A computational Framework for generating rotation invariant features and its application in diffusion MRI

In this work, we present a novel computational framework for analytically generating a complete set of algebraically independent Rotation Invariant Features (RIF) given the Laplace-series expansion of a spherical function. Our computational framework provides a closed-form solution for these new invariants, which are the natural expansion of the well known spherical mean, power-spectrum and bispectrum invariants. We highlight the maximal number of algebraically independent invariants which can be obtained from a truncated Spherical Harmonic (SH) representation of a spherical function and show that most of these new invariants can be linked to statistical and geometrical measures of spherical functions, such as the mean, the variance and the volume of the spherical signal. Moreover, we demonstrate their application to dMRI signal modeling including the Apparent Diffusion Coefficient (ADC), the diffusion signal and the fiber Orientation Distribution Function (fODF). In addition, using both synthetic and real data, we test the ability of our invariants to estimate brain tissue microstructure in healthy subjects and show that our framework provides more flexibility and open up new opportunities for innovative development in the domain of microstructure recovery from diffusion MRI.     

A computational diffusion MRI and parametric dictionary learning framework for modeling the diffusion signal and its features

In this work, we first propose an original and efficient computational framework to model continuous diffusion MRI (dMRI) signals and analytically recover important diffusion features such as the Ensemble Average Propagator (EAP) and the Orientation Distribution Function (ODF). Then, we develop an efficient parametric dictionary learning algorithm and exploit the sparse property of a well-designed dictionary to recover the diffusion signal and its features with a reduced number of measurements. The properties and potentials of the technique are demonstrated using various simulations on synthetic data and on human brain data acquired from 7T and 3T scanners. It is shown that the technique can clearly recover the dMRI signal and its features with a much better accuracy compared to state-of-the-art approaches, even with a small and reduced number of measurements. In particular, we can accurately recover the ODF in regions of multiple fiber crossing, which could open new perspectives for some dMRI applications such as fiber tractography.     

Prospective and retrospective motion correction in diffusion magnetic resonance imaging of the human brain

Diffusion-weighting in magnetic resonance imaging (MRI) increases the sensitivity to molecular Brownian motion, providing insight in the micro-environment of the underlying tissue types and structures. At the same time, the diffusion weighting renders the scans sensitive to other motion, including bulk patient motion. Typically, several image volumes are needed to extract diffusion information, inducing also inter-volume motion susceptibility. Bulk motion is more likely during long acquisitions, as they appear in diffusion tensor, diffusion spectrum and q-ball imaging. Image registration methods are successfully used to correct for bulk motion in other MRI time series, but their performance in diffusion-weighted MRI is limited since diffusion weighting introduces strong signal and contrast changes between serial image volumes.In this work, we combine the capability of free induction decay (FID) navigators, providing information on object motion, with image registration methodology to prospectively - or optionally retrospectively - correct for motion in diffusion imaging of the human brain. Eight healthy subjects were instructed to perform small-scale voluntary head motion during clinical diffusion tensor imaging acquisitions.The implemented motion detection based on FID navigator signals is processed in real-time and provided an excellent detection performance of voluntary motion patterns even at a sub-millimetre scale (sensitivity ≥ 92%, specificity > 98%). Motion detection triggered an additional image volume acquisition with b = 0 s/mm² which was subsequently co-registered to a reference volume. In the prospective correction scenario, the calculated motion-parameters were applied to perform a real-time update of the gradient coordinate system to correct for the head movement.Quantitative analysis revealed that the motion correction implementation is capable to correct head motion in diffusion-weighted MRI to a level comparable to scans without voluntary head motion. The results indicate the potential of this method to improve image quality in diffusion-weighted MRI, a concept that can also be applied when highest diffusion weightings are performed.     

