Accelerating the Standardisation of Mass Spectrometry Imaging — The Industry Moves from ‘Each to Their Own’ to ‘Comparable and Reproducible’

For an analytical technique to progress from scientific exploration to widespread industrial application, it must first overcome a key hurdle: standardisation. Mass spectrometry imaging technology currently stands on the threshold of this hurdle.

In recent years, with the growth in the number of mass spectrometry imaging systems installed and the increasing demand for clinical translation, there has been a marked rise in the industry’s focus on data comparability, method reproducibility and standards for result evaluation. The lack of a unified reference for data obtained from different laboratories, different instruments and different ionisation methods has become a key obstacle limiting the clinical submission and regulatory approval of this technology. Standardisation organisations in the domestic mass spectrometry sector have begun to advance relevant work, and technical specifications for mass spectrometry imaging sources and ion sources have also been included in the scope of discussion.

The practical dilemma of incomparable data

The field of mass spectrometry imaging has long faced an awkward reality: imaging results for the same tissue sample may vary significantly between different laboratories; indeed, even data collected at different times within the same laboratory are difficult to compare directly.

The causes of this dilemma are multi-faceted.

At the instrumental level, mass spectrometry imaging instruments from different manufacturers exhibit inherent differences in mass analyser type (TOF, Orbitrap, Ion Trap), ion transfer efficiency and detector response; the signal intensity of the same molecule may vary by a factor of several when analysed on different instruments. At the ionisation level, different ionisation methods—such as DESI, MALDI, LDI and SIMS—exhibit varying ionisation efficiencies and fragmentation patterns for the same molecule, imposing fundamental limitations on the comparability of imaging results. At the operational level, differences in operational conditions—such as the composition of the spray solvent, laser energy, matrix selection and scanning parameters—further compound data deviations.

This implies that whilst Laboratory A may publish the conclusion that “cholesterol is enriched in the white matter of mouse brains”, Laboratory B, using different instruments and conditions, may obtain entirely different signal intensity values, and even the distribution patterns may differ. For scientific exploration, consistency in qualitative conclusions may suffice; however, if mass spectrometry imaging is to be applied to clinical pathological diagnosis, the absolute quantitative capability of the data and cross-laboratory reproducibility become mandatory requirements.

Three Dimensions of Standardisation

Domestic standardisation efforts for mass spectrometry are currently being pursued across three dimensions.

Instrument performance evaluation standards. Organisations such as the Analytical Instrumentation Branch of the China Instrumentation Society are currently discussing the formulation of a performance evaluation indicator system for mass spectrometry imaging instruments, covering measurement methods and reporting specifications for core parameters such as spatial resolution, mass resolution, mass accuracy, sensitivity and dynamic range. Once these standards are implemented, there will be a unified benchmark for comparing the performance of instruments from different manufacturers, and purchasers will no longer have to contend with technical specifications that are merely “self-declared” by individual manufacturers.

Method validation guidelines. Method validation guidelines for mass spectrometry imaging in specific application areas (such as tumour margin identification and quantitative drug distribution) are currently being developed. The guidelines will specify evaluation methods for metrics required for method validation—including precision, accuracy, detection limits and linear range—as well as operational standards for the selection of internal standards, the preparation of calibration curves and quality control samples.

Data formats and reporting standards. The storage formats for mass spectrometry imaging data currently vary between manufacturers, resulting in poor data interoperability. Industry organisations are promoting the adoption of open data formats whilst discussing reporting standards for imaging results—which should, at a minimum, include key information such as instrument model, ionisation method, spatial resolution, mass range and scan parameters—to ensure that imaging data in published literature is traceable and reproducible.

Standardisation of Imaging Ion Sources: A Neglected Key Aspect

In discussions regarding the standardisation of mass spectrometry imaging, the imaging ion source is an aspect that is easily overlooked yet is of critical importance.

The imaging ion source is the core module within a mass spectrometry imaging system that directly determines ‘which molecules are observed’ and ‘how clearly they are observed’. There are significant differences in molecular detection range, sensitivity and spatial resolution between different imaging sources. In the absence of uniform performance evaluation standards, users face severe information asymmetry when selecting an imaging source—marketing claims such as “10-fold signal enhancement” provided by manufacturers may be based on optimal results under specific conditions, whilst actual performance in practice may be significantly lower.

