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Tumor segmentation with CFLOW-AD:

Unsupervised tumor segmentation method using an adapted version of CFlow, an anomaly detection model. This model was trained to learn the distribution of tumor tiles extracted from whole slide images (WSI), so that non-tumor areas could be detected at the time of inference.

• Original article: D. Gudovskiy CFlow-AD, WACV 2022.
• Original code: https://github.com/gudovskiy/cflow-ad
• Aplication inspired from E. Mathian, HaloAE Visapp 2023
• Method used for tumor segmentation tasks in "Assessment of the current and emerging criteria for the histopathological classification of lung neuroendocrine tumours in the lungNENomics project." ESMO Open 2023 (under review)

Installation

• Clone this repository: tested on Python 3.8
• Install PyTorch: tested on v2.1.2
• Install Torchvison tested on v0.16.2
• Install Timm tested on v0.6.11
• Install cudatoolkit tested on 11.8.0
• Install pytorch-cuda tested on 11.8
• Install scikit-image tested on 0.19.3
• Install scikit-learn tested on 1.3.0
• Install pillow tested on 10.0.1
• Install any version of pandas, numpy, matplotlib
• For simplicity FrEIA Flows: tested on the recent branch has already be cloned in this repository
• Other dependencies in environment.yml

Install all packages with this command:

$ conda env create -f environment.yml

Datasets

This method has been tested for 3 types of histological images:

• Haematoxylin and Eosin (HE) | Haematoxylin, Eosin Saffron (HES) stained WSI:
  • Number of tumor tiles (for train and test) = 12,991 (69 patients)
  • Number of non-tumor tiles (for test) = 4,815 (33 patients)
• Ki-67 immunohistochemical stained WSI:
  • Number of tumor tiles (for train and test) = 19,053 (77 patients)
  • Number of non-tumor tiles (for test) = 10,259 (40 patients)
• Phosphohistone histone H3 (PHH3)-stained WSIs can be segmented using Ki-67 tumor tiles as a training set.

These two dataset are available on request from mathiane[at]iarc[dot]who[dot]int and will soon be available online.

Code Organization

• ./custom_datasets - contains dataloaders for TumorNormalDataset :

  • The dataloader is based on a file listing the path to the tiles.
  • Examples: ./Datasets/ToyTrainingSetKi67Tumor.txt and ./Datasets/ToyTestSetKi67Tumor.txt

• ./custom_models

  • contains pretrained resnet feature extractors:
    • For the tumor segmentations tasks we used a wide-Resnet 50 (see: resnet.py line 352)
    • Note: additional features extrators can be found in the original CFlow AD repository
  • the utils contains functions to save and load the checkpoint

• ./FrEIA - clone from https://github.com/VLL-HD/FrEIA repository.

• models - Build encoder and decoder

  • The encoder is based on a pretrained resnet (see: custom_models/resnet.py)
  • The decoder is based on FrEIA modules

• main: Main script to train and test the model.

Training Models

• An example of the configurations used to segment HE/HES, Ki-67 and PHH3 WSI is available in Run/Train/TumorNormal/TrainToyDataKi67.sh
• Configs can be viwed in config.py
• The commands below are used to train the model based on the toy data set:

bash Run/Train/TumorNormal/TrainToyDataKi67.sh

• Warnings: Network weights will be saved for all epochs in config.weights-dir/config.class-name/meta-epoch/ModelName_ClassName_MetaEpoch_SubEpoch.pt. Each checkpoint creates is associated 903MB file.

Testing Pretrained Models

• Download pretrained weights are available on request and will be soon available online
• An example of the configurations used to infer the test set is gien in Run/Test/TumorNormal/TestToyDataset.sh

bash Run/Test/TumorNormal/TestToyDataset.sh

• Main configurations:
  • checkpoint: Path to model weights to be loaded to infer the test tiles.
  • viz-dir: Directory where the result table will be saved.
  • viz-anom-map: If specified, all anomaly maps will be written to the viz-dir directory in .npy format.

Results exploration

For each tile, results_table.csv summarises:

• Its path, which may include the patient ID
• Binary tile labels, useful for sorted datasets: Tumour = 2 and Non-tumour = 1
• Max anomaly scores: value of the highest anomaly score of the tile
• Mean anomaly scores: average anomaly score of the tile

The distributions of these score are used to segment the WSI.

An example of result exploration for the segmentation of HE/HES WSI is given in ExploreResultsHETumorSeg.html.

Get tumor segmentation map

The TumorSegmentationMaps.py script is used to create the tumour segmentation map for a WSI. An example configuration is given in ExRunTumorSegmentationMap.sh. The results of this script are stored in the Example_SegmentationMap_PHH3 folder, which also gives an example of the model's performance in segmenting a PHH3-immunostained WSI.

TO DO LIST

• :construction: Check parallel training
• :construction: Check parallel test
• :construction: Model checkpoints Ki-67 and HES/HE