Registration of multimodal fluorescein images sequence of the retina

In this study, we present a Y-feature extraction method for registering color and fluorescein angiograms of the retina. The registration of multimodal fluorescein imagery requires the identification of strong geometric features in the retinal images that are invariant across modalities and to temporal grey level variations due to the propagation of the dye in the vessels. The most informative features, invariant across the considered modalities, are the locations of vessels´ ramification: the so-called Y-features. We propose a Y-feature extraction method based on the local classification of image gradient information and an articulated model. An appropriate cost function is proposed for fitting the model using a gradient based approach. The fitted Y-features are subsequently matched across the images for registering the color and fluorescein images. Experimental results obtained on a large database validate the proposed method.