CellProfiler and PyImageJ - RunImageJScript
One initial goal in the development of PyImageJ was to improve integration of ImageJ with CellProfiler, a Python-based open-source tool for creating modular image analysis pipelines.
While CellProfiler has had an existing integration with Java for many years [1, 2], more recently the JPype library has become very robust and now serves as an ideal library for accessing Java resources from Python. PyImageJ offers a new opportunity to better bridge these applications in a lightweight manner without requiring fundamental structural changes to either platform, yielding a connection that is simpler, more powerful and more performant. We have accomplished this through the RunImageJScript CellProfiler module. RunImageJScript functions like any other CellProfiler module, allowing the user to execute an ImageJ2 script as part of their workflow. PyImageJ enables translation between structures in each domain, mapping script inputs and outputs to CellProfiler workflow settings. This allows CellProfiler to benefit from image-analysis algorithms and functionality exclusive to ImageJ without the speed penalty incurred by previous bridge attempts [3].
As an example use case, we demonstrated a >3-fold increase in performance of a CellProfiler workflow that identifies and measures cells (see Figure below) using ImageJ’s Trainable Weka Segmentation plugin (TWS) via PyImageJ. We used the Broad Biomage Benchmark Collection (BBBC) image set [4] BBBC030, a set of DIC images of Chinese Hamster Ovary cells [5]; in order to assess segmentation performance as well as cell merges and splits, the ground truth outlines were converted to label matrices in CellProfiler and lightly edited with the original authors’ permission. A single image from the set of 60 was trained with the TWS plugin to distinguish background from cell centers and cell boundaries, and the classifier model was exported. RunImageJScript was then used from inside CellProfiler, invoking TWS to apply the classifier onto each of the 60 images and first segment cell centers and then cell boundaries; we have previously found17 that separate prediction of cell interiors versus boundaries decreases the numbers of cells accidentally split into more than one object or merged with a neighboring cell. This approach outperformed two CellProfiler-only classical image processing methods of identifying the cells (Panel B), one using the EnhanceOrSuppressFeatures module to distinguish the cells from background by their texture, and the other using the EnhanceEdges module to distinguish the cells from background by looking for edges in the image, especially at the task of minimizing incorrect merges and splits (Panel C). As none of the CellProfiler workflows attempted to identify cells touching the edges of the image, segmentation accuracy was assessed both for the entire set of ground truth cells and for only the ground truth cells not touching the cell border, yielding similar results.
Figure: RunImageJScript, built on PyImageJ, allows running CellProfiler workflows on the BBBC030 data set. CellProfiler 4.1 introduced the RunImageJMacro module which relies upon writing images to disk in order to exchange data with ImageJ.
A. Runtime of a pipeline using either an internal CellProfiler module (Smooth) vs rolling ball background subtraction in ImageJ via RunImageJMacro or RunImageJScript. Comparing execution time indicates that RunImageJScript is more than 3x faster than RunImageJMacro and has comparable performance to pipelines that do not use an ImageJ plugin.
B. Accuracy of three segmentation approaches on BBBC030 in CellProfiler. At all Intersection-over-Union (IoU) thresholds, using RunImageJScript to call ImageJ’s Trainable Weka Segmentation equals or outperforms CellProfiler-only approaches. Solid lines are performance on all cells; dashed lines are performance on non-edge-touching cells, which CellProfiler did not try to segment.
C. Across all cells, RunImageJScript misses the fewest cells at IoU 0.7, as well as better balancing errors in splitting and merging.
D. Outlines of segmented classified cells. Cells outlined in teal are classified as touching at least one other cell, while cells outlined in orange are classified as isolated. High performance at this task requires minimizing incorrect merges and splits.