DICOM metadata as RDF

DICOM (Digital Imaging and Communications in Medicine) is an industry standard for medical imaging. We present an OWL ontology for DICOM metadata and dicom2rdf-a tool to extract RDF metadata out of DICOM files (Media type application/dicom, filename extension .dcm). We discuss benefits, use cases, limitations and possible enhancements. 1 The DICOM standard DICOM objects consist of sets of attribute-value pairs that allow nesting (the values can be other DICOM objects). There are several thousand official attributes, an extension mechanism for private attributes and 27 data types called value representations (VR) for the values [NE5a]. The data type for each official attribute is fixed. The entity an attribute applies to is determined by its context: Attributes are organized into macros and modules of several attributes. An attribute can be used in several macros or modules. Modules are organized into information object definitions (IOD), describing one or more real world objects called information entities (IE) like patient, study, series or image. The standard defines the IE (real world entity) a module describes in every IOD. 1.1 DICOM sequences Sequence attributes in DICOM allow nesting of data. They create attributes containing sequences of one or more sequence items, effectively nesting DICOM objects. A sequence item is a set of attribute/value-pairs and does not necessarily correspond to an information object definition. It can also represent some kind of real world entity that is only implicitly defined by DICOM or some kind of abstract entity created by the particular organization of information in DICOM.