# load required packages

1 Installation

# Install the package from Bioconductor
if (!requireNamespace("BiocManager", quietly = TRUE)) {


2 Overview

The simpleSeg package extends existing bioconductor packages such as cytomapper and EBImage by providing a structured pipeline for creating segmentation masks from multiplexed cellular images in the form of tiff stacks. This allows for the single cell information of these images to be extracted in R, without the need for external segmentation programs. simpleSeg also facilitates the normalisation of cellular features after these features have been extracted from the image, priming cells for classification / clustering. These functions leverage the functionality of the EBImage package on Bioconductor. For more flexibility when performing your segmentation in R we recommend learning to use the EBimage package. A key strength of simpleSeg is that we have coded multiple ways to perform some simple segmentation operations as well as incorporating multiple automatic procedures to optimise key parameters when these aren’t specified.

3 Load example data

In the following we will reanalyse two MIBI-TOF images from (Risom et al., 2022) profiling the spatial landscape of ductal carcinoma in situ (DCIS), which is a pre-invasive lesion that is thought to be a precursor to invasive breast cancer (IBC). These images are stored in the “extdata” folder in the package. When the path to this folder is identified, we can read these images into R using readImage from EBImage and store these as a CytoImageList using the cytomapper package.

# Get path to image directory
pathToImages <- system.file("extdata", package = "simpleSeg")

# Get directories of images

imageDirs <- dir(pathToImages, "Point", full.names = TRUE)
names(imageDirs) <- dir(pathToImages, "Point", full.names = FALSE)

# Get files in each directory
files <- files <- lapply(
  pattern = "tif",
  full.names = TRUE

# Read files with readImage from EBImage
images <- lapply(files, EBImage::readImage, = TRUE)

# Convert to cytoImageList
images <- cytomapper::CytoImageList(images)
mcols(images)$imageID <- names(images)

4 Segmentation

simpleSeg accepts an Image, list of Image’s, or CytoImageList as input and generates a CytoImageList of masks as output. Here we will use the histone H3 channel in the image as a nuclei marker for segmentation. By default, simpleseg will isolate individual nuclei by watershedding using a combination of the intensity of this marker and a distance map. Nuclei are dilated out by 3 pixels to capture the cytoplasm. The user may also specify simple image transformations using the transform argument.

masks <- simpleSeg::simpleSeg(images,
                              nucleus = "HH3",
                              transform = "sqrt")

4.1 Visualise separation

The display and colorLabels functions in EBImage make it very easy to examine the performance of the cell segmentation. The great thing about display is that if used in an interactive session it is very easy to zoom in and out of the image.

# Visualise segmentation performance one way.

4.2 Visualise outlines

The plotPixels function in cytomapper make it easy to overlay the masks on top of the intensities of 6 markers. Here we can see that the segmentation appears to be performing reasonably.

# Visualise segmentation performance another way.
cytomapper::plotPixels(image = images[1], 
                       mask = masks[1], 
                       img_id = "imageID", 
                       colour_by = c("PanKRT", "GLUT1", "HH3", "CD3", "CD20"), 
                       display = "single",
                       colour = list(HH3 = c("black","blue"), 
                                     CD3 = c("black","purple"),
                                     CD20 = c("black","green"),
                                     GLUT1 = c("black", "red"),
                                     PanKRT = c("black", "yellow")),
                       bcg = list(HH3 = c(0, 1, 1.5), 
                                     CD3 = c(0, 1, 1.5),
                                     CD20 = c(0, 1, 1.5),
                                     GLUT1 = c(0, 1, 1.5),
                                     PanKRT = c(0, 1, 1.5)),
                       legend = NULL)