Elastic registration of 3D whole body CT and PET images by quaternion-based interpolation of multiple piecewise linear rigid-body registrations

Abstract

We report an algorithm for automatic elastic registration of whole body computed tomography (CT) and positron emission tomography (PET) images, which would allow accurate localization of viable tumors visible clearly in the perfusion PET image with respect to the anatomy that is better delineated in the CT image. The algorithm generates an elastic transformation field (TA) from a unique quaternion-based interpolation of multiple rigid-body registrations (based on maximization of normalized mutual information), each obtained for hierarchically subdivided image blocks. Fifteen pairs of clinically acquired CT and PET scans were registered using our algorithm. All image pairs registered visually correct. For validation, a set of anatomic landmarks was identified independently by two clinical experts in both images of each CT-PET pair. Based on each expert's marked points, two thin-plate spline-based deformation fields (TE1, TE2) were determined for each image pair. Interobserver variability calculated as the mean difference between transformed locations obtained using each of 'TE1', 'TE2' and 'TA' (5.8 mm) was comparable to the interobserver variability calculated as the mean difference in transformed locations obtained using only 'TE1' and 'TE2' (4.5 mm), suggesting that the accuracy of the registration algorithm is comparable to that of the experts.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.