Multilingual Ontology Enrichment for Semantic Annotation and Retrieval of Medical Information

Background: Knowledge management in the European project Noesis addresses concept-based annotation and multilingual Information Retrieval of documents. Objective: Multilingual enrichment of a concept-based terminology in the medical field. Experience and evaluation in the domain of cardiovascular diseases by enriching a subset of the MeSH thesaurus in six European languages. This terminology, represented in the OWL standard ontology language, has been used for manual semantic annotation of medical texts, for automatic indexing and Information Retrieval. Methods: A subset of 2500 cardiovascular-related concepts has been extracted from the MeSH thesaurus and represented in OWL. Multilingual enrichment has been done in two phases: automatically, through the UMLS metathesaurus and its associated vocabulary, and manually, by considering the terms extracted from a corpus of English texts of the cardiovascular domain. Manual enrichment from the English corpus was done first; it consisted in extracting the candidate terms, selecting them and determining the concepts they represent. The vocabulary for the five other considered languages has been obtained mostly by translation. A computer environment based on ontology edition has been designed to support the enrichment task. Results: Each concept is represented on average by 3.2 terms in the initial English MeSH vocabulary. After automatic enrichment through UMLS the average is 7 and eventually 8.5 after manual enrichment from a corpus of texts. For the other languages, the UMLS enrichment yields from 1 term (Italian) to 4 terms (Spanish) per concept. The environment supporting multilingual enrichment is publicly available. Conclusions: The choice of the MeSH thesaurus was a reasonable decision in the context of the Noesis project. However, the poorness of its structure, which is far from an ontology, limited the work to terminology enrichment, while the need for new concepts and a better structure was often experienced.