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。     

Acceptance Test of a Commercially Available Software for Automatic Image Registration of Computed Tomography (CT), Magnetic Resonance Imaging (MRI) And 99mTc-methoxyisobutylisonitrile (MIBI) Single-Photon Emission Computed Tomography (SPECT) Brain Images

This note describes a method to characterize the performances of image fusion software (Syntegra) with respect to accuracy and robustness. Computed tomography (CT), magnetic resonance imaging (MRI), and single-photon emission computed tomography (SPECT) studies were acquired from two phantoms and 10 patients. Image registration was performed independently by two couples composed of one radiotherapist and one physicist by means of superposition of anatomic landmarks. Each couple performed jointly and saved the registration. The two solutions were averaged to obtain the gold standard registration. A new set of estimators was defined to identify translation and rotation errors in the coordinate axes, independently from point position in image field of view (FOV). Algorithms evaluated were local correlation (LC) for CT-MRI, normalized mutual information (MI) for CT-MRI, and CT-SPECT registrations. To evaluate accuracy, estimator values were compared to limiting values for the algorithms employed, both in phantoms and in patients. To evaluate robustness, different alignments between images taken from a sample patient were produced and registration errors determined. LC algorithm resulted accurate in CT-MRI registrations in phantoms, but exceeded limiting values in 3 of 10 patients. MI algorithm resulted accurate in CT-MRI and CT-SPECT registrations in phantoms; limiting values were exceeded in one case in CT-MRI and never reached in CT-SPECT registrations. Thus, the evaluation of robustness was restricted to the algorithm of MI both for CT-MRI and CT-SPECT registrations. The algorithm of MI proved to be robust: limiting values were not exceeded with translation perturbations up to 2.5 cm, rotation perturbations up to 10° and roto-translational perturbation up to 3 cm and 5°.     

多语者第二语言脑加工的功能磁共振成像

目的 研究多语者默读英语时,脑的功能活动.方法 12名广州话母语右利手大学生,男7女5,年龄21～22岁.默英语单词,运用功能性磁共振成像对作业过程中的被试进行扫描,用AFNI软件对数据进行统计分析.结果 执行英语单词默读作业时,小脑,右(BA18),右颞叶下部(BA20),左前额叶下部(BA47),左前额叶中部(B10),右豆状核,左前额叶上部(BA9),左前额叶上部(BA6)有明显激活.结果 显示,左侧额叶与英语加工有关,右侧颞叶、小脑参与.结论 英语加工,多语者布洛卡脑区激活不显著,主要分布在其他区域.     

精神分裂症患者工作记忆的功能磁共振成像

目的:探讨精神分裂症患者工作记忆受损的中枢机制。方法:采用组块设计,让10名正常对照和20名精神分裂症患者进行数字再认(识记2或5个数字并判断是否出现过)和箭头方向判断(左或右),并同时进行血氧水平依赖对比功能磁共振(BOLD-fMRI)成像。结果:与对照组相比在高、低认知负荷下,精神分裂症患者基底节区(尾状核)激活均增高(P<0.001),左背外侧前额皮层(DLPFC)激活区域有增大趋势。结论:基底节和背外侧前额皮层(DLPFC)功能异常可能是精神分裂症患者工作记忆受损的中枢基础。     

基于统计参数图的脑功能磁共振成像数据处理方法

介绍了基于统计参数图的脑功能磁共振成像数据处理方法。脑功能磁共振成像由于其高的时间、空间分辨率、无创性等特点而得到广泛的应用。使用统计参数图进行脑功能成像的数据处理过程主要分为:原始数据的读取、图像预处理、统计分析和统计推论。图像预处理包括运动伪影的消除、图像标准化、图像空间平滑;统计分析包括广义线性模型的建立;统计推论包括T检验等。重点介绍了各个过程所使用的传统的处理方法和最新的处理方法。     

磁共振成像的电磁安全与限值标准

磁共振成像(MRI)是一种将外源电磁能量输入人体后产生物理效应并转换为医学图像信息的技术,包括静磁场、射频场、梯度场共3种电磁场。这3种电磁场均对生物体产生效应,并且在足够的强度下会对人体产生健康危险,如梯度场的神经刺激、射频场(RF)的热效应等电磁危险性。近10年来,美国食品药品监督管理局(FDA)发出MRI检查导致带动脉夹患者死亡的警告、MRI对带植入性神经刺激器患者伤害的通告、MRI对带金属背衬经皮给药帖片患者带来灼伤的通告。然而,当电磁场强度被限制在一定范围内时,MRI仍然是安全的。分析这3种电磁场主要的生物效应和健康危险,讨论国内外有关MRI电磁安全的限值标准。     

