Semiautomatic brain region extraction: a method of parcellating brain regions from structural magnetic resonance images

Structural MR imaging has become essential to the evaluation of regional brain changes in both healthy aging and disease-related processes. Several methods have been developed to measure structure size and regional brain volumes, but many of these methods involve substantial manual tracing and/or landmark identification. We present a new technique, semiautomatic brain region extraction (SABRE), for the rapid and reliable parcellation of cortical and subcortical brain regions. We combine the SABRE parcellation with tissue compartment segmentation [NeuroImage 17 (2002) 1087] to produce measures of gray matter (GM), white matter (WM), ventricular CSF, and sulcal CSF for 26 brain regions. Because SABRE restricts user input to a few easily identified landmarks, inter-rater reliability is high for all volumes, with all coefficients between 0.91 and 0.99. To assess construct validity, we contrasted SABRE-derived volumetric data from healthy young and older adults. Results from the SABRE parcellation and tissue segmentation showed significant differences in multiple brain regions in keeping with regional atrophy described in the literature by researchers using lengthy manual tracing methods. Our findings show that SABRE is a reliable semiautomatic method for assessing regional tissue volumes that provides significant timesavings over purely manual methods, yet maintains information about individual cortical landmarks.     

Phantom-based performance evaluation: application to brain segmentation from magnetic resonance images

This paper presents a new technique for assessing the accuracy of segmentation algorithms, applied to the performance evaluation of brain editing and brain tissue segmentation algorithms for magnetic resonance images. We propose performance evaluation criteria derived from the use of the realistic digital brain phantom Brainweb. This 'ground truth' allows us to build distance-based discrepancy features between the edited brain or the segmented brain tissues (such as cerebro-spinal fluid, grey matter and white matter) and the phantom model, taken as a reference. Furthermore, segmentation errors can be spatially determined, and ranged in terms of their distance to the reference. The brain editing method used is the combination of two segmentation techniques. The first is based on binary mathematical morphology and a region growing approach. It represents the initialization step, the results of which are then refined with the second method, using an active contour model. The brain tissue segmentation used is based on a Markov random field model. Segmentation results are shown on the phantom for each method, and on real magnetic resonance images for the editing step; performance is evaluated by the new distance-based technique and corroborates the effective refinement of the segmentation using active contours. The criteria described here can supersede biased visual inspection in order to compare, evaluate and validate any segmentation algorithm. Moreover, provided a 'ground truth' is given, we are able to determine quantitatively to what extent a segmentation algorithm is sensitive to internal parameters, noise, artefacts or distortions.     

Normal brain anatomy on magnetic resonance imaging

The exquisite detail provided by brain magnetic resonance imaging scans can make interpretation simultaneously straightforward and complicated, particularly to the novice. For this reason, it is essential to become familiar with normal structures before describing the pathologic condition. This article serves as a practical reference point to further enhance knowledge of the intracranial anatomy.     

Graph-partitioned spatial priors for functional magnetic resonance images

Spatial models of functional magnetic resonance imaging (fMRI) data allow one to estimate the spatial smoothness of general linear model (GLM) parameters and eschew pre-process smoothing of data entailed by conventional mass-univariate analyses. Recently diffusion-based spatial priors [Harrison, L.M., Penny, W., Daunizeau, J., and Friston, K.J. (2008). Diffusion-based spatial priors for functional magnetic resonance images. NeuroImage.] were proposed, which provide a way to formulate an adaptive spatial basis, where the diffusion kernel of a weighted graph-Laplacian (WGL) is used as the prior covariance matrix over GLM parameters. An advantage of these is that they can be used to relax the assumption of isotropy and stationarity implicit in smoothing data with a fixed Gaussian kernel. The limitation of diffusion-based models is purely computational, due to the large number of voxels in a brain volume. One solution is to partition a brain volume into slices, using a spatial model for each slice. This reduces computational burden by approximating the full WGL with a block diagonal form, where each block can be analysed separately. While fMRI data are collected in slices, the functional structures exhibiting spatial coherence and continuity are generally three-dimensional, calling for a more informed partition. We address this using the graph-Laplacian to divide a brain volume into sub-graphs, whose shape can be arbitrary. Their shape depends crucially on edge weights of the graph, which can be based on the Euclidean distance between voxels (isotropic) or on GLM parameters (anisotropic) encoding functional responses. The result is an approximation the full WGL that retains its 3D form and also has potential for parallelism. We applied the method to high-resolution (1 mm³) fMRI data and compared models where a volume was divided into either slices or graph-partitions. Models were optimized using Expectation-Maximization and the approximate log-evidence computed to compare these different ways to partition a spatial prior. The high-resolution fMRI data presented here had greatest evidence for the graph partitioned anisotropic model, which was best able to preserve fine functional detail.     

