The rapid and automatic combination of proton MRSI data using multi-channel coils without water suppression

The use of multi-channel coils can efficiently increase the signal-to-noise ratio (SNR) of magnetic resonance spectroscopy data if the signals from multiple channels are optimally combined. Combining multi-channel signals requires proper alignment of the phases of the signals from each of the elements of the coil and then accurately weighting the summation of those signals. We present a procedure for acquiring proton magnetic resonance spectroscopic imaging (MRSI) data using an eight-channel coil without water suppression and a rapid and robust method that uses unsuppressed water signal as a reference both for aligning the phases and for weighting the summation of signals that originate in the multiple coil elements. We use both computer simulation and in vivo proton MRSI data to demonstrate the advantages of our method for optimizing the SNR of the combined signal compared with the SNRs of signals that were acquired either using a standard volume head coil or using an eight-channel coil with a metabolite signal as the reference for combination.     

多道电刺激信号透皮传输的微线圈阵列

微线圈阵列和匹配电容谐振可以实现植入电刺激器多路信息的并行传输。为提高微线圈阵列接收各通道信息的精确性与可靠性,并减小植入系统的体积,实验中利用印刷电路板(printedcircuit board,PCB)和柔性电路板(flexible printed circuit,FPC),工艺加工微线圈阵列,将其用于2*2阵列的多通道传输装置,并测试2种工艺线圈在理想耦合、空间失配以及不同负载下的耦合效率情况。结果表明空间失配对两种线圈都有影响,但若控制横向失配在3 mm内、角度失配在30度内,并增大负载,目前实验室阶段2种线圈均可实现植入电刺激器信号的透皮传输,各通道输出信号能满足神经电刺激的要求。在系统可靠性方面,FPC线圈更具有优势,且其柔性的特点更适于植入人体。     

基于注入变频信号法的消弧线圈控制器

介绍了注入恒流变频信号法测量系统电容电流的方法,即通过注入恒流变频信号,寻找谐振频率,进而计算系统电容电流。采用陷波滤波法计算谐振电压,利用注入信号法研制出消弧线圈控制器,试验证明其性能良好。     

一种用于磁感应成像中灵敏度矩阵的计算方法

生物组织中的磁感应成像(MIT)是一种通过测量交变磁场中因扰动导体所引起的感应电压来重建复合电导率分布的方法.灵敏度矩阵即是映射电导率分布的变化与接收线圈中感应电压变化的对应关系.基于有限元方法和补偿原理,提出一种快速计算灵敏度矩阵的方法,并应用这种方法进行了多种仿真分析实验.结果表明,通过该方法可以快速地对单个扰动和多个扰动的灵敏度矩阵进行有效求解,即为MIT中逆问题的图像重建提供了有效的方法.     

Development of a temperature-variable magnetic resonance imaging system using a 1.0T yokeless permanent magnet

A temperature variable magnetic resonance imaging (MRI) system has been developed using a 1.0 T permanent magnet. A permanent magnet, gradient coils, radiofrequency coil, and shim coil were installed in a temperature variable thermostatic bath. First, the variation in the magnetic field inhomogeneity with temperature was measured. The inhomogeneity has a specific spatial symmetry, which scales linearly with temperature, and a single-channel shim coil was designed to compensate for the inhomogeneity. The inhomogeneity was drastically reduced by shimming over a wide range of temperature from −5 °C to 45 °C. MR images of an okra pod acquired at different temperatures demonstrated the high potential of the system for visualizing thermally sensitive properties.     

新型驱动线圈温度场和流场耦合仿真研究

同步感应线圈炮是线圈型电磁发射器中的一种,是目前国内外电磁发射领域研究中的一个重要方向,也是我军新概念武器预先研究的重点.它具有发射过程可控性好、发射效率高、成本低以及后勤保障简单、安全性高等特点,具有广泛的应用前景.以驱动线圈为研究对象,采用热-流-固耦合的研究方法,将传统的温度场计算方法割裂的固体计算区域和流体计算...     

线圈绕Y轴倾斜时方腔内空气磁力与重力耦合对流的数值模拟

数值分析了微重力与重力环境下圆形载流线圈绕Y轴倾斜时方腔内空气热磁对流。磁场计算采用毕奥萨伐定律;控制方程基本变量采用控制容积法离散,求解采用SIMPLE算法。计算过程中Ra数的变化范围为104~105,线圈倾斜角yeuler的变化范围为-90°~90°,磁场力数γ数的变化范围为0~200。获得了空气热磁对流的流场和温...     

Vortex counter-current chromatography

A novel counter-current chromatographic system is developed by mounting a vortex column on a type-I coil planet centrifuge. The column is fabricated from a high-density polyethylene disk (16 cm diameter and 5 cm thick) by making multiple holes of various diameters (3-12.5 mm) each arranged in a circle and connected with narrow transfer ducts. The performance of this vortex column is tested with three different two-phase solvent systems with a broad range in hydrophobicity. The results indicated that the smallest diameter column (3mm diameter, 120 units with 42.8 ml capacity) yielded the best separation with the height equivalent to a theoretical plate of 2 cm compared with 20 cm required by the conventional multilayer coil column of high-speed CCC. By avoiding the use of an Archimedean Screw Force, the system shows a low column pressure which would permit safe operation of a large preparative column without a risk of leakage of solvent and column damage.     

Toroidal coil chromatography: the effect of scale-up and "g" field on stage efficiency

Selected test results have been taken from various publications and resolution and stage efficiency measured using an established model. All experiments used the same sample and, where possible, the same sample loading. The results show that stage mixing efficiencies have increased from 1.1% in 1998 to greater than 25% in the latest scaled-up version of a Toroidal coil chromatography (TCC) instrument working at 240 g.