Magnetic resonance imaging
(Redirected from MRi)
- Magnetic resonance imaging
- Magnetic fields applied to the body align hydrogen atoms in the body
- When the fields are released, radio waves are released
- These radio waves are detected, and the frequency of the waves depend on the environment of the atoms (the tissues)
- Especially used for CNS, joints, heart, angiography (visualization of vessels)
- Can’t be used for people with old pacemakers
- (Can be used with new pacemakers)
- MRi contrast agents
- Molecular basis of them (I don’t understand what these mean)
- Water content
- Restricted water movement
- Macromolecular motion
- Lipid content
- Paramagnetic ions
- Molecular basis of them (I don’t understand what these mean)
- Types
- T1 weighted
- Fat is white
- Water is dark
- Brain, muscle is gray
- Bone itself is dark BUT bone marrow (fat) is white
- This makes bone look white
- Gadolinium (contrast material) is white
- More effective at visualizing normal anatomy
- T2 weighted
- Fat is dark
- Blood, oedema, CSF is white
- Brain, muscle is gray
- More effective at visualizing inflammation
- Diffusion weighted (DWI)
- Measures how easy it is for water molecules to move around in a tissue
- Ischaemic tissue is white
- Proton density weighted (PD)
- Flow sensitive
- Time of flight (TOF)
- Can measure flow of fluids without contrast
- MR angiography
- MR venography
- CSF flow studies
- Fat or water saturation
- Fluid-attenuated inversion recovery (FLAIR)
- Short tau inversion recovery (STIR)
- Diffusion tensor (DTI)
- Susceptibility-weighted (SWI)
- T1 weighted
- Advantages
- No radiation
- Disadvantages
- Motion causes artifacts
- Expensive
- Strong magnets
- Magnetic fields applied to the body align hydrogen atoms in the body