Image reconstruction in magnetic resonance imaging: the Phantom, Cat Woman and Transformers

Magnetic Resonance Imaging (MRI) is a technique now commonly used in hospitals to image soft tissue in the body. The advantage is that it can often give clear images non-invasively, that is, without surgery. The images we see, however, are not "photographs" of body organs, but rather they are mathematically recreated using Fourier Transforms. This technique can be shown to be accurate, provided that the background magnetic field varies linearly with position in the body. In reality, of course, the magnetic field contains non-linear components, and these can distort the recreated image, giving incorrect locations for body organs, or else indicating shadowy regions in the image which are not really present ("false positives"). This talk will discuss the use of a Phantom image, which in principle can remove the effects of these field non-linearities entirely. The idea is simple, and will be illustrated on a photographic image. In the process, we will endeavor to exceed Schrodinger's Cat in sheer cuteness.