语言功能磁共振成像任务设计的研究进展

随着脑功能影像技术的成熟,对大脑语言功能区定位及语言文字加工的神经机制的认识已经较为深刻,但既往研究中应用的语言功能磁共振成像任务多种多样,缺少一个稳定、标准的语言功能磁共振成像任务,就有关语言功能磁共振成像任务设计的研究予以综述。     

语言功能磁共振成像任务设计的研究进展

随着脑功能影像技术的成熟,对大脑语言功能区定位及语言文字加工的神经机制的认识已经较为深刻,但既往研究中应用的语言功能磁共振成像任务多种多样,缺少一个稳定、标准的语言功能磁共振成像任务,就有关语言功能磁共振成像任务设计的研究予以综述。     

The clinical potential of functional magnetic resonance imaging

Functional magnetic resonance imaging (fMRI) has had a huge impact on understanding the healthy human brain. To date it has had much less impact in clinical neuroscience or clinical practice. The reasons for this are in part that the image acquisition, paradigm design, and data analysis strategies used presently are not sufficiently standardized. This makes the comparison of results across individuals, scanning sessions, and centers difficult. Nevertheless, there are emerging applications for clinical fMRI, and as the field matures the number of applications is likely to grow. It seems certain that fMRI has an important role to play in helping us understand the mechanisms of neuropsychiatric diseases and in helping to identify effective therapeutic strategies.     

静息态功能磁共振成像技术对右侧小脑参与语言功能的应用研究

目的 通过静息态功能磁共振成像技术来探讨小脑在产生语言中的作用机制。 方法 运用西门子3.0T磁共振仪获得静息态数据,用DPARSF软件对静息态数据进行预处理。首先对12例卒中后失语患者和20例正常对照者进行低频振荡振幅（ALFF）分析,在REST软件中行两样本t检验,得到失语组右侧小脑的某一脑区ALFF信号低于正常对照组,然后把此脑区作为种子点和ROI选取区,在正常对照组中进行单样本t检验,得到功能连接图。 结果 与正常对照组相比,失语组左侧颞中回、左侧前额叶内侧回、右侧小脑的ALFF减低;右侧小脑在正常对照组功能连接的脑区有小脑蚓部、左侧颞中回、左侧额上回内侧面、辅助运动区。 结论 右侧小脑本身及通过影响与其存在功能连接和解剖连接的脑区参与语言的产生。     

PACS-based functional magnetic resonance imaging.

The picture archiving and communication system (PACS) technology reaches its 10th anniversary. Retrospectively no one could foresee the impact the PACS would have to the health care enterprise, but it is common consent today, that PACS is the key technology crucial to daily clinical image operations and especially to image related basic and clinical research. During the past 10 years the PACS has been matured from a research and developmental stage into commercial products which are provided by all major modality and health care equipment vendors. The PACS, originally implemented in the Radiology Department, needs to grow and has already carried well beyond departmental limits conquering all image relevant areas inside the hospital. During the past 10 years a dramatic development in imaging techniques especially within MRI emerged. Advanced 3D- and 4D-MR imaging techniques result in much more images and more complex data objects than ever before which need to be implemented into the existing PACS. These new imaging techniques require intensive post-processing apart from the imaging modality which need to be integrated into the image workflow and the PACS implementation. Along with these new imaging techniques new clinical applications, e.g. stroke detection, and research applications, e.g. study of heart and brain function, in Neurology and Cardiology require changes to the traditional PACS concept. Therefore inter-disciplinary image distribution will become the high-water mark for the next 10 years in the PACS endeavor. This paper focuses on one new advanced imaging technique, functional magnetic resonance imaging (fMRI), and discusses how fMRI data is defined, what fMRI requires in terms of clinical and research applications and how to implement fMRI in the existing PACS.     

Esophageal invasion by thyroid carcinomas: prediction using magnetic resonance imaging

PURPOSE: We evaluated the accuracy of magnetic resonance imaging (MRI) in predicting esophageal invasion by thyroid carcinomas and established an optimal criterion for diagnosing esophageal invasion. METHOD: The MRI findings (size and margins of tumor, ratio of tumor contact to the esophagus, shape and displacement of the esophagus, and tumor invasion to the outer and inner layers of the esophagus) in 67 patients with thyroid carcinomas were retrospectively reviewed and correlated with surgical and pathologic findings. Logistic modeling was used to determine the significant factors for predicting esophageal invasion. RESULTS: Seventeen (34%) of the 67 patients had pathologically or surgically verified esophageal invasion. The logistic modeling revealed that outer layer invasion (P < 0.001) and poorly defined margins (P = 0.001) were the significant factors. The outer layer invasion showed the highest accuracy of 91%, with 82% sensitivity and 94% specificity. The addition of poorly defined margins to this criterion did not improve its accuracy. CONCLUSION: Esophageal invasion by thyroid carcinoma was accurately predicted with MRI, and an MRI finding of outer layer invasion was optimal for diagnosing esophageal invasion.     

