Spatial resolution: Just how small can the ‘pixels’ in mass spectrometry imaging actually be?
2026-07-10 65
Spatial resolution refers to the minimum distance between two adjacent measurement points that can be distinguished in mass spectrometry imaging; it is usually expressed as the side length of each pixel (e.g. 20 μm, 2 μm). It determines how fine a structure can be seen in the image—the smaller the resolution value, the finer the pixels, and the smaller the tissue structures that can be resolved.
Why resolution is an engineering trade-off
Resolution is determined by the size of the primary desorption spot or droplet spot, but is also constrained by detection sensitivity. The concentration of compounds available for desorption within each pixel is extremely low; the higher the resolution, the smaller the amount of material within a single pixel and the weaker the signal. Consequently, in high-resolution imaging, there is a trade-off between sensitivity and spatial resolution; improving the effective ionisation efficiency is crucial for achieving high-resolution imaging.
Resolution orders of magnitude for different ionisation methods
Based on the technical parameters summarised in the Wikipedia article “Mass spectrometry imaging”:
SIMS: <10 μm; NanoSIMS can reach approximately 50 nm, entering the subcellular scale.
MALDI: approximately 20 μm.
DESI: approximately 50 μm, suitable for large-area scanning.
Nano-DESI: approximately 10 μm.
MALDI+SICRIT (cold plasma post-ionisation): up to approximately 0.25 μm.
LA+SICRIT (laser ablation + post-ionisation): <5 μm.
Examples of high resolution in authoritative research
The t-AP-LDI/PI method developed by Pan Yang’s research group at the University of Science and Technology of China achieved a spatial resolution of 4 μm, enabling clear resolution of subregional structures in mouse hippocampal tissue (dentate gyrus, superior colliculus, hippocampal horns, etc.). The relevant results were published as a cover article in *Analytical Chemistry* 2024 (DOI: 10.1021/acs.analchem.3c05605).
Relation to Neo Source products
Neo Source INSTRUMENT’s MSI DPI imaging ion source has a spatial resolution of approximately 20–200 μm, making it suitable for tissue-scale imaging; The MSI LDPI imaging ion source has a resolution of 2–3 μm, enabling high-resolution imaging at the single-cell and subcellular scales. The two are compatible with mass spectrometers from Agilent, AB SCIEX and Thermo, respectively.
References
Wikipedia: Mass spectrometry imaging. https://en.wikipedia.org/wiki/Mass_spectrometry_imaging
University of Science and Technology of China: New progress in the development of a compact photoionisation mass spectrometry imaging source. https://kyb.ustc.edu.cn/_t1002/2024/0401/c6076a634490/page.htm
Qi K, et al. Development of Transmission Ambient Pressure Laser Desorption Ionisation/Post-photoionisation Mass Spectrometry Imaging. Analytical Chemistry. 2024. DOI:10.1021/acs.analchem.3c05605