Radiation-Induced Microbleeds after Cranial Irradiation: Evaluation by Phase-Sensitive Magnetic Resonance Imaging with 3.0 Tesla

Background

Although there are many reports regarding radiation-induced microbleeds, its frequency, relation to dose and latency after radiation are not fully elucidated. The purpose of this study was to evaluate the frequency, latency, patient factors and dose relation of radiation-induced microbleeds after cranial irradiation using phase-sensitive magnetic resonance imaging (PSI) at 3.0 T.

Methods

Retrospective evaluation of 34 patients (age range, 13–78 years; mean, 49 years; follow-up period, 3–169 months; mean 29 months) who had undergone cranial irradiation using magnetic resonance (MR) imaging including PSI was performed. Twenty-three patients received high-dose irradiation (44–60 Gy), and 11 patients received 24–30 Gy whole brain irradiation. When microbleeds were detected on MR imaging in these high-dose irradiation patients, dose distribution maps were reproduced by reviewing the clinical records. Then the irradiated areas were divided into 6 radiation-dose classes: regions > 55 Gy, 45–55 Gy, 35–45 Gy, 25–35 Gy, 15–25 Gy and 5–15 Gy. The frequency of microbleeds in each radiation-dose class was analyzed.

Results

Microbleeds were detected in 7 (21%) of 34 patients on T2-weighted imaging, whereas they were detected in 16 (47%) of the 34 patients on PSIs. The frequency of microbleeds was higher than previously reported. The latency of radiation-induced microbleeds after radiation was 3 months to 9 years (mean, 33 months). In high-dose irradiation patients, the frequency of microbleeds significantly was associated with radiation dose. There were no foci that were observed in regions that had received < 25 Gy.

Conclusion

Radiation-induced microbleeds occurred more frequently in the present study than has been previously reported. PSI can be used to detect these vascular changes earlier than other conventional MR imaging techniques.     

精神分裂症患者一级亲属脑组织磁共振质子波谱成像的初步研究

目的 探讨精神分裂症患者一级亲属及正常对照组脑组织磁共振质子波谱分析(1H-MRS)的结果间是否存在差异.方法首先对精神分裂症患者一级亲属36人、正常对照组21人进行左侧前额叶、丘脑、海马、桥脑的1H-MRS分析,之后对所得结果进行独立样本t检验.结果 精神分裂症患者一级亲属与正常对照组在左侧前额叶、丘脑、海马、桥脑的...     

Evaluation of Novel Genetic Algorithm Generated Schemes for Positron Emission Tomography (PET)/Magnetic Resonance Imaging (MRI) Image Fusion

The use and benefits of a multimodality approach in the context of breast cancer imaging are discussed. Fusion techniques that allow multiple images to be viewed simultaneously are discussed. Many of these fusion techniques rely on the use of color tables. A genetic algorithm that generates color tables that have desired properties such as satisfying the order principle, the rows, and columns principle, have perceivable uniformity and have maximum contrast is introduced. The generated 2D color tables can be used for displaying fused datasets. The advantage the proposed method has over other techniques is the ability to consider a much larger set of possible color tables, ensuring that the best one is found. We asked radiologists to perform a set of tasks reading fused PET/MRI breast images obtained using eight different fusion techniques. This preliminary study clearly demonstrates the need and benefit of a joint display by estimating the inaccuracies incurred when using a side-by-side display. The study suggests that the color tables generated by the genetic algorithm are good choices for fusing MR and PET images. It is interesting to note that popular techniques such as the Fire/Gray and techniques based on the HSV color space, which are prevalent in the literature and clinical practice, appear to give poorer performance.     

