Modeling of Imaging Action

Option One

278110001|Radiographic imaging - action (qualifier value) groups all of the different radiographic procedures that are based on X-ray. As a result of this the concept should be used sparingly in the procedure hierarchy because it will subsume all concepts that are modeled using a descendant imaging method such as 312251004|Computed tomography imaging - action (qualifier value).  Retain to use for grouper concepts, use it sparingly for new content in the procedure hierarchy and add a text definition and clear editorial guidance for its use.

Option Two

Take an approach where 278110001|Radiographic imaging - action (qualifier value) means exactly the same as 312254007|Plain X-ray imaging - action (qualifier value) and is therefore a duplicate and should be inactivated. All existing content to be remodeled with a method of 312254007|Plain X-ray imaging - action (qualifier value). This would have a large-scale impact across the imaging procedure hierarchy and require wide impact assessment and consultation.

Modeling Recommendation

It is recommended that 'Option One' be implemented with a small number of concepts that use 278110001|Radiographic imaging - action (qualifier value) remaining with the purpose of 'grouping' all of the different radiographic procedures that use X-ray. The following concepts should be modelled with the method 278110001|Radiographic imaging - action (qualifier value) and act as grouper concepts:

• 363680008|Radiographic imaging procedure (procedure) - has 3646 subtypes (January 2021 release)

• 108273007|Radiographic imaging procedure by site (procedure) - has 3337 subtypes (January 2021 release)

• 418542003|Radiologic guidance procedure (procedure) - has 1215 subtypes (January 2021 release)

• 27483000|Diagnostic radiography with contrast media (procedure) - has 1474 subtypes (January 2021 release)

The current descendants of these concepts are mostly modeled with a body structure, which suggests that the original intent was plain X-ray imaging of a particular structure and not a higher-level grouper.

With the exception of the four grouper concepts listed above 312254007|Plain X-ray imaging - action (qualifier value) should be used as the method for all of the concepts that are descendants of 363680008|Radiographic imaging procedure (procedure)| that use the terms "X-ray, plain X-ray, radiographic imaging, radiography.' Where a descendant concept has a more granular description and method such as 312251004|Computed tomography imaging - action (qualifier value)| this is excluded from this proposal.

The changes proposed for 'Option One' would rectify existing inconsistencies in the current modeling of content that is resulting in unwanted inferences.

For example in the January 2021 release 277666002|X-ray guided biopsy (procedure) is a sibling of 277673007|Plain X-ray guidance (procedure). It would be expected that the 277666002|X-ray guided biopsy (procedure) be a child of 277673007|Plain X-ray guidance (procedure).

 
By remodeling the concept 277666002|X-ray guided biopsy (procedure) to have an method of 312254007|Plain X-ray imaging - action (qualifier value), subsumption is improved.  Subtypes should be assessed and remodeled to align with this proposed change to ensure that the correct attributes and values are included and ensure subsumption is as expected.

Open

It is however acknowledged that there are areas of the content where this change would have considerable impact.  For example, the concept 268425006|Pelvis X-ray (procedure) is modeled with the method 278110001|Radiographic imaging - action (qualifier value) and so has descendants that include 169071000|Computed tomography of pelvis (procedure).

If 268425006|Pelvis X-ray (procedure) is remodeled with a method of 312254007|Plain X-ray imaging - action (qualifier value) this will result in equivalency between 268425006|Pelvis X-ray (procedure) and 713021002|Plain radiography of pelvis (procedure). The current grouper concept 268425006|Pelvis X-ray (procedure) will be remodeled or inactivated which will result in changes to the inferred relationships for descendant concepts.

This issue is replicated throughout the hierarchy with another similar example:
424398008|Radiographic imaging of bone (procedure) versus 426945003|X-ray of bone (procedure)

Open

Modeling Test Case

In order to test the impact of the proposed change, one small area of content was remodeled:
1225002|Radiography of humerus (procedure) was remodeled with method 312254007|Plain X-ray imaging - action (qualifier value).

After the change is made there is equivalency between 1225002|Radiography of humerus (procedure) and 713026007|Plain x-ray of humerus (procedure)

This necessitates the inactivation of one of the concepts 713026007|Plain x-ray of humerus (procedure) with a SAME_AS relationship to 1225002|Radiography of humerus (procedure). 1225002|Radiography of humerus (procedure) also requires an update to the FSN to 'X-ray of humerus (procedure).'

It is arguable that both concepts could be maintained, both modeled with a different method and also following an agreed description convention. However maintaining both concepts is likely to persist the existing problems of duplication and confusion across the hierarchy.

The addition of high-level grouper concepts such as 'Radiographic imaging of X' cannot be entirely prohibited and could be added on request if there is a specific international use case to be supported however these instances should be rare.

713026007|Plain x-ray of humerus (procedure) was added for the January 2016 release, this is despite the presence of the existing concept 1225002|Radiography of humerus (procedure) which has a synonym of X-ray of humerus. This supports the assertion that there is confusion for both terminologists and users of SNOMED CT with the current content in this area.

The recommended action would resolve the issue with duplication and ambiguous interchangeable use of descriptions and so improve overall quality of this content area in SNOMED CT.

