由水分子扩散张量计算脑组织电导率张量的新方法

脑组织电导率在脑电/磁研究中是一个重要参数.为了获取脑组织电导率,本研究利用扩散张量成像(DTI)技术,从电化学角度出发,提出了基于Stokes-Einstein与Nernst-Einstein方程的计算脑组织电导率的一种新方法,以三个正交方向上的电导率作为不同脑组织的电导率张量特征值.在人体头部DTI数据上进行计算,并与不同脑组织(白质、灰质、脑脊液)的经验电脑率值进行了对比,发现扩散各向异性越严重的组织,其电导率张量特征值偏离经验值越远,进一步证明了在脑电,磁计算中要考虑脑组织电导率各向异性的必要性.所提出的方法,基于扩散张量,考虑脑液体中各种离子浓度等因素,为获取脑组织各向异性电导率分布提供了一种新的有效途径.     

基于扩散张量成像技术的大脑组织核磁共振电导率重构的仿真研究

将核磁共振电阻抗成像(MREIT)技术应用于人体头部大脑组织电导率重构上.采用基于径向基函数(RBF)神经网络的均质电导率重构MREIT算法,对建立在扩散张量核磁共振成像(DT-MRI)数据基础上的白质组织各向异性电导率和各向同性的灰质、脑脊液目标电导率进行重构.在五层真实形状头模型(包括头皮、颅骨、脑脊液、灰质和白质组织)上进行的仿真实验结果表明,该算法具有一定的抗噪声能力,重构的头部电导率分布图像具有较高的精确性.研究证明了MREIT技术用于头部复杂组织结构电导率重构上的合理性与可行性,在无创头部组织电导率检测领域具有潜在的应用价值.     

磁共振扩散张量成像的可视化方法研究进展

磁共振扩散张量成像(DT-MRI)与传统的扩散加权成像(DWI)相比能够更加准确地反映分子扩散的方向.大脑白质区的水分子扩散表现出显著的各向异性,因而DT-MRI技术在显示白质神经纤维和功能束的走行方向以及三维形态等方面具有极大的优越性.主要介绍了该技术的基本原理及目前常用的数据集可视化的方法.     

基于DT-MRI的纤维跟踪及可视化研究

磁共振扩散张量成像(DT-MRI)是一种新的成像技术,比传统的扩散加权成像(DWI)能够更加准确地反映分子扩散的方向.在脑白质这样具有大量纤维束的组织中,水分子的扩散表现出显著的各向异性,从而有可能从张量信息的各向异性入手,跟踪得到白质纤维束的走行方向.本文介绍了DTI的原理、数据采集与处理方法,提出了一种可变步长的纤维跟踪方法,并以VC /ITK/VTK为开发工具实现了DTI分析和纤维跟踪与可视化.     

基于Log-Euclidean矩阵的脑白质扩散张量场的正则化处理

在临床诊断时为了较快获得数据,扩散张量图像的质量常常不能得到保证,其正则化处理特别重要。为此,本研究提出一种基于Log-Euclidean矩阵的新算法对张量图像进行评估预处理,首先对张量特征值进行自然指数运算以实现张量场到Log-Euclidean矢量场的转换,再通过有限差分法计算矢量场梯度函数最小值,从而实现矢量场的去噪平滑,之后对矢量场取自然对数运算映射回张量空间。在1名志愿者脑扩散张量图像上进行白质纤维束跟踪测试,结果表明该方法有效避免了白质纤维束跟踪中杂从的出现,提高了跟踪平滑性。     

基于模糊K-近邻规则的多谱磁共振脑图像分割方法的研究

本文在K 近邻 (K nearestneighbor ,简称KNN)规则的基础上 ,基于模糊C 均值聚类 (FuzzyC meansclustering ,简称FCM)技术 ,提出了模糊K 近邻算法 (FuzzyK nearestneighbor ,简称FKNN) ,并利用该算法对磁共振脑图像进行分割研究。首先对磁共振颅脑图像进行预分割 ,剔除颅骨和肌肉等非脑组织 ,只保留大脑结构 ;然后利用FKNN算法对大脑结构进行分割 ,从脑组织中分别提取出白质、灰质和脑脊液。实验结果表明 ,FKNN方法能有效地从大脑结构中分割出白质、灰质和脑脊液 ,分割效果明显优于KNN方法。     

基于扩散形状的DTI纤维跟踪算法研究

到目前为止，研究者们已经提出了许多种神经纤维束的三维可视化技术，其中，基于扩散跟踪的白质束成像技术在白质纤维束的可视化和分析中使用得最多。本文针对现有纤维跟踪算法存在的问题，提出了基于扩散形状的纤维跟踪算法，该算法结合了流线跟踪（streamline tracking，STT）法与张量弯曲（tensor deflection，TEND）法的优点，对不同的扩散形状采用不同的跟踪方向，尤其在平面扩散的情况提出了更接近纤维走行的跟踪方法，减少了跟踪方向与实际纤维走行的误差，能更完整、更准确地显示大脑白质的纤维走行。     

