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WEHI-SODA-Hub/sp_segment: Usage

Introduction

Samplesheet input

You will need to create a samplesheet with information about the samples you would like to analyse before running the pipeline. Use this parameter to specify its location. It has to be a comma-separated or YAML file with a header row as shown in the examples below.

--input '[path to samplesheet file]'

Multiple runs of the same sample

Ensure that each row has a unique sample name. Even if you want to run two both Mesmer and Cellpose on the same sample, you will have to give them different sample names to run both methods without collisions.

If you only want too perform background subtraction, the minimal sample sheet is:

sample,run_backsub,tiff
sample1,true,/path/to/sample1.tiff
sample2,true,/path/to/sample2.tiff

Full samplesheet

A full sample sheet is shown below:

sample,run_backsub,run_mesmer,run_cellpose,run_cellsam,tiff
sample1,true,true,false,false,/path/to/sample1.tiff
sample2,true,false,true,false,/path/to/sample2.tiff
sample3,false,false,false,true,/path/to/sample3.tiff

You may also prefer to use YAML for your samplesheet, either is supported:

samplesheet.yml:

- sample: sample1
  run_backsub: true
  run_mesmer: true
  run_cellpose: false
  run_cellsam: false
  tiff: /path/to/sample1.tiff
- sample: sample2
  run_backsub: true
  run_mesmer: false
  run_cellpose: true
  run_cellsam: false
  tiff: /path/to/sample2.tiff
- sample: sample3
  run_backsub: false
  run_mesmer: false
  run_cellpose: false
  run_cellsam: true
  tiff: /path/to/sample3.tiff
Column Description
sample Custom sample name.
run_backsub Run background subtraction on the image
run_mesmer Run Mesmer segmentation on the image (only one of run_mesmer, run_cellpose, run_cellsam can be true per row).
run_cellpose Run Cellpose segmentation on the image (only one of run_mesmer, run_cellpose, run_cellsam can be true per row).
run_cellsam Run CellSAM segmentation on the image (only one of run_mesmer, run_cellpose, run_cellsam can be true per row).
tiff OME-TIFF for COMET or multi-channel TIFF from MIBI

An example samplesheet has been provided with the pipeline.

Running the pipeline

The typical command for running the pipeline is as follows:

nextflow run WEHI-SODA-Hub/sp_segment \
   -profile <docker/singularity/.../institute> \
   --input samplesheet.csv \
   --outdir <OUTDIR>

This will launch the pipeline with the docker configuration profile. See below for more information about profiles.

Note that the pipeline will create the following files in your working directory:

work                # Directory containing the nextflow working files
<OUTDIR>            # Finished results in specified location (defined with --outdir)
.nextflow_log       # Log file from Nextflow
# Other nextflow hidden files, eg. history of pipeline runs and old logs.

If you wish to repeatedly use the same parameters for multiple runs, rather than specifying each flag in the command, you can specify these in a params file.

Pipeline settings can be provided in a yaml or json file via -params-file <file>.

:::warning Do not use -c <file> to specify parameters as this will result in errors. Custom config files specified with -c must only be used for tuning process resource specifications, other infrastructural tweaks (such as output directories), or module arguments (args). :::

The above pipeline run specified with a params file in yaml format:

nextflow run WEHI-SODA-Hub/sp_segment -profile docker -params-file params.yaml

with:

input: "./samplesheet.csv"
outdir: "./results/"

You can also generate such YAML/JSON files via nf-core/launch.

Background subtraction parameters

Parameter Name Description
remove_markers Marker channels to remove from the background subtracted image.

Cell processing parameters

Parameter Name Description
use_whole_cell_only Use only the whole-cell segmentation to process cells (skip nuclear segmentation).

Combine channel parameters

Works for both mesmer and sopa segmentation.

Parameter Name Description
combine_method Method used to combine membrane channels (max or product).

