Comparison of in vivo1H MRS of human brain tumours with1H HR-MAS spectroscopy of intact biopsy samples in vitro

High resolution magic angle spinning (MAS)¹H nuclear magnetic resonance (NMR) spectroscopy has been employed to study intact human brain tumour tissue and comparison with the corresponding in vivo spectrum has been made. Two dimensional¹H MAS-NMR measurements, including J-resolved and homonuclear shift correlation spectra, were obtained to aid metabolite signal assignment. MAS gave greatly improved line-shape and reduced line-width in comparison to conventional high resolution in vivo¹H MRS of intact tissue, permitting the simultaneous detection of cellular lipids and metabolites. The technique provides the most direct method for comparison of in vivo spectra with high resolution spectra in vitro and hence allows more reliable peak assignment of in vivo¹H MRS spectra.     

In vivo lipolysis induced by heparin injection or fasting: a proton MR spectroscopy analysis of human plasma

The impact of induced lipolysis on the composition of plasma lipids is analyzed by proton magnetic resonance spectroscopy (MRS) in humans. The variations of the methylene and methyl resonances from lipids in lipoproteins are studied under two sets of lipolytic conditions: acute endovascular lipolysis induced by an intravenous injection of heparin and subacute lipolysis induced by short fasting. During acute lipolysis, the degradation of the very low density lipoproteins structures is well correlated to the modifications observed in the areas of CH₂ and CH₃ MRS signals. The comparison of regular spectra, spectra with water signal suppression, and spectra recorded with a spin-echo sequence provides information on the behavior of the different parts of the lipoproteins, that is, the neutral core, little affected by heparine-induced lipoprotein lipase (LPL) activation, and the surface layer supplying substrates to LPL. During 48 h of fasting, only limited modifications occur on the MR spectra, and lipolysis cannot be documented in details.Address for correspondence: CRMBM-CNRS, Faculté de Médecine, 27, bd Jean Moulin, 13005 Marseille, France.     

Application of LCModel for quality control and quantitative in vivo1H MR spectroscopy by short echo time STEAM sequence

The linear combination of model spectra (LCModel) calculation of a parameter for long-term quality control,k _T, was introduced, representing the ratio of the temporal and nominal intensities of CH₃ groups of lactate and acetate in a quality control phantom. This procedure is a part of the quality assurance of the scanner using fully automatic measurement and calculation ofk _T parameters, and utilizing Shewhart regulation control charts for continuous evaluation of the magnetic resonance (MR) scanner setting. The application of thek _T parameter for the correction of in vivo data increases the precision of molar concentration determination by about 4%. This was tested by the quantitative in vivo MR determination of the molar concentrations of 13 prominent metabolites (N-acetylaspartate (NAA),N-acetylaspartylgutamate, creatine and phosphocreatine (Cr), choline-containing compounds (Cho), myo-inositol, scyllo-inositol., γ-aminobutyric acid, glutamine, glutamate, glucose, lactate, alanine, taurine) in the white matter and hippocampus of the brain in groups of volunteers, using a short echo time stimulated echo acquisition mode sequence (echo time =10 ms) and the LCModel technique. The repeatability of the measurement of prominent metabolites such as NAA, Cr and Cho was found to be around 10% (relative standard deviation,n=6); precision in a group of volunteers (n=20 and 28, respectively) was in the range of approximately 13–20%. For other metabolites, which are measured with a lower signal-to-noise ratio, the precision can be much lower.     

In vivo MR investigation of skeletal muscle function in small animals

In vivo ³¹P-MRS investigations have been widely used in small animals to study skeletal muscle function under normal and pathological conditions. Paradoxically in these studies, the benefit provided by ³¹P-MRS in terms of non-invasiveness is lost because of the utilization of experimental setups that integrate invasive devices for inducing muscle contractions and for measuring mechanical performance. These traditional methodologies, which require surgical preparations, have obvious limitations regarding repeatability in the same animal. The purpose of this review is to highlight the technical aspects of the in vivo MR investigations of skeletal muscle function in small animal models. We will more particularly address the issue related to the invasiveness of different procedures used so far in order to show finally that a further step into non-invasiveness can be achieved, in particular with the support of muscle functional ¹H-MRI.     