应用DTI技术对人脑白质纤维束的初步研究

目的建立扩散张量纤维束成像对人脑白质纤维的显示方法,并应用中国数字化可视人体数据进行对照观察,验证扩散张量成像(DTI)方法的可靠性。方法选择5名健康志愿者进行DTI成像,采用DtiStudio软件进行分析处理,重建出部分各向异性(FA)图、容积比(VR)图、相对各向异性(RA)图、表面扩散系数(ADC)图以及二维彩色张量图。应用中国数字化可视人体数据集断面图像、FA图及彩色FA图进行对照观察,利用fibertracking纤维跟踪软件及3DMRI软件进行三维重建显示脑内主要白质纤维束,辨认脑内白质纤维束的位置、形态。结果应用DTI纤维束成像可以清晰准确地描绘脑白质内主要神经纤维束的解剖图谱,包括联络纤维如弓形纤维、钩束、扣带束、上纵束和下纵束,连合纤维如胼胝体、前连合和穹隆,投射纤维如锥体束、视放射、内侧丘系等。DTI纤维束成像结果与已知解剖知识、中国可视化人体断面图像具有很好的一致性。结论应用DTI纤维束成像可以清晰准确地描绘脑白质内主要神经纤维束的解剖图谱,其结果与中国可视化人体断面图像、已知解剖知识是一致的,应用DTI纤维束成像研究脑内纤维连通性是可靠的。     

人脑扩散MR参考图像研究

本文阐述了扩散-MRI，扩散张量成像（DTI）的原理以及平均扩散率D-map的导出关系，由于不同人脑大小，形态，结构跟人体相貌有差异一样也存在大小的差异。本文对七个健康志愿者的脑D-map进行了归一化处理，之后利用基于小波金子塔的图像配准，融合方法把七个人脑D-map配准后融合在一起，导出有统计意义的参数图像，为将来计算机自动认读图像，辅助诊断铺平道路，理论，算法，实验都已取得初步成功并给出了实验结果，只是需要进一步提高精度，提高信噪比。     

磁共振扩散张量成像评价小儿脑病的初步应用

目的应用扩散张量成像（DTI）来进一步评价小儿脑疾病，探讨DTI的诊断价值。方法对15例患各种脑病的小儿进行MRI检查，其中男性10例，女性5例，年龄为生后3天至11岁（平均年龄4．8岁）。采用Philips Intera Achieva 3．0 Tesla的超导MRI仪，用回波平面成像（EPI）的DTI技术，b为800s／mm^2，15个方向。观察彩色分数各向异性（FA）图和三维彩色编码图。结果15例患儿中，发育畸形2例，分别是胼胝体发育不良、巨脑回；脑室旁白质软化（PVL）7例；缺氧缺血性脑病3例；脑软化2例；脑积水1例。在巨脑回病例，常规MRI见右侧脑回发育不良，呈巨脑回畸形，右侧脑室扩大，在DTI上见右侧病变区白质束明显较对侧少。胼胝体发育不良病例在DTI张量图见胼胝体菲薄。在PVL和缺氧缺血性脑病病例均可见白质纤维束在放射冠颜色混杂，方向性混乱。脑软化病例可见白质纤维束部分中断。在脑积水病例可见白质束受压推移。结论DTI能够显示白质束的走向、绕行、交叉及推挤、中断等异常，可能对今后评估小儿脑病的预后转归有帮助。     

Polymerization of cyclopentene, 3-methylcyclopentene,and 3-methylcyclohexene

The cycloolefins cyclopentene, 3-methylcyclopentene, and 3-methylcyclohexene have been polymerized. The polymerization rates were very low. Depending on the particular monomer, ZIEGLER and/or cationic catalysts were effective. Cyclopentene polymerizes both by double bond opening (producing enchained cyclopentane rings) and by ring opening to give cis and trans polypentenamers. The resulting polymers are partially crystalline and have birefringence melting points between 120 and 150°C. The 3-methylcyclopentene and 3-methylcyclohexene monomers polymerize (at least partly) by 1,3-addition following a 3,2-hydride shift. The 3-methylcyclohexene polymers are also partly crystalline and have birefringence melting points between 200 and 250°C. Little ring-opening polymerization of the methylcycloolefins occurs. Polymerization mechanisms are discussed.     

Topography of 3H-DHA, 3H-QNB, 3H-Dopamine, and 3H-DAGO Binding Sites Distribution in the Central Part of the Sinoatrial Node in Rat Heart