Mesmer parameters

The following Mesmer parameters can be set:

Parameter Name Description
mesmer_segmentation_level Segmentation level (legacy parameter).
mesmer_maxima_threshold Controls segmentation level directly in mesmer, (lower values = more cells, higher values = fewer cells).
mesmer_interior_threshold Controls how conservative model is in distinguishing cell from background (higher values = more conservative interior therefore smaller nuclei & cells).
mesmer_maxima_smooth Smooths signal peaks (higher values = less irregular shapes/nuclei).
mesmer_min_nuclei_area Minimum area of nuclei to keep in square pixels.
mesmer_remove_border_cells Remove cells that touch the image border.
mesmer_pixel_expansion Manual pixel expansion after segmentation.
mesmer_padding Number of pixels to crop the image by on each side before segmentation.

Cellpose parameters

Parameter Name Description
cellpose_diameter Diameter of cells in pixels for cellpose.
cellpose_min_area Minimum area of cells in square pixels for cellpose.
cellpose_flow_threshold Flow threshold for cellpose.
cellpose_cellprob_threshold Cell probability threshold for cellpose.
cellpose_model_type Cellpose model to use for segmentation (e.g., nuclei, cyto, cyto2, cyto3 etc.).
cellpose_pretrained_model Path to a pre-trained Cellpose model.

CellSAM segmentation

CellSAM is an optional segmentation backend for whole-cell and nuclear masks. Enable it per sample with run_cellsam: true in the samplesheet.

For gated model downloads, set your DeepCell token as a Nextflow secret:

nextflow secrets set DEEPCELL_ACCESS_TOKEN $YOUR_TOKEN

If no token is provided, CellSAM uses the bundled default model.

CellSAM parameters

Parameter Name Description
cellsam_bbox_threshold Confidence threshold for bounding-box detections (default: 0.4).
cellsam_block_size Tile size in pixels used when processing large images (default: 600).
cellsam_overlap Overlap in pixels between adjacent tiles (default: 250).
cellsam_iou_depth Search depth (pixels) for IoU-based duplicate removal at tile boundaries (default: 250).
cellsam_iou_threshold IoU threshold for non-maximum suppression across tiles (default: 0.5).
cellsam_use_wsi Enable whole-slide-image tiling mode (default: true).
cellsam_gauge_cell_size Automatically estimate cell size from the image before segmentation (default: false).
cellsam_low_contrast_enhancement Apply contrast enhancement before segmentation for low-contrast images (default: false).
cellsam_model_path Path to a custom CellSAM model checkpoint. If null the built-in default model is used (default: null).
cellsam_min_area Minimum cell area in square pixels; smaller objects are discarded (default: 0).

KRONOS embeddings

KRONOS is an optional embedding step that runs after cell measurement and writes per-cell embeddings plus a merged GeoJSON with KRONOS features.

To enable KRONOS:

nextflow run WEHI-SODA-Hub/sp_segment \
   -profile <docker/singularity/.../institute> \
   --input samplesheet.csv \
   --outdir <OUTDIR> \
   --enable_kronos true \
   --kronos_model_path /path/to/kronos_model_dir \
   --kronos_marker_metadata /path/to/marker_metadata.csv

Channel names are matched case-insensitively to KRONOS marker metadata. Use kronos_marker_mapping when image channel names need explicit remapping.

KRONOS embedding parameters

Parameter Name Description
enable_kronos Enable the KRONOS embedding step entirely (default: false).
kronos_model_path Required path to the directory containing the pre-trained KRONOS .pt checkpoint.
kronos_marker_metadata Required path to a CSV file mapping marker channel names to KRONOS input slots.
kronos_config_path Path to a KRONOS YAML config file overriding default model settings (default: null).
kronos_patch_size Size in pixels of the square patch extracted around each cell for embedding (default: 64).
kronos_batch_size Number of patches processed per inference batch (default: 32).
kronos_num_workers Number of PyTorch DataLoader worker processes (default: 4).
kronos_max_value Maximum pixel intensity used for per-channel normalisation (default: 65535).
kronos_marker_mapping JSON string or path mapping pipeline channel names to KRONOS marker names. Uses identity mapping when null (default: null).
kronos_distance_threshold Maximum distance in pixels between a cell centroid and its matched nucleus; larger gaps are left unmatched (default: 5.0).