Assessment of cerebral blood flow reserve using functional magnetic resonance imaging

Imaging of activated brain areas based on changes of blood deoxyhemoglobin levels is now possible with MRI. Acetazolamide (ACZ) increases cerebral blood flow (CBF) without changing cerebral oxygen consumption; this results in signal changes observed in gradient echo MR images from the areas with an increase in CBF. We assessed signal changes after ACZ application in seven healthy subjects with a conventional 1.5-T MRI scanner. The susceptibility-sensitized three-dimensional fast low-angle shot (FLASH) sequence was used to visualize signal changes induced by ACZ. We analyzed anatomic localization of different ranges of detected signal changes. ACZ caused significant signal changes in the gray matter and at the edge of the cerebral cortex, the latter corresponding to draining surface veins. No significant differences were seen among different brain areas within the same slice. Using the maximum intensity projection technique, we were able to partially separate signal changes originating in draining veins from signal originating in the gray matter microvasculature. Signal changes from the microvessels reflect cerebrovascular reserve. Blood-oxygen-level-dependent (BOLD) based MRI can evaluate CBF reserve with high spatial and temporal resolution. To assess cerebrovascular reserve, it is necessary to separate signal changes originating in large vessels from signal from brain microvasculature.     

Clinical applications of functional magnetic resonance imaging

Despite its immediate success as a tool for basic research, the clinical application of functional MRI(fMRI) is still limited. FMRI has proven useful for presurgical functional mapping of the eloquent cortices. Localization of the sensorimotor cortex by fMRI may be of relatively limited value because the sensorimotor cortex can often be readily localized by means of anatomical methods. In contrast, the language cortices may not be localized anatomically and the language dominant hemisphere has been determined by invasive Wada test. Previous reports have shown that fMRI can be a promising alternative to the Wada test. A recent clinical trial has suggested that fMRI can be used to diagnose Alzheimer's disease in its earliest stage, detecting subclinical deterioration of the memory function. FMRI may be useful to predict the future decline of memory in people with genetic risks. Monitoring of the functional recovery of post-stroke brains may be another promising clinical application of fMRI. FMRI has demonstrated functional reorganization of the brain that may be related to the restoration of motor and language functions.     

Spatially filtering functional magnetic resonance imaging data

When constructing MR images from acquired spatial frequency data, it can be beneficial to apply a low-pass filter to remove high frequency noise from the resulting images. This amounts to attenuating high spatial frequency fluctuations that can affect detected MR signal. A study is presented of spatially filtering MR data and possible ramifications on detecting regionally specific activation signal. It is shown that absolute activation levels are strongly dependent on the parameters of the filter used in image construction and that significance of an activation signal can be enhanced through appropriate filter selection. A comparison is made between spatially filtering MR image data and applying a Gaussian convolution kernel to statistical parametric maps.     

Retrospective coregistration of functional magnetic resonance imaging data using external monitoring.

Coregistration is essential for correcting head motion artifacts in functional magnetic resonance imaging (fMRI). Coregistration algorithms typically realign images through optimization of a similarity measure based on voxel signal intensities. However, coregistration can also be performed through external monitoring, whereby a tracking device measures head motion directly and independently of the imaging data. This paper describes development of external monitoring using fMRI-compatible infrared cameras. Three subjects participated in block-design fMRI experiments consisting of bilateral finger tapping alone and tapping combined with visuomotor tracking to produce controlled task-correlated head motion. Functional MRI time-series were coregistered using the external monitoring technique and a known image-based algorithm for comparison. Over various performance characteristics, external monitoring and image-based coregistration exhibited good agreement, in particular reducing signals correlated with millimeter task-correlated motions by 50-100%, with a 5% difference between the two techniques. These results promise future applications and refinements of external monitoring in patient populations where head motion is especially problematic. Possibilities include 3D prospective coregistration during real-time fMRI, coregistration of individual slices, and motion correction in anatomic MRI.     

Special considerations for functional magnetic resonance imaging of pediatric populations

Functional MRI (fMRI) provides a noninvasive means of studying both typical and atypical brain development in vivo. However, the developmental and clinical status of the populations of interest impact how neuroimaging data should be collected, analyzed, and interpreted. In the present work, we review methodological and theoretical issues relevant to developmental and clinical neuroimaging research and provide possible approaches for addressing each. These issues include accounting for differences in biological noise, neuroanatomy, motion, and task performance. Finally, we emphasize the importance of a converging methods approach in constraining and supporting interpretations of pediatric imaging results.     

Applications of functional magnetic resonance imaging in psychiatry

While the use of MRI techniques has become a cornerstone of the neurology clinic, the application of such methods in psychiatry was rather limited until the advent of functional magnetic resonance imaging (fMRI). Over the past decade fMRI has superseded radionuclide-imaging techniques and blossomed into a widely used psychiatric research tool. This review focuses on the neurobiological findings from fMRI research in three less well-documented psychiatric disorders: attention deficit hyperactivity disorder (ADHD), depression, and obsessive-compulsive disorder (OCD). Although there was some disparity in early findings, greater standardization of image acquisition, analysis, and paradigms, and improved clinical classification are leading to a greater convergence of observations from different laboratories. fMRI is also beginning to realize its potential as an important mediator between genes and phenotypes, and may thus contribute to a better understanding of the pathophysiology of major neuropsychiatric diseases. The role of fMRI in the objective assessment of therapeutic intervention and early prediction of response to treatment is also discussed.     

