Robust Large Image Acquisition at High Spatial Resolution Using the DESI™ XS Source Coupled to a Xevo™ G3 QTof Mass Spectrometer

Importance of the Topic

Mass spectrometry imaging (MSI) provides spatially resolved chemical maps that are essential for understanding tissue heterogeneity, biomarker localization, and drug distribution at high resolution.

Study Objectives and Overview

This work evaluates the performance of the Xevo G3 QTof mass spectrometer coupled to a DESI XS source for large-scale, high-resolution MSI. A whole rat sagittal brain section was acquired at 10 µm pixel resolution, generating 2 321 700 pixels and 364 GB of raw data during a continuous 35-hour run. The study assesses image consistency, spectral fidelity, mass accuracy stability, and data processing capacity.

Used Instrumentation

• Mass spectrometer: Xevo G3 QTof MS
• Ion source: DESI XS with high-performance sprayer and heated transfer line
• Solvent delivery: ACQUITY M-Class BSM with 1.7 µm C18 column and 45 µm I.D. capillary

Methodology

An 18 µm sagittal rat brain slice was placed on glass without additional preparation. Key acquisition parameters in positive ion mode:

• Cone voltage: 80 V; source temperature: 150 °C
• m/z range: 50–1200; analyzer mode: sensitivity
• Pixel size: 10 µm; scan rate: 20 Hz (200 µm/s)
• Solvent: 95% methanol, 5% water at 250 nL/min

Data were lockmass-corrected (m/z 826.572) via continuous correction and processed in MassLynx and HDI software.

Main Results and Discussion

• Complete dataset of 2 321 700 pixels over ~35 hours acquired without interruption, yielding 364 GB of raw data.
• RGB overlay of lipid signals (e.g., PC/PE at m/z 760.5848, 772.5253, 782.5668) showed uniform image quality throughout.
• Zoomed views of cerebellum and striatum confirmed consistent clarity and structural detail at 10 µm resolution.
• Spectral comparisons at 2.2 h and 20.3 h demonstrated stable profiles and resolution (~27 000 FWHM), with no adverse effects from detector contamination.
• Mass accuracy for selected lipids remained within ±2 ppm over 32 hours (RMS deviations: 0.77, 0.44, 0.35, 0.51 ppm).

Benefits and Practical Applications

• Robust, reproducible MSI platform for large-area, high-resolution imaging.
• Stable long-term performance minimizes batch effects and source fouling.
• Efficient handling of >350 GB datasets in standard imaging software supports applications in neuroscience, pharmacology, and QA/QC.

Future Trends and Potential Applications

• Push pixel sizes below 5 µm for subcellular mapping.
• Integrate MS/MS for definitive lipid identification and structural analysis.
• Apply machine learning for rapid interpretation of very large MSI datasets.
• Combine DESI with orthogonal imaging modalities for multimodal tissue characterization.

Conclusion

The Xevo G3 QTof MS paired with the DESI XS source achieves high-resolution, large-area imaging with excellent stability over extended acquisitions. The workflow supports processing of hundreds of gigabytes of MSI data, making it well suited for advanced research and industrial analysis.

References

1. Petkovic M, Schiller J, Mueller M, et al. Anal Biochem. 2001;289:202.
2. Schiller J, Suss R, Petkovic M, et al. Anal Biochem. 2002;309:311.