Why does an MRI take so long?

A scanner does not take a picture: it measures k‑space, the image's frequencies, one line at a time, and each line takes half a second (here they go eight times as fast). Today's patient is a cat, which keeps still for about half a minute. Scan every line and it takes over a minute. Scan fewer and the cat folds over itself, unless something fills in the missing lines: the scanner's coils, or a neural network that has learned what cats look like.