Investigations of the human visual system using functional magnetic resonance imaging (FMRI)

The application of functional magnetic resonance imaging (fMRI) in studies of the visual system provided significant advancement in our understanding of the organization and functional properties of visual areas in the human cortex. Recent technological and methodological improvements allowed studies to correlate neuronal activity with visual perception and demonstrated the ability of fMRI to observe distributed neural systems and to explore modulation of neural activity during higher cognitive processes. Preliminary applications in patients with visual impairments suggest that this method provides a powerful tool for the assessment and management of brain pathologies. Recent research focuses on obtaining new information about the spatial localization, organization, functional specialization and participation in higher cognitive functions of visual cortical areas in the living human brain and in further establishment of the method as a useful clinical tool of diagnostic and prognostic significance for various pathologic processes affecting the integrity of the visual system. It is anticipated that the combined neuroimaging approach in patients with lesions and healthy controls will provide new insight on the topography and functional specialization of cortical visual areas and will further establish the clinical value of the method for improving diagnostic accuracy and treatment planning.     

Probabilistic analysis of functional magnetic resonance imaging data

Probability theory is applied to the analysis of fMRI data. The posterior distribution of the parameters is shown to incorporate all the information available from the data, the hypotheses, and the prior information. Under appropriate simplifying conditions, the theory reduces to the standard statistical test, including the general linear model. The theory is particularly suited to handle the spatial variations in the noise present in fMRI, allowing the comparison of activated voxels that have different, and unknown, noise. The theory also explicitly includes prior information, which is shown to be critical in the attainment of reliable activation maps.     

高场强术中磁共振结合语言功能神经导航技术在胶质瘤手术中的应用

目的探讨高场强术中磁共振系统与语言功能导航技术联合应用对优势大脑半球语言功能区胶质瘤手术切除效果的影响。方法收集2009年2月-2010年7月与优势大脑半球弓形束关系密切的胶质瘤患者20例,男12例,女8例,年龄20~61岁,平均43.6岁,根据术前失语评分(AQ)将患者分为语言功能正常组(n=9)和语言功能障碍组(n=11)。所有患者均接受高场强术中磁共振及弓形束导航辅助下手术,采用1.5T移动磁体、双室设计的术中磁共振系统,术前通过软件将弓形束重建的3D图像整合入神经导航系统,并在术中联合应用显微镜下功能神经导航。术前及术后2~4周、3~6个月进行随访(包括MRI检查及西方失语成套测验)。结果 20例患者均完成术前及术中弓形束重建,将3D重建图像整合入神经导航系统后成功实现了显微镜下导航。术后2~4周,语言功能正常组AQ(94.5±5.5)保持在正常水平,只有1例出现新发的传导性失语症状(AQ=81.8),而语言功能障碍组AQ(89.4±5.8)与术前比较(84.9±8.7)有明显改善(P<0.05)。术后3~6个月,语言功能正常组中除2例因肿瘤复发出现语言功能恶化外,其余患者AQ(98.3±0.5)均在正常范围,而语言功能障碍组AQ(95.2±2.6)较术后2~4周也有了明显改善(P<0.05)。两组患者术后均未出现其他新的神经功能障碍,无死亡病例。结论高场强术中磁共振结合功能神经导航是一项可靠、稳妥的技术,在肿瘤毗邻重要语言功能区及传导束时,可辅助外科手术最大限度地切除肿瘤,减轻神经功能损伤,有利于术后功能恢复。     

Present clinical status of magnetic resonance imaging

Magnetic resonance imaging has achieved clinical importance and has become the primary tool in the investigation of head, spinal cord, pelvis, cancellous bone, pericardium (with gating), gallbladder, lymph node masses, and very soon, in the evaluation of joints. In many areas, particularly with respiratory and ECG gating, this method promises to replace all other imaging modalities with the precision of information obtained. Today the exceptions are the alimentary tube and its mesentery, between the esophagus and rectum, and the peripheral lung.     

Cardiac imaging using gated magnetic resonance

To overcome the limitations of magnetic resonance (MR) cardiac imaging using nongated data acquisition, three methods for acquiring a gating signal, which could be applied in the presence of a magnetic field, were tested: an air-filled plethysmograph, a laser-Doppler capillary perfusion flowmeter, and an electrocardiographic gating device. The gating signal was used for timing of MR imaging sequences (IS). Application of each gating method yielded significant improvements in structural MR image resolution of the beating heart, although with both plethysmography and laser-Doppler velocimetry it was difficult to obtain cardiac images from the early portion of the cardiac cycle due to an intrinsic delay between the ECG R wave and peripheral detection of the gating signal. Variations in the temporal relationship between the R wave and plethysmographic and laser-Doppler signals produced inconsistencies in the timing of IS. Since the ECG signal is virtually free of these problems, the preferable gating technique is IS synchronization with an electrocardiogram. The gated images acquired with this method provide sharp definition of internal cardiac morphology and can be temporarily referenced to end diastole and end systole or intermediate points.