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image is MTI NLM Medical Text Indexer Providing Indexing Assistance Since 2002 with three arrows on bottom signifying data flow. Biomedical Literature > MTI/MTIFL > MeSH Suggestions
Current MTI Processing Flow
Current System (2013):

The NLM Medical Text Indexer (MTI) system is the primary product and focus of the Indexing Initiative. MTI produces both semi- and fully-automated indexing recommendations based on the Medical Subject Headings (MeSH®) controlled vocabulary and has been in use at NLM since 2002. MTI is in daily use to assist Indexers, Catalogers, and NLM's History of Medicine Division (HMD) in their indexing efforts.

Every weeknight MTI provides recommendations for approximately 4,000 new citations for Indexing and processes a mixed file of approximately 7,000 old and new records for both Cataloging and HMD. MTI was also used on a regular basis between 2002 and 2012 to provide fully-automated keyword indexing for NLM's Gateway meeting abstract collection, which was not manually indexed. In 2011, MTI was designated as the First-Line Indexer (MTIFL) for 14 journals (89 in 2013) because of its success with those publications. For MTIFL journals, MTI indexing is treated like human indexing and, of course, subject to the normal manual review process. MEDLINE® Indexers and Revisers consult MTI recommendations for approximately 58% of the articles they index, and the MTI recommendations are tightly integrated into the Cataloging and HMD system. Although mainly used in indexing efforts for processing MEDLINE citations consisting of identifier, title, and abstract, MTI is also capable of processing arbitrary biomedical text.

MTI provides an ordered list of MeSH Main Headings (MH), Subheadings (SH), and CheckTags (CT) as a final result. MHs are the main descriptors or headings from the MeSH Vocabulary (e.g., Lung). SHs are used to qualify the MHs (e.g., Lung/abnormalities means that the article is about the abnormalities associated with the Lung more than the Lung itself), and CTs are a special type of MHs that are required to be included for each article and cover species, sex, human age groups, historical periods, pregnancy, and various types of research support (e.g., Male).


Individual Component Descriptions:

link to Phrasex description link to MetaMap Indexing algorithm description link to Trigram algorithm description link to PubMed Related Citations algorithm description link to Restrict to MeSH process description link to Extract MeSH Descriptors process description link to Clustering and Ranking process description image is the processing flow for the original production MTI system which includes the Trigram method in addition to the current system diagram
Initial MTI Production System
Initial Production System (2002):

The MTI system consists of software for applying alternative methods of discovering MeSH headings for citation titles and abstracts and then combining them into an ordered list of recommended indexing terms. The top portion of the diagram consists of three paths, or methods, for creating a list of recommended indexing terms: MetaMap Indexing, Trigrams and PubMed Related Citations. The first two paths actually compute UMLS Metathesaurus® concepts which are passed to the Restrict to MeSH process. The results from each path are weighted and combined using the Clustering process. The system is highly parameterized not only by path weights but also by several parameters specific to the Restrict to MeSH and Clustering processes.

A prototype MTI system described below had two additional indexing methods which were removed because their results were subsumed by the three remaining methods.







image is the processing flow for the original prototype MTI system which includes INQUERY, Approximate Matching, and Trigram methods in addition to the current system diagram
Original MTI Prototype System
Original Indexing Initiative Prototype System: (~1996):

The Indexing Initiative Prototype System consists of software for applying alternative methods of discovering MeSH headings for citation titles and abstracts and then combining them into an ordered list of recommended indexing terms. The top portion of the diagram consists of five paths, or methods, for creating a list of recommended indexing terms: the INQUERY method, MetaMap Indexing, Barrier Words with Approximate Matching, Trigrams and PubMed Related Citations. The middle three paths actually compute UMLS Metathesaurus® concepts which are passed to the Restrict to MeSH process, and the outer two paths compute MeSH headings directly. The results from each path are weighted and combined using the Clustering process. The system is highly parameterized not only by path weights but also by several parameters specific to the Restrict to MeSH and Clustering processes.

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