3-DIMENSIONAL REGISTRATION OF MULTIMODALITY MEDICAL IMAGES USING THE PRINCIPAL AXES TECHNIQUE

Registration of volumetric images from different medical imaging modalities is performed by matching surfaces using the principal axes technique. Translation, rotation, and scaling transformations are calculated by eigenvalue analysis of the scatter matrix. After applying the transformations, reslicing along comparable planes is carried out. The method is applied to a clinical case of X-ray computed tomography (CT) and magnetic resonance imaging (MRI) brain scans. The accuracy, measured as the distance between recognizable reference points in the registered CT and MRI slices, was 1.5 mm. Visual confirmation of the quality of the registration is provided by compositing the registered images. The method is simple to implement and computationally efficient; calculation of the transformation takes less than 1 s of computer time. This method requires full scan coverage in both scans and assumes local distortions are not present. Potential applications of this technique include radiation therapy, Surgical planning, functional/anatomical correlation, and retrospective studies.