Proton spin relaxation studies of fatty tissue and cerebral white matter

Proton spin longitudinal (T1) and transverse (T2) relaxation and proton density studies were carried out on human fatty tissue and bovine white matter, both in the native state and after immersion in D2O. It is concluded that nuclear magnetic resonance signals from fatty tissue result mainly from methyl and methylene protons of hydrocarbons. No contribution from lipid protons could be detected for white matter, although it contains a high percentage of lipids. Imaging experiments, resulting in T1, T2, and proton density maps, support the results obtained with spectroscopic relaxation studies.     

F 2-FDG NMR imaging of the brain in rat

Images of the rat head reflecting glucose utilization were obtained using 2-fluoro-2-deoxy-D-glucose (2-FDG) and ¹⁹F nuclear magnetic resonance (NMR) imaging. Spatial heterogeneity of glucose utilization in the rat head was clearly demonstrated showing significantly higher glucose utilization in the brain as compared to the surrounding tissues. Although the potential adverse effects of the high doses of 2-FDG (400 mg/kg) needed to perform the study preclude immediate application of this technique to clinical quantitative glucose utilization studies, the present study shows potential for future development of glucose utilization imaging by NMR.     

颅脑损伤后抗利尿激素分泌不当综合征的诊断和治疗

目的:探讨颅脑损伤后抗利尿激素分泌不当综合征的诊断和治疗。方法:回顾性分析我科近6a收治的9例颅脑损伤后抗利尿激素分泌不当综合征的临床特点。结果:9例经限制液体摄入和适量的补盐治疗,低钠症状10d内改善。治愈8例,死亡1例。结论:低钠血症、低血浆渗透压、高尿钠及尿渗透压高于血浆渗透压是颅脑损伤后抗利尿激素分泌不当综合征的诊断依据。限制液体入量、适量补盐及调节ACTH/ADH的平衡是安全有效的治疗方法。     

On the sensitivity of ASL MRI in detecting regional differences in cerebral blood flow

Arterial-spin-labeling (ASL) magnetic resonance imaging (MRI) provides a noninvasive tool to measure cerebral blood flow (CBF) and is increasingly used as a surrogate for baseline neural activity. However, the power of ASL MRI in detecting CBF differences between patient and control subjects is hampered by inter-subject variations in global CBF, which are associated with non-neural factors and may contribute to the noise in the across-group comparison. Here, we investigated the sensitivity of this technique and proposed a normalization strategy to better detect such a difference. A “model” situation was employed in which two visual stimuli (i.e. cross fixation and flashing checkerboard) were presented to two groups of subjects to mimic “control” and “patient” groups (N=7 for each group), respectively. It was found that absolute CBF (aCBF) in the occipital lobe in the checkerboard group was 26.0% greater compared to the fixation group, but the level of significance was modest (P=.03). In contrast, when normalizing the CBF with whole-brain CBF or CBF in a reference region [termed relative CBF (rCBF)], the statistical significance was improved considerably (P<.003). For voxel-based analysis, the rCBF indices correctly detected CBF differences in the occipital lobe in the across-group comparison, while aCBF failed to detect any significant cluster using the same statistical threshold. We also performed Monte Carlo simulation to confirm the experimental findings and found that the power improvement was most pronounced when signal-to-noise-ratio is moderate and the underlying CBF difference was small. The simulation also showed that, with the proposed normalization, a detection power of 80% can be achieved using a sample size of about 20. In summary, rCBF is a more sensitive index to detect small differences in CBF, rather than the much-sought-after aCBF, since it reduces data noise caused by inter-subject variations in global CBF.     

Reliability and reproducibility of perfusion MRI in cognitively normal subjects

Arterial spin labeling (ASL) magnetic resonance imaging (MRI) is becoming a popular method for measuring perfusion due to its ability of generating perfusion maps noninvasively. This allows for frequent repeat scanning, which is especially useful for follow-up studies. However, limited information is available regarding the reliability and reproducibility of ASL perfusion measurements. Here, the reliability and reproducibility of pulsed ASL was investigated in an elderly population to determine the variation in perfusion among cognitively normal individuals in different brain structures. Intraclass correlation coefficients (ICC) and within-subject variation coefficients (wsCV) were used to estimate reliability and reproducibility over a period of 1 year. Twelve cognitively normal subjects (75.5±5.3 years old, six male and six female) were scanned four times (at 0, 3, 6 and 12 months). No significant difference in cerebral blood flow (CBF) was found over this period. CBF values ranged from 46 to 53 ml/100 g per minute in the medial frontal gyrus (MFG) and from 40 to 44 ml/100 g per minute over all gray matter regions in the superior part of the brain. Data obtained from the first two scans were processed by two readers and showed high reliability (ICC >0.97) and reproducibility (wsCV <6%). However, over the total period of 1 year, reliability reduced to a moderate level (ICC=0.63–0.74) with wsCVs of gray matter, left MFG, right MFG of 13.5%, 12.3%, and 15.4%, respectively. In conclusion, measurement of CBF with pulsed ASL provided good agreement between inter-raters. A moderate level of reliability was obtained over a 1-year period, which was attributed to variance in slice positioning and coregistration. As such pulsed ASL has the potential to be used for CBF comparison in longitudinal studies.     

