Text-Driven Tumor Synthesis.

Tumor synthesis can generate challenging cases that AI often misses or over-detects. Training on these cases improves AI performance. However, most existing synthesis methods are either unconditional- generating images from random variables-or conditioned only on tumor shape. As a result, they lack control over clinically important tumor characteristics, such as texture, heterogeneity, boundary, and pathology. The generated tumors are therefore overly similar or duplicates of existing training cases, failing to effectively address AI's weaknesses. We propose a new text-driven tumor synthesis approach, termed TextoMorph, that provides textual control over tumor characteristics in conjunction with mask control. This approach is particularly beneficial for examples that confuse the AI the most, such as early tumor detection (improving Sensitivity by + 6.5%), tumor segmentation for precise radiotherapy (improving NSD by + 3.1%), and classification between benign and malignant tumors (improving Sensitivity by + 8.2%). By incorporating text mined from radiology reports into the synthesis process, we increase the variability and controllability of the synthetic tumors to target AI's failure cases more precisely. Moreover, TextoMorph uses contrastive learning across different texts and CT scans, significantly reducing dependence on scarce image-report pairs (only 141 pairs used in this study) by leveraging a large corpus of 34,035 radiology reports. Finally, we have developed rigorous tests to evaluate synthetic tumors, showing that our synthetic tumors is realistic and diverse in texture, heterogeneity, boundary, and pathology. Code and models are available at https://github.com/MrGiovanni/TextoMorph.