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相关概念视频

NMR Spectrometers: Overview01:20

NMR Spectrometers: Overview

2.5K
NMR spectrometers consist of a strong magnet, a radiofrequency transmitter, and a detector attached to a computer console for recording spectra of samples containing NMR-active nuclei. In first-generation NMR instruments called continuous-wave spectrometers, the resonance frequencies of the nuclei are determined by frequency-sweep or field-sweep methods. The magnetic field strength is fixed and the rf signal is swept in the former, while the radiofrequency signal is fixed and the magnetic field...
2.5K
Atomic Nuclei: Magnetic Resonance01:05

Atomic Nuclei: Magnetic Resonance

1.4K
The number of nuclear spins aligned in the lower energy state is slightly greater than those in the higher energy state. In the presence of an external magnetic field, as the spins precess at the Larmor frequency, the excess population results in a net magnetization oriented along the z axis. When a pulse or a short burst of radio waves at the Larmor frequency is applied along the x axis, the coupling of frequencies causes resonance and flips the nuclear spins of the excess population from the...
1.4K
NMR Spectrometers: Resolution and Error Correction01:14

NMR Spectrometers: Resolution and Error Correction

1.2K
When magnetic nuclei in a sample achieve resonance and undergo relaxation, the signal detected in NMR is an approximately exponential free induction decay. Fourier transform of an exponential decay yields a Lorentzian peak in the frequency domain. Lorentzian peaks in an NMR spectrum are defined by their amplitude, full width at half maximum, and position, where the peak width is governed by the spin-spin relaxation time alone. In real experiments, however, the applied magnetic field is rendered...
1.2K
NMR Spectrometers: Radiofrequency Pulses and Pulse Sequences01:17

NMR Spectrometers: Radiofrequency Pulses and Pulse Sequences

2.1K
A pulse is a short burst of radio waves distributed over a range of frequencies that simultaneously excites all the nuclei in the sample. Upon passing a radio frequency pulse along the x-axis, the nuclei absorb energy corresponding to their Larmor frequencies and achieve resonance. This shifts the net magnetization vector from the z-axis toward the transverse plane. This angle of rotation of the magnetization vector, or the flip angle, is proportional to the duration and intensity of the pulse.
2.1K
Insensitive Nuclei Enhanced by Polarization Transfer (INEPT)01:15

Insensitive Nuclei Enhanced by Polarization Transfer (INEPT)

1.2K
Insensitive Nuclei Enhanced by Polarization Transfer (INEPT) is an advanced Nuclear Magnetic Resonance (NMR) technique specifically designed to detect and enhance the signals of low-abundance nuclei, such as carbon-13 and nitrogen-15, in small molecules. The fundamental principle behind INEPT is the transfer of polarization from a more abundant and highly polarizable nucleus, typically hydrogen-1, to the low-abundance nucleus of interest. This process effectively boosts the NMR signal of the...
1.2K
Double Resonance Techniques: Overview01:12

Double Resonance Techniques: Overview

861
Double resonance techniques in Nuclear Magnetic Resonance (NMR) spectroscopy involve the simultaneous application of two different frequencies or radiofrequency pulses to manipulate and observe two distinct nuclear spins. One important application of double resonance is spin decoupling, which selectively suppresses coupling with one type of nucleus while observing the NMR signal from another nucleus, simplifying the spectrum and enhancing resolution.
Spin decoupling is usually achieved by...
861

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Updated: Apr 11, 2026

Quantitative Magnetic Resonance Imaging of Skeletal Muscle Disease
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一个只有接收的频率转换系统,具有自动相位校正,用于同时进行多核核MRI/MRS.

Jue Hou, Courtney Bauer, Mary P McDougall

    IEEE transactions on bio-medical engineering
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    概括
    此摘要是机器生成的。

    本研究介绍了多核核磁共振成像中自动相位校正的硬件解决方案,改进了实时数据采集. 该方法从仅接收的频率转换中纠正相位不一致,从而实现灵活的扫描调整.

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    科学领域:

    • 磁共振成像 (MRI) 是一种磁共振成像技术.
    • 核磁共振 (NMR) 光谱学 核磁共振 (NMR) 光谱学

    背景情况:

    • 仅接收频率转换允许X核核磁共振扫描仪进行同时/交联的多核实验.
    • 这种技术避免了修改传输路径,但由于局部振荡器频率不同而引入相位不一致.
    • 目前需要追溯相位校正,限制扫描灵活性.

    研究的目的:

    • 提出一个硬件解决方案,用于MRI扫描期间的自动实时相位校正.
    • 消除在多核收购中需要追溯阶段校正的需要.
    • 为了使扫描参数在同时/间隔多核实验中灵活调整.

    主要方法:

    • 硬件解决方案可以实时检测和纠正局部振荡器 (LO) 的相位变化.
    • 实现需要编程备用TTL信号,并访问扫描系统LO.
    • 阶段校正应用于传输和接收之间的翻译器LO.

    主要成果:

    • 硬件解决方案有效地纠正了仅接收频率转换带来的相位不一致.
    • 由于相位校正不完善,在31P和23Na频率下观察到大约3%的SNR损失.
    • 经过校正的23Na信号显示了8度的相位标准偏差,而参考信号则为6度.

    结论:

    • 提出的硬件解决方案成功地纠正了多核核磁共振成像中的相位不一致.
    • 在相位校正中存在轻微的缺陷,在未来的升级中有可能得到改进.
    • 这种方法增强了实时数据采集和扫描参数灵活性,用于多核核磁共振成像.