中耳胆脂瘤的影像诊断:高分辨率计算机断层成像与磁共振成像的比较研究

目的:评估和比较高分辨率计算机断层成像(high resolution computer tomography,HRCT)与磁共振成像(magnetic resonance imaging,MRI)对中耳胆脂瘤的诊断价值。方法:回顾性分析临床初步诊断为中耳胆脂瘤患者55人(63耳)在术前5天内进行的16排HRCT和1.5T MRI诊断结果,以病理诊断为基础对HRCT和MRI的诊断结果进行对比研究,统计分析HRCT和MRI的灵敏度、特异度、阳性预期值、阴性预期值,以及Kappa检验两者之间的内在观察一致性。结果:63耳中,病理确诊为中耳胆脂瘤40耳。HRCT正确诊断30例,假阳性11例,假阴性10例,灵敏度、特异度、阳性预期值以及阴性预期值分别为75%、52.17%、73.17%、54.55%。MRI正确诊断37例,假阳性和假阴性各为3例,灵敏度、特异度、阳性预期值以及阴性预期值分别为92.5%、86.96%、75%和86.96%。HRCT与MRI诊断结果之间的内在观察一致性Kappa=0.274(P0.05)。剔除既往有手术史的10耳,只针对无手术史的53耳,HRCT与MRI诊断结果之间的内在观察一致性增高,吻合度一般,Kappa=0.462(P0.05)。结论:MRI的总体阳性检出率高于HRCT,尤其是对中耳胆脂瘤手术后复发的诊断;HRCT与MRI两者相结合对于中耳胆脂瘤的明确诊断具有互补作用。     

SD大鼠磁共振成像技术

目的：在常规磁共振成像仪（magnetic resonance imaging,MRI）上进行小型动物实验,探讨SD大鼠MRI最佳成像参数,为小型动物影像学实验研究提供参考.方法：采用西门子1.5T超导MR成像仪（Siemens Sonata, Erlangen, Germany）,膝关节专用线圈.选取雄性SD大鼠41只,体重250～400g,分5组依次进行T1加权（T1WI）、T2加权（T2WI）及质子密度加权成像,并比较5组参数成像的图像质量,确立Siemens Sonata 1.5T超导MR成像仪应用于大鼠的最佳成像参数.结果：T1WI采用SE序列、T2WI及质子密度加权采用TSE序列;T1WI、T2WI及质子密度加权的最佳成像参数分别为TR 350 ms/TE 12 ms、TR 2500 ms/TE 75 ms和TR 3000 ms/TE 15 ms.在MRI成像相关参数中,重复时间（TR）、回波时间（TE）主要影响对比度,决定权重;扫描野（FOV）、矩阵（Matrix）主要影响空间分辨率;层厚、激励次数（Nex）、带宽（Bandwidth）主要影响信噪比.结论：在常规MRI上进行小型动物实验切实可行,通过综合调节相应参数,不仅可以发现肝脏病变,证实了肝癌模型的成功建立,而且可以获得较理想的图像质量.     

磁共振成像设备发展趋势

本文主要叙述了磁共振设备的原理、构造、产品发展趋势。并对提高磁共振图像分辨的新技术,如Tim全景矩阵成像、自由浪潮技术、高清晰MRI技术和双梯度技术作了综述。     

High Dynamic Range Processing for Magnetic Resonance Imaging

Purpose

To minimize feature loss in T₁- and T₂-weighted MRI by merging multiple MR images acquired at different T_R and T_E to generate an image with increased dynamic range.

Materials and Methods

High Dynamic Range (HDR) processing techniques from the field of photography were applied to a series of acquired MR images. Specifically, a method to parameterize the algorithm for MRI data was developed and tested. T₁- and T₂-weighted images of a number of contrast agent phantoms and a live mouse were acquired with varying T_R and T_E parameters. The images were computationally merged to produce HDR-MR images. All acquisitions were performed on a 7.05 T Bruker PharmaScan with a multi-echo spin echo pulse sequence.

