颈椎扩散张量成像数据处理系统构建

颈椎扩散张量成像能够清晰地反应颈髓的病变情况,已经广泛应用于临床诊断.基于对核磁共振成像数据的前处理、扩散张量成像数据的计算、感兴趣区域选取、各向异性分数和平均扩散率等临床诊断指标的计算以及扩散张量成像数据插值等问题进行研究,构建了针对颈椎扩散张量成像数据的处理系统,实现了对扩散张量数据的可视化显示和系统处理,为准确的临床诊断提供了重要参考依据,并构建了扩散张量成像的数学研究平台.     

Image restoration using total variation and anisotropic diffusion equation

This paper proposes a new model for the image restoration which combines the total variation minimization with the “pure” anisotropic diffusion equation of Alvarez and Morel. According to the introduction of new diffusion term, this model can not only remove noise but also enhance edges and keep their locality. And it can also keep textures and large-scale fine features that are not characterized by edges. Due to these favorable characteristics, the processed images turn much clearer and smoother, meanwhile, their significant details are kept, which results in appealing vision. __________ Translated from Journal of Xidian Universiy, 2006, 33(5): 759–762 [译自: 西安电子科技大学学报 (自学科学版)]     

基于ITK和VTK的脊髓扩散张量成像实现

扩散张量成像是一种新的磁共振成像技术,比传统的扩散加权成像更能够准确地反映出水分子的扩散情况.在脊髓的扩散张量成像方面的研究成果并不多,且存在很大的发展空间.提出并实现了基于ITK和VTK的脊髓图像扩散张量成像系统,其中使用ITK实现图像三维配准和扩散张量及其旋转不变量的计算等功能,使用VTK辅助完成三维图像显示,为脊...     

Echo planar magnetic resonance imaging of anisotropic diffusion in asparagus stems

MR diffusion-weighted imaging (DWI) uses the signal loss associated with the random thermal motion of water molecules in the presence of magnetic field gradients to derive a number of parameters that reflect the translational mobility of the water molecules in tissues. In highly organized but asymmetric structures, this mobility may be affected by the obstacles present and this in a direction-dependent way. Important examples of this are white brain matter and the stem of certain plants, both containing fibrous components where diffusion of water molecules across fibers is much more restricted than along the fibers. Diffusion that exhibits such directional dependence is said to be anisotropic, and diffusion tensor magnetic resonance imaging allows localized characterization of this behavior. Interpretation of the information obtained in terms of the underlying tissue structure is often hampered by the complexity of factors that can produce the observed behavior. A phantom that exhibits well-defined anisotropic diffusion and yields sufficient signal can help the experimental testing of the relevant methods and models. In this paper, we have used a phantom consisting of asparagus stems as a test object for assessing the value of the acquisition and postprocessing techniques commonly used in the clinic for this kind of investigation. Because of its strongly fibrous and cylindrically symmetric morphology, exhibiting a well-defined sub-classification of cells on the basis of size and shape, asparagus allows a relatively simple interpretation of the results obtained in the diffusion experiments. Our experiments show that the known structural information about the main cell types encountered correlates well with the behavior patterns of the diffusion parameters.     

Accelerating cardiac diffusion tensor imaging combining local low-rank and 3D TV constraint

Magnetic Resonance Materials in Physics, Biology and Medicine - Diffusion tensor magnetic resonance imaging (DT-MRI, or DTI) is a promising technique for invasively probing biological tissue...     

White and grey matter development in utero assessed using motion-corrected diffusion tensor imaging and its comparison to ex utero measures

Objective

Fetal brain diffusion tensor imaging (DTI) offers quantitative analysis of the developing brain. The objective was to 1) quantify DTI measures across gestation in a cohort of fetuses without brain abnormalities using full retrospective correction for fetal head motion 2) compare results obtained in utero to those in preterm infants.

Materials and methods

Motion-corrected DTI analysis was performed on data sets obtained at 1.5T from 32 fetuses scanned between 21.29 and 37.57 (median 31.86) weeks. Results were compared to 32 preterm infants scanned at 3T between 27.43 and 37.14 (median 33.07) weeks. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) were quantified by region of interest measurements and tractography was performed.