SOPA patching parameters

Parameter Name Description
technology Image type used for zarr conversion, only ome_tif is supported (COMET)
patch_width_pixel Width and height of image patch in pixels
patch_overlap_pixel Number of pixels that image patches will overlap

Mask smoothing options

Parameter Name Description
smooth_masks Enable mask smoothing before cell measurement to reduce polygon complexity (default: false). Prevents StackOverflowError in QuPath's GeoJSON export for images with complex cell boundaries.
smooth_method Smoothing method: morphological (close+open with disk kernel, conservative) or gaussian (blur+threshold, stronger smoothing). Default: morphological.
smooth_kernel_size Kernel size for smoothing. For morphological: disk radius (integer). For gaussian: sigma. Larger values = more smoothing. Default: 2.

Cell measurement options

Parameter Name Description
enable_measurements Calculate intensity and shape measurements for cell compartments (disabling will decrease execution time)
percentiles Comma-separated list of percentiles to calculate per channel. Enable measurements must be set to true to use this parameter.
pixel_size_microns Pixel size in microns, use 0.28 for COMET and 0.390625 for MIBI
estimate_cell_boundary_dist Where no matching membrane ROI exists, expand the nucleus by this many pixels
dist_threshold Maximum centroid distance in pixels for matching a nucleus to a whole-cell ROI (default: 10.0).
downsample_factor Integer downsample factor applied to image and masks before measurement, 1 = disabled (default: 1.0).
tile_size Tile size in pixels for measurement image reads (default: 2048). Aim for 2-4x more tiles than the thread count.
tile_overlap Tile overlap in pixels for measurement image reads (default: 200). Set at least as large as the largest cell diameter.
neighbors Number of nearest neighbours for neighbourhood feature aggregation, 0 = disabled (default: 5).
erosion_steps Measure intensity in 5 equal-area erosion bins from the cell/nucleus boundary inward (default: true).
expansion_steps Measure intensity in 5 equal-area expansion bins within 20 µm outward from the cell boundary (default: true).
environment_expansion Measure a pericellular 20 µm environment zone around each cell (default: true).
gzip_geojson Gzip-compress the output GeoJSON (produces .geojson.gz). Recommended for large whole-slide images (default: true).

Report parameters

Parameter Name Description
generate_report Generate segmentation report for QC

Updating the pipeline

When you run the above command, Nextflow automatically pulls the pipeline code from GitHub and stores it as a cached version. When running the pipeline after this, it will always use the cached version if available - even if the pipeline has been updated since. To make sure that you're running the latest version of the pipeline, make sure that you regularly update the cached version of the pipeline:

nextflow pull WEHI-SODA-Hub/sp_segment

Reproducibility

It is a good idea to specify a pipeline version when running the pipeline on your data. This ensures that a specific version of the pipeline code and software are used when you run your pipeline. If you keep using the same tag, you'll be running the same version of the pipeline, even if there have been changes to the code since.

First, go to the WEHI-SODA-Hub/sp_segment releases page and find the latest pipeline version - numeric only (eg. 1.3.1). Then specify this when running the pipeline with -r (one hyphen) - eg. -r 1.3.1. Of course, you can switch to another version by changing the number after the -r flag.

This version number will be logged in reports when you run the pipeline, so that you'll know what you used when you look back in the future.

To further assist in reproducbility, you can use share and re-use parameter files to repeat pipeline runs with the same settings without having to write out a command with every single parameter.

:::tip If you wish to share such profile (such as upload as supplementary material for academic publications), make sure to NOT include cluster specific paths to files, nor institutional specific profiles. :::

Core Nextflow arguments

:::note These options are part of Nextflow and use a single hyphen (pipeline parameters use a double-hyphen). :::

-profile

Use this parameter to choose a configuration profile. Profiles can give configuration presets for different compute environments.

Several generic profiles are bundled with the pipeline which instruct the pipeline to use software packaged using different methods (Docker, Singularity, Podman, Shifter, Charliecloud, Apptainer, Conda) - see below.

:::info We highly recommend the use of Docker or Singularity containers for full pipeline reproducibility. Conda is currently not supported for the pipeline. :::

The pipeline also dynamically loads configurations from https://github.com/nf-core/configs when it runs, making multiple config profiles for various institutional clusters available at run time. For more information and to see if your system is available in these configs please see the nf-core/configs documentation.

