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相关概念视频

Atomic Nuclei: Nuclear Relaxation Processes01:23

Atomic Nuclei: Nuclear Relaxation Processes

1.2K
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis,  the precessing magnetic moments are randomly oriented around the z-axis.
1.2K
Double Resonance Techniques: Overview01:12

Double Resonance Techniques: Overview

665
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...
665
NMR Spectrometers: Resolution and Error Correction01:14

NMR Spectrometers: Resolution and Error Correction

1.0K
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...
1.0K
Atomic Nuclei: Types of Nuclear Relaxation01:28

Atomic Nuclei: Types of Nuclear Relaxation

873
Nuclear relaxation restores the equilibrium population imbalance and can occur via spin–lattice or spin–spin mechanisms, which are first-order exponential decay processes.
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers...
873
Atomic Nuclei: Magnetic Resonance01:05

Atomic Nuclei: Magnetic Resonance

1.1K
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...
1.1K
¹³C NMR: ¹H–¹³C Decoupling01:04

¹³C NMR: ¹H–¹³C Decoupling

1.7K
The probability of having two carbon-13 atoms next to each other is negligible because of the low natural abundance of carbon-13. Consequently, peak splitting due to carbon-carbon spin-spin coupling is not observed in spectra. However, protons up to three sigma bonds away split the carbon signal according to the n+1 rule, resulting in complicated spectra.
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
1.7K

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相关实验视频

Updated: Jan 8, 2026

Quantifying Mixing using Magnetic Resonance Imaging
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Quantifying Mixing using Magnetic Resonance Imaging

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MC BTS:同时解决多个组件的磁化转移效应和放松.

Albert Jang1,2, Hyungseok Jang3, Nian Wang4

  • 1Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA.

Magnetic resonance in medicine
|December 16, 2025
PubMed
概括
此摘要是机器生成的。

一种新的MRI方法通过同时测量放松和磁化转移效应,即使在传输场不均的情况下,也能准确量化组织特性. 这种强大的框架在大脑和膝盖组织中得到了验证.

关键词:
在BTS中,BTS是BTS.布洛赫-西格特 (Bloch-Siegert) 是一个著名的科学家.磁化转移的转移方式多元组件的多元组件.定量成像技术 定量成像技术

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Optimizing Magnetic Force Microscopy Resolution and Sensitivity to Visualize Nanoscale Magnetic Domains
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Author Spotlight: Exploring Intrinsically Disordered Protein Dynamics Through NMR Relaxation Experiments
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相关实验视频

Last Updated: Jan 8, 2026

Quantifying Mixing using Magnetic Resonance Imaging
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Optimizing Magnetic Force Microscopy Resolution and Sensitivity to Visualize Nanoscale Magnetic Domains
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Author Spotlight: Exploring Intrinsically Disordered Protein Dynamics Through NMR Relaxation Experiments
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科学领域:

  • 磁共振成像 (MRI) 是一种磁共振成像技术.
  • 生物物理建模 生物物理建模
  • 组织分析的定量分析.

背景情况:

  • 准确的多组分组织量化对于理解组织特性至关重要.
  • 现有的MRI方法往往难以同时评估放松,磁化转移 (MT) 和传输场 (B1+) 的不均性.
  • 开发一个统一的框架对于全面的组织表征至关重要.

研究的目的:

  • 提出一个新的信号采集和建模框架,用于多组分组织量化.
  • 为了同时考虑发射场不均性,多元件放松和磁化转移 (MT) 效应.
  • 通过模拟和体内实验来验证拟议的框架.

主要方法:

  • 采用了一种RF破坏的梯度回声序列,具有非共振辐射和多个回声时间.
  • 开发了一个三池模型来描述旋转动态,包括放松和旋转交换.
  • 用布洛赫模拟和蒙特卡洛分析来推导和验证分析信号方程.
  • 该方法的可行性在人脑和膝盖组织上进行了体内测试.

主要成果:

  • 模拟显示了分析信号方程和数值模型之间的良好一致.
  • 蒙特卡洛模拟证实了三组参数估计管道在各种信号噪声比率的稳定性.
  • 在体内对大脑和膝盖进行多参数测试,结果与现有文献一致.
  • 该方法有效地弥补了B1+的不均性.

结论:

  • 已经开发了一种经过验证的信号采集和建模框架,用于多组件组织量化.
  • 该框架有效地结合了磁化转移效应和B1+不均性.
  • 模拟和实验数据都证实了该方法的稳定性和适用于各种组织的可用性.