Results

Fetal DTI was successful in 84% of fetuses for whom there was sufficient data for DTI estimation, and at least one tract could be obtained in 25 cases. Fetal FA values increased and ADC values decreased with age at scan (PLIC FA: p = 0.001; R² = 0.469; slope = 0.011; splenium FA: p < 0.001; R² = 0.597; slope = 0.019; thalamus ADC: p = 0.001; R² = 0.420; slope = − 0.023); similar trends were found in preterm infants.

Conclusion

This study demonstrates that stable DTI is feasible on fetuses and provides evidence for normative values of diffusion properties that are consistent with aged matched preterm infants.

     

3D MRI of explanted sheep hearts with submillimeter isotropic spatial resolution: comparison between diffusion tensor and structure tensor imaging

Magnetic Resonance Materials in Physics, Biology and Medicine - The aim of the study is to&nbsp;compare structure tensor imaging (STI) with diffusion tensor imaging (DTI) of the sheep heart...     

Ultra-high field diffusion tensor imaging of articular cartilage correlated with histology and scanning electron microscopy

Object

To investigate the relationship of the different diffusion tensor imaging (DTI) parameters (ADC, FA, and first eigenvector (EV)) to the constituents (proteoglycans and collagen), the zonal arrangement of the collagen network, and mechanical loading of articular cartilage.

Material and methods

DTI of eight cartilage-on-bone samples of healthy human patellar cartilage was performed at 17.6 T. Three samples were additionally imaged under indentation loading. After DTI, samples underwent biomechanical testing, safranin-O staining for semiquantitative proteoglycan estimation, and scanning electron microscopy (SEM) for depicting collagen architecture.

Results

From the articular surface to the bone–cartilage interface, ADC continuously decreased and FA increased. Cartilage zonal heights calculated from EVs strongly correlated with SEM-derived zonal heights (P r ²=0.87). Compression reduced ADC in the superficial 30% of cartilage and increased FA in the superficial 5% of cartilage. Reorientation of the EVs indicative of collagen fiber reorientation under the indenter was observed. No significant correlation was found between ADC, FA, and compressive stiffness.

Conclusions

Correlating ADC and FA with proteoglycan and collagen content suggests that diffusion is dominated by different depth-dependent mechanisms within cartilage. Knowledge of the spatial distribution of the DTI parameters and their variation contributes to form a database for future analysis of defective cartilage.     

Distribution and fibre field similarity mapping of the human anterior commissure fibres by diffusion tensor imaging

Object

The anterior commissure is a critical interhemispheric pathway in animals, yet its connections in humans are not clearly understood. Its distribution has shown to vary greatly between species, and it is thought that in humans it may convey axons from a larger territory than previously thought. The aim was to use an anatomical mapping tool to look at the anterior commissure fibres and to compare the distribution findings with published anatomical understanding.

Materials and methods

Two different diffusion-weighted imaging data sets were acquired from eight healthy subjects using a 3 Tesla MR scanner with 32 gradient directions. Diffusion tensor imaging tractography was performed, and the anterior commissure fibres were selected using three-dimensional regions of interest. Distribution of the fibres was observed by means of registration with T2-weighted images. The fibre field similarity maps were produced for five of the eight subjects by comparing each subject’s fibres to the combined map of the five data sets.

Results

Fibres were shown to lead into the temporal lobe and towards the orbitofrontal cortex in the majority of subjects. Fibres were also distributed to the parietal or occipital lobes in all five subjects in whom the anterior commissure was large enough for interhemispheric fibres to be tracked through. The fibre field similarity maps highlighted areas where the local distances of fibre tracts were displayed for each subject compared to the combined bundle map.

Conclusion

The anterior commissure may play a more important role in interhemispheric communication than currently presumed by conveying axons from a wider territory, and the fibre field similarity maps give a novel approach to quantifying and visualising characteristics of fibre tracts.     

