Word sense disambiguation in the clinical domain: A comparison of knowledge-rich and knowledgepoor unsupervised methods

Abstract

Objective: To evaluate state-of-the-art unsupervised methods on the word sense disambiguation (WSD) task in the clinical domain. In particular, to compare graphbased approaches relying on a clinical knowledge base with bottom-up topic-modeling-based approaches. We investigate several enhancements to the topic-modeling techniques that use domain-specific knowledge sources. Materials and methods: The graph-based methods use variations of PageRank and distance-based similarity metrics, operating over the Unified Medical Language System (UMLS). Topic-modeling methods use unlabeled data from the Multiparameter Intelligent Monitoring in Intensive Care (MIMIC II) database to derive models for each ambiguous word. We investigate the impact of using different linguistic features for topic models, including UMLS-based and syntactic features. We use a sense-tagged clinical dataset from the Mayo Clinic for evaluation. Results: The topic-modeling methods achieve 66.9% accuracy on a subset of the Mayo Clinic's data, while the graph-based methods only reach the 40-50% range, with a most-frequent-sense baseline of 56.5%. Features derived from the UMLS semantic type and concept hierarchies do not produce a gain over bag-ofwords features in the topic models, but identifying phrases from UMLS and using syntax does help. Discussion : Although topic models outperform graphbased methods, semantic features derived from the UMLS prove too noisy to improve performance beyond bag-of-words. Conclusions : Topic modeling for WSD provides superior results in the clinical domain; however, integration of knowledge remains to be effectively exploited.