Magnetic resonance imaging

From greek.doctor
  • 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
    • 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)
    • Advantages
      • No radiation
    • Disadvantages
      • Motion causes artifacts
      • Expensive
      • Strong magnets

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