Evolutionary Architecture Optimization for Retinal Vessel Segmentation

Retinal vessel segmentation (RVS) is crucial in medical image analysis as it helps identify and monitor retinal diseases. Deep learning approaches have shown promising results for RVS, but designing optimal neural network architecture is challenging and time-consuming. Neural architecture search (NAS) is a recent technique that automates the design of neural network architectures within a predefined search space. This study proposes a new NAS method for U-shaped networks, MedUNAS, that discovers deep neural networks with high segmentation performance and lower inference time for RVS problem. We perform opposition-based differential evolution (ODE) and genetic algorithm (GA) to search for the best network structure and compare discrete and continuous encoding strategies on the proposed search space. To the best of our knowledge, this is the first NAS study that performs ODE for RVS problems. The results show that the MedUNAS ODE and GA yield the best and second-best results regarding segmentation performance with less than 50% of the parameters of U-shaped state-of-the-art methods on most of the compared datasets. In addition, the proposed methods outperform the baseline U-Net on four datasets with networks with up to 15 times fewer parameters. Furthermore, ablation studies are performed to evaluate the generalizability of the generated networks to medical image segmentation problems that differ from the trained domain, revealing that such networks can be effectively adapted to new tasks with fine-tuning. The MedUNAS can be a valuable tool for automated and efficient RVS in clinical practice.