C. Acceleration via incoherence

In MRI, we sample the object’s frequency (rather than physical) domain. The number of possible sampling strategies is, in this case, equal to the number of ways one can traverse a three dimensional space – hence almost unlimited. Still, 99% of MRI scans employ a conventional Cartesian grid, due to its robustness to hardware inaccuracies, and due the simplicity of reconstructing images using fast Fourier transform as opposed complexity of reconstructing non-Cartesian data. This being said, non-Cartesian sampling can be highly advantageous owing to several unique characteristics:

  • High robustness to motion artifacts, leading to sharper imaging point-spread function
  • Immunity to aliasing (“ghosting”) artifacts, allowing to image at arbitrary field-of-views, and thereby offering higher spatial resolutions.
  • Incoherent undersampling artifacts, which makes this sampling scheme an ideal for accelerated scans techniques such as compressed sensing or model-based reconstruction.