Ordinal Multiple-Instance Learning for Ulcerative Colitis Severity Estimation with Selective Aggregated Transformer

Kaito Shiku, Kazuya Nishimura, Daiki Suehiro, Kiyohito Tanaka, Ryoma Bise; Proceedings of the Winter Conference on Applications of Computer Vision (WACV), 2025, pp. 4290-4299

Patient-level diagnosis of severity in ulcerative colitis (UC) is common in clinical practice where the most severe score for a patient is typically recorded as the diagnosis result. However previous UC classification methods (i.e. image-level estimation) mainly assumed the input was a single image. Thus these methods can not utilize severity labels recorded in real clinical settings. In this paper we propose a patient-level severity estimation method by a transformer with selective aggregator tokens where a severity label is estimated from multiple images taken from a patient similar to a clinical setting. Our method can effectively aggregate features of severe parts from a set of images captured in each patient and it facilitates improving the discriminative ability between adjacent severity classes. Experiments demonstrate the effectiveness of the proposed method on two datasets compared with the state-of-the-art MIL methods. Moreover we evaluated our method using real clinical data and confirmed that our method outperformed the previous image-level methods. The code is publicly available at https://github.com/Shiku-Kaito/Ordinal-Multiple-instance-Learning-for-Ulcerative-Colitis-Severity-Estimation.