Time-varying three-dimensional vector eld visualisation for the analysis of retrobulbar fat mobility during eye motion

Retrobulbar fat, or the fat behind the eyeball, plays in important role in eye motion. In order to gain a better understanding of retrobulbar fat mobility during eye motion, MRI datasets of the eyes of a healthy subject were acquired during seven differ- ent gaze directions. The Demons deformable regis- tration algorithm was used to derive time-dependent three-dimensional deformation vector elds from these datasets. Visualisation techniques were ap- plied to these datasets in order to investigate fat mo- bility in specic regions of interest. In two of the three regions of interest, fat moved half as fast as the embedded structures. In other words, when the muscles and the optic nerve that are embedded in the fat move, the fat partly moves along with these structures and partly o ws around them. This raises compelling research questions.