Missing K-Space Lines
View the Remove Even Lines page
Yes, but only in the phase-encoding direction! (The distance between the lines in the phase encoding direction, ∆ky, is proportional to 1/FOVy.) We've sampled as far out into k-space as in the original data (and changed nothing else), and so the spatial resolution won't change. The reason you would do this is to save time, because you don't need to acquire every other line in k-space. The image produced by the scanner would be "zoomed in" to the area denoted by the red box in the following image:
If the whole reconstructed image was shown, foldover as seen in the image here would be seen.
This is the same as selecting "50% RFOV" on the scanner (R = "rectangular"). (50%RFOV may also be known as "half-phase FOV".) If the object of interest extends outside of the RFOV, the foldover may obscure the region of interest.
The downside of selecting a RFOV is reduced SNR (which we'd expect since we're acquiring less data).
Here are two helpful rules to get your head around problems like these:
- The line spacing in k-space is inversely proportional to the FOV in real space.
- How "far out" we acquire data in k-space is inversely proportional to the resolution in real space.