Using nnU-Net with 2D RGB images and custom data splits

nnU-Net is now considered a standard and state-of-the-art tool for medical image segmentation, but, I think that it is opinionated in the following ways that affect how I may use it: It enforces a specific training and evaluation workflow, including assumptions about data splits. This means using custom train-valid-test splits requires some workarounds. It assumes 3D volumetric data, and while 2D data is supported, it’s the not the primary use case. It assumes grayscale images, and does not support RGB images out of the box. This again means that RGB images require some workarounds. A lot of researchers, however, happily use nnU-Net for 3D volumetric medical images, so these limitations may not be relevant to them. ...

January 17, 2026 · 5 min · Kumar Abhishek

Beyond Pixel-Wise Supervision for Segmentation

Here are some slides I made to present this MIDL 2021 paper in our reading group:

December 7, 2022 · 1 min · Kumar Abhishek

Aggregating Multi-Annotator Segmentations for Medical Images

Just like the last term, I decided to present on a topic spanning 2-3 papers instead of a single paper. This time, I chose to present on how existing works “aggregate” multi-annotator segmentations for medical images. These are the papers that I covered in this presentation: Warfield et al., “Simultaneous Truth and Performance Level Estimation (STAPLE): An Algorithm for the Validation of Image Segmentation”, IEEE Transactions on Medical Imaging, 2004 [URL]. Kats et al., “A Soft STAPLE Algorithm Combined with Anatomical Knowledge”, MICCAI 2019 [URL]. Zhang et al., “Learning to Segment When Experts Disagree”, MICCAI 2020 [URL]. Here are the slides I made to present this topic in our reading group: ...

July 28, 2022 · 1 min · Kumar Abhishek

Deep Learning for Unsupervised Image Segmentation

This term, I really wanted to present this one ICASSP paper I found very interesting, but then I realized that the authors followed up their work with another journal paper (IEEE TIP), so I decided to discuss both. Both of these papers deal with the topic of unsupervised image segmentation: Kanezaki, “Unsupervised Image Segmentation by Backpropagation”, ICASSP 2018 [URL]. Kim et al. “Unsupervised Learning of Image Segmentation Based on Differentiable Feature Clustering”, IEEE Transactions on Image Processing, 2020 [URL]. Here are the slides I made to present this topic in our reading group: ...

March 31, 2022 · 1 min · Kumar Abhishek

Augmenting Data by Learning Spatial and Appearance Transformations

Here are some slides I made to present this CVPR 2019 paper in our reading group:

June 20, 2019 · 1 min · Kumar Abhishek