  The common practice in developing computer-aided diagnosis (CAD) models based
on transformer architectures usually involves fine-tuning from ImageNet
pre-trained weights. However, with recent advances in large-scale pre-training
and the practice of scaling laws, Vision Transformers (ViT) have become much
larger and less accessible to medical imaging communities. Additionally, in
real-world scenarios, the deployments of multiple CAD models can be troublesome
due to problems such as limited storage space and time-consuming model
switching. To address these challenges, we propose a new method MeLo (Medical
image Low-rank adaptation), which enables the development of a single CAD model
for multiple clinical tasks in a lightweight manner. It adopts low-rank
adaptation instead of resource-demanding fine-tuning. By fixing the weight of
ViT models and only adding small low-rank plug-ins, we achieve competitive
results on various diagnosis tasks across different imaging modalities using
only a few trainable parameters. Specifically, our proposed method achieves
comparable performance to fully fine-tuned ViT models on four distinct medical
imaging datasets using about 0.17% trainable parameters. Moreover, MeLo adds
only about 0.5MB of storage space and allows for extremely fast model switching
in deployment and inference. Our source code and pre-trained weights are
available on our website (https://absterzhu.github.io/melo.github.io/).