FPGA实现旋转变压器R2D变换方法的研究

旋转变压器到数字信号转换的过程称之为R2D变换,也可称之为解码。实现R2D有专用的解码芯片,但实际使用中发现解码芯片很难通过电磁兼容实验,尝试采用软件的方式来实现。软件实现关键是对反三角函数的求解,经典方法是采用CORDIC算法实现,CORDIC在求解超越函数有一定的优越性,流水线结构更是可以满足高速运算,因此应用较为广泛。但解码方法是多样的,还同时介绍了一种角度跟随实现解码的方法,该方法通过构建反馈模型实现角度的逐渐逼近,最终实现解码。这两种方法都很容易在FPGA内实现,仿真分析表明它们的精度都能够满足需求,适合于大多数应用场合。     

31P MR spectroscopy and in vitro markers of oxidative capacity in type 2 diabetes patients

Background: Skeletal muscle mitochondrial function in type 2 diabetes (T2D) is currently being studied intensively. In vivo ³¹P magnetic resonance spectroscopy (³¹P MRS) is a noninvasive tool used to measure mitochondrial respiratory function (MIFU) in skeletal muscle tissue. However, microvascular co-morbidity in long-standing T2D can interfere with the ³¹P MRS methodology. Aim: To compare ³¹P MRS-derived parameters describing in vivo MIFU with an in vitro assessment of muscle respiratory capacity and muscle fiber-type composition in T2D patients. Methods: ³¹P MRS was applied in long-standing, insulin-treated T2D patients. ³¹P MRS markers of MIFU were measured in the M. vastus lateralis. Muscle biopsy samples were collected from the same muscle and analyzed for succinate dehydrogenase activity (SDH) and fiber-type distribution. Results: Several ³¹P MRS parameters of MIFU showed moderate to good correlations with the percentage of type I fibers and type I fiber-specific SDH activity (Pearson’s R between 0.70 and 0.75). In vivo and in vitro parameters of local mitochondrial respiration also correlated well with whole-body fitness levels (VO _2peak) in these patients (Pearson’s R between 0.62 and 0.90). Conclusion: Good correlations exist between in vivo and in vitro measurements of MIFU in long-standing insulin-treated T2D subjects, which are qualitatively and quantitatively consistent with previous results measured in healthy subjects. This justifies the use of ³¹P MRS to measure MIFU in relation to T2D.     

考虑弯道环流影响的平面二维水沙数学模型(Ⅱ)——模型的验证

运用Chang的S型弯道断面流速分布和中性物质浓度分布,及实际河道的河床冲淤对修正后平面二维水流运动方程和悬移质不平衡输沙方程进行验证,并与修正前的模型进行比较.模拟结果发现修正后模型计算结果较修正前模型计算结果与实测值符合更好.表明二次流项及横向输沙项的加人能更有效地模拟出弯道处的环流水力特性及横向输沙特性.     

Integrated RF probe for in vivo multinuclear spectroscopy and functional imaging of rat brain using an 11.7 Tesla 89 mm bore vertical microimager

To acquire high quality in vivo NMR data from rat brain using a vertical 89-mm bore magnet, specially designed NMR probes with integrated RF coils and animal handling capability are required. An RF probe design that is also capable of rat head fixation, body support and suitable for physiology monitoring and maintenance was constructed for an 89 mm bore, 11.7 T, vertical microimager which is equipped with a 57-mm i.d. gradient insert. Design concept and practical aspects of probe construction are described in detail. The device allows accurate and highly reproducible positioning of rat head inside the magnet while providing excellent RF performance. Typical results from fMRI, localized in vivo proton and multinuclear spectroscopy using this probe system are presented.     

In vivo quantification of response to treatment in patients with multiple myeloma by <Superscript>1</Superscript>H magnetic resonance spectroscopy of bone marrow

Object Magnetic resonance imaging (MRI) is the gold standard non-invasive technique to detect malignant disease in the bone marrow. Proton magnetic resonance spectroscopy (MRS) can be performed as a quick adjunct to routine spinal MRI. We performed proton MRS to patients with multiple myeloma (MM) at diagnosis and after treatment to investigate the possible correlation of MRS data with response to therapy. Patients and methods Twenty-one patients with newly diagnosed MM underwent combined MRI/MRS explorations of a transverse center section in the fifth lumbar vertebral body. MRS was acquired with STEAM and 40 ms TE. Areas of unsuppressed water and lipid resonances were used to calculate the lipid-to-water ratio (LWR). Results No association was detected between initial LWRs and the clinical characteristics of patients. Post treatment MRS was available in 16 patients of whom 11 (69%) presented an LWR increase, this included all complete responders (8/8, 100%, P = 0.012). A post-treatment LWR value equal to or larger than one is proposed as a non-invasive marker of complete response to treatment. Conclusion Only patients responding to treatment presented a significant increase in bone marrow LWR after therapy. MRS may provide an adequate quantification of response to chemotherapy in patients with MM.     