Associated Future Modeling Recommendation

Also of note is the presence of a number of concepts that do not make reference to a specific imaging modality and have their own naming convention of 'gram' or 'graphy'.
For example 168854009|Cystogram (procedure) is modelled with an action of radiographic imaging and subsumes more granular concepts.

Open

However it is not clear if this concept is intended to be an X-ray imaging procedure or a higher-level grouper concept. It would be advantageous to review this type of concept to ensure that the concepts can be modeled with an imaging modality and be fully defined. The question was raised with the expert group who advised that this procedure should be refined to a specific imaging modality, in this case X-ray, as the presence of a concept that does not incorporate a specific imaging modality is ambiguous to end users who are unsure which procedure to record.

Recommendation for Changes to Existing Descriptions 

As demonstrated, across SNOMED CT there is variation in the naming convention that has been implemented into the FSN and synonyms. It is recommended a consistent naming convention be implemented and incorporated into Editorial Guidance and also existing and future templates.

It is recommended that X-ray of X (procedure) be implemented for concepts that use the terms ‘radiographic imaging,’ ‘radiography,’ ‘X-ray’ and ‘plain X-ray’ with the following exceptions which will be retained as 'high level groupers':

• 363680008|Radiographic imaging procedure (procedure) - 3646 subtypes (January 2021 release)

• 108273007|Radiographic imaging procedure by site (procedure)- 3337 subtypes (January 2021 release)

• 418542003|Radiologic guidance procedure (procedure) - 1215 subtypes (January 2021 release)

• 27483000|Diagnostic radiography with contrast media (procedure) - 1474 subtypes (January 2021 release)

Note: a small number of further concepts may not align with the proposed naming convention for example 241209000|Sinogram (procedure) however the FSN should incorporate an imaging modality and these concepts can be treated on a case by case basis as exceptions.

It is recommended the descriptions follow this pattern:

• FSN: X-ray of X (procedure)

• Preferred term: X-ray of X

Acceptable synonyms:

• Plain X-ray of X

• Plain film of X

• Plain radiography of X

It is not compulsory to add these variations to a new concept they can be added upon request. Note: the expert group indicated that 'plain' is not commonly used within the clinical environment however this may vary from country to country.

Radiograph of X is a broader synonym and therefore should not be accepted as a new synonym for concepts that have the FSN X-ray of X. However instances of released concepts where this description already exists should remain active to prevent the need for large-scale retirements assuming that the synonym only appears on that single concept. Maintaining the broader synonyms will facilitate searching. This information should be incorporated into the editorial guide.

RadLex http://www.radlex.org/RID/RID10351 uses the naming convention of 'Radiography.' However the method of image capture (screen film or digital) is listed as a separate entity and this differs from the convention in SNOMED CT. Also of significance RadLex uses a post-coordinated approach where the imaging site and imaging modality are coded separately.

DICOM http://www.dicomlibrary.com/dicom/modality/ also uses the name "Radiographic imaging" for its imaging procedures and this encompasses conventional film/screen image capture. The question of whether there is a requirement to distinguish between digital and conventional film capture in SNOMED CT was raised with the expert group who advised that the imaging procedure itself is not altered by the method of storage for the image. The group did not advocate the inclusion of new content for digital or conventional image capture.

Duplicate synonyms across separate concepts are not acceptable except in very rare cases as described in the editorial guidance. Instances of duplication will require inactivation of descriptions. Application of the existing editorial guidance for broader and narrower synonyms will assist in determining which concept should retain the duplicate synonym and which should be inactivated.

Text Definition

It is recommended that a text definition be applied to the concepts 278110001|Radiographic imaging - action (qualifier value) and 312254007|Plain X-ray imaging - action (qualifier value) and also to the concepts 363680008|Radiographic imaging procedure (procedure) and 168537006|Plain radiography (procedure) to prevent future inconsistency in the manner these concepts are used.

Significant design or implementation decisions / compromises

Addressing any inconsistency in released concepts may require changes to way the concept is modeled or changes to descriptions. This is likely to result in changes to inferred relationships after classification. As noted above, in order to resolve this content issue it is recommended that changes be made to the descriptions and modeling of existing content rather than the large scale inactivation and replacement of content.

It is likely that the proposed changes will uncover equivalency between released concepts and this will need to be managed using inactivation and historical relationships. The impact of the proposed changes on end users is difficult to assess however the benefits of improvement in the quality of existing content without large scale inactivations is intended to mitigate any associated implementation burden.

Evaluation of Design

Exceptions and Problems

Generally where a concept has a mixture of descriptions and is also inconsistent in the way in which its axiom(s) have been assigned, it would be considered to be ambiguous. This would lead to concept inactivation. The recommendations of this content project do not include large-scale inactivation of existing inconsistent content. However this will result in changes to released FSN that cannot be considered to be minor as defined in the Editorial Guidance Fully Specified Name 

This potential problem can be mitigated by consultation with stakeholders prior to implementation of these changes. Stakeholder consultation should include Editorial Advisory Committee, Content Managers Advisory Group and also users such as DICOM and NICIP along with notification via the 'early visibility' Confluence page.