The topography of distribution of ³H-dihydroalprenolol, ³H-quinucledinyl benzilate, ³H-dopamine, and ³H-DAGO binding sites in the central part of the sinoatrial node in rat heart was studied by autoradiography after electrophysiological identification of the dominant pacemaker region location. Receptor asymmetry between the lateral and median regions of the central part of the sinoatrial node was shown. The dominant pacemaker region lay in the lateral area of the sinoatrial node; the number of binding sites for all four ligands was minimum in it. The number of binding sites gradually increased in the cranial and caudal directions from the dominant pacemaker region along the sinoatrial node artery (more smoothly in the caudal direction). The relative densities of bindings sites for ³H-dihydroalprenolol and ³H-dopamine were higher in the lateral region compared to the perinodal working myocardium, while the densities for ³H-quinucledinyl benzilate and ³H-DAGO were virtually the same. The distribution of binding sites along the artery in the median region of the sinoatrial node was even for ³H-quinucledinyl benzilate and ³H-DAGO. For ³H-DAGO these parameters were close to those in the perinodal atrial myocardium, for ³H-quinucledinyl benzilate somewhat lower. Curves presenting the distribution of binding site densities for ³H-dihydroalprenolol and ³H-dopamine in the median region of the sinoatrial node were similar, with a pronounced peak in the region contralateral to the dominant pacemaker region, and significantly higher binding parameters compared to those for the perinodal atrial myocardium. The difference consisted in higher density of ³H-dopamine binding sites in the median region of the sinoatrial node in comparison with the lateral region. Binding activity was maximum in the wall of the sinoatrial node artery. The distribution of binding sites for ligands to the main autonomic nervous system neurotransmitters in the rat heart sinoatrial node is heterogeneous. __________ Translated from Byulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 140, No. 10, pp. 472–477, October, 2005     

In vitro biocompatibility and degradation of terpolyester 3HB-co-4HB-co-3HHx, consisting of 3-hydroxybutyrate, 4-hydroxybutyrate and 3-hydroxyhexanoate

A terpolyester consisting of 3-hydroxybutyrate (3HB), 4-hydroxybutyrate (4HB) and 3-hydroxyhexanoate (3HHx), abbreviated as P(3HB-co-4HB-co-3HHx), was studied for possible application as an implant biomaterial. L929 mouse fibroblasts, MC3T3-E1 murine osteoblasts and a human cell line of immortalized human keratinocyte (HaCat cells) were used to study the biocompatibility of P(3HB-co-4HB-co-3HHx). Cell morphology and cell activity were studied using scanning electron microscopy (SEM) and the MTT assay, respectively. All three cell types showed higher activities when grown on films of P(3HB-co-4HB-co-3HHx) compared with their growth on poly(lactic acid) (PLA), co-polyester PHBHHx films and on polylysine-coated plates (blank), respectively. The three cell types grown on the terpolyester also demonstrated a well-spread cell shape and large number of pseudopods due to strong cell-cell and cell-material interactions. It was clearly observed that P(3HB-co-4HB-co-3HHx) had a much faster degradation rate than PHBHHx after 15 weeks of incubation in phosphate-buffered saline under dynamic conditions. The results proved that the terpolyester had favorable biocompatibility and biodegradability compared with the well-studied polyesters PLA and PHBHHx.     

In vitro biocompatibility and degradation of terpolyester 3HB-co-4HB-co-3HHx,consisting of 3-hydroxybutyrate, 4-hydroxybutyrate and 3-hydroxyhexanoate

A terpolyester consisting of 3-hydroxybutyrate (3HB), 4-hydroxybutyrate (4HB) and 3-hydroxyhexanoate (3HHx), abbreviated as P(3HB-co-4HB-co-3HHx), was studied for possible application as an implant biomaterial. L929 mouse fibroblasts, MC3T3-E1 murine osteoblasts and a human cell line of immortalized human keratinocyte (HaCat cells) were used to study the biocompatibility of P(3HB-co-4HB-co-3HHx). Cell morphology and cell activity were studied using scanning electron microscopy (SEM) and the MTT assay, respectively. All three cell types showed higher activities when grown on films of P(3HB-co-4HB-co-3HHx) compared with their growth on poly(lactic acid) (PLA), co-polyester PHBHHx films and on polylysine-coated plates (blank), respectively. The three cell types grown on the terpolyester also demonstrated a well-spread cell shape and large number of pseudopods due to strong cell–cell and cell–material interactions. It was clearly observed that P(3HB-co-4HB-co-3HHx) had a much faster degradation rate than PHBHHx after 15 weeks of incubation in phosphate-buffered saline under dynamic conditions. The results proved that the terpolyester had favorable biocompatibility and biodegradability compared with the well-studied polyesters PLA and PHBHHx.     

急性阑尾炎围手术期血清FT3、FT4、T3、T4、rT3测定的临床意义

目的:探讨急性阑尾炎围手术期甲状腺激素水平的变化规律及其临床意义.方法:选择82例急性阑尾炎患者,分别于手术前、手术后1、3、5、7、14d取空腹静脉血,利用放射免疫分析检测FT3、FT4、T3、T4、rT3及TSH水平,同时分析甲状腺激素水平与临床病理分型、并发症的关系.结果:本文患者手术前均存在不同程度的低FT3、FT4、T3、T4血症和高rT3血症,且以坏疽性和穿孔性阑尾炎最明显.这种现象均于术后(5～7)d恢复正常,但当出现感染性并发症时血清FT3、FT4、T3、T4持续低下,而临床治愈后则恢复正常水平.结论:急性阑尾炎患者甲状腺内分泌功能均受到不同程度的抑制,围手术期动态观察FT3、FT4、T3、T4、rT3血液激素水平,有利于判断病情轻重、临床病理分型和感染性并发症的存在,有利于临床治疗方案的制定.