Results

HDR-MRI delineated bright and dark features that were either saturated or indistinguishable from background in standard T₁- and T₂-weighted MRI. The increased dynamic range preserved intensity gradation over a larger range of T₁ and T₂ in phantoms and revealed more anatomical features in vivo.

Conclusions

We have developed and tested a method to apply HDR processing to MR images. The increased dynamic range of HDR-MR images as compared to standard T₁- and T₂-weighted images minimizes feature loss caused by magnetization recovery or low SNR.     

Diffusion Tensor Magnetic Resonance Imaging of the Pancreas

Purpose

To develop a diffusion-tensor-imaging (DTI) protocol that is sensitive to the complex diffusion and perfusion properties of the healthy and malignant pancreas tissues.

Materials and Methods

Twenty-eight healthy volunteers and nine patients with pancreatic-ductal-adenocacinoma (PDAC), were scanned at 3T with T2-weighted and DTI sequences. Healthy volunteers were also scanned with multi-b diffusion-weighted-imaging (DWI), whereas a standard clinical protocol complemented the PDAC patients’ scans. Image processing at pixel resolution yielded parametric maps of three directional diffusion coefficients λ1, λ2, λ3, apparent diffusion coefficient (ADC), and fractional anisotropy (FA), as well as a λ1-vector map, and a main diffusion-direction map.

Results

DTI measurements of healthy pancreatic tissue at b-values 0,500 s/mm²yielded: λ1 = (2.65±0.35)×10⁻³, λ2 = (1.87±0.22)×10⁻³, λ3 = (1.20±0.18)×10⁻³, ADC = (1.91±0.22)×10⁻³ (all in mm²/s units) and FA = 0.38±0.06. Using b-values of 100,500 s/mm² led to a significant reduction in λ1, λ2, λ3 and ADC (p<.0001) and a significant increase (p<0.0001) in FA. The reduction in the diffusion coefficients suggested a contribution of a fast intra-voxel-incoherent-motion (IVIM) component at b≤100 s/mm², which was confirmed by the multi-b DWI results. In PDACs, λ1, λ2, λ3 and ADC in both 0,500 s/mm² and 100,500 s/mm² b-values sets, as well as the reduction in these diffusion coefficients between the two sets, were significantly lower in comparison to the distal normal pancreatic tissue, suggesting higher cellularity and diminution of the fast-IVIM component in the cancer tissue.

Conclusion

DTI using two reference b-values 0 and 100 s/mm² enabled characterization of the water diffusion and anisotropy of the healthy pancreas, taking into account a contribution of IVIM. The reduction in the diffusion coefficients of PDAC, as compared to normal pancreatic tissue, and the smaller change in these coefficients in PDAC when the reference b-value was modified from 0 to 100 s/mm², helped identifying the presence of malignancy.     

Magnetic Resonance Imaging Interpretation in Patients with Sciatica Who Are Potential Candidates for Lumbar Disc Surgery

Background

Magnetic Resonance Imaging (MRI) is considered the mainstay imaging investigation in patients suspected of lumbar disc herniations. Both imaging and clinical findings determine the final decision of surgery. The objective of this study was to assess MRI observer variation in patients with sciatica who are potential candidates for lumbar disc surgery.

Methods

Patients for this study were potential candidates (n = 395) for lumbar disc surgery who underwent MRI to assess eligibility for a randomized trial. Two neuroradiologists and one neurosurgeon independently evaluated all MRIs. A four point scale was used for both probability of disc herniation and root compression, ranging from definitely present to definitely absent. Multiple characteristics of the degenerated disc herniation were scored. For inter-agreement analysis absolute agreements and kappa coefficients were used. Kappa coefficients were categorized as poor (<0.00), slight (0.00–0.20), fair (0.21–0.40), moderate (0.41–0.60), substantial (0.61–0.80) and excellent (0.81–1.00) agreement.