Some domestic enterprises are actively promoting technical transparency regarding imaging sources. In the technical documentation for its MSI DPI electrospray/photochemical ionisation mass spectrometry imaging sources and MSI LDPI laser/photochemical ionisation mass spectrometry imaging sources, Hefei Xinceyuan Instrument Technology Co., Ltd. clearly specifies the test conditions for signal gain (sample type, molecular species, instrument model) and provides the range of gain under different conditions (1–3 orders of magnitude), rather than a single optimal value. Although this approach is conservative, it provides users with more realistic technical expectations.

In discussions on standardisation, the core parameters requiring specification for mass spectrometry imaging ion sources may include: molecular detection range (polar/non-polar coverage), sensitivity gain (multiplier of signal enhancement relative to traditional single ionisation modes and test conditions), spatial resolution (definition and measurement methods), ion transfer efficiency, and the range of compatibility with different mass spectrometers. The standardisation of these parameters will enable direct comparability between imaging source products from different manufacturers.

Clinical translation drives standardisation

The true driving force behind standardisation stems from the practical demands of clinical translation.

Research into the application of mass spectrometry imaging technology in tumour pathological diagnosis has been ongoing for many years—using molecular distribution maps to distinguish the boundaries between tumour and normal tissue, thereby assisting in the assessment of surgical margins. However, moving this technology from research to clinical application requires medical device registration and approval, and one of the core requirements for such approval is the reproducibility and standardisability of the method.

Regulatory authorities need to confirm whether, when the same model of mass spectrometry imaging instrument is used by different operators in different hospitals, the test results for the same type of sample are consistent. If the discrepancies between results from different laboratories are too great to establish uniform diagnostic criteria, the technology cannot be approved for clinical diagnosis.

This regulatory requirement is driving standardisation across the entire mass spectrometry imaging industry chain. Instrument manufacturers must provide reproducible performance metrics; imaging source manufacturers must provide standardised ionisation parameters; reagent suppliers must provide internal standards and calibrators of consistent quality; and laboratories must establish standardised sample preparation and operating procedures. Every link in the chain must be traceable and verifiable.

International Benchmarking and Opportunities for Localisation

At the international level, the American Society for Mass Spectrometry (ASMS) and the European Mass Spectrometry Society (EMS) have already made initial progress regarding standards for mass spectrometry imaging data reporting, proposing minimum information requirements for imaging data reports (similar to the MIAME standard in the biomedical field). Domestic standardisation efforts must align with international norms whilst formulating more practical guidelines tailored to the characteristics of the domestic mass spectrometry imaging industry.

For domestic mass spectrometry imaging instrument manufacturers, standardisation presents both a challenge and an opportunity. The challenge lies in the fact that standardisation will eliminate information asymmetry, requiring manufacturers to compete on the basis of genuine technical specifications rather than relying on marketing rhetoric. The opportunity lies in the fact that, once standardisation is implemented, domestic enterprises that can demonstrate within the standard framework that their performance metrics match those of imported brands will gain the trust of procurers—the standard itself serves as the best endorsement for “domestic substitution”.

The participation of domestic imaging ion source manufacturers, such as Xinceyuan, in standardisation discussions will also help ensure that the distinctive features of domestic technologies—such as the full-polarity detection capability of post-photoionisation and modular, compatible designs—are incorporated into the standards. This will prevent standards from being formulated solely on the basis of imported technologies, thereby overlooking the unique advantages of domestic technologies.

Industry Outlook

The standardisation of mass spectrometry imaging is a systematic undertaking involving multiple levels—including instruments, methods, data and personnel—and cannot be achieved overnight. However, the very launch of this process is a positive sign in itself—it signifies that mass spectrometry imaging technology has reached a sufficiently mature stage, and industry participants are beginning to give serious thought to how the technology can ‘move out of the laboratory and into industrial applications’.

For manufacturers of mass spectrometry imaging systems and imaging ion sources, actively participating in standardisation efforts is not only a social responsibility but also a strategic opportunity to shape the industry’s narrative. Those who participate in the formulation of standards will gain a first-mover advantage in the next phase of industrial competition.