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QUESTIONS
» K-Space

K-space is a mind-numbing mystery. (Not really.) It is really. (No it's not.) Yes it is.

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K-Space Q&A

These questions are concerned with k-space.

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  1. Why are the signals stronger (larger amplitude) across the centre of k-space, as opposed to the signals acquired at the edges?
  2. Describe the relationship between the centre of k-space and the centre of the image.
  3. What are spatial frequencies?
  4. The K-Space Tool illustrates the effect of a low pass filter. Does this change the field-of-view (FOV) changed compared to the original data? If so, how?
  5. Why do we use a Fourier transform in MRI? What does it do?
  6. Why is k-space called k-space?
  7. Look at the images on the "random motion artefacts" page of the K-Space Tool. Did motion occur upwards in the xy plane of the scanner, or left to right in the xy plane?
    [up-down: phase encoding direction]
    [left-right: frequency encoding direction]
  8. Sometimes k-space is introduced as a raw data space, which is simply a matrix into which the digitised MR signal data is placed. What is the difference between data space and k-space?
  9. Why isn't the conjugate symmetry of k-space always exploited, to save scan time? What's the downside? Why does it occur?
  10. Why do we keep k-space symmetrical (N x N) such that N is a power of 2, even when we aren't acquiring all of k-space?
  11. Refer to the "remove even lines" page of the K-Space Tool. Has the field-of-view (FOV) changed compared to the original data? If so, how?
  12. What is phase oversampling?
  13. For the keen: Consider the non-acquisition of every other line in k-space (the "remove even lines" page of the K-Space Tool). What SENSE-factor is this equivalent to?
  14. What is the difference between linear and centric k-space ordering?

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