PMID- 35345884 OWN - NLM STAT- MEDLINE DCOM- 20220509 LR - 20220509 IS - 1559-4106 (Electronic) IS - 1559-4106 (Linking) VI - 17 IP - 2 DP - 2022 Mar 28 TI - Applications of multivariate analysis and unsupervised machine learning to ToF-SIMS images of organic, bioorganic, and biological systems. PG - 020802 LID - 10.1116/6.0001590 [doi] AB - Time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging offers a powerful, label-free method for exploring organic, bioorganic, and biological systems. The technique is capable of very high spatial resolution, while also producing an enormous amount of information about the chemical and molecular composition of a surface. However, this information is inherently complex, making interpretation and analysis of the vast amount of data produced by a single ToF-SIMS experiment a considerable challenge. Much research over the past few decades has focused on the application and development of multivariate analysis (MVA) and machine learning (ML) techniques that find meaningful patterns and relationships in these datasets. Here, we review the unsupervised algorithms-that is, algorithms that do not require ground truth labels-that have been applied to ToF-SIMS images, as well as other algorithms and approaches that have been used in the broader family of mass spectrometry imaging (MSI) techniques. We first give a nontechnical overview of several commonly used classes of unsupervised algorithms, such as matrix factorization, clustering, and nonlinear dimensionality reduction. We then review the application of unsupervised algorithms to various organic, bioorganic, and biological systems including cells and tissues, organic films, residues and coatings, and spatially structured systems such as polymer microarrays. We then cover several novel algorithms employed for other MSI techniques that have received little attention from ToF-SIMS imaging researchers. We conclude with a brief outline of potential future directions for the application of MVA and ML algorithms to ToF-SIMS images. FAU - Gardner, Wil AU - Gardner W AUID- ORCID: 0000000269031978 AD - Centre for Materials and Surface Science and Department of Chemistry and Physics, La Trobe University, Bundoora, Victoria 3086, Australia. FAU - Winkler, David A AU - Winkler DA AUID- ORCID: 0000000273016076 AD - La Trobe Institute for Molecular Sciences, La Trobe University, Bundoora, Victoria 3086, Australia. FAU - Muir, Benjamin W AU - Muir BW AUID- ORCID: 0000000288583217 AD - CSIRO Manufacturing, Clayton, Victoria 3086, Australia. FAU - Pigram, Paul J AU - Pigram PJ AUID- ORCID: 000000027972492X AD - Centre for Materials and Surface Science and Department of Chemistry and Physics, La Trobe University, Bundoora, Victoria 3086, Australia. LA - eng PT - Journal Article PT - Research Support, Non-U.S. Gov't PT - Review DEP - 20220328 PL - United States TA - Biointerphases JT - Biointerphases JID - 101275679 SB - IM MH - Algorithms MH - Machine Learning MH - Multivariate Analysis MH - *Spectrometry, Mass, Secondary Ion/methods MH - *Unsupervised Machine Learning EDAT- 2022/03/30 06:00 MHDA- 2022/05/10 06:00 CRDT- 2022/03/29 05:37 PHST- 2022/03/29 05:37 [entrez] PHST- 2022/03/30 06:00 [pubmed] PHST- 2022/05/10 06:00 [medline] AID - 10.1116/6.0001590 [doi] PST - epublish SO - Biointerphases. 2022 Mar 28;17(2):020802. doi: 10.1116/6.0001590.