Deviations from the diffusion tensor model as revealed by contour plot visualization using high angular resolution diffusion-weighted imaging (HARDI)

The standard diffusion tensor model is limited in its ability to provide detailed information about multidirectional fiber architecture in human white matter. Additional directional acquisition of diffusivity properties with high angular resolution diffusion-weighted imaging (HARDI) acquisition schemes may deliver more information on areas with fiber crossings than standard DTI. However, representation of the additional information and the rating and visualization of fiber complexity is challenging. We used projection 2D-plots in combination with a HARDI acquisition scheme of 129 diffusion directions and compared the spherical diffusion variance index (SDI) with the relative anisotropy index (RAI). In normal controls, white matter areas with unidirectional fiber arrangement and areas with more complex fiber composition were identified with this approach. HARDI confirms and can visualize deviations from the tensor-like representation, thereby providing information on fiber structure complexity, which may be of considerable interest for clinical studies.     

玻璃钢／复合材料风力机叶片的开发

随着风机单机容量的增大,对风机叶片的设计、制造提出了更高的要求。由于玻璃钢/复合材料具有强度高、容易成型、耐腐蚀性能好、抗震性能较高等特点,因而目前在大型兆瓦级风机叶片制造中得到了广泛应用。介绍了国内外风机叶片的发展概况,分析了玻璃钢/复合材料风机叶片的特点,并从气动设计、结构设计、工艺设计、认证规范和产业化等方面介绍了风机叶片的开发过程。     

Assessment of diffusion tensor imaging indices in calf muscles following postural change from standing to supine position

Object

To investigate whether postural change from erect to recumbent position affects calf muscle water diffusivity.

Materials and methods

Ten healthy adults (27.2 ± 4.9 years, 3 females) were imaged at baseline (following assumption of recumbent position), and after 34 min (session 2) and 64 min (session 3) of laying supine within a 3T MRI scanner. Diffusion tensor imaging (DTI) eigenvalues, fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were evaluated in five calf muscles (anterior and posterior tibialis and triceps surae) during each of the three imaging sessions.

Results

Significant decreases were observed in all of the eigenvalues and ADC in each of the muscles with postural change. These reductions ranged from 3.2 to 6.7 % and 3.4 to 7.5 % for the various DTI metrics, following 34 and 64 min of supine rest, respectively (P < 0.05). No significant differences were noted in ADC or eigenvalues between the second and third imaging sessions for any muscle. FA did not change significantly with postural manipulation in any muscle compartment.

Conclusion

Diffusion tensor imaging indices were altered with postural change. As differences were not apparent between the latter two imaging sessions, we suggest that a short supine resting period (~34 min) is sufficient for muscle diffusivity to stabilize prior to quantitative MR imaging in healthy young adults.     

基于改进各向异性扩散的图像去噪算法

针对纹理等细节信息丢失和图像边缘退化的问题,本文提出了一种基于l_(2)范数的改进各向异性扩散模型。本文首先将PM模型和LCC模型相结合,根据图像梯度的变化,构建局部图像梯度模值与扩散强度之间的关系,不同的梯度模值选择不同的扩散函数;然后利用l_(2)范数确定扩散函数中的梯度阈值,进一步提高去噪模型的泛化能力。实验结果表明,该模型不仅可以解决传统PM模型存在的孤立点问题,而且能够有效地保护图像边缘特征和轮廓结构的完整性,与原始算法相比图像信噪比提升了1.47~1.57 dB,结构相似度提高了17%,在保证去噪效果的同时提高了去噪效率。     

In vivo diffusion tensor mapping of the brain of squirrel monkey, rat, and mouse using single-shot STEAM MRI

The purpose was to assess the potential of half Fourier diffusion-weighted single-shot STEAM MRI for diffusion tensor mapping of animal brain in vivo. A STEAM sequence with image acquisition times of about 500 ms was implemented at 2.35 T using six gradient orientations and b values of 200, 700, and 1200 s mm^–2. The use of half Fourier phase-encoding increased the signal-to-noise ratio by 45% relative to full Fourier acquisitions. Moreover, STEAM-derived maps of the relative anisotropy and main diffusion direction were completely free of susceptibility-induced signal losses and geometric distortions. Within measuring times of 3 h, the achieved resolution varied from 600×700×1000 m³ for squirrel monkeys to 140×280×720 m³ for mice. While in monkeys the accessible white matter fiber connections were comparable to those reported for humans, detectable fiber structures in mice focused on the corpus callosum, anterior commissure, and hippocampal fimbria. In conclusion diffusion-weighted single-shot STEAM MRI allows for in vivo diffusion tensor mapping of the brain of squirrel monkeys, rats, and mice without motion artifacts and susceptibility distortions.     

