Imaging Modality Extension¶
| Canonical | ../StructureDefinition/nexus-imaging-modality |
|---|---|
| Status | draft · 1.26.0 |
| Base | Extension (constraint) |
| Context | DiagnosticReport (element) |
| Source | FSH · JSON |
The acquisition modality this imaging report came from -- DX, US, CT, MR, MG.
FSH
The authored source of truth: extensions/ImagingModalityExtension.fsh (edit on GitHub). One FSH file may define several related artifacts.
// ImagingModalityExtension.fsh
// The acquisition modality of an imaging report -- DX, US, CT, MR, MG.
//
// WHY THIS EXISTS, AND WHY IT IS AN EXTENSION RATHER THAN AN ELEMENT. Imaging order entry and
// results are a required capability (ON RFP 1.5.4.2), and modality is one of the fields an imaging
// report is expected to carry. R4 has nowhere to put it on `DiagnosticReport`: modality is an
// `ImagingStudy` element, and 1.22.0 WITHDREW this guide's ImagingStudy profile because nothing in
// this estate produces DICOM acquisition metadata. Without this extension the requirement has no
// home at all.
//
// THE STUDY CODE IS NOT A SUBSTITUTE, which is the objection worth answering. `DiagnosticReport.code`
// carries the study -- "Chest X-ray", "Abdominal ultrasound" -- and a reader who knows radiology can
// infer the modality from it. A results list cannot: filtering "show me the CT reports" against a
// SNOMED procedure code means maintaining a procedure-to-modality mapping outside the record, and
// getting it wrong silently. An implied fact that every consumer must re-derive is not a recorded
// fact.
//
// IT DESCRIBES THE REPORT, NOT AN ACQUISITION. This is the distinction that lets the estate carry
// modality while still declining to model ImagingStudy: saying a report came from a CT asserts
// nothing about series, instances or SOP UIDs, and needs no PACS to be honest about. It is a
// property of the document, at the granularity the document is at.
//
// BINDING. Extensible to DICOM CID 29, the SAME value set and the SAME strength R4 binds
// `ImagingStudy.modality` to, so a consumer that already knows R4's imaging model needs no second
// rule. Extensible rather than required for the reason the withdrawn profile gave: DCM is the
// expected system, and heritage feeds carry local modality codes that a required binding would make
// nonconformant on ingestion.
//
// REPEATS, because a study can be multi-modality (PET-CT is the ordinary case) and a report covering
// two of them should say two rather than pick one.
Extension: NexusImagingModality
Id: nexus-imaging-modality
Title: "Imaging Modality Extension"
Description: """
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.
"""
* ^url = "../StructureDefinition/nexus-imaging-modality"
* ^status = #draft
* ^context[0].type = #element
* ^context[0].expression = "DiagnosticReport"
* extension 0..0
* url 1..1
* value[x] 1..1 MS
* value[x] only Coding
* value[x] from http://dicom.nema.org/medical/dicom/current/output/chtml/part16/sect_CID_29.html (extensible)
* valueCoding ^short = "Acquisition modality (DICOM DCM: DX, US, CT, MR, MG, ...)"
* valueCoding ^definition = "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."