Robust determination of the fibre orientation distribution in diffusion MRI: non-negativity constrained super-resolved spherical deconvolution

Diffusion-weighted (DW) MR images contain information about the orientation of brain white matter fibres that potentially can be used to study human brain connectivity in vivo using tractography techniques. Currently, the diffusion tensor model is widely used to extract fibre directions from DW-MRI data, but fails in regions containing multiple fibre orientations. The spherical deconvolution technique has recently been proposed to address this limitation. It provides an estimate of the fibre orientation distribution (FOD) by assuming the DW signal measured from any fibre bundle is adequately described by a single response function. However, the deconvolution is ill-conditioned and susceptible to noise contamination. This tends to introduce artefactual negative regions in the FOD, which are clearly physically impossible. In this study, the introduction of a constraint on such negative regions is proposed to improve the conditioning of the spherical deconvolution. This approach is shown to provide FOD estimates that are robust to noise whilst preserving angular resolution. The approach also permits the use of super-resolution, whereby more FOD parameters are estimated than were actually measured, improving the angular resolution of the results. The method provides much better defined fibre orientation estimates, and allows orientations to be resolved that are separated by smaller angles than previously possible. This should allow tractography algorithms to be designed that are able to track reliably through crossing fibre regions.     

Shirley Clift modified-TG 小鼠基因组DNA提取方法及其在Gene -Trap中的应用

目的介绍一种简单、快速、高效同时从数十、甚至上百个小鼠尾巴中提取基因组DNA的方法.方法 Shirley Clift modified-TG 小鼠Gene-Trap DNA提取法.结果 使用该法从小鼠尾巴中获取的基因组DNA的数量、纯度完全适用各种实验,如在C3H/HCJ-Mgrn1md转基因小鼠杂交C57BL/6小鼠Mahogunin基因变异传代培殖实验中,应用鼠尾抽提的DNA 进行Gene-trap.类推该法到小鼠其它组织如肝、肾、肌肉和心脏,也同样得到了高质量的基因组DNA.结论 该技术可以连续、高效、快速、批量从小鼠组织中提取基因组DNA,为国内利用小鼠进行基因遗传疾病的研究提供了基础方法.     

一种新的经皮膀胱穿刺造瘘方法的临床运用

目的 介绍一种简易安全的经皮膀胱穿刺造痿方法,并探讨其在临床中的运用.方法 采用微创经皮肾穿刺取石术之穿刺造瘘方法,在耻骨上经皮膀胱穿刺,使用筋膜扩张器扩张,置入鞘管即建立膀胱造瘘通道.结果 16例均成功,建立膀胱造瘘时间平均6 min.无肠管损伤以及大出血等并发症.结论 该经皮膀胱穿刺造瘘方法疗简单、安全、疗效满意,可作为经尿道手术的有益补充.     

Shirley Clift modified-TG小鼠基因组DNA提取方法及其在Gene-Trap中的应用

目的：介绍一种简单、快速、高效同时从数十、甚至上百个小鼠尾巴中提取基因组DNA的方法。方法Shirley Clift modified-TG小鼠Gene-Trap DNA提取法。结果使用该法从小鼠尾巴中获取的基因组DNA的数量、纯度完全适用各种实验,如在C3H/HCJ-Mgrn1md转基因小鼠杂交C57BL/6小鼠Mahogunin基因变异传代培殖实验中,应用鼠尾抽提的DNA进行Gene-trap。类推该法到小鼠其它组织如肝、肾、肌肉和心脏,也同样得到了高质量的基因组DNA。结论该技术可以连续、高效、快速、批量从小鼠组织中提取基因组DNA,为国内利用小鼠进行基因遗传疾病的研究提供了基础方法。     

压缩感知技术及其在MRI上的应用

压缩感知是基于应用数学的一种创新的信号获取及处理理论,其原理是通过对所采集的信号进行适当域变换得到可压缩信号,直接采集压缩后的信号并利用重构算法实现快速优质信号重建。运用该技术成像不仅具有出色的时间分辨率优势,同时具有满意的空间分辨率,因此近年来其在医学成像领域的应用逐渐成为研究热点。作者在阐述压缩感知理论基本原理的基础上,进一步对其在MRI上的研究现状和发展前景进行综述。     