Cardiac Flow Analysis Applied to Phase Contrast Magnetic Resonance Imaging of the Heart

Phase contrast magnetic resonance imaging is performed to produce flow fields of blood in the heart. The aim of this study is to demonstrate the state of change in swirling blood flow within cardiac chambers and to quantify it for clinical analysis. Velocity fields based on the projection of the three dimensional blood flow onto multiple planes are scanned. The flow patterns can be illustrated using streamlines and vector plots to show the blood dynamical behavior at every cardiac phase. Large-scale vortices can be observed in the heart chambers, and we have developed a technique for characterizing their locations and strength. From our results, we are able to acquire an indication of the changes in blood swirls over one cardiac cycle by using temporal vorticity fields of the cardiac flow. This can improve our understanding of blood dynamics within the heart that may have implications in blood circulation efficiency. The results presented in this paper can establish a set of reference data to compare with unusual flow patterns due to cardiac abnormalities. The calibration of other flow-imaging modalities can also be achieved using this well-established velocity-encoding standard. Medical image processing software named Medflovan, which is developed by Kelvin K. L. Wong, is used to produce the results displayed in this paper. The research-based version of this software system is utilized to provide cardiac flow visualization and analysis effectively.     

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.     

Correlations of Dynamic Contrast-Enhanced Magnetic Resonance Imaging with Morphologic,Angiogenic, and Molecular Prognostic Factors in Rectal Cancer

Purpose

To investigate the correlations between parameters of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and prognostic factors in rectal cancer.

Materials and Methods

We studied 29 patients with rectal cancer who underwent gadolinium contrast-enhanced, T1-weighted DCE-MRI with a three Tesla scanner prior to surgery. Signal intensity on DCE-MRI was independently measured by two observers to examine reproducibility. A time-signal intensity curve was generated, from which four semiquantitative parameters were calculated: steepest slope (SLP), time to peak (Tp), relative enhancement during a rapid rise (Erise), and maximal enhancement (Emax). Morphologic prognostic factors including T stage, N stage, and histologic grade were identified. Tumor angiogenesis was evaluated in terms of microvessel count (MVC) and microvessel area (MVA) by morphometric study. As molecular factors, the mutation status of the K-ras oncogene and microsatellite instability were assessed. DCE-MRI parameters were correlated with each prognostic factor using bivariate correlation analysis. A p-value of <0.05 was considered significant.

Results

Erise was significantly correlated with N stage (r=-0.387 and -0.393, respectively, for two independent data), and Tp was significantly correlated with histologic grade (r=0.466 and 0.489, respectively). MVA was significantly correlated with SLP (r=-0.532 and -0.535, respectively) and Erise (r=-0.511 and -0.446, respectively). MVC was significantly correlated with Emax (r=-0.435 and -0.386, respectively). No significant correlations were found between DCE-MRI parameters and T stage, K-ras mutation, or microsatellite instability.

Conclusion

DCE-MRI may provide useful prognostic information in terms of histologic differentiation and angiogenesis in rectal cancer.     

Coexistence of Dense and Sparse Areas in the Longitudinal Smooth Muscle of the Anal Canal: Anatomical and Histological Analyses Inspired by Magnetic Resonance Images

Magnetic resonance images of the anal canal show small, circular, low-intensity areas arranged in a row and a high-intensity area surrounding them internally and externally in the longitudinal muscle layer that cannot be explained by current anatomical findings. The purpose of this study was to elucidate the detailed structure of the longitudinal smooth muscle of the anal canal and to interpret the magnetic resonance image of the longitudinal muscle. Specimens for macroscopic anatomy and histology were obtained from six and seven cadavers, respectively. The histological nature of the longitudinal muscle was examined by staining serial transverse and coronal sections of the lateral wall of the anal canal with Masson's trichrome stain and using immunohistochemistry for smooth and skeletal muscle fibers. Dense and sparse areas of smooth muscle fibers coexisted in the longitudinal muscle layer. The dense areas formed columnar muscle bundles approximately 1.0–1.5 mm in diameter, and they continued from the longitudinal muscle bundles of the rectum. The columnar muscle bundles of the longitudinal anal muscle were internally and externally surrounded by sparsely arranged smooth muscle fibers that ran longitudinally. The coexistence of dense and sparse areas of smooth muscle fibers suggests that the structure of the smooth muscle is optimized for its function. This histological nature is probably reflected in the magnetic resonance image of the longitudinal muscle as the coexistence of low- and high-intensity areas. Clin. Anat. 33:619–626, 2020. © 2019 Wiley Periodicals, Inc.     

