The importance of imaging biomarkers in biomedical research and drug design is well-acknowledged in the literature, calling for appropriate standards and guidelines for imaging biomarker development, validation and quali cation. The objective of this work is to de ne explicitly, by means of an ontology, the vocabulary pertaining to imaging biomarkers' domain.
IBO involves many diverse entities related to imaging biomarkers that concern many domains (medical imaging, metrology, clinical research, informatics, etc.). Therefore, most of classes are aligned with the Basic Formal Ontology (BFO) and were developed according to the OBO foundry principles, thus facilitating the integration of terms. Extraction was made following the MIREOT principles, thanks to the OntoFox tool. We have reused several ontologies belonging to the OBO foundry - e.g. Ontology for Biomedical Investigations (OBI), Phenotypic Quality Ontology (PATO), Chemical Entities of Biological Interest (ChEBI) Ontology and Foundational Model of Anatomy (FMA) ontology - but also ontologies from other origins, e.g. OntoNeuroLOG.
Our proposed ontology, IBO, articulates three basic aspects related to imaging biomarkers namely, facet 1: measured biological characteristics, facet 2: measurement protocols and facet 3: role in decision making applications. The rst facet de nes physical qualities related to imaged objects or processes. We have distinguished between two kinds of qualities: qualities that are related to a continuant (e.g. tumor size, longest diameter, tumor volume, tissue radioactivity concentration) and qualities that describe an occurrent (e.g. volume change between two time points or more complex processes as volume change speed). The second facet speci es imaging requirements and describes performed measurement processes leading to imaging biomarker values. Measurement processes are composed of many sub-processes (subject preparation, image acquisition, image processing, etc.) that involve many material entities (image acquisition device, imaging agent, imaging subject, etc.) as well as roles realized in the context of the processes in which they participate. The third facet represents imaging biomarker applications, namely: diagnosis, prediction, prognosis, treatment assessment and therapy monitoring. All imaging biomarker applications involve some imaging biomarker values which bear a particular role, e.g. predictive, diagnostic, prognostic and enable clinicians to answer to their clinical questions. 4
The aim of IBO is to de ne explicitly the domain of imaging biomarkers in the health care context, we have based our work on preliminary work from QIBO and BiomRKRS as well as relevant OBO foundry's ontologies. Future work will aim at applying IBO for representing imaging biomarkers in brain gliomas.