Results

Excellent agreement was found on the affected disc level (kappa range 0.81–0.86) and the nerve root that most likely caused the sciatic symptoms (kappa range 0.86–0.89). Interobserver agreement was moderate to substantial for the probability of disc herniation (kappa range 0.57–0.77) and the probability of nerve root compression (kappa range 0.42–0.69). Absolute pairwise agreement among the readers ranged from 90–94% regarding the question whether the probability of disc herniation on MRI was above or below 50%. Generally, moderate agreement was observed regarding the characteristics of the symptomatic disc level and of the herniated disc.

Conclusion

The observer variation of MRI interpretation in potential candidates for lumbar disc surgery is satisfactory regarding characteristics most important in decision for surgery. However, there is considerable variation between observers in specific characteristics of the symptomatic disc level and herniated disc.     

Fetal Eye Movements on Magnetic Resonance Imaging

Objectives

Eye movements are the physical expression of upper fetal brainstem function. Our aim was to identify and differentiate specific types of fetal eye movement patterns using dynamic MRI sequences. Their occurrence as well as the presence of conjugated eyeball motion and consistently parallel eyeball position was systematically analyzed.

Methods

Dynamic SSFP sequences were acquired in 72 singleton fetuses (17–40 GW, three age groups [17–23 GW, 24–32 GW, 33–40 GW]). Fetal eye movements were evaluated according to a modified classification originally published by Birnholz (1981): Type 0: no eye movements; Type I: single transient deviations; Type Ia: fast deviation, slower reposition; Type Ib: fast deviation, fast reposition; Type II: single prolonged eye movements; Type III: complex sequences; and Type IV: nystagmoid.

Results

In 95.8% of fetuses, the evaluation of eye movements was possible using MRI, with a mean acquisition time of 70 seconds. Due to head motion, 4.2% of the fetuses and 20.1% of all dynamic SSFP sequences were excluded.Eye movements were observed in 45 fetuses (65.2%). Significant differences between the age groups were found for Type I (p = 0.03), Type Ia (p = 0.031), and Type IV eye movements (p = 0.033). Consistently parallel bulbs were found in 27.3–45%.

Conclusions

In human fetuses, different eye movement patterns can be identified and described by MRI in utero. In addition to the originally classified eye movement patterns, a novel subtype has been observed, which apparently characterizes an important step in fetal brainstem development. We evaluated, for the first time, eyeball position in fetuses. Ultimately, the assessment of fetal eye movements by MRI yields the potential to identify early signs of brainstem dysfunction, as encountered in brain malformations such as Chiari II or molar tooth malformations.     

核磁功能成像在前列腺癌诊断中的应用

磁共振成像是诊断早期前列腺癌及评价分期最好的影像学技术之一,然而常规MRI-T2WI在诊断中存在较低的特异性缺陷.随着核磁技术的发展,对前列腺癌的诊断发展到从定性到定量、从形态到功能的变化,本文主要就近年来的磁共振功能成像技术在前列腺癌诊断中的研究进展作一论述.     

脑功能磁共振成像的研究现状

脑功能磁共振成像是近年来磁共振成像技术的一项新发展,为从单一形态学研究到形态与功能相结合的系统研究开辟了一条崭新的道路。本文主要介绍了人脑的功能活动磁共振成像的概念、原理、试验设计、临床的研究现状。     

Multi-Parametric Representation of Voxel-Based Quantitative Magnetic Resonance Imaging

