Chapter 4 Study Questions

  1. What is an image? What do MR images represent?
  2. Explain the following equation in simple language:
  3. What happens to transverse magnetization over time as a result of T2 decay?
  4. Explain the following sentence: “The total signal measured in MRI combines the changes in net magnetization generated by every excited voxel.”
  5. Why are magnetic field gradients important for image formation?
  6. What is slice selection? How is it typically accomplished in MRI?
  7. Why do most fMRI imaging sequences use interleaved slice acquisition?
  8. Why are some gradients called “frequency encoding gradients” and others called “phase encoding gradients”?
  9. What is the Fourier transform, and when is it used in MRI?
  10. Why must excitation pulses have the form of a sine function in order to excite a rectangular slice?
  11. What is the definition of a point in k-space? How is k-space different from normal image space?
  12. How does the center of k-space contribute to an image? How does the periphery of k-space contribute to an image?
  13. What is reconstruction?
  14. If we want an image with a higher spatial resolution, how must we change our sampling of k-space? What if we want an image with a larger field of view?
  15. Why do gradient inhomogeneities cause stretching or skewing of images? Refer to the concept of k-space in your answer.
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