Spatially resolved kinetics of skeletal muscle exercise response and recovery with multiple echo diffusion tensor imaging (MEDITI): a feasibility study

Objectives

We describe measurement of skeletal muscle kinetics with multiple echo diffusion tensor imaging (MEDITI). This approach allows characterization of the microstructural dynamics in healthy and pathologic muscle.

Materials and methods

In a Siemens 3-T Skyra scanner, MEDITI was used to collect dynamic DTI with a combination of rapid diffusion encoding, radial imaging, and compressed sensing reconstruction in a multi-compartment agarose gel rotation phantom and within in vivo calf muscle. An MR-compatible ergometer (Ergospect Trispect) was employed to enable in-scanner plantar flexion exercise. In a HIPAA-compliant study with written informed consent, post-exercise recovery of DTI metrics was quantified in eight volunteers. Exercise response of DTI metrics was compared with that of T2-weighted imaging and characterized by a gamma variate model.

Results

Phantom results show quantification of diffusivities in each compartment over its full dynamic rotation. In vivo calf imaging results indicate larger radial than axial exercise response and recovery in the plantar flexion-challenged gastrocnemius medialis (fractional response: nT2w?=?0.385?±?0.244, nMD?=?0.163?±?0.130, nλ₁?=?0.110?±?0.093, nλ_rad?=?0.303?±?0.185). Diffusion and T2-weighted response magnitudes were correlated (e.g., r?=?0.792, p?=?0.019 for nMD vs. nT2w).

Conclusion

We have demonstrated the feasibility of MEDITI for capturing spatially resolved diffusion tensor data in dynamic systems including post-exercise skeletal muscle recovery following in-scanner plantar flexion.

     

Multimodal nonlinear endomicroscopic imaging probe using a double-core double-clad fiber and focus-combining micro-optical concept

Multimodal non-linear microscopy combining coherent anti-Stokes Raman scattering, second harmonic generation, and two-photon excited fluorescence has proved to ...     

Reproducibility of diffusion tensor imaging-derived parameters: implications for the streptozotocin-induced type 1 diabetic rats

Magnetic Resonance Materials in Physics, Biology and Medicine - Diffusion tensor imaging (DTI) is a useful approach for studying neuronal integrity in animals. However, the test–retest...     

Development of fault point locating system for underground transmission lines using optical fiber current sensors

Fault point locating systems based on surge current detection have recently been used for fast recovery of underground transmission lines from faults. Electromagnetic induction type sensors have mainly been used for the detection of surge current. However, they are susceptible to electromagnetic noise which causes unstable system operation. To solve this problem, Tokyo Electric Power Co., Toko Electric Corporation, and Fujikura Ltd. jointly developed a new system using optical fiber current sensors. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(1): 21–28, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.20981     

碳基电化学电容器及其研究进展

电化学电容器与常规的电解电容器相比,显著地提高了比能量;而与电池相比,虽然比能量较低,但其比功率却是电池的数量级倍数。用于制造电化学电容器的材料可分为碳基材料、金属氧化物材料和导电聚合物材料。与其他材料相比,碳基电化学电容器是目前已较好商业化的一种。简要介绍了碳基电化学电容器的工作原理、特点及应用,并简要介绍了碳材料的制备和改性。通过改性可以增加表面积和孔隙率,从而提高电容器的比容量。简要评述了电化学电容器用碳材料的研究进展     

Development of cable fault location method using fiber optic distributed temperature sensor

When ground-fault problems occur on a cable line, immediate fault location and restoration are required. Therefore, various new methods to locate the fault point instantaneously have been investigated to replace such conventional methods as the Murray loop method and the pulse radar method [1]. These methods require a long time to locate the fault point. One possible fault location method is to sense the temperature rise following a ground fault using a fiber optic distributed temperature sensor. Application of this method was found feasible through sensing the temperature rise at a ground-fault test using a thermocouple as a temperature sensor with test cables [4]. A power/optical composite cable was prepared experimentally and after verifying its thermal mechanical performance, the temperature rise at an incidence of a fault was determined and the anticipated performance was demonstrated in a ground-fault test. This article describes the outline of the test.