The aim of the study was to explore the possibilities of multi-parametric representations of voxel-wise quantitative MRI data to objectively discriminate pathological cerebral tissue in patients with brain disorders. For this purpose, we recruited 19 patients with Multiple Sclerosis (MS) as benchmark samples and 19 age and gender matched healthy subjects as a reference group. The subjects were examined using quantitative Magnetic Resonance Imaging (MRI) measuring the tissue structure parameters: relaxation rates, R and R, and proton density. The resulting parameter images were normalized to a standard template. Tissue structure in MS patients was assessed by voxel-wise comparisons with the reference group and with correlation to a clinical measure, the Expanded Disability Status Scale (EDSS). The results were visualized by conventional geometric representations and also by multi-parametric representations. Data showed that MS patients had lower R and R, and higher proton density in periventricular white matter and in wide-spread areas encompassing central and sub-cortical white matter structures. MS-related tissue abnormality was highlighted in posterior white matter whereas EDSS correlation appeared especially in the frontal cortex. The multi-parameter representation highlighted disease-specific features. In conclusion, the proposed method has the potential to visualize both high-probability focal anomalies and diffuse tissue changes. Results from voxel-based statistical analysis, as exemplified in the present work, may guide radiologists where in the image to inspect for signs of disease. Future clinical studies must validate the usability of the method in clinical practice.     

Radiology: Magnetic Resonance Imaging of Musculoskeletal Tumors

The Scientific Board of the California Medical Association presents the following inventory of items of progress in radiology. Each item, in the judgment of a panel of knowledgeable physicians, has recently become reasonably firmly established, both as to scientific fact and important clinical significance. The items are presented in simple epitome, and an authoritative reference, both to the item itself and to the subject as a whole, is generally given for those who may be unfamiliar with a particular item. The purpose is to assist busy practitioners, students, researchers, or scholars to stay abreast of these items of progress in radiology that have recently achieved a substantial degree of authoritative acceptance. Whether in their own field of special interest or another.The items of progress listed below were selected by the Advisory Panel to the Section on Radiology of the California Medical Association, and the summaries were prepared under its direction.     

产前胎儿磁共振成像的临床应用及研究进展

出生缺陷已经成为影响我国人口素质的重要卫生问题,产前诊断是减少患儿出生缺陷的有效预防手段和措施。作为产前超声诊断重要补充的手段,胎儿MRI检查具有多方位、多参数、高质量、大视野成像的特点。尤其在中枢神经系统方面具有US无法比拟的优势,随着宫内治疗技术的开展和提高,其潜在的价值和应用前景越来越明显。近年来,随着各种快速MR成像方法的应用,胎儿MRI研究有了很大进步,不仅能有效地评估胎儿的正常解剖、发育变异及病理改变,而且功能MRI也正积极尝试用于胎儿正常发育及疾病的研究中。正硝地解释胎儿MRI的影像学表现仍是今后一段时间内胎儿MRI研究的方向。客观地认识MRI在产前检查中的优势与劣势、合理地应用不同的成像序列,有利于更准确地检出病变。     

Semi-automatic Method for Low-Grade Gliomas Segmentation in Magnetic Resonance Imaging

Background: Analyzing MR scans of low-grade glioma, with highly accurate segmentation will have an enormous potential in neurosurgery for diagnosis and therapy planning. Low-grade gliomas are mainly distinguished by their infiltrating character and irregular contours, which make the analysis, and therefore the segmentation task, more difficult. Moreover, MRI images show some constraints such as intensity variation and the presence of noise.Methods: To tackle these issues, a novel segmentation method built from the local properties of image is presented in this paper. Phase-based edge detection is estimated locally by the monogenic signal using quadrature filters. This way of detecting edges is, from a theoretical point of view, intensity invariant and responds well to the MR images. To strengthen the tumor detection process, a region-based term is designated locally in order to achieve a local maximum likelihood segmentation of the region of interest. A Gaussian probability distribution is considered to model local images intensities.Results: The proposed model is evaluated using a set of real subjects and synthetic images derived from the Brain Tumor Segmentation challenge –BraTS 2015. In addition, the obtained results are compared to the manual segmentation performed by two experts. Quantitative evaluations are performed using the proposed approach with regard to four related existing methods.Conclusion: The comparison of the proposed method, shows more accurate results than the four existing methods.     