Research on Split Augmented Largrangian Shrinkage Algorithm in Magnetic Resonance Imaging Based on Compressed Sensing

This paper aims to meet the requirements of reducing the scanning time of magnetic resonance imaging （MRI）, accelerating MRI and reconstructing a high quality image from less acquisition data as much as possible. MRI method based on compressed sensing （CS） with multiple regularizations （two regularizations including total variation （TV） norm and L1 norm or three regularizations consisting of total variation, L1 norm and wavelet tree structure） is proposed in this paper, which is implemented by applying split augmented lagrangian shrinkage algorithm （SALSA）. To solve magnetic resonance image reconstruction problems with linear combinations of total variation and L1 norm, we utilized composite spht denoising （CSD） to split the original complex problem into TV norm and L1 norm regularization subproblems which were simple and easy to be solved respectively in this paper. The reconstructed image was obtained from the weighted average of solutions from two subprohlems in an iterative framework. Because each of the splitted subproblems can be regarded as MRI model based on CS with single regularization, and for solving the kind of model, split augmented lagrange algorithm has advantage over existing fast algorithm such as fast iterative shrinkage thresholding（FIST） and two step iterative shrinkage thresholding （TWIST） in convergence speed. Therefore, we proposed to adopt SALSA to solve the subproblems. Moreover, in order to solve magnetic resonance image reconstruction problems with linear combinations of total variation, L1 norm and wavelet tree structure, we can split the original problem into three subproblems in the same manner, which can be processed by existing iteration scheme. A great deal of experimental results show that the proposed methods can effectively reconstruct the original image. Compared with existing algorithms such as TVCMRI, RecPF, CSA, FCSA and WaTMRI, the proposed methods have greatly improved the quality of the reconstructed images and have better visual effect.     

功能性磁共振成像在轻度认知障碍检测诊断的研究综述

现代社会中,阿尔茨海默病已经成为严重影响和限制个人日常生活甚至危及患者生命安全的一种疾病.轻度认知障碍作为阿尔茨海默病的前一个阶段,对其精确诊断有助于干预或降低患者转化为阿尔茨海默病的几率.目前,功能磁共振成像技术已经广泛应用于轻度认知障碍的检测诊断研究中.从特征提取、特征选择、数据降维和分类识别等方面,对fMRI在M...     

基于磁共振图像的帕金森病计算机辅助诊断研究进展

近年来,由于帕金森病(PD)的临床复杂性与多模态磁共振(MR)图像的高维性,如何有效挖掘图像中特异性标记PD的影像生物标志物、建立高效的PD计算机辅助诊断(CAD)模型是研究中极具挑战性的问题。综述目前国内外研究进展,进一步分析MR多模态特征提取、特征选择、分类器模型等传统机器学习方法建立CAD模型的关键技术,并简要概述基于深度学习方法在早期PD分类诊断中的应用。指出基于多模态MR图像,采用机器学习或深度学习方法构建CAD模型,能够客观、准确地识别PD患者,对提高早期PD诊断的准确性具有很大价值和应用前景。今后研究应更深入挖掘多模态MR图像中的潜在标记PD的影像生物指标,开发更高阶的CAD模型,以辅助早期PD的临床智能诊断。     

Measurement of Signal-to-Noise and Contrast-to-Noise in the fBIRN Multicenter Imaging Study

The ability to analyze and merge data across sites, vendors, and field strengths depends on one's ability to acquire images with the same image quality including image smoothness, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). SNR can be used to compare different magnetic resonance scanners as a measure of comparability between the systems. This study looks at the SNR and CNR ratios in structural fast spin-echo T₂-weighted scans acquired in five individuals across ten sites that are part of Functional Imaging Research of Schizophrenia Testbed Biomedical Informatics Research Network (fBIRN). Different manufacturers, field strengths, gradient coils, and RF coils were used at these sites. The SNR of gray matter was fairly uniform (41.3–43.3) across scanners at 1.5 T. The higher field scanners produced images with significantly higher SNR values (44.5–108.7 at 3 T and 50.8 at 4 T). Similar results were obtained for CNR measurements between gray/white matter at 1.5 T (9.5–10.2), again increasing at higher fields (10.1–28.9 at 3 T and 10.9 at 4 T).     

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。