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相关概念视频

Magnetic Resonance Imaging01:24

Magnetic Resonance Imaging

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Magnetic resonance imaging (MRI) is a noninvasive medical imaging technique based on a phenomenon of nuclear physics discovered in the 1930s, in which matter exposed to magnetic fields and radio waves was found to emit radio signals. In 1970, a physician and researcher named Raymond Damadian noticed that malignant (cancerous) tissue gave off different signals than normal body tissue. He applied for a patent for the first MRI scanning device in clinical use by the early 1980s. The early MRI...
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Magnetic Field Of A Current Loop01:16

Magnetic Field Of A Current Loop

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Consider a circular loop with a radius a, that carries a current I. The magnetic field due to the current at an arbitrary point P along the axis of the loop can be calculated using the Biot-Savart law.
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Atomic Nuclei: Magnetic Resonance01:05

Atomic Nuclei: Magnetic Resonance

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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...
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Potential Due to a Magnetized Object01:24

Potential Due to a Magnetized Object

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Magnetic dipoles in magnetic materials are aligned when placed under an external magnetic field. For paramagnets and ferromagnets, dipole alignment occurs in the direction of the magnetic field. However, the dipoles align opposite to the field in the case of diamagnets. This state of magnetic polarization due to the external field is called magnetization. Magnetization is defined as the dipole moment per unit volume. It plays a similar role to polarization in electrostatics.
The vector...
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Diamagnetism01:26

Diamagnetism

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Materials consisting of paired electrons have zero net magnetic moments. However, when these materials are placed under an external magnetic field, the moments opposite to the field are induced. Such materials are called diamagnets. Diamagnetism is the response of the diamagnets when placed in an external magnetic field.
Diamagnetism was discovered by Anton Brugmans in 1778 when he observed that bismuth gets repelled by magnetic fields, thus theorizing that diamagnets get repelled by magnets....
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Magnetic Field Due to Two Straight Wires01:18

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Consider two parallel straight wires carrying a current of 10 A and 20 A in the same direction and separated by a distance of 20 cm. Calculate the magnetic field at a point "P2", midway between the wires. Also, evaluate the magnetic field when the direction of the current is reversed in the second wire.
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Updated: Jun 13, 2025

MRM Microcoil Performance Calibration and Usage Demonstrated on Medicago truncatula Roots at 22 T
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非线性元材料增强的表面线圈阵列用于并行磁共振成像.

Bingbai Li1, Rongbo Xie1, Zhenci Sun1

  • 1Department of Precision Instrument, Tsinghua University, Beijing, 100084, China.

Nature communications
|September 11, 2024
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这项研究引入了一种新的非线性超材料,可以显著提高并行磁共振成像 (MRI) 中的信号噪声比 (SNR). 超材料增强MRI扫描,改善临床应用的图像质量.

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科学领域:

  • 医疗成像医学成像
  • 材料科学 材料科学 材料科学
  • 电磁主义 电磁主义

背景情况:

  • 并行磁共振成像 (MRI) 可以加速扫描,但往往会损害信号噪声比 (SNR).
  • 超材料具有增强MRI SNR和提高并行MRI质量的潜力.

研究的目的:

  • 开发和验证一种非线性超材料,用于MRI的选择性射频接收场增强.
  • 研究超材料在提高并行MRI性能方面的潜力.

主要方法:

  • 非线性元原子的设计用于选择性射频增强.
  • 开发用于分析和优化的电磁场电路联合模拟.
  • 用表面线圈阵列对元材料集成的实验验证.

主要成果:

  • 非线性超材料可以选择性地增强射频接收场.
  • 在具有元材料集成的并行MRI中,SNR增加了3倍.
  • 观察到与无线电频率传输场的干扰最小.

结论:

  • 非线性超材料可以在并行MRI中显著改善SNR.
  • 这项技术在临床MRI环境中具有实际应用的前景.
  • 超材料集成为医学成像能力提供了实质性的增强.