  Unpaired image-to-image translation of retinal images can efficiently
increase the training dataset for deep-learning-based multi-modal retinal
registration methods. Our method integrates a vessel segmentation network into
the image-to-image translation task by extending the CycleGAN framework. The
segmentation network is inserted prior to a UNet vision transformer generator
network and serves as a shared representation between both domains. We
reformulate the original identity loss to learn the direct mapping between the
vessel segmentation and the real image. Additionally, we add a segmentation
loss term to ensure shared vessel locations between fake and real images. In
the experiments, our method shows a visually realistic look and preserves the
vessel structures, which is a prerequisite for generating multi-modal training
data for image registration.
