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1.
头部扩散张量磁共振成像扫描方案的优选   总被引:10,自引:4,他引:6       下载免费PDF全文
目的 探索扩散张量磁共振成像应用于临床的合理扫描方案。方法 对20名成年健康志愿者行头部扩散张量成像,比较不同扫描参数(层厚/层间距、b值及扩散敏感梯度方向数)对图像质量的影响。结果 在三种不同的扫描参数中,以层厚/层间距对图像信噪比的影响最大,层厚/层间距越大,图像信噪比越高。高b值扫描虽然ADC图灰白质对比明显,但FA图噪声较大。方向数越多,图像信噪比越高,但扫描时间相应延长。结论 层厚/层间距3mm/1mm、b值=1000s/mm^2、扩散敏感梯度方向25个,此方案适用于研究脑白质的细微结构,是应用于临床的合理扫描方案。  相似文献
2.
Diffusion tensor MRI (DTI) fiber tracking is the first non-invasive and in vivo technique for the delineation and quantitation of specific white matter pathways. In this study, quantitative fiber tracking was used to assess the structural development of the motor tract and somatosensory radiation in premature human newborns. These pathways are unmyelinated in the youngest premature infants and begin to myelinate during late preterm maturation. Previous studies have only been able to delineate parts of these pathways that could be manually outlined in 2D based on anatomical landmarks. Furthermore, these previous studies could not separate motor and sensory regions. A high-sensitivity neonatal head coil was employed in conjunction with an MR-compatible incubator to perform high-resolution imaging of the premature infant brain. The motor and somatosensory tracts were successfully delineated with 3D DTI fiber tracking in 37 exams of preterm newborns between 28 and 43 weeks gestational age. Both streamline deterministic and probabilistic methods were employed to perform quantitative fiber tractography. Tract-specific measurements of diffusion parameters including fractional anisotropy, directionally averaged diffusivity, and eigenvalues were obtained from the motor and sensory pathways. Using both deterministic and probabilistic fiber tracking, all tract-specific diffusion parameters were found to be significantly correlated with age and the motor tracts were found to have higher anisotropy and lower diffusivity than the sensory pathway. By segmenting the 3D fiber tracks by slice, measurements from different axial levels of the brain were found to vary with region and age. In summary, deterministic and probabilistic DTI fiber tracking methods were used to quantify the developmental changes of motor and somatosensory pathways in premature infants.  相似文献
3.
Diffusion tensor imaging (DTI) studies in schizophrenia demonstrate lower anisotropic diffusion within white matter due either to loss of coherence of white matter fiber tracts, to changes in the number and/or density of interconnecting fiber tracts, or to changes in myelination, although methodology as well as localization of such changes differ between studies. The aim of this study is to localize and to specify further DTI abnormalities in schizophrenia by combining DTI with magnetization transfer imaging (MTI), a technique sensitive to myelin and axonal alterations in order to increase specificity of DTI findings. 21 chronic schizophrenics and 26 controls were scanned using Line-Scan-Diffusion-Imaging and T1-weighted techniques with and without a saturation pulse (MT). Diffusion information was used to normalize co-registered maps of fractional anisotropy (FA) and magnetization transfer ratio (MTR) to a study-specific template, using the multi-channel daemon algorithm, designed specifically to deal with multidirectional tensor information. Diffusion anisotropy was decreased in schizophrenia in the following brain regions: the fornix, the corpus callosum, bilaterally in the cingulum bundle, bilaterally in the superior occipito-frontal fasciculus, bilaterally in the internal capsule, in the right inferior occipito-frontal fasciculus and the left arcuate fasciculus. MTR maps demonstrated changes in the corpus callosum, fornix, right internal capsule, and the superior occipito-frontal fasciculus bilaterally; however, no changes were noted in the anterior cingulum bundle, the left internal capsule, the arcuate fasciculus, or inferior occipito-frontal fasciculus. In addition, the right posterior cingulum bundle showed MTR but not FA changes in schizophrenia. These findings suggest that, while some of the diffusion abnormalities in schizophrenia are likely due to abnormal coherence, or organization of the fiber tracts, some of these abnormalities may, in fact, be attributed to or coincide with myelin/axonal disruption.  相似文献
4.
DTI纤维追踪法定量分析90名正常国人脑白质老化   总被引:5,自引:1,他引:4       下载免费PDF全文
目的 采用DTI纤维追踪法定量比较不同年龄组正常自愿者椎体束从大脑脚到中央前回部分(PRPT)FA值的差别及其意义.方法 将90名正常志愿者按年龄分为6组,进行基于纤维追踪的定量DTI研究,图像标准化后分析各组PRPT的FA值与年龄组老化的关系.结果 各年龄组双侧PRPT的FA值分布相似,最低点在放射冠处,最高峰为内囊后肢;各段FA值随年龄增长呈下降趋势,表明这些部位的纤维随年龄增长发生了老化,其中以额叶老化最为明显;并发现额叶及大脑脚白质老化过程中存在突然变化.结论 DTI可以作为评价脑组织细微结构变化和老化过程的敏感工具;额叶及大脑脚白质老化过程中存在突变是否为脑生理上老化的标志有待进一步研究.  相似文献
5.