A case of necrotizing fasciitis caused by coagulase-negative staphylococcus: utility of magnetic resonance imaging for the preoperative diagnosis of necrotizing fasciitis

A 70-year-old woman presented with fever and pain in the right lower extremity. Fat-suppressed gadolinium-enhanced T1-weighted magnetic resonance imaging (MRI) showed contrast-enhanced fascia, fluid accumulation, and hypointense signals in the muscles. Surgical interventions including incisions and insertion of drainage tubes were performed on the basis of the MRI findings. The histopathological examinations of surgically obtained biopsy specimens demonstrated suppurative fasciitis, widespread myonecrosis, and thromboses of the vessels, all of which were compatible with a diagnosis of necrotizing fasciitis. The bacterial cultures were positive for a coagulase-negative staphylococcus. Following the surgical interventions, the patient was successfully treated by aggressive antimicrobial therapy. MRI can thus be useful for differentiating necrotizing fasciitis from nonnecrotizing soft tissue infection and for planning the treatment of necrotizing fasciitis.     

The value of intraoperative ultrasound during hepatic resection compared with improved preoperative magnetic resonance imaging

BACKGROUND: Patients with colorectal metastases confined to the liver may be cured by resection. Combined bimanual palpation and intraoperative ultrasound (IOUS) augment the detection of colorectal hepatic metastases. The importance of IOUS in the surgical management of hepatic tumors has been demonstrated and should arguably be considered the final diagnostic procedure. OBJECTIVE: To determine the relevance of routine IOUS prior to hepatic resection compared with improved preoperative Magnetic resonance imaging (MRI). PATIENTS AND METHODS: Eighty patients with metastatic colorectal adenocarcinoma underwent hepatic resection between 1998 and 2001. The IOUS results were compared with preoperative MRI, bimanual palpation, and resection histopathology. The preoperative surgical plan was compared with the surgical procedure performed. Data were retrospectively analyzed. RESULTS: IOUS provided additional useful information not available preoperatively for 37 (47%) patients, including the identification of subcentimetre metastatic lesions, characterization of the lesion, and the anatomy of the hepatic vasculature. The preoperative surgical plan was changed secondary to the IOUS findings alone in 14/80 (18%) patients. IOUS did not provide any additional useful information for 43 (53%) patients. A correlation was demonstrated between the preoperative diagnosis, intraoperative findings, and resection histopathology. CONCLUSION: Accurate diagnostic studies facilitate critically decisive actions during planned hepatic resection(s). The current findings suggest that IOUS provide the most useful additional information for hepatic lesions, despite recent improvements in preoperative MRI scanning. Furthermore, routine IOUS should be employed during hepatic resection for colorectal metastases.     

胰腺分裂的磁共振胰胆管成像诊断

目的：总结磁共振胰胆管成像(MRCP)对胰腺分裂的诊断价值和影像表现。方法：回顾108例行MRCP病例，分析总结胰腺分裂MRCP的表现。结果：108例中12例(11．1％)诊断为胰腺分裂，包括5例不完全性胰腺分裂。其中1例因胰腺分裂合并有反复发作性腹痛，1例合并慢性胰腺炎胰管结石。结论：作为一种无创伤性检查，MRCP对胰腺分裂可作出明确诊断，对胰腺分裂合并不明原因反复发作性腹痛或急性胰腺炎反复发作病例的治疗有指导意义一     

碘油在磁共振上信号特点的探讨

目的探讨碘油在磁共振上信号特点。方法收集2例肝癌插管化疗栓塞（TACE）患者，于0．5T的MR仪行常规腹部磁共振检查，包括SE序列T1WI、T2WI。制备样品：碘油样品取作肝栓塞剂的碘化油，并各取12ml的蒸馏水、泛影葡胺、碘海醇、碘（分析纯）、大豆色拉油、菜子油、血清置试管内作为对照。将试管顺序排列，于0．5T的MR仪进行多参数扫描；同时，将各制备品试管置于随机选取的常规扫描者体侧，获得试管与身体组织共同扫描图象，计算SNR值进行对比。结果在不同的磁场强度中碘油产生的信号强度不同，但可以通过调整扫描参数使信号强度趋于一致。碘油在体外SE序列T1WI上呈高信号，T2WI上低信号。体内成像的表现与周围环境的信号对比有关，在与正常肝脏对比中均为低信号。碘在MRI各个序列上均不成像，并且影响其他物质的碘油的信号强度低于油脂的信号强度。自旋回波长TR多回波的图像上信号强度SNR，TE30=6．3、TE60=2．8，TE90=1．6。结论可以用在自旋回波长TR多回波的图像来区分碘油，判断碘油的沉积情况，同时显示残存肿瘤的信号。     