Measurement of relative cerebral blood volume using BOLD contrast and mild hypoxic hypoxia

Relative cerebral blood volume (CBV) was estimated using a mild hypoxic challenge in humans, combined with BOLD contrast gradient-echo imaging at 3 T. Subjects breathed 16% inspired oxygen, eliciting mild arterial desaturation. The fractional BOLD signal change induced by mild hypoxia is expected to be proportional to CBV under conditions in which there are negligible changes in cerebral perfusion. By comparing the regional BOLD signal changes arising with the transition between normoxia and mild hypoxia, we calculated CBV ratios of 1.5±0.2 (mean±S.D.) for cortical gray matter to white matter and 1.0±0.3 for cortical gray matter to deep gray matter.     

虎纹镇痛肽对脑缺血损伤大鼠神经保护作用的研究

采用Pullsinelli的四血管闭塞法制作了SD大鼠全脑缺血结合蛛网膜下腔置管实验动物模型,测定全脑缺血10min再灌注后海马区的过氧化脂质(MDA)和超微量ATP酶含量变化,并在显微镜下观察HWTX-I对其病理改变的影响.结果发现HWTX-I可降低海马区MDA含量(P<0.05),使ATP酶活性上升(P<0.05);还可明显降低海马CA1区锥体神经元的损伤.可见HWTX-I对大鼠全脑缺血再灌注引起的海马区神经元损伤有保护作用.     

脑血栓形成患者用精制蝮蛇抗栓酶(Svate-3)治疗前后头发微量元素分析

对１２６例脑血栓形成患者用精制蝮蛇抗栓酶（Ｓｖａｔｅ－３）治疗，检测用药前后头发中Ｃｒ、Ｍｎ、Ｓｅ、Ｍｏ、Ｃｏ元素含量。发现脑血检患者用Ｓｖａｔｅ－３治疗后发Ｃｒ、Ｍｎ、Ｓｅ含量明显高于用药前，它们之间都有显著性差异，Ｐ＜０．０１；Ｍｏ、Ｃｏ元素的含量在用药前后无显著性差异Ｐ＞０．０５，提示发Ｃｒ、Ｍｎ、Ｓｅ与脑血栓有关。     

单纯性急性外伤性硬膜下血肿63例治疗分析

目的探讨单纯性急性外伤性硬膜下血肿的治疗特点。方法本组共63例,急诊手术25例,保守治疗38例(其中有9例保守治疗失败后中转手术)。手术方式:小骨窗开颅24例,颞肌下减压7例,标准外伤大骨瓣开颅3例;术前根据受伤机制、临床表现、CT资料等初步确定出血位置及性质。结果按3月后GOS评分,良好46例(73.02%),中残8例(12.70%),重残0例(0%),植物生存1例(1.59%),死亡2例(3.17%)。结论单纯性硬膜下血肿保守治疗指征可适当放宽,手术方式首选小骨窗开颅,可减少创伤,加快病人康复。     

白藜芦醇诱导VEGF表达促进缺血再灌注小鼠新生血管形成

研究白藜芦醇能否诱导小鼠缺血,再灌注后缺血区域新生血管形成及其与血管内皮细胞生长因子(VEGF)表达的相关性,用90只雄性BALB/c小鼠随机分为单纯缺血组、白藜芦醇组及假手术组,采用大脑中动脉线栓法制作局灶性脑缺血模型,免疫组化法测定微血管密度,Western blot检测VEGF蛋白表达.结果白藜芦醇处理组与单纯缺血对照组微血管计数存在差异,并且有统计学意义(P<0. 05),白藜芦醇处理组在各时间点VEGF蛋白表达水平均较高(P<0.05).说明白藜芦醇可以诱导脑缺血后VEGF早期表达,促进缺血区域新生血管形成,发挥脑保护作用.