Diamagnetism
Diamagnetism is the property of materials that have no intrinsic atomic magnetic moment, but when placed in a magnetic field weakly repel the field, resulting in a small negative magnetic susceptibility. Materials like water, copper, nitrogen, barium sulfate, and most tissues are diamagnetic.
The figure illustrates the effect of a diamagnetic material (grey circle) on the magnetic field flux lines (blue). The weak negative magnetic susceptibility contributes to the loss of signal seen in bowel on MRI after administration of barium sulfate suspensions.
Related Radiopaedia articles
Physics and Imaging Technology: MRI
- MRI (introduction)
-
MRI physics
- echo time
- flip angle
- repetition time
- B0
- magnetic susceptibility
- electromagnetic induction
- eddy currents
- magnetic field gradient
- dependence of magnetisation (proton density, field strength and temperature)
- magnetism
- Larmor frequency
- magnetic dipole
- net magnetisation vector
- resonance and radiofrequency (RF)
- chemical shift
- relaxation
- Ernst angle
- molecular tumbling rate effects on T1 and T2
- units of magnetism
- MRI hardware
- signal processing
-
MRI pulse sequences (basics | abbreviations | parameters)
- spin echo sequences
- inversion recovery sequences
- gradient echo sequences
- fat-suppressed imaging sequences
- diffusion weighted sequences (DWI)
-
perfusion-weighted imaging
- techniques
- derived values
- CSF flow studies
- susceptibility-weighted imaging (SWI)
- saturation recovery sequences
- echo-planar pulse sequences
- metal artifact reduction sequence (MARS)
- T1 rho
- spiral pulse sequences
- MR angiography (and venography)
-
MR spectroscopy (MRS)
- Hunter's angle
- lactate peak: resonates at 1.3 ppm
- lipids peak: resonate at 1.3 ppm
- alanine peak: resonates at 1.48 ppm
- N-acetylaspartate (NAA) peak: resonates at 2.0 ppm
- glutamine-glutamate peak: resonate at 2.2-2.4 ppm
- gamma-aminobutyric acid (GABA) peak: resonates at 2.2-2.4 ppm
- 2-hydroxyglutarate peak: resonates at 2.25 ppm
- citrate peak: resonates at 2.6 ppm
- creatine peak: resonates at 3.0 ppm
- choline peak: resonates at 3.2 ppm
- myoinositol peak: resonates at 3.5 ppm
- functional MRI (fMRI)
- MR fingerprinting
-
MRI artifacts
- MRI hardware and room shielding
- MRI software
- patient and physiologic motion
- tissue heterogeneity and foreign bodies
- Fourier transform and Nyqist sampling theorem
- MRI contrast agents
- MRI safety
Factors affecting T1
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