Chapter 3: Self-assessment Questions

 

  1. What is the difference between “magnetic moment” and “angular momentum”? How do physicists describe nuclei that possess both?
  2. What is precession? What kind of objects precess and why?
  3. What is net magnetization?
  4. What is the difference between longitudinal magnetization and transverse magnetization?
  5. What happens during excitation?
  6. What is the gyromagnetic ratio? Why is it important for MRI?
  7. What are the parallel and anti-parallel states of a nucleus? How does a nucleus change from one to another?
  8. What is the Larmor Frequency? How does it relate to the gyromagnetic ratio? How does it relate to magnetic resonance?
  9. How does the net magnetization of a spin system (e.g., a set of atomic nuclei in a voxel) change over time, when exposed to a strong magnetic field?
  10. How is an excitation pulse calibrated to have maximum effect upon a spin system?
  11. Why do we need to tip the net magnetization from the longitudinal plane to the transverse plane?
  12. What are off-resonance effects, and why do they occur?
  13. How do we measure MR signal?
  14. What is T­1 relaxation? Does it relate primarily to longitudinal or transverse magnetization? Is it best thought of as recovery or decay?
  15. What is T2 relaxation? Does it relate primarily to longitudinal or transverse magnetization? Is it best thought of as recovery or decay?
  16. What is T2* relaxation? Why is it important for fMRI?
  17. What is the Bloch equation, and why is it important?