Wide-area, Fast, and High-definition MS Imaging of Mouse Brain Using iMScope QT

Significance of the Topic

The ability to visualize the spatial distribution of biomolecules directly within tissue sections is critical for advancing research in drug discovery, pathology, and metabolomics. Mass spectrometry imaging (MSI) bridges the gap between molecular identification and histology by combining an optical microscope with high-resolution mass analysis. The new iMScope QT further enhances MSI capabilities, delivering wider coverage, faster acquisition, and greater mass accuracy—features that expand its utility across diverse fields of analytical chemistry.

Objectives and Study Overview

This study evaluates the performance of the iMScope QT imaging mass microscope, comparing it to its predecessor (iMScope TRIO). By performing large-area MSI on whole mouse brain slices and high-resolution imaging of the cerebellum, the work aims to demonstrate improvements in measurable area, acquisition speed, spatial resolution, mass accuracy, and mass resolution.

Methodology and Instrumentation

Experiments employed MALDI-MSI in negative ion mode to map lipids in mouse brain tissue. Key parameters included a measurement pitch of 15 μm for whole-slice scans and 5 μm for cerebellar regions, with the analysis range set to m/z 750–950. A 9-aminoacridine (9-AA) matrix was applied, and each pixel was irradiated with 50 laser shots at 10 kHz using a beam diameter of approximately 5 μm. The instrument’s high repetition frequency (up to 20 kHz), combined with a Q-TOF analyzer, facilitated rapid, high-definition data acquisition.

Used Instrumentation

• iMScope QT imaging mass microscope (optical microscope combined with MALDI source and Q-TOF mass spectrometer)
• Matrix: 9-Aminoacridine
• Laser: 10 kHz repetition rate, ~5 μm beam diameter, 50 shots per pixel
• Negative ion detection in the m/z 750–950 range

Main Results and Discussion

Wide-area imaging of a whole mouse brain slice (~17 mm × 9.4 mm) was achieved at 15 μm spatial resolution over 1,048,576 pixels. Two lipid species—phosphatidylinositol PI(38:4) at m/z 885.557 and sulfatide C24:1 at m/z 888.631—were clearly visualized. The full dataset (702,624 pixels) was acquired in approximately six hours, an eight-fold speed improvement over the previous model. High-resolution scans of the cerebellum at 5 μm spatial resolution resolved isotopic species of PI(38:4) (m/z 888.573) and C24:1 sulfatide (m/z 888.631), enabled by mass accuracy better than 1 ppm and mass resolution exceeding 30,000.

Practical Benefits of the Method

• Expanded analysis area allows single-run imaging of entire tissue sections.
• Accelerated data collection reduces instrument time and improves throughput.
• High mass accuracy and resolution enable confident molecular identification and isotopic distinction.
• Fine spatial resolution supports detailed mapping of substructures in complex tissues.

Future Trends and Applications

Ongoing developments may include integration with other imaging modalities (e.g., fluorescence, electron microscopy), real-time 3D reconstruction of molecular distributions, and single-cell MSI. Enhanced software for automated data processing, coupled with further hardware improvements in laser throughput and detector sensitivity, will broaden MSI use in clinical diagnostics, neurobiology, and pharmaceutical research.

Conclusion

The iMScope QT marks a significant advancement in MSI technology, offering unparalleled coverage, speed, and analytical precision. Its ability to generate high-definition molecular maps rapidly and accurately positions it as a powerful tool for both academic and industrial analytical laboratories.