Ion Mobility Heatmap Visualization

ion-mobility-heatmap-visualization

Summary

Generate extracted ion mobility (XIM) heatmaps from raw LC-IMS-MS data by specifying m/z and arrival-time ranges, enabling visualization of ion intensity distributions across mobility and retention time dimensions. This skill is essential for interpreting ion separation and structural dynamics in multidimensional mass spectrometry.

When to use

You have raw LC-IMS-MS data (Agilent, Thermo, Bruker, or mzML format) and need to visualize and export the spatial distribution of a specific ion species (or ion family) across both ion mobility and retention time dimensions. Apply this skill when you want to extract a subset of ions by m/z and arrival-time range, generate a 2D heatmap representation, and export the visualization as PDF or tabular data (CSV) for publication or further analysis.

When NOT to use

• Input data is from a traditional LC-MS (without ion mobility dimension) — use extracted ion chromatogram (XIC) instead.
• You require MS/MS fragmentation spectra or spectral library matching — use TandemMatch or Mirador's MS/MS mirror plot feature instead.
• You need to compare heatmaps across multiple acquisition methods or cohorts — use Comparador for harmonized feature comparison.

Inputs

• Raw mass spectrometry data file (Agilent .d directory, Thermo .raw, Bruker .d, or mzML format)
• m/z range and tolerance (e.g., 500–510 m/z, ±5 ppm)
• Retention time (RT) range in seconds or minutes
• Arrival time (ion mobility) range in milliseconds or inverse reduced mobility units

Outputs

• Extracted ion mobility (XIM) heatmap in PDF format
• Tabular XIM data in CSV format (retention time, arrival time, intensity matrix)
• Optional: customized visualization parameters logged for reproducibility

How to apply

Load raw MS data in a supported instrument format (Agilent .d, Thermo .raw, Bruker .d, or mzML) into Mirador. Specify the target m/z range (with user-defined tolerance, typically ppm-based), the retention time window, and the arrival-time (mobility) range boundaries. Mirador extracts all ion intensity signals matching these three-dimensional constraints, bins them into a 2D grid indexed by (retention time, arrival time), and generates a heatmap where intensity is represented as color or gradient. Export the result as both a high-resolution PDF visualization (suitable for figures) and a CSV table containing the binned intensity matrix. Verify output by confirming that the m/z, RT, and arrival-time ranges match your input parameters and that intensity maxima align with expected ion separation patterns for your compounds.

Related tools

• Mirador (Primary tool for raw MS data visualization and XIM heatmap generation, supporting customizable m/z, RT, and arrival-time range extraction and PDF/CSV export.) — https://github.com/pnnl/IonToolPack
• IonToolPack (Container suite providing unified GUI access to Mirador and companion tools; handles multi-format data loading and no-installation deployment.) — https://github.com/pnnl/IonToolPack
• PeakQC (Optional companion tool for quality assessment of ion signals used to generate heatmaps; applies PCA-based QC and outlier detection on MS1 data.) — https://github.com/pnnl/IonToolPack

Evaluation signals

• Verify that the exported heatmap intensity range corresponds to the ion count or signal intensity in the input raw file; compare min/max values to raw data statistics.
• Confirm that the CSV matrix dimensions match the binned retention time and arrival-time grid; check for missing or zero-padded cells at grid edges.
• Visual inspection: heatmap should show clustered intensity in expected mobility and RT regions; absence of signal outside specified m/z tolerance indicates correct extraction.
• Reproducibility check: regenerate the heatmap with identical parameters and verify pixel-for-pixel match with previous output.
• Cross-validation: overlay exported CSV data on the PDF heatmap to ensure color/intensity mapping is consistent and colorbar labels are accurate.

Limitations

• XIM heatmaps require ion mobility (IMS) dimension in the input data; conventional LC-MS data will not produce meaningful 2D mobility separations.
• Arrival-time range and tolerance parameters are instrument-specific and user-defined; incorrect settings may exclude target ions or include chemical noise.
• Export formats (PDF, CSV) are suitable for static visualization and tabular export but do not preserve raw centroid or profile peak shapes; users working with high-resolution isotope patterns may need to inspect raw data directly.
• No changelog provided in repository; version-to-version changes in Mirador heatmap binning or export precision are not formally documented.

Evidence

• [readme] Mirador: Raw MS data visualization and export (PDF, CSV) including extracted ion chromatograms (XIC), extracted ion mobility (XIM) heatmaps, and MS/MS mirror plots: "Mirador: Raw MS data visualization and export (PDF, CSV) including extracted ion chromatograms (XIC), extracted ion mobility (XIM) heatmaps, and MS/MS mirror plots with customizable m/z, RT, and"
• [other] Generate extracted ion mobility (XIM) heatmaps for the specified m/z and arrival-time ranges: "Generate extracted ion mobility (XIM) heatmaps for the specified m/z and arrival-time ranges."
• [readme] Supported formats include Agilent 'd', Thermo '.raw', Bruker 'd', and mzML, and for different types of MS acquisition methods: LC-MS, LC-IMS-MS: "Supported formats include Agilent 'd', Thermo '.raw', Bruker 'd', and mzML, and for different types of MS acquisition methods: * LC-MS * LC-IMS-MS"
• [other] Parse user-specified m/z, retention time (RT), and arrival-time (mobility) range parameters: "Parse user-specified m/z, retention time (RT), and arrival-time (mobility) range parameters."
• [other] Export all visualizations and tabular data as PDF and CSV files: "Export all visualizations and tabular data as PDF and CSV files."