What is registration ?
Registration is a preprocessing technique used to match two image datasets or objects within images as closely as possible. This can be performed with a rigid transformation (using translation and rotation operations) or with a non-rigid transformation (also using deformation operations). For example, one may register PET and CT image datasets acquired from a patient to create hybrid PET/CT images. As another example, one may register MRI scans acquired from a patient on two separate occasions to aid in detection of disease change over time.