(NMR) Nuclear Magnetic Resonance is a physical phenomenon of the magnetic property of nuclei, which have a positive nuclear spin quantum number.
Under the influence of an external static magnetic field this nuclei will precess about the direction of the magnetic field with an angular frequency (Larmor frequency). Through absorption and emission of RF energy (gradients, RF coils) at the resonance frequency (Larmor equation) and the processing of this raw data by the Fourier transformation - physical, chemical, electronic, and structural information about molecules can be obtained (NMR Magnetic Resonance Spectroscopy, Magnetic Resonance Imaging).

A state occurring when the Larmor frequency of a spin isochromat is different from that of the exciting RF field.

See also Magnetization Transfer Contrast.

A state occurring when the Larmor frequency of a spin isochromat is the same as that of the exciting RF field.

See also Magnetization Transfer Contrast.

When a magnetic moment (e.g. hydrogen nuclei) is placed within an external magnetic field (e.g. B0), it begins to oscillate about the direction of the field; this motion is called precession. The frequency of the precession (Larmor frequency) of the nuclide depends on this particular field strength. A higher field strength results in a higher frequency of the precession.

See also Precession.

Precession is a wobbling motion that occurs when a spinning object is the subject of an external force. Relevant to MRI, the proton of a hydrogen nucleus spins around its axis giving it an angular moment (quantum mechanics). Through the protons positive charge and its spin it generates a magnetic field and gets a magnetic dipole moment (MDM) parallel to the rotation axis. If placed in a magnetic field the magnetic dipole moment will precess about the direction of the magnetic field with an angular frequency (Larmor frequency). The Larmor equation dictates that the frequency of the precession at higher field strengths is higher.