Magnetic Resonance Imaging of Cerebral Aspergillosis: Imaging and Pathological Correlations

Cerebral aspergillosis is associated with a significant morbidity and mortality rate. The imaging data present different patterns and no full consensus exists on typical imaging characteristics of the cerebral lesions. We reviewed MRI findings in 21 patients with cerebral aspergillosis and correlated them to the immune status of the patients and to neuropathological findings when tissue was available. The lesions were characterized by their number, topography, and MRI signal. Dissemination to the brain resulted from direct spread from paranasal sinuses in 8 patients, 6 of them being immunocompetent. Hematogenous dissemination was observed in 13 patients, all were immunosuppressed. In this later group we identified a total of 329 parenchymal abscesses involving the whole brain with a predilection for the corticomedullary junction. More than half the patients had a corpus callosum lesion. Hemorrhagic lesions accounted for 13% and contrast enhancement was observed in 61% of the lesions. Patients with hematogenous dissemination were younger (p = 0.003), had more intracranial lesions (p = 0.0004) and had a higher 12-week mortality rate (p = 0.046) than patients with direct spread from paranasal sinuses. Analysis of 12 aneurysms allowed us to highlight two distinct situations. In case of direct spread from the paranasal sinuses, aneurysms are saccular and located on the proximal artery portions, while the hematogenous dissemination in immunocompromised patients is more frequently associated with distal and fusiform aneurysms. MRI is the exam of choice for cerebral aspergillosis. Number and type of lesions are different according to the mode of dissemination of the infection.     

Bayesian Spatiotemporal Inference in Functional Magnetic Resonance Imaging

Mapping of the human brain by means of functional magnetic resonance imaging (fMRI) is an emerging field in cognitive and clinical neuroscience. Current techniques to detect activated areas of the brain mostly proceed in two steps. First, conventional methods of correlation, regression, and time series analysis are used to assess activation by a separate, pixelwise comparison of the fMRI signal time courses to the reference function of a presented stimulus. Spatial aspects caused by correlations between neighboring pixels are considered in a separate second step, if at all. The aim of this article is to present hierarchical Bayesian approaches that allow one to simultaneously incorporate temporal and spatial dependencies between pixels directly in the model formulation. For reasons of computational feasibility, models have to be comparatively parsimonious, without oversimplifying. We introduce parametric and semiparametric spatial and spatiotemporal models that proved appropriate and illustrate their performance applied to visual fMRI data.     

Diaphragm Postural Function Analysis Using Magnetic Resonance Imaging

We present a postural analysis of diaphragm function using magnetic resonance imaging (MRI). The main aim of the study was to identify changes in diaphragm motion and shape when postural demands on the body were increased (loading applied to a distal part of the extended lower extremities against the flexion of the hips was used). Sixteen healthy subjects were compared with 17 subjects suffering from chronic low back pain and in whom structural spine disorders had been identified. Two sets of features were calculated from MRI recordings: dynamic parameters reflecting diaphragm action, and static parameters reflecting diaphragm anatomic characteristics. A statistical analysis showed that the diaphragm respiratory and postural changes were significantly slower, bigger in size and better balanced in the control group. When a load was applied to the lower limbs, the pathological subjects were mostly not able to maintain the respiratory diaphragm function, which was lowered significantly. Subjects from the control group showed more stable parameters of both respiratory and postural function. Our findings consistently affirmed worse muscle cooperation in the low back pain population subgroup. A clear relation with spinal findings and with low back pain remains undecided, but various findings in the literature were confirmed. The most important finding is the need to further address various mechanisms used by patients to compensate deep muscle insufficiency.     

Iron Oxide Nanoparticle-Micelles (ION-Micelles) for Sensitive (Molecular) Magnetic Particle Imaging and Magnetic Resonance Imaging

Background

Iron oxide nanoparticles (IONs) are a promising nanoplatform for contrast-enhanced MRI. Recently, magnetic particle imaging (MPI) was introduced as a new imaging modality, which is able to directly visualize magnetic particles and could serve as a more sensitive and quantitative alternative to MRI. However, MPI requires magnetic particles with specific magnetic properties for optimal use. Current commercially available iron oxide formulations perform suboptimal in MPI, which is triggering research into optimized synthesis strategies. Most synthesis procedures aim at size control of iron oxide nanoparticles rather than control over the magnetic properties. In this study, we report on the synthesis, characterization and application of a novel ION platform for sensitive MPI and MRI.