早产儿脑白质损伤的磁共振诊断及预后判断   总被引:5,自引:3,他引:2       下载免费PDF全文
早产儿脑白质损伤(WMD)常造成永久性痉挛运动障碍(脑麻痹),学龄期25%~50%的患儿表现出广泛的认知和学习障碍,是最常见的早产儿脑损伤。影像学是白质病变的确诊依据。本文对WMD的MR诊断和预后判断做一综述。  相似文献
6.
脑老化过程中的白质损害与P300变化的关系   总被引:4,自引:2,他引:2  
目的观察脑白质变化(WML)与事件相关电位P300变化关系,认识P300是否能够反映WML时认知功能改变。方法观察35例老龄及老龄前期个体的MRI及事件相关电位P300变化,并对WML与P300潜伏期变化进行相关分析。结果轻度WML11例,中度17例,重度7例,P300潜伏期明显延长,随WML的程度加重而加重,相关分析提示两者呈正相关。结论观察老年性WML主要依靠T像或质子密度加权像。WML能引起事件相关电位P300延长,其损害程度与P300潜伏期变化呈正相关。  相似文献
7.
精神分裂症患者脑白质的磁共振扩散张量成像研究   总被引:4,自引:2,他引:2       下载免费PDF全文
目的应用磁共振扩散张量成像技术(DTI)对精神分裂症患者额叶及胼胝体压部脑白质损伤情况与临床症状之间的关系进行初步研究。方法对22例精神分裂症患者和20例健康志愿者进行脑部DTI扫描后,测量双侧额叶和胼胝体压部的各向异性分数值(FA),应用成组t检验对精神分裂症患者和正常健康对照组的相应区域进行比较,并用部分相关性检验对精神分裂症患者脑中各部位相应FA值与PANSS量表评分之间的关系进行统计。纤维束成像技术(DTT)重建胼胝体和扣带束。结果精神分裂症患者双侧额叶和胼胝体压部的FA值与正常对照组存在显著性差异(P<0.05),额叶FA值与PANSS量表评分之间存在正相关性(r=0.703,P<0.05),纤维束成像技术不能显示病例组和对照组的差别。结论精神分裂症患者与正常健康对照组存在脑白质细微结构的差异,DTI技术能够在一定程度上反映精神分裂症患者脑白质受损与临床症状的关系。  相似文献
8.
目的定量分析正常成人大脑不同部位白质纤维各向异性所存在的差异.方法测量52名正常志愿者大脑白质纤维不同部位的FA值和ADC值,测量的部位有:外囊、内囊前肢、内囊后肢、胼胝体膝部和胼胝体压部.结果 FA值以胼胝体压部为最高是0.893±0.0645.统计分析大脑白质各部位间FA值的差别均有统计学意义(P<0.01).结论 FA值可定量分析大脑不同部位的白质纤维的各向异性程度.  相似文献
9.
一种数字人脑部切片图像分割新方法   总被引:4,自引:2,他引:2       下载免费PDF全文
目的 提出一种人脑切片图像自动分割算法,以克服现有的方法对大量人工参与的依赖.方法 针对人脑切片图像的特征,提出一种基于区域生长的灰度直方图阈值化分割算法.首先通过区域生长过程对图像进行初始的粗分割,再用直方图阈值化方法进行二次细分割提取目标区域.结果 采用此方法准确有效地分割出了大脑白质和大脑皮质.结论 此算法结合切片图像的全局信息和局部信息应用于分割,是一种比较好的分割方法.  相似文献
10.
Studies on the prevalence of MRI signal abnormalities in the brains of migraineurs have yielded controversial results. In order to provide further data on this issue we reviewed the MRI scans of 38 migraine patients without current neurologic symptoms (mean age 35.8 +/- 11.9 years). In addition, we compared the findings in those 24 migraineurs under 50 years without major cerebrovascular risk factors (mean age 30.1 +/- 9.0 years) to that in 14 headache and risk factor free volunteers (mean age 37.8 +/- 5.3 years). Overall, focal areas of hyperintense signal were seen in 15 (39%) patients. They were present on both proton density and T2-weighted spin-echo sequences. Lesion prevalence varied according to the type of headache (18% in migraine without aura, 53% in migraine with typical aura, 38% in basilar migraine). The subset of migraine patients under 50 years exhibited MRI signal abnormalities more than twice as often as controls (33% vs. 14%). Punctate white matter hyperintensities were the predominant finding and were seen in 10 of 15 individuals with MRI lesions. More striking signal abnormalities consisted of symmetrical areas of hyperintensity lateral to the posterior horns in two 24 year old patients and of extensive white matter damage with lacunar infarcts in a 59 year old woman. Our findings confirm a higher prevalence of MRI lesions in a mixed group of migraineurs than in headache free individuals. Signal abnormalities are most often non-specific, however their occurrence relates to the type of migraine.  相似文献
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