Incorporating neighbourhood feature derivatives with Mutual Information to improve accuracy of multi-modal image registration

In this paper we present an improved method for performing image registration of different modalities. Russakoff [1] proposed the method of Regional Mutual Information (RMI) which allows neighbourhood information to be considered in the Mutual Information (MI) algorithm. We extend this method by taking local multi-scale feature derivatives in a gauge coordinate frame to represent the structural information of the images [2]. By incorporating these images into RMI, we can combine aspects of both structural and neighbourhood information together, which provides a high level of registration accuracy that is essential in application to the medical domain. Our images to be registered are retinal fundus photographs and SLO (Scanning Laser Ophthalmoscopy) images. The combination of these two modalities has received little attention in image registration, yet could provide much useful information to an Ophthalmic clinician. One application is the detection of glaucoma in its early stages, where prevention of further infection is possible before irreversible damage occurs. Results indicate that our method offers a vast improvement to Regional MI, with 25 of our 26 test images being registered to a high standard