Assignment of glial brain tumors in humans byin vivo 1H-magnetic resonance spectroscopy and multidimensional metabolic classification

This study presents a simple approach for the noninvasive assignment of glial brain tumors according to malignancy by single-voxel proteon magnetic resonance spectroscopy at short echo times (TE≦50 milliseconds). Based on peak area ratios, a five-dimensional data set was obtained for each investigated subject. This vector was then projected along metabolic coordinates in a two-dimensional metabolic space. These coordinates had been determined in a previous study (Hagberg G et al., 1995,Magn Reson Med 34: 242–252). Tumor assignment was done without any knowledge of histology by comparing the location of the new cases to the features of the previous study. All 11 investigated glioblastomas multiforme, as well as 4 of 5 astrocytomas grade II, could easily be assigned to the groups of high- and low-grade tumors, respectively. Classification was more difficult in the case of a cystic astrocytoma grade II and one astrocytoma grade III. Two spectra measured in normal-appearing matter of glioblastoma patients were not classified as healthy. Using single-voxel proton magnetic resonance spectroscopy at short echo times with the knowledge of a base study, a straightforward, fast, and noninvasive differential diagnosis of glial brain tumors is possible. Supported by the Swiss National Science Foundation Research Grants No. 31-32533.91 (to J.S.) and 32.39773.93 (to W.S.).W.R. and E.W.R. have been supported by the Krebsliga beider Basel. A preliminary account of this work was given at the Third Annual Scientific Meeting of the International Society for Magnetic Resonance in Medicine, Nice, France, August 1995, abstract 1719.     

Investigation of multidrug resistance in cultured human renal cell carcinoma cells by 31P-NMR spectroscopy and treatment survival assays

KTCTL-26 and KTCTL-2 are renal cell carcinoma (RCC) lines with high and lowexpression of P-170 glycoprotein, respectively. Inherent differences between the two cell lines in terms of phosphate metabolites and growth characteristics in culture were examined for possible association with multidrug resistance (MDR). Differences in response to drug treatment were investigated for 40 h incubations with various doses of vinblastine (VBL) alone or as cotreatments with various concentrations of the calcium antagonist diltiazem (DIL) and/or interferon–α (IFN-α). Treatment effects were quantitated using the MTT survival assay and ³¹P magnetic resonance spectroscopy (MRS) to determine phosphate metabolite profiles in intact cells. KTCTL-2 and KTCTL-26 cells exhibited significant inherent differences in phosphocholine, glycerophosphocholine, glycerophosphoethanolamine, and phosphocreatine levels. KTCTL-26 cells were more sensitive than KTCTL-2 to 0.011μM VBL alone (87% vs. 102% survival) or to 0.011μM BL + 10μM DIL (55% vs. 80% survival). The latter treatment resulted in a significant decrease in the ratio of phosphocholine to glycerophosphocholine in KTCTL-26 cells but no significant changes in phosphate metabolites in KTCTL-2 cells. Metabolomic ³¹P MRS detects different metabolite profiles for RCC cell lines with different MDR phenotypes and may be useful for noninvasive characterization of tumors in a clinical setting.This revised version was published online in August 2005 with a corrected sequence of authors.     

二维核磁共振测井时序与反演算法实验研究

本文提出了一种"改进型CPMG DE"二维核磁共振测井序列,同时获取地层流体扩散系数D和横向弛豫时间T2,克服了"改变回波间隔,测量多组CPMG自旋回波"时序在测量长扩散时间方面的缺陷;并结合奇异值分解(SVD)与Tikhonov正则化算法提出了一种与该时序对应的反演解释方法,极大地减少了反演过程的计算量和复杂性,有效获取流体扩散-弛豫(D-T2)二维分布。数值模拟显示,对同时含有稠油和束缚水的地层,当原始信号SNR>40dB时,该算法可有效区分稠油和束缚水。在自行研发的二维核磁测井仪上的初步实验室研究表明,本文设计时序与算法可有效获取CuSO4溶液的二维分布。     

LiMn2O4在水系电液中嵌脱锂的EIS研究

运用电化学阻抗谱（EIS）研究尖晶石LiMn2O4电极在1mol／L的LiNO3水溶液中的贮存和首次脱锂过程。实验结果表明：尖晶石LiMn2O4电极在上述水溶液电解液中,无论是在贮存还是在充放电过程中,均会受到不同程度的腐蚀,致使锂离子在尖晶石LiMn2O4中的嵌脱过程变得困难。     

