5.2. Image Registration. Image registration is the process of bringing two or
more images into spatial correspondence (aligning them). In the context of medical
imaging, image registration allows for the concurrent use of images taken with different
modalities (e.g. MRI and CT), at different times or with different patient positions.
In surgery, for example, images are acquired before (pre-operative), as well
as during (intra-operative) surgery. Because of time constraints, the real-time intraoperative
images have a lower resolution than the pre-operative images obtained
before surgery. Moreover, deformations which occur naturally during surgery make
it difficult to relate the high-resolution pre-operative image to the lower-resolution
intra-operative anatomy of the patient. Image registration attempts to help the
surgeon relate the two sets of images.