MSCT与MRI在脑膜瘤诊断及手术入路评估中的临床应用价值

目的分析脑膜瘤的CT及MRI特征,评估CT及MRI在脑膜瘤术前定位、定性诊断及制定手术方案中的价值。方法回顾性分析经手术病理证实的27例脑膜瘤患者的CT及MRI资料,并与手术及术后病理结果对照。结果 27例脑膜瘤患者,MSCT平扫诊断率70.37%,MSCTA清晰显示肿瘤相邻的动脉与骨性解剖标志之间的三维关系;MRI平扫27例定位为颅内脑实质外肿瘤;MRI增强扫描诊断率96.30%,其中15例静脉窦旁脑膜瘤清晰显示肿瘤与静脉窦的相邻关系及静脉窦受压闭塞程度。依据MRI增强扫描及MSCTA定位诊断结果制定手术入路及方式,其中1例鞍旁脑膜瘤包绕颈内动脉虹吸部,另1例视神经管区域脑膜瘤包埋视神经部分予以残留;2例与矢状窦关系密切行脑膜瘤大部切除;余23例脑膜瘤完全切除。术后均无明确偏瘫、失明、失语等神经系统医源性损害症状。术后观察或随访1~24个月,无死亡病例。结论CT及MRI在脑膜瘤诊断、评估手术入路、保护肿瘤相邻动脉及静脉窦、减少医源性神经功能损害方面有重要价值。     

An approach to the three-dimensional display of left ventricular function and viability using MRI

Cardiac MRI was performed in human volunteers to determine the magnitude of the misregistration (MSR) of cardiac landmarks due to variability in the diaphragm position for repeated breath-holds. Seven normal volunteers underwent MR imaging of the left ventricle (LV) to evaluate the magnitude of the endocardial centroid MSR. The MSR for a mid-ventricle short-axis image was 3.01 ± 1.68 mm through-plane and 4.16 ± 1.62 mm in-plane. A second order polynomial fit through the LV centroid coordinates minimized the in-plane component of the MSR error. Short-axis cine images, corrected for MSR, provided high-resolution 2D data from which an accurate anatomical model of the LV was generated. Anatomical landmarks were used to register parametric maps of myocardial perfusion and viability to the three-dimensional (3D) model, with the corresponding parameters displayed as color-encoded values on the endo- and epicardial surfaces of the LV. Registration of regional wall motion, perfusion and viability to the 3D model was performed for three patients with a history of cardiovascular disease. The proposed 3D reconstruction technique allows visualization in 3D of the LV anatomy, in combination with parametric mapping of its functional status.     

A new approach for mapping regional land cover and the application of this approach in Australia

Detailed and accurate land cover data are widely used for various purposes, such as global land use change detection. This study aimed to investigate Australian land use and cover change by using 774 Landsat scenes in 2000 and 2010. The reference data included pictures or high-resolution images from Google Earth, global land cover data, Shuttle Radar Topography Mission data, and other literature. Australian land cover was automatically classified into nine main classes, namely cropland, forest, grassland, shrubs, wetland, water, artificial covering, bare land, and others, by using a global land cover decision tree developed for computer-based image classification. Obvious mistakes were subsequently modified manually. Finally, the classifications were found to have overall accuracies of 93.24% and 92.79% evaluated by using 2820 and 3820 sample points, respectively.     

血氧水平依赖功能MRI及弥散张量成像评估IgA肾病患者肾功能

目的 观察血氧水平依赖功能MRI（BLOD-fMRI）及弥散张量成像（DTI）评估IgA肾病（IgAN）患者肾功能的价值。方法 对50例经病理证实的IgAN患者（IgAN组）及30名健康志愿者（正常组）采集腹部BLOD-fMRI及DTI。IgAN组分期11例1期,10例2期,11例3期,9例4期,9例5期,分别归入相应亚组。比较正常组与IgAN各亚组间R2^*及各项异性分数（FA）差异,分析IgAN患者R2^*及FA与尿素氮的相关性。采用受试者工作特征（ROC）曲线,计算相应曲线下面积（AUC）,评价MRI参数诊断IgAN的价值。结果 正常组和IgAN组左、右侧肾皮、髓质R2^*及FA差异均无统计学意义（P均>0.05）。正常组及IgAN组肾髓质R2^*均明显高于皮质（t=47.87、71.14,P均<0.01）。IgAN各亚组肾皮、髓质R2^*与正常组总体差异均有统计学意义（F=23.57、20.65,P均<0.01）;IgAN患者肾皮、髓质R2^*与尿素氮均呈正相关（r=0.58、0.59,P均<0.05）。正常组及IgAN组肾髓质FA明显高于皮质（t=56.39、70.84,P均<0.01）。IgAN各亚组肾皮、髓质FA与正常组间总体差异均有统计学意义（F=35.40、49.46,P均<0.01）;IgAN患者肾皮、髓质FA与尿素氮均呈负相关（r=－0.66、－0.69,P均<0.05）。肾皮质R2^*、髓质R2^*及肾皮质FA、髓质FA诊断IgAN的AUC分别为0.84、0.85、0.82及0.84。结论 BLOD-fMRI可监测IgAN患者肾脏血氧状态,DTI可检测其肾脏细微结构改变,二者均对评估IgAN肾功能具有一定临床价值。     

