共振弥散张量各向异性扩散滤波去噪

弥散张量磁共振成像(DTI)是无创研究大脑白质结构及其他人体纤维状组织结构的主要工具。由于合成DTI数据的弥散加权成像数据(DWI)易受噪声干扰,需要有效去噪以保证DTI数据精度和后续应用的实现。使用各向异性扩散滤波理论,综合考虑各方向通道DWI数据的几何形态和结构特点,重构其特征向量和特征值,获得统一平滑的结构张量,以期在有效去噪的基础上最大程度地保持DTI数据几何结构和特征。利用所提出方法在合成弥散张量数据上进行仿真,并在真实脑部DTI数据上进行实验。仿真和实验结果表明,该方法能有效减少噪声对DTI数据的影响,较之现有的时频分析去噪方法,可更准确地恢复DTI数据,减少主分量方向的偏差和部分各向异性值的误差。     

首发精神分裂症患者脑磁共振质子波谱的对照研究

目的研究首发精神分裂症患者脑磁共振质子波谱(1HMRS)的变化。方法对26例首发精神分裂症患者和12例正常人分别进行MRI常规扫描和1HMRS检查,1HMRS采用定点分辨率波谱序列(TR2000毫秒,TE135毫秒),所测定的代谢产物包括N-乙酰基天门冬氨酸(NAA)、肌酸复合物(Cr)、胆碱复合物(Cho)、肌醇(MI)、乳酸(Lac)、谷氨酸及谷氨酰胺(Glu-Gln)。结果精神分裂症患者前额叶背外侧回中NAA/Cr值和NAA/Cho值显著低于对照组前额叶背外侧回(1.83±0.15/2.42±0.13,t=3.202,P<0.01,2.37±0.16/2.06±0.24,t=2.453,P<0.05);患者组海马区中NAA/Cr值(1.65±0.19)和NAA/Cho值(1.12±0.21)显著低于对照组海马中的NAA/Cr值(1.83±0.27,t=2.532,P<0.05)和NAA/Cho值(1.34±0.12,t=2.641,P<0.05);且NAA/Cr的水平与简明精神障碍评定量表阴性症状总分呈负相关(r=-0.416,P<0.05);而丘脑、颞叶颞横回、枕叶脑区的NAA/Cr和NAA/Cho两组无显著性差异(P>0.05)。结论精神分裂症患者的1HMRS与正常人存在显著差异,提示精神分裂症存在神经元功能的异常,其前额叶背外侧回和海马两处脑区功能低下。     

Brachial-Ankle Pulse Wave Velocity as a Screen for Arterial Stiffness: A Comparison with Cardiac Magnetic Resonance

Purpose

Despite technical simplicity and the low cost of brachial-ankle pulse wave velocity (BA-PWV), its use has been hampered by a lack of data supporting its usefulness and reliability. The aim of this study was to evaluate the usefulness of BA-PWV to measure aortic stiffness in comparison to using cardiovascular magnetic resonance (CMR).

Materials and Methods

A total of 124 participants without cardiovascular risk factors volunteered for this study. BA-PWV was measured using a vascular testing device. On the same day, using CMR, cross-sectional areas for distensibility and average blood flow were measured at four aortic levels: the ascending, upper thoracic descending, lower thoracic descending, and abdominal aorta.

Results

Compared to PWV measured by CMR, BA-PWV values were significantly higher and the differences therein were similar in all age groups (all p<0.001). There was a significant correlation between BA-PWV and PWV by CMR (r=0.697, p<0.001). Both BA-PWV and PWV by CMR were significantly and positively associated with age (r=0.652 and 0.724, p<0.001). The reciprocal of aortic distensibility also demonstrated a statistically significant positive correlation with BA-PWV (r=0.583 to 0.673, all p<0.001).

Conclusion

BA-PWV was well correlated with central aortic PWV and distensibility, as measured by CMR, regardless of age and sex.     

3.0T 3D-TOF MRA对颅内动脉瘤检出率的临床应用研究

目的评价3.0 T时间飞跃法磁共振血管成像(3.0 T 3D-TOF MRA)对颅内动脉瘤的诊断价值。方法选择25例有颅内动脉瘤相关症状患者,其中男性14例,女性11例;年龄25～74岁,平均年龄57岁。对其3.0 T 3D-TOF MRA诊断为颅内动脉瘤患者的磁共振资料进行回顾性分析,并与数字减影血管造影(DSA)对照。结果3.0 T 3D-TOF MRA共显示28个动脉瘤,其中单发22例,3例为多发动脉瘤,起自颈内动脉系统25个;起自基底动脉系统3个;DSA检查共显示27个动脉瘤。结论3.0 T 3D-TOF MRA虽然对于直径≤3 mm的微小动脉瘤的诊断存在一定的误诊及漏诊率,但其诊断颅内动脉瘤时能比较全面地显示动脉瘤,三维信息对临床确立治疗方案有很大帮助。3.0 T 3D-TOF MRA不失为高危人群或临床怀疑颅内动脉瘤患者筛查及随诊观察的有效手段。     