脑胶质瘤分级诊断的磁共振研究新进展

脑胶质瘤是较为常见的中枢神经系统肿瘤,表现为向外浸润性生长,具有侵袭性且容易复发,目前手术切除仍是该病的主要治疗手段,脑胶质瘤的早期诊断及分级对治疗方案的制定及预后具有重要意义。随着影像技术的发展,磁共振成像技术在脑胶质瘤的分级诊断中发挥着越来越重要的作用。作者就几项磁共振新技术在脑胶质瘤分级诊断中的应用予以综述。     

Gd2O3 nanoparticles: size‐dependent nuclear magnetic resonance

In this communication, we demonstrate that there is an optimum gadolinium oxide (Gd₂O₃) nanoparticle size of 2.3 nm; in the presence of Gd₂O₃ particles smaller and larger than this critical size, the spin‐lattice relaxation rate (T₁ = 1/r₁) of water protons at 7.0 T drastically decreases. Since r₁ is directly related to the quality of magnetic resonance imaging, the results presented here have significant implications for clinical diagnostics. Copyright © 2012 John Wiley & Sons, Ltd.     

磁共振质子波谱无创性分析活体情况下阿尔茨海默 病人脑组织生化代谢改变

目的用磁共振质子波谱(MRS)的方法研究Alzheimer病(Alzheimerdisease,AD)内侧颞叶代谢的改变,试图为临床诊提供客观依据。方法对15例AD病人和15例正常老年人的内侧颞叶进行磁共振质子波谱(MRS)(采用STEAM序列)采集。并对代谢产物的变化与临床简易精神测量评分(MMSE)之间和与海马结构体积测量值之间进行相关性分析。结果AD病人NAA/Cr的降低与MMSE评分和海马体积呈正相关,mI/Cr的升高与MMSE评分和海马体积改变呈负相关。结论MRS能无创性检查AD脑部的代谢变化,1H-MRS所显示的AD的NAA降低和mI升高能提高中早期AD的诊断正确率。     

基于磁共振弹性成像技术的肝纤维化分级方案

目的 探讨一种基于磁共振弹性成像技术的肝纤维化分级方案.方法 在介绍磁共振弹性成像原理和生物力学模型的基础上,讨论肝脏磁共振弹性成像需要考虑的关键技术和细节.结果 给出了具体可行的研究方案与实验步骤.结论 研究方案与实验步骤具有可操作性,动物体模预临床研究可弥补临床难以获取整个纤维化程度的缺陷.     

Dendritic PARACEST contrast agents for magnetic resonance imaging

MRI contrast agents based on chemical exchange‐dependent saturation transfer (CEST), such as Yb(III)DOTAM complexes, are highly suitable for pH mapping. In this paper, the synthesis of Yb(III)DOTAM‐functionalized poly(propylene imine) dendrimers is described. The applicability of these dendritic PARACEST MRI agents for pH mapping has been evaluated on a 7 T NMR spectrometer and on a 3 T clinical MRI scanner. As expected, based on the different numbers of exchangeable amide protons, the lowest detectable concentration of the first and third generation dendritic PARACEST agents is by a respective factor of about 4 and 16 lower than that of a mononuclear reference complex. The pH dependence of the CEST effect observed for these compounds depends on the generation of the poly(propylene imine) dendrimer. Upon going to higher generations of the Yb(III)DOTAM‐terminated dendrimer, a shift of the maximum CEST effect towards lower pH values was observed. This allows for a fine‐tuning of the responsive pH region by varying the dendritic framework. Copyright © 2007 John Wiley & Sons, Ltd.     

核磁共振技术在心肺复苏中对脑功能的评价及应用

心搏骤停心肺复苏成功后脑功能的恢复,以及对患者预后的评价已经成为临床医务人员越来越关注的问题.在评价复苏成功后各种治疗措施的疗效和患者的预后方面,核磁共振技术以其独特的优势,为研究提供重要帮助.     