血小板功能检测及其应用的研究进展

血小板在正常止血过程中十分重要,当血小板数量或功能发生变化时,机体易于发生出血或血栓。目前,检测血小板功能的方法日益增加,包括测定血小板粘附、聚集和活化的能力等。近年来随着对血小板激活机制的深入研究以及生物化学、免疫和分子生物学技术的不断发展,检测血小板的方法巳不断用于临床相关疾病的诊断和抗血小板药物治疗的研究。     

The adoption and diffusion of CT and MRI in the United States. A comparative analysis

This study examines and compares the rates and patterns of diffusion of computerized tomography (CT) and magnetic resonance imaging (MRI) over the first 4 years of their availability. Although early diffusion of CT was more rapid than that of MRI, adoption of MRI in nonhospital settings equaled that of CT. Analysis of attributes of the technologies and attributes of the regulatory, reimbursement, and market environments surrounding the early diffusion of these technologies provides insight into their different diffusion patterns. In particular, the technical and financial uncertainties surrounding MRI have inhibited its diffusion compared with that of CT. Medicare's DRG-based prospective reimbursement system and certificate-of-need (CON) regulation by states have reduced overall MRI diffusion and stimulated purchases of MRI by nonhospital organizations. The FDA's premarket approval (PMA) program has changed marketing strategies and influenced the diffusion of MRI to a lesser degree. This analysis identifies problems in how the present health care system evaluates and adopts new, expensive, diagnostic technologies and suggests changes to make the system more responsive to present needs.     

血小板功能检测及其在多种疾病中的研究进展

血小板数量与质量异常是导致出血性和血栓性疾病发生的重要原因。同时,它们还参与一些疾病的病理过程,如糖尿病并发症的产生、心血管疾病、肿瘤及炎症反应。检测血小板功能,尤其是血小板的聚集功能和活化功能,可为临床疾病的预防与诊断提供更好的途径,对疾病的治疗及监测的研究尤为重要。     

A method for obtaining tract-specific diffusion tensor MRI measurements in the presence of disease: application to patients with clinically isolated syndromes suggestive of multiple sclerosis

The aim of this study was to investigate whether neurological symptoms related to a specific axonal fiber tract in brain white matter were associated with a higher degree of tissue damage in that region, in patients at presentation with clinically isolated syndromes (CIS) suggestive of multiple sclerosis. To this end, a magnetic resonance imaging (MRI) method to segment and evaluate the fiber bundle of interest was implemented, taking care to circumvent the problems caused by pathology. Diffusion tensor (DT) MRI tractography was used to construct, from healthy volunteer data, a probability map for the pyramidal tract (PYT), and this map was applied to patients to calculate DT-derived metrics inside the PYT. In CIS patients with clinical symptoms related to motor function, the DT-derived mean diffusivity and the lesion volume in the PYT were found to be increased, while the fractional anisotropy was no different, when compared to those patients without motor symptoms. These results may be explained by several microstructural changes in the damaged tissue, such as changes in the permeability of axonal cell membranes, decreases of axonal density and edema. The approach taken to analyze a specific fiber tract was possible because the axons in the tract have a high orientational coherence, allowing tissue structure changes to be isolated from the tissue architecture. Its extension to other white matter fiber bundles is therefore limited to bundles with high orientational coherence.     

Biodistribution of pH-responsive liposomes for MRI and a novel approach to improve the pH-responsiveness.

