Hi,

Image registration can take different forms depending on the domain it is applied to. For example, it is quite common to see research papers discussing the best approaches to register multi-modality scans (e.g., CT and PET scan images, rigid and non-rigid MR and CT registration, etc.). In microbiology, image registration can be helpful in visualising the response of cells under several conditions. In 3D reconstruction, in light microscopy, we did a work where we optimised the post-alignment values of tomographic projections for fine tuning 3D sectioning.

A good start for you to read could be the below slides.

Regards,

Abbas

https://www.robots.ox.ac.uk/~jmb/lectures/InformaticsLecture7.pdf

Image registration is the first step for image fusion. ie. Fusion of MRI-CT or PET -MRI or PET -CT images. 

image-aided navigation.-- using images registered to something like Google Earth to find out where you are and update inertial navigation systems...

Image Registration is the process of aligning   2 images using various techniques . For example ,  to fuse  MRI and CT images of a same patient into a single image and the combined image is called Fused MR-CT image. 

Then the main difficulty may be one Image ( Ex: MRI) is taken in one angle and another image (CT) is taken in another angle [ Assume one is 85 Degree Inclined and another is 80 Degree inclined ]. So for fusing the both modalities  we need to make sure that both the images are with same orientation .

Commonly  Rotation (R), Scaling (S) , Translation (T) are used for aligning the images .