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BeNeLux Bioinformatics Conference – Antwerp, December 7-8 <strong>2015</strong><br />

Abstract ID: P<br />

Poster<br />

10th Benelux Bioinformatics Conference <strong>bbc</strong> <strong>2015</strong><br />

P53. FLOWSOM WEB: A SCALABLE ALGORITHM TO VISUALIZE AND<br />

COMPARE CYTOMETRY DATA IN THE BROWSER<br />

Arne Soete 2 , Sofie Van Gassen 1,2,3 , Tom Dhaene 1 , Bart N. Lambrecht 2,3 & Yvan Saeys 2,3 .<br />

Department of Information Technology, Ghent University-iMinds, Ghent, Belgium 1 ; Inflammation Research Center, VIB,<br />

Ghent, Belgium 2 ; Department of Respiratory Medicine, Ghent University Hospital, Ghent, Belgium 3 .<br />

We developed FlowSOM Web, a web-tool which visualizes cytometry data based on Self-Organizing Maps. Similar cells<br />

are clustered and visualized via star charts. This allows us to process and display millions of cells efficiently.<br />

Additionally, different biological samples (e.g. healthy versus diseased mice) can be compared.<br />

INTRODUCTION<br />

Cytometry data describes cell characteristics in<br />

biological samples. Cells are labeled with fluorescent<br />

antibodies and a flow cytometer measures the properties<br />

of millions of cells one by one. Biologists use this<br />

information to get more insight in diseases and to<br />

diagnose patients. Most of them still analyse this data<br />

manually to differentiate between the different cell types<br />

present. This is done by plotting the data in 2D scatter<br />

plots and selecting groups of cells in a hierarchical way.<br />

This process is called `gating'. Recently, the number of<br />

properties that can be measured simultaneously has<br />

strongly increased. As the number of possible 2D scatter<br />

plots increases exponentially with the number of<br />

properties measured, it becomes infeasible to analyze<br />

them all and relevant information that is present in the<br />

data might be missed.<br />

METHODS<br />

We present FlowSOM, a new algorithm for the<br />

visualization and interpretation of cytometry data (Van<br />

Gassen, et al,. <strong>2015</strong>). Using a twolevel clustering and<br />

star charts, our algorithm helps to obtain a clear<br />

overview of how all markers are behaving on all cells,<br />

and to detect subsets that might be missed otherwise.<br />

Our algorithm consists of 4 steps: pre-processing the<br />

data, building a self-organizing map, building a minimal<br />

spanning tree and computing a meta-clustering result.<br />

RESULTS & DISCUSSION<br />

Although our results are quite similar to SPADE, another<br />

state-of-the art algorithm for the visualization of<br />

cytometry data, our results can be computed much faster<br />

and use less memory. By providing star-charts and an<br />

automatic meta-clustering step, much more information<br />

can be visualised in a single tree than is done by the<br />

SPADE algorithm.<br />

Additionally, multiple states can be compared (e.g.<br />

healthy versus diseased mice) with one another and the<br />

differences between the two states can be visualized via<br />

star-charts.<br />

On this conference, we would like to demonstrate a<br />

recently developed web interface to the underlying R<br />

functionality. This interface allows to upload cytometry<br />

data, run the aforementioned analysis, compare different<br />

cell states and explore the results, via interactive<br />

visualizations, all from the comfort of the browser.<br />

FIGURE 1. Example of a FlowSOM star chart.<br />

REFERENCES<br />

Van Gassen, et al. (<strong>2015</strong>), FlowSOM: Using self-organizing maps for<br />

visualization and interpretation of cytometry data. Cytometry,<br />

87: 636–645<br />

97

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