Nuclear Magnetic Resonance Studies of Bone Water

Mineralized bone tissue has a significant water component. Bone water is associated with the collagen fibers or mineral fraction or occurring as pore water of the Haversian and lacuno–canalicular system. Among the multiple physiologic functions that include signaling and providing to bone its viscoelastic properties, bone water enables the transport of ions and nutrients to and waste products from the cells. In addition, it plays a key role during mineralization whereby collagen-bound water is gradually replaced by calcium apatite-like mineral. In this review it is shown how nuclear magnetic resonance (NMR) allows the study of various physiologically relevant properties of bone water nondestructively. Isotope exchange experiments are described from which the apparent water diffusion coefficient can be calculated. The method is based on monitoring the migration of H₂O into the D₂O after immersion of the specimen in heavy water. Data obtained from rabbit cortical bone in the normal and mineral-depleted skeleton provide evidence for the hypothesized reciprocal relationship between bone water and mineral. Further, from the diffusion coefficient (D_a = (7.8 ± 1.5) × 10^–7 cm²/s) measured at 40°C it can be inferred that diffusive transport of small molecules from the bones microvascular system to the osteocytes occurs within minutes. Finally, whereas isotope exchange is not feasible in vivo, it is shown that bone water can be imaged by proton MRI.     

Assessment of Islet Graft Survival Using a 3.0‐Tesla Magnetic Resonance Scanner

Some studies have recently described a magnetic resonance (MR) method for detection of iron‐labeled islets transplanted into the liver. The aim of this work was to assess the survival of islet graft using a clinical 3.0‐T scanner. Islets from Lewis rats were cultured in the presence of iron oxide nanoparticles. One thousand iron‐labeled islets were transplanted into the portal vein of diabetic rats. Blood glucose levels were measured daily through day 14 post‐transplantation. MR imaging of the same section of the liver was performed on 1, 3, 7, 10, and 14 days post‐transplantation. The labeled islets were visualized by MR as distinct hypointensive spots distributed in the liver. There was a linear correlation between the relative value of delta R relaxometry multiplied by the cubic diameter (relative value of the iron volume, I_r) and blood glucose level on 14 days post‐transplantation in allograft and isograft (P < 0.05). The relative value of delta R relaxometry, diameter, and number of hypointensive spots could be calculated to assess the survival of the iron‐labeled islet grafts. Assessment of iron‐labeled islet grafts using a clinical 3.0‐T magnetic resonance scanner represents a useful method that has potential for clinical use. Anat Rec, 2008. © 2008 Wiley‐Liss, Inc.     

基于多对比度磁共振颈动脉图像的配准算法研究

基于在血管壁增强显示方面的强大潜力,近年来多对比度核磁共振成像已成为斑块分析研究的有力工具,但其效能受到多序列图像血管不匹配的影响。为实现多序列图像的准确血管配准,在管腔分割的基础上提出一种由粗到精的两步配准策略:先采用迭代最近点实现多对比度图像中心线的刚性配准,再采用薄板样条实现基于血管边界点的非刚性配准。在第二步配准中,为准确寻找不同序列血管边界的匹配点,创新使用形状上下文描述子对边界点进行筛选,并应用确定性退火技术进行全局优化。采用新型三维多对比度磁共振血管成像序列,对提出算法的有效性进行定量评价。结果表明,配准后不同序列的边界重合度均达到95%以上,平均表面距离0.12 mm,可有效提高配准精度,为后续斑块成分的分析奠定基础。     

基于磁共振图像与波谱的专家辅助诊断系统的设计

神经系统疾病是影响人类寿命和生存质量的常见疾病,磁共振图像(MRI)和磁共振波谱(MRS)分别提供了病变结构像和代谢物含量改变信息。综合分析MRI和MRS信息有助于医生更好地诊断疾病和制定治疗方案,因此磁共振数据共享与辅助诊断平台的建设受到广泛关注。基于MRI和MRS的专家辅助诊断系统以脑肿瘤、阿尔茨海默症、轻度认知障碍为重点,以DICOM格式标准的MR图像和LCModel量化后的MRS结果为数据基础,使用MySQL建立后台数据库存储和管理医学数据,并采用Java进行系统的后台和前端开发。该系统提供了病人信息查询、MRI及其属性标签查看与下载、MRS量化结果显示与下载、MRS与MRI的位置配准及其空间可视化等功能,为医生、研究人员、管理员等提供不同权限的需要。该系统的建立为医生的病情诊断和科研人员实施研究提供了极大帮助,推进了远程资料共享和自动化诊断的进程,并促进临床和科研的学术交流。