基底节区常见肿块样病变的MRI诊断

目的探讨基底节区常见肿瘤的临床和MRI特点。方法回顾分析2012年1月~2015年10月之间经病理证实的基底节区肿块性病变的临床、病理和影像资料,观察病变的影像特点及差异。结果基底节区病变常见囊性变,以胶质瘤和生殖细胞肿瘤多见,脂肪信号仅见于生殖细胞肿瘤;生殖细胞肿瘤水肿程度较轻,低级别胶质瘤和胶质母细胞瘤更明显;出血多见于胶质母细胞瘤和生殖细胞肿瘤;低级别胶质瘤多表现为轻、中度强化,胶质母细胞瘤和淋巴瘤多表现为明显强化。结论基底节区肿块样病变在影像表现各征象上有一定差别,可以为鉴别诊断提供帮助。     

椎基底动脉供血不足患者的椎动脉MRA表现

目的探讨椎基底动脉供血不足患者核磁共振血管成像( MRA)的表现及临床诊断价值.方法 97例患者中女性 63例,男性 34例.年龄 34～ 79岁,平均 50.78岁.分别进行椎动脉 MRA及 TCD检查.符合椎基底动脉供血不足诊断标准.结果 97例患者中椎动脉 MRA异常 61例 (占 62.88% ), TCD异常 83例 (占 85.56% ).结论椎动脉本身退变因素导致椎基底动脉供血不足是一个主要因素.     

丘脑底核磁共振成像技术研究进展

丘脑底核(subthalamic nucleus,STN)是我国帕金森病患者接受脑深部电刺激(deep brain stimulation,DBS)治疗的主要核团。磁共振(MRI)影像个体化、精确植入电极至STN的感觉运动部要求MRI成像对STN边界清晰划分,并确保图像保真。目前使用的MRI序列可分为3大类:基于自旋回波序列的T_2加权成像、反转恢复序列、扩散张量成像、各向异性分数;基于磁化转移技术的磁敏感加权成像、自由衰减的T_2*成像等;基于磁敏感图像重建技术的定量磁敏感图谱。其中,定量磁敏感图谱的STN与周边的信噪比最优、边界最清晰,T_2*技术次之;T_2加权成像在患者戴框架时几何精度较高,适合戴框架直接定位使用。     

基于多尺度多模态磁共振图像的直方图特征在脑胶质瘤分级上的应用

目的  提出一种基于多尺度多模态磁共振图像的直方图特征,并采用机器学习的方法进行脑胶质瘤的分级应用。方法  收集临床60例脑胶质瘤病例,其中Ⅱ级胶质瘤弥漫型星形细胞瘤和少突胶质细胞瘤22例,Ⅲ级胶质瘤间变型少突星形细胞瘤和间变星形细胞瘤18例,Ⅳ级胶质瘤胶质母细胞瘤例20例。病例图像信息包含平扫T2加权序列、T2加权压水压脂序列以及增强后的T1序列。对3种序列图像做多尺度化处理,对多尺度化后的图像做纹理分析,以病灶核心区域为感兴趣区,计算纹理参数,探究纹理参数与脑胶质瘤的内在关联含义,行Ⅱ级与Ⅲ级间纹理参数的ROC曲线分析,以及Ⅲ级与Ⅳ级间纹理参数的ROC曲线分析。以支持向量机作为机器学习核心,通过交叉验证法,得出本文纹理分析方法在不同级别胶质瘤的分级上的准确度和整体分级准确度。结果  多尺度多模态磁共振图像直方图特征结合支持向量机模型的鉴别系统在Ⅱ级和Ⅲ级脑胶质瘤间总体参数准确率为91.5%,在Ⅲ级和Ⅳ级脑胶质瘤间的总体参数准确率为97.9%。整体的三分类支持向量机模型在交叉验证法的分级准确率为91.67%。结论  多尺度多模态磁共振图像的直方图特征结合支持向量机模型的鉴别系统,可以在脑胶质瘤肿瘤分级上为临床提供重要信息。     

Management of branch duct-type intraductal papillary mucinous tumor of the pancreas based on magnetic resonance imaging

Background: We assessed the usefulness of magnetic resonance imaging (MRI) in identifying nonmalignant intraductal papillary mucinous tumors (IPMTs) of the pancreas.Methods: Thirty-three patients with branch duct-type IPMT diagnosed by endoscopic retrograde cholangiopancreatography were prospectively examined with magnetic resonance cholangiopancreatography followed by dynamic gadolinium-enhanced MRI examinations, and patients with no findings suggestive of malignancy, including a solid mass, mural nodules, a main pancreatic duct wider than 5 mm in diameter, and stenosis of the main pancreatic duct, were prospectively followed up with sequential MRI examinations once or twice a year.Results: Twenty-six (79%) patients showed no findings suggestive of malignancy in the initial MRI examination. The diameter (mean ± standard error) of the main pancreatic duct was 3.9 ± 0.7 mm and that of the ectatic branch pancreatic duct was 36.0 ± 9.1 mm. Twenty-three patients were prospectively followed for more than 36 months and 22 of them showed no findings suggestive of malignancy during follow-up periods ranging from 39 to 77 months (mean = 55 months).Conclusion: MRI was useful to identify nonmalignant IPMTs of the branch duct type, and close follow-up observation with serial MRI examinations may be appropriate in the management of such patients.