Note that multiple profiles can be loaded, for example: -profile test,docker - the order of arguments is important! They are loaded in sequence, so later profiles can overwrite earlier profiles.

If -profile is not specified, the pipeline will run locally and expect all software to be installed and available on the PATH. This is not recommended, since it can lead to different results on different machines dependent on the computer enviroment.

  • test
    • A profile with a complete configuration for automated testing
    • Includes links to test data so needs no other parameters
  • docker
    • A generic configuration profile to be used with Docker
  • singularity
    • A generic configuration profile to be used with Singularity
  • podman
    • A generic configuration profile to be used with Podman
  • shifter
    • A generic configuration profile to be used with Shifter
  • charliecloud
    • A generic configuration profile to be used with Charliecloud
  • apptainer
    • A generic configuration profile to be used with Apptainer
  • wave
    • A generic configuration profile to enable Wave containers. Use together with one of the above (requires Nextflow 24.03.0-edge or later).
  • conda
    • A generic configuration profile to be used with Conda. Not supported for this pipeline.

-resume

Specify this when restarting a pipeline. Nextflow will use cached results from any pipeline steps where the inputs are the same, continuing from where it got to previously. For input to be considered the same, not only the names must be identical but the files' contents as well. For more info about this parameter, see this blog post.

You can also supply a run name to resume a specific run: -resume [run-name]. Use the nextflow log command to show previous run names.

-c

Specify the path to a specific config file (this is a core Nextflow command). See the nf-core website documentation for more information.

Custom configuration

Resource requests

Whilst the default requirements set within the pipeline will hopefully work for most people and with most input data, you may find that you want to customise the compute resources that the pipeline requests. Each step in the pipeline has a default set of requirements for number of CPUs, memory and time. For most of the steps in the pipeline, if the job exits with any of the error codes specified here it will automatically be resubmitted with higher requests (2 x original, then 3 x original). If it still fails after the third attempt then the pipeline execution is stopped.

To change the resource requests, please see the max resources and tuning workflow resources section of the nf-core website.

Custom Containers

In some cases you may wish to change which container or conda environment a step of the pipeline uses for a particular tool. By default nf-core pipelines use containers and software from the biocontainers or bioconda projects. However in some cases the pipeline specified version maybe out of date.

To use a different container from the default container or conda environment specified in a pipeline, please see the updating tool versions section of the nf-core website.

Custom Tool Arguments

A pipeline might not always support every possible argument or option of a particular tool used in pipeline. Fortunately, nf-core pipelines provide some freedom to users to insert additional parameters that the pipeline does not include by default.

To learn how to provide additional arguments to a particular tool of the pipeline, please see the customising tool arguments section of the nf-core website.

nf-core/configs

In most cases, you will only need to create a custom config as a one-off but if you and others within your organisation are likely to be running nf-core pipelines regularly and need to use the same settings regularly it may be a good idea to request that your custom config file is uploaded to the nf-core/configs git repository. Before you do this please can you test that the config file works with your pipeline of choice using the -c parameter. You can then create a pull request to the nf-core/configs repository with the addition of your config file, associated documentation file (see examples in nf-core/configs/docs), and amending nfcore_custom.config to include your custom profile.

See the main Nextflow documentation for more information about creating your own configuration files.

If you have any questions or issues please send us a message on Slack on the #configs channel.

Running in the background

Nextflow handles job submissions and supervises the running jobs. The Nextflow process must run until the pipeline is finished.

The Nextflow -bg flag launches Nextflow in the background, detached from your terminal so that the workflow does not stop if you log out of your session. The logs are saved to a file.

Alternatively, you can use screen / tmux or similar tool to create a detached session which you can log back into at a later time. Some HPC setups also allow you to run nextflow within a cluster job submitted your job scheduler (from where it submits more jobs).

Nextflow memory requirements

In some cases, the Nextflow Java virtual machines can start to request a large amount of memory. We recommend adding the following line to your environment to limit this (typically in ~/.bashrc or ~./bash_profile):

NXF_OPTS='-Xms1g -Xmx4g'