The software identifies corresponding information in each dataset and uses it to estimate a spatial transformation. Shared landmarks provide recognizable reference points, voxel intensity patterns compare image values across locations, and anatomical features contribute structure-based matches. These inputs help determine how one image should be positioned relative to another, allowing subsequent comparisons to refer to the same anatomical locations.
Rigid registration preserves the existing shape of the anatomy while adjusting the dataset’s spatial position relative to another image. Nonrigid registration can accommodate tissue deformation, so it is suited to comparisons in which corresponding anatomy may not retain the same shape. The choice therefore depends on whether alignment requires position changes alone or also must represent anatomical deformation.
Accuracy depends on the quality of the shared landmarks, voxel intensity patterns, or anatomical features used to estimate the transformation. The selected images must contain information that can be meaningfully related, even when they provide different views of anatomy, structure, or function. A suitable transformation then supports interpretation of corresponding regions across the image datasets.
A typical workflow begins by selecting the image datasets to be compared, such as MRI, CT, PET, ultrasound, or sequential examinations. Registration software then identifies shared landmarks, intensity patterns, or anatomical features and estimates a transformation. The datasets are aligned using that transformation, enabling combined interpretation or comparison of the resulting spatially corresponding images.
Combining modalities allows clinicians and researchers to interpret complementary information within a common spatial framework. MRI, CT, PET, and ultrasound can contribute different information about anatomy, structure, or function, while co-registration places related regions into corresponding coordinates. This integrated view can support more comprehensive assessment than interpreting each dataset separately.
The technique is useful when decisions require information from more than one image dataset to be interpreted together. In treatment planning and image-guided procedures, aligned images can relate anatomical structures to complementary structural or functional information. This supports localization and combined assessment, including applications in radiotherapy targeting and procedures that rely on image-based guidance.
Sequential scans can be aligned so that the same anatomical regions occupy corresponding spatial coordinates at different time points. This makes comparisons between examinations more meaningful because observed differences can be interpreted in relation to the same structures. In medicine, that temporal comparison supports monitoring of disease progression and evaluation of treatment response.