One task in tumor imaging is to evaluate the tumor growth and monitor treatment. Two images acquired over time need to be registered before they can be used for quantitative comparison.
Tumors are often distinguished by their unique physiological properties such as vascular permeability. Functional imaging modalities such as PET and DCE MRI are used to study tumor physiology. However, these functional images are usually lower in resolution and do not display anatomy well. High-resolution images such as CT are needed to view the structures. The registration between functional images and structural images will present both functional activity and anatomic structure in the same view.
In some dynamic imaging studies, where multiple sequences of images need to be taken at different phases of the contrast injection, the patient might move between image sequences. This movement might compromise the accuracy of image analysis. The registration between different sequences of images in the same study can offset the patient movement, which is also called motion correction. Image subtraction may be applied after the motion correction to show the change of contrast agents in the tissues.
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