Methods and Results

IONs were synthesized using a thermal-decomposition method and subsequently phase-transferred by encapsulation into lipidic micelles (ION-Micelles). Next, the material and magnetic properties of the ION-Micelles were analyzed. Most notably, vibrating sample magnetometry measurements showed that the effective magnetic core size of the IONs is 16 nm. In addition, magnetic particle spectrometry (MPS) measurements were performed. MPS is essentially zero-dimensional MPI and therefore allows to probe the potential of iron oxide formulations for MPI. ION-Micelles induced up to 200 times higher signal in MPS measurements than commercially available iron oxide formulations (Endorem, Resovist and Sinerem) and thus likely allow for significantly more sensitive MPI. In addition, the potential of the ION-Micelle platform for molecular MPI and MRI was showcased by MPS and MRI measurements of fibrin-binding peptide functionalized ION-Micelles (FibPep-ION-Micelles) bound to blood clots.

Conclusions

The presented data underlines the potential of the ION-Micelle nanoplatform for sensitive (molecular) MPI and warrants further investigation of the FibPep-ION-Micelle platform for in vivo, non-invasive imaging of fibrin in preclinical disease models of thrombus-related pathologies and atherosclerosis.     

Brain Characterization Using Normalized Quantitative Magnetic Resonance Imaging

Objectives

To present a method for generating reference maps of typical brain characteristics of groups of subjects using a novel combination of rapid quantitative Magnetic Resonance Imaging (qMRI) and brain normalization. The reference maps can be used to detect significant tissue differences in patients, both locally and globally.

Materials and Methods

A rapid qMRI method was used to obtain the longitudinal relaxation rate (R₁), the transverse relaxation rate (R₂) and the proton density (PD). These three tissue properties were measured in the brains of 32 healthy subjects and in one patient diagnosed with Multiple Sclerosis (MS). The maps were normalized to a standard brain template using a linear affine registration. The differences of the mean value ofR₁, R₂ and PD of 31 healthy subjects in comparison to the oldest healthy subject and in comparison to an MS patient were calculated. Larger anatomical structures were characterized using a standard atlas. The vector sum of the normalized differences was used to show significant tissue differences.

Results

The coefficient of variation of the reference maps was high at the edges of the brain and the ventricles, moderate in the cortical grey matter and low in white matter and the deep grey matter structures. The elderly subject mainly showed significantly lower R₁ and R₂ and higher PD values along all sulci. The MS patient showed significantly lower R₁ and R₂ and higher PD values at the edges of the ventricular system as well as throughout the periventricular white matter, at the internal and external capsules and at each of the MS lesions.

Conclusion

Brain normalization of rapid qMRI is a promising new method to generate reference maps of typical brain characteristics and to automatically detect deviating tissue properties in the brain.     

直肠癌MRI研究进展

MRI是目前直肠癌诊断、分期的首选影像学方法。在判断肿瘤对邻近器官、结构的浸润程度上具有明显优势,尤其是对有较高复发风险的低位肿瘤。常规MRI尤其是高分辨MRI能够清晰显示直肠相关解剖,结合扩散加权成像(Diffusion weighted imaging,DWI)通过确定肿瘤边界,直肠系膜有无受侵,淋巴结及远处转移情况,可以准确有效的进行术前诊断、分期;DWI有助于鉴别辅助治疗后失活与存活组织、筛选出辅助治疗有效的患者,在评估治疗后疗效、提示患者预后方面发挥重要作用,也为临床制定治疗方案提供依据。同时也发现准确进行淋巴结分期、鉴别复发仍然存在困难,需要在以后进一步探讨,提高评估的准确性。本文就近年来MRI在直肠癌术前评价、术后疗效评估、复发监测及表观弥散系数(Apparent diffusion coefficient,ADC)的应用做一综述。