K-Space Tool: Introduction
K-space can seem like an obscure mystery. However, if one understands k-space, much of the reasoning behind many advanced imaging techniques becomes straightforward. Perseverance is well rewarded.
Advanced techniques become more understandable because they are all concerned with filling k-space…or not filling some of it, or filling it faster, or in a different order, or with a different trajectory, or dividing up when different parts of it are filled, or by calculating some of it, et cetera. If we understand what k-space is and how it affects the final image, the implications, advantages and disadvantages of these options becomes clearer. We can also improve our understanding of image artefacts and how to minimise or avoid them.
Admittedly it may seem—when learning about k-space—that one has to be an expert to understand the basics. How can we understand k-space without reference to phase encoding? How can we understand phase encoding without reference to k-space? This is the nature of MRI, so keep plugging away at it and the whole thing will begin to make sense.
In my experience, every approach to k-space is both a help and a dead end. The route to fuller understanding is to go up all the dead ends; read different textbooks and websites and get new perspectives. Your understanding of k-space and spatial encoding will tend less to retreat into the foggy recesses of your mind. On this site there are animated k-space tutorials, k-space Q&A, and this interactive tool in which you can alter k-space and see the effects.
Here is an MRI image, with its corresponding k-space (in which the data in k-space has been converted to greyscale values in order to display the data set as an image). We shall manipulate these data and see the effect on the image.
Choose from the list below alter k-space.