Extended Data Fig. 3: Illustration of how the embeddings for COVID-19, Pneumonia and Normal evolve in t-SNE³⁸.

From Ark⁺ (a) to Ark⁺_+covid (b), an upgraded Ark⁺ model is created by incrementally and continually pretraining Ark⁺ with the COVID-19 diagnostic task. Ark⁺_+covid has more distinct embeddings for the three conditions, revealing its newly-acquired capacity for capturing the features specific to COVID-19. This capability can be further enhanced through fine-tuning (c). d–g illustrate how the embeddings for COVID-19, Pneumonia and Normal evolve in t-SNE from the pretrained Ark⁺ (d) to fine-tuning Ark⁺ with increasing numbers of samples continually (e–g). Ark⁺ obtains distinguishable embeddings when the training data reach 3,000, representing 10% of the full training set (f). This highlights Ark⁺’s ability to efficiently develop distinct feature representations, markedly enhancing its diagnostic accuracy and adaptability to new information.