MRI stands for Magnetic Resonance Imaging. So, the SpokePOV uses a Magnet to measure wheel rotation, and derives the Resonant frame rate by timing Magnet readings, and then it makes the Image appear, as if by some kind of circular magic, on the bicycle wheel! Thank you Adafruit, for this super cool toy! I use it to make legit brain-scan on a bike! I made two images of brains and fine-tuned in the SpokePOV software.