Entities and relations in medical imaging: An analysis of computed tomography reporting

Biomedical ontologies define entities and relations in order to represent knowledge in the biomedical domain. In addition, many ontologies further represent supplementary knowledge by linking terms from an external controlled vocabulary to the entities defined within the ontology itself. In this paper we concentrate on the domain of medical imaging, for which controlled vocabularies are emerging, but no ontology currently exists. We analyzed computed tomography reports in order to determine to which entities terms used in such reports refer and which relations are used with regard to the recently published Open Biomedical Ontologies (OBO) Relation Ontology. Our analysis revealed that the majority of entities referred to in radiological reporting practice are anatomical entities and anatomical coordinates. Based on the Open Biomedical Ontologies (OBO) Relation Ontology we provide a set of additional relations for the ontological structuring of image features such as shape, morphology, size and signal, frequently found in the reports. On the basis of these results we conclude that the construction of an imaging ontology may benefit greatly from already existing reference ontologies such as the Foundational Model of Anatomy (FMA), which represent those entities to which radiological reports most frequently refer.