Guided image generation for improved surgical image segmentation

The lack of large datasets and high-quality annotated data often limits the development of accurate and robust machine-learning models within the medical and surgical domains. In the machine learning community, generative models have recently demonstrated that it is possible to produce novel and diverse synthetic images that closely resemble reality while controlling their content with various types of annotations. However, generative models have not been yet fully explored in the surgical domain, partially due to the lack of large datasets and due to specific challenges present in the surgical domain such as the large anatomical diversity. We propose Surgery-GAN, a novel generative model that produces synthetic images from segmentation maps. Our architecture produces surgical images with improved quality when compared to early generative models thanks to the combination of channel- and pixel-level normalization layers that boost image quality while granting adherence to the input segmentation map. While state-of-the-art generative models often generate overfitted images, lacking diversity, or containing unrealistic artefacts such as cartooning; experiments demonstrate that Surgery-GAN is able to generate novel, realistic, and diverse surgical images in three different surgical datasets: cholecystectomy, partial nephrectomy, and radical prostatectomy. In addition, we investigate whether the use of synthetic images together with real ones can be used to improve the performance of other machinelearning models. Specifically, we use Surgery-GAN to generate large synthetic datasets which we then use to train five different segmentation models. Results demonstrate that using our synthetic images always improves the mean segmentation performance with respect to only using real images. For example, when considering radical prostatectomy, we can boost the mean segmentation performance by up to 5.43%. More interestingly, experimental results indicate that the performance improvement is larger in the set of classes that are under-represented in the training sets, where the performance boost of specific classes reaches up to 61.6%.