Tag: Neuroradiology

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12. MRI in a few (too) easy steps:

  1. Hydrogen protons have a constant spin, with random orientation of spinning axes at rest. (T/F?)
  2. In a strong static magnetic field, all the axes the spinning electrons orient along magnet’s longitudinal axes. (T/F?)
  3. An excitatory infrared-frequency pulse at right angles to the axis of the magnetic field knocks hydrogen protons out of alignment with the magnetic field and forces them into phase with other hydrogen protons. (T/F?)
  4. The nuclei go out of phase after switching off the radio frequency (T1 time). (T/F?)
  5. T2 is a measure of the time taken for spinning protons to realign with the external magnetic field. (T/F?)
  6. As protons move back into alignment with the magnetic field, and fall out of “phase” with each other, they emit RF energy. (T/F?)

  1. T
  2. T
  3. F
  4. F
  5. F
  6. T

  1. An excitatory radiofrequency (RF) pulse at right angles to the axis of the magnetic field knocks hydrogen protons out of alignment with the magnetic field and forces them into phase with other hydrogen protons.
  2. Time needed for hydrogen nuclei to go out of faze after switching off the radiofrequency field is called T2.
  3. The T1 relaxation time (spin lattice relaxation time or longitudinal relaxation time) is a measure of the time that is needed for spinning protons to realign with the external magnetic field.