考虑旋转磁通的PMSM铁心损耗数值计算

为了准确计算交流永磁同步电机(PMSM)铁心损耗,采用二维有限元法对PMSM定子与磁极区域电磁场进行了分析研究,阐述了定子铁心不同区域磁场的变化规律及磁极区域涡流场的分布规律.在此基础上,借助谐波分析的方法,综合考虑电机中交变与旋转磁场的影响,给出了一种较准确求解定子铁心损耗和PMSM转子涡流损耗的计算方法,并与传统的计算方法进行了比较.结果表明,考虑旋转磁场及谐波磁通密度影响时的定子铁心损耗计算值与传统的仅考虑交变基波磁通密度时的损耗计算值相比有显著增加,更接近于实际测量值,磁极涡流损耗值与定子槽口大小密切相关,占电机总损耗的比重较大,是不可忽略的.     

A continuous-flow perfusion system for the maintenance and NMR study of small tissue samples in vitro

To describe and evaluate a novel perfusion system developed to maintain excised tissue in a flowing, oxygenated bathing solution during acquisition of nuclear magnetic resonance (NMR) data, and in addition allow precise data to be acquired continuously while altering the composition of the bathing solution surrounding the tissue. A chamber to house the tissue sample was constructed of interlocking sections of polyethylene tubing, and had approximate internal dimensions of 4 mm in diameter and 4 mm in height. Temperature-controlled, physiologically appropriate buffer solution was pumped via an infusion pump through the chamber, entering and exiting by way of small openings on either end. Immediately surrounding the polyethylene chamber was a tight-fitting four-loop solenoid RF coil. Measured proton NMR parameters were found to be fairly insensitive to the flow rate of the buffer if this coil was used only for reception and a larger-volume transmit-only coil was used for excitation. Temperature control of the sample was successfully implemented between 25 and 40°C. The perfusion system was found to be resistant to the effects of flow rate, as well as a useful tool for the administration of drugs or agents to the tissue. Changes in buffer composition could be performed on the fly without the need to reposition the sample each time a change was made. This avoidance of repositioning was found to yield a fivefold improvement in the precision of T₂ spectral parameters (using frog sciatic nerve as a sample).The authors wish to acknowledge the Canadian Institutes of Health Research (CIHR) for funding and the In Vivo NMR Facility of the University of Alberta for infrastructural support     

聚丙烯酸及其钠盐在碱性锌锰电池中的应用

概述了碱性锌锰电池锌膏增稠剂的技术进步。通过对比试验,分析了羧甲基纤维素钠、聚丙烯酸、聚丙烯酸钠、聚丙烯酸酯对电池主要性能的影响。试验表明:采用聚丙烯酸或与聚丙烯酸钠以一定比例混合作锌膏增稠剂,锌膏和制成的电池具有较低的析气量,电池的电性能、贮存性能、抗振动性能等均较理想,工艺适应性也较好。     

Contribution of various substrates to total citric acid cycle flux and ]anaplerosis as determined by13C isotopomer analysis and O2 consumption in the heart

A simple relationship between parameters derived from a¹³C NMR isotopomer analysis and O₂ consumption is presented that allows measurement of the absolute rate of acetyl-CoA oxidation and anaplerotic flux in tissues oxidizing a mixture of four substrates. The method was first applied in a study of the effects of work state and -adrenergic stimulation on net acetate oxidation and anaplerosis in the isolated working rat heart. The results demonstrate that the anticipated ratio of 2 between O₂ consumption and TCA cycle flux for hearts oxidizing only acetate holds at low workload when anaplerosis is low, but deviates toward a factor of 3 under high workload conditions when anaplerosis is increased. This analysis was also extended to hearts that oxidize a more physiological mixture of substrates including long-chain fatty acids, acetoacetate, lactate, pyruvate, and glucose. We show that the contribution each substrate makes to total TCA cycle flux can be determined by combined¹³C NMR and O₂ consumption measurements. The present study also demonstrates that stimulation of anaplerosis (by addition of propionate) can significantly alter the relative contribution each substrate makes to total TCA cycle flux. We conclude that if¹³C labeling patterns are selected appropriately, a comprehensive picture of flux through all major metabolic pathways feeding the cycle can be determined in a single experiment even when complex physiological mixtures of substrates are provided.