Source Matters: Source Dataset Impact on Model Robustness in Medical Imaging

Transfer learning has become an essential part of medical
imaging classification algorithms, often leveraging ImageNet weights.
The domain shift from natural to medical images has prompted alternatives such as RadImageNet, often showing comparable classification performance. However, it remains unclear whether the performance gains
from transfer learning stem from improved generalization or shortcut
learning. To address this, we conceptualize confounders by introducing
the Medical Imaging Contextualized Confounder Taxonomy (MICCAT)
and investigate a range of confounders across it – whether synthetic or
sampled from the data – using two public chest X-ray and CT datasets.
We show that ImageNet and RadImageNet achieve comparable classification performance, yet ImageNet is much more prone to overfitting to
confounders. We recommend that researchers using ImageNet-pretrained
models reexamine their model robustness by conducting similar experiments. Our code and experiments are available at https://github.com/
DovileDo/source-matters
.