Net magnetization vector
The net magnetization vector in MRI is the summation of all the magnetic moments of the individual hydrogen nuclei.
In the absence of an external magnetic field, the individual magnetic moments are randomly oriented and since they are in opposition, the net magnetization vector is considered to be zero.
If hydrogen nuclei are placed within a strong external magnetic field, they become aligned within the field in one of two directions parallel to the direction of the field (see: energy difference between spin up and spin down states).
In MRI, the main magnetic field is termed B0.
- aligned in the direction of B0 (parallel)
- aligned in the opposite direction of B0 (antiparallel)
A parallel and antiparallel hydrogen nuclei have equal but opposite magnetic moments and cancel each other out. However, there are always slightly more hydrogen nuclei parallel to B0 and this slight difference is termed the NMV (net magnetization vector) and given the symbol M.
Related Radiopaedia articles
Imaging physics
- imaging physics
- imaging in practice
- imaging technology
-
x-ray physics
- ionizing radiation
- interaction with matter
- x-ray spectrum
- radiation units
- effective dose
- exposure
- legacy units
- radiation safety
- radiation damage (biomolecular)
- radiation damage (skin injury)
- stochastic effect
- CT physics
-
MRI physics
- B0
- chemical shift
- dependence of magnetization (proton density, field strength and temperature)
- echo time
- eddy currents
- electromagnetic induction
- Ernst angle
- flip angle
- Larmor frequency
- magnetic dipole magnetic field gradient
- magnetic susceptibility
- magnetism
- molecular tumbling rate effects on T1 and T2
- net magnetization vector (NMV)
- relaxation
- repetition time
- resonance and radiofrequency (RF)
- units of magnetism
- ultrasound physics
- nuclear medicine physics
Unable to process the form. Check for errors and try again.