The acquisition modality this imaging report came from -- DX, US, CT, MR, MG.
On the report, not on a study. R4 puts modality on ImagingStudy, which this guide does not
profile: the estate models the imaging REPORT and holds no DICOM acquisition metadata. Saying a
report came from a CT asserts nothing about series, instances or SOP UIDs.
Not derivable from DiagnosticReport.code in practice. The study code names the study, and a
human reader can infer modality from it; a results list filtering "CT reports" cannot, without
maintaining a procedure-to-modality mapping outside the record and getting it wrong silently.
Bound extensible to DICOM CID 29 -- the same value set and strength R4 binds
ImagingStudy.modality to, so a consumer that knows R4's imaging model needs no second rule.
Heritage feeds carrying local modality codes stay conformant.
Repeats: a PET-CT report says two.
May be used to represent additional information that is not part of the basic definition of the element. To make the use of extensions safe and manageable, there is a strict set of governance applied to the definition and use of extensions. Though any implementer can define an extension, there is a set of requirements that SHALL be met as part of the definition of the extension.
Comments
There can be no stigma associated with the use of extensions by any application, project, or standard - regardless of the institution or jurisdiction that uses or defines the extensions. The use of extensions is what allows the FHIR specification to retain a core level of simplicity for everyone.
Source of the definition for the extension code - a logical name or a URL.
Comments
The definition may point directly to a computable or human-readable definition of the extensibility codes, or it may be a logical URI as declared in some other specification. The definition SHALL be a URI for the Structure Definition defining the extension.
The modality the report's study was acquired on, coded from the DICOM modality vocabulary (http://dicom.nema.org/resources/ontology/DCM). A report covering more than one modality repeats this extension rather than choosing between them.