An MRI scanner can be thought of as a strange kind of camera: it has no lens, it captures no light, and its pictures begin with protons responding to a magnetic field. At heart, MRI has more in common with spectroscopy than with photography. Its images are not snapshots, but matrices of data assembled from signals through spatial encoding, mathematics, and a considerable amount of computation.
Those signals can be persuaded to tell many different stories. With them, we can reveal anatomy, map brain activity, measure blood flow and hemodynamic responses, probe metabolism, characterize tissue, monitor responses to therapy—and much more. Molecular and nanoscale contrast agents expand these possibilities by making otherwise invisible biological processes visible, while emerging theranostic approaches bring imaging and therapy together.
In this Christmas tale, we will follow MRI from protons to pixels and from rodents to patients. Along the way, we will discover how physics, biology, nanotechnology, and image processing come together to bring the inside of the body out, and how modern computational tools help uncover information hidden within the data.
After all, an MR image is much more than a picture—and its most interesting features may be the ones we cannot see.