The potential of pH-sensitive paramagnetic liposomes as a probe for monitoring acidic pH in tumours with magnetic resonance imaging has recently been demonstrated. If the blood retention time is prolonged, such liposomes can accumulate in tumour interstitium due to increased vascular permeability and interstitial retention. In the present study, biodistribution studies in healthy rats showed rapid clearance of the pH-sensitive system dipalmitoylphosphatidylethanolamine (DPPE)/dipalmitoylglycerosuccinate (DPSG) liposomal GdDTPA-BMA from the blood circulation with most of the Gd dose in the liver at 15 min post intravenous injection. Incorporation of 1.5 mol% polyethylene glycol (PEG) grafted DPPE (DPPE-PEG) in the above-mentioned formulation resulted in a significantly prolonged blood circulation time. However, the relaxometric pH-response of the DPPE/DPSG/DPPE-PEG system decreased as a function of mol% DPPE-PEG. Therefore, a compromise would be necessary between long blood residence time and a suitable pH-sensitivity of the liposomes. A possible approach to compensate for the reduced pH-sensitivity was investigated. Gadofosveset, a low-molecular weight Gd-chelate with high affinity for albumin, was encapsulated within DPPE/DPSG liposomes. This promising system showed in blood a markedly higher relaxometric response than the corresponding system with GdDTPA-BMA, due to release of gadofosveset at low pH and subsequent binding to albumin.     

全自动提取大量全血样本基因组DNA方法的建立及其在HLA基因分型中的应用

目的研究和建立从大量全血样本中提取基因组DNA的有效方法,以应用于Luminex HLA流式磁珠基因分型。方法使用自动工作站(瑞士TECAN公司)提取基因组DNA,提取的DNA样本用紫外分光光度仪测定其浓度和纯度,DNA的完整性用琼脂糖电泳检测,并统计分析每一DNA样本流式磁珠HLA-A、B和DRB1基因扩增产物经探针分子杂交后的荧光信号强度。结果从60μl全血中提取基因组DNA,产量平均为(1.584±0.824)μg,样本的A260/A280值平均为1.741±0.229。琼脂糖电泳法测得DNA的分子量约为21kb。结论本方法适用于从大量全血样本中快速提取基因组DNA,所得基因组DNA适用于高通量HLA流式磁珠基因分型等下游的分子生物学实验。     

Assessment of a developed HPLC-MS/MS approach for determining plasma eupatorin in rats and its application in pharmacokinetics analysis

Eupatorin, a bioactive compound extracted from Java tea (Orthosiphon stamineus), possesses potent anti-cancer, anti-inflammatory and vasodilation activities. To date, no pharmacokinetics studies on eupatorin have yet been performed. Here, we established and validated a sensitive and selective LC-MS/MS (liquid chromatography-tandem mass spectrometry) approach for determining plasma eupatorin in rats. Chromatographic fractionation was conducted on a Wonda Cract ODS-2 C18 Column (4.6 mm × 150 mm, 5 μm) with a mobile phase containing aqueous 0.1% formic acid and acetonitrile using a flow rate of 0.8 ml min⁻¹. In multiple reaction monitoring mode, precursor-to-product ion transitions for quantification of eupatorin and the internal standard were set at 343.1 → 328.1 and 252.0 → 155.9, respectively. The intra- and inter-day precision and accuracy were found to be below 6.72% and within ±8.26% in rat plasma, respectively. Meanwhile, all values of the matrix effect, recovery and stability were within the accepted ranges. Furthermore, we carried out the pharmacokinetic analysis using the developed method. The pharmacokinetic study revealed that while the C_max (maximum plasma concentration) of eupatorin and time for reaching the C_max (T_max) were 974.886 ± 293.898 μg L⁻¹ and 0.25 h, respectively, the half-life was 0.353 ± 0.026 h. This study will be of great significance to the research on the pharmacology, clinical pharmacy and drug action mechanism of eupatorin.

Eupatorin, a bioactive compound extracted from Java tea (Orthosiphon stamineus), possesses potent anti-cancer, anti-inflammatory and vasodilation activities.     

全自动提取大量全血样本基因组DNA方法的建立及其在HLA基因分型中的应用

目的 研究和建立从大量全血样本中提取基因组DNA的有效方法,以应用于Luminex HLA 流式磁珠基因分型.方法 使用自动工作站(瑞士TECAN公司)提取基因组DNA,提取的DNA样本用紫外分光光度仪测定其浓度和纯度,DNA的完整性用琼脂糖电泳检测,并统计分析每一DNA样本流式磁珠HLA-A、B和DRB1基因扩增产物经探针分子杂交后的荧光信号强度.结果 从60μl全血中提取基因组DNA,产量平均为(1.584±0.824)μg,样本的A260/A280值平均为1.741±0.229.琼脂糖电泳法测得DNA的分子量约为21kb.结论 本方法适用于从大量全血样本中快速提取基因组DNA,所得基因组DNA适用于高通量HLA流式磁珠基因分型等下游的分子生物学实验.