| 摘要 |
An improved method for magnetic resonance imaging of a sample includes the following steps: producing a magnetic field to orient the magnetic dipoles of a sample along the z axis of an x,y,z Cartesian coordinate system; applying a first radio frequency (rf) pulse along a different axis, near the resonance frequency of the magnetic dipoles (for example, the hydrogen atoms in water); applying a gradient pulse for a time tg in order to modulate the magnetization along a preferred axis in space (for example, the z axis); allowing the magnetization to evolve for a time /zq, during which time the local variations in the susceptibility affect the excited spins; applying a second radio frequency pulse near the resonance frequency of the magnetic dipoles; allowing the sample to evolve for a second time interval TE to create observable magnetization; then detecting this magnetization, using gradients to spatially resolve the signal.
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