Intro to MRI

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Author:
Bilon
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65756
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Intro to MRI
Updated:
2011-02-11 20:00:58
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MRI
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Intro to MRI
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  1. Some research shows what biologic change in MRI?
    ECG characteristics
  2. In MRI, what changes body temperature?
    Radiofrequency
  3. Projectiles can have a velocity of ___ mph when pulled by a 1.5 T.
    40
  4. MRI can cause what to implants and prosthesis?
    Torque, heat, and unpredictable movement in the body
  5. These cause death in MRI:
    aneurysm clips (intracranial vascular clips)
  6. RF can increase:
    body temperature and specific absorption rasio (SAR)
  7. RF power absorbed per unit of mass of an object; measured in W/kg.
    SAR Specific Absorption Ratio
  8. During excitation, nuclei ____. During relaxation, nuclei ____.
    absorb energy; give off energy
  9. Loss of absolute zero temperature of magnet:
    Quenching
  10. What escapes during quenching?
    Helium
  11. If pressure builds inside the scan room:
    break the glass partition
  12. Purpose of magnet in MRI:
    aligns nuclei into parallel (low energy) and anti-parallel (high energy)
  13. The RF source in MRI does what?
    excites nuclei and aligns nuclei away from Bo. Also receives magnetic property of a tissue.
  14. Hardware required for MRI:
    Magnet, RF source, Image receptor, computer system
  15. The image receptor in MRI records:
    magnetic property of a tissue as data
  16. Magnetic dipole is also termed:
    magnetic moment
  17. Classifications of magnet:
    Diamagnetic, Paramagnetic, Ferromagnetic
  18. Deliberate quenching should be done:
    only in emergency; i.e. fire
  19. Most widely used magnet:
    permanent
  20. Moving electrical charges induce magnetic fields around themselves:
    electromagnets
  21. Made of super conducting material; shows zero resistance after critical temperature and is super cooled by cryogen:
    superconducting electromagnet
  22. Hydrogen protons are used in routine MRI imaging because of:
    it's abundance in the body
  23. What is the precession frequency of H?
    42.6 MHz/T
  24. With the influence of a magnet, H protons want to:
    line up with the magnet in the longitudinal direction
  25. With the influence of a magnet, what happens to low energy and high energy protons?
    Low energy protons spin up (parallel) while high energy protons spin down (anti-parallel).
  26. The relative balance between spin up and spin down nuclei is called:
    Net Magnetization Vector (NMV)
  27. Large NMV results in:
    high signal that will appear light
  28. Small NMV results in:
    low signal that will appear dark
  29. A secondary spin caused by the magnet on a hydrogen atom which is spinning on it's own axis:
    Precession
  30. The speed at which an atom wobbles:
    Precessional frequency
  31. Precessional frequency is determined by:
    Magnet strength and gyro-magnetic ratio
  32. Phenomenon that occurs when an object is exposed to an oscillating perturbation that has a frequency close to it's own natural frequency:
    Resonance
  33. The angle to which the NMV moves out of alignment:
    flip angle
  34. Flip angle is usually set to reach
    90 degrees
  35. Process by which hydrogen loses it's energy:
    relaxation
  36. T1 recovery is also called _____ and results in nuclei giving up their energy to ____.
    spin lattice; the environment
  37. T2 decay is also called _____ and is caused by nuclei exchanging their energy with ____.
    spin-spin relaxation; neighboring nuclei
  38. Intrinsic factors of MRI:
    T1 recovery, T2 decay, proton density, flow apparent diffusion coefficient
  39. Extrinsic factors of MRI:
    TR, TE, Flip angle, T1, and Turbo fact
  40. Time from the application of on RF pulse to the next; determines T1 relaxation and hence T1 weighting:
    TR, or Repetition Time
  41. Time from the application of RF pulse to the peak of echo measured in the coil:
    TE, or Echo Time
  42. Molecular motion of fat is ____ and fat molecules release energy in to their environment ____.
    slow, easily
  43. T1 time of fat is _____.
    short, 200 ms
  44. Molecular motion of water is ____ and it is ____ for water molecules to release energy to their environment.
    fast, difficult
  45. The T1 and T2 time of water is ____.
    long, 2500 ms
  46. T2 weighted images have ____ fat and ____ water signals.
    darker; brighter
  47. Long TE results in ____ fat while short TE results in ____ fat.
    darker; brighter
  48. Series of RF and gradient pulses used to disturb and manipulate the orientation of the net magnetization of protons and to spatially encode the information contained within the MR echoes.
    Pulse Sequences
  49. Two major groups of pulse sequences:
    Spin echo and Gradient echo
  50. Which pulse sequence is called the gold standard for most imaging?
    Spin Echo Pulse Sequence; conventional
  51. Which pulse sequence was introduced to cut time and how?
    Gradient Echo; uses short TR
  52. Which pulse sequence is mainly used for cardiac imaging?
    GE pulse sequence
  53. Which pulse sequence is used for diagnosing bone bruise?

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