> For the complete documentation index, see [llms.txt](https://docs.snomed.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.snomed.org/snomed-ct-specifications/snomed-ct-editorial-guide/readme/authoring/domain-specific-modeling/procedure/index-1/index/contrast-for-imaging.md).

# Contrast for Imaging

It is essential to express when contrast is part of a procedure and that descriptions are constructed consistently.

* For example,
  * 702501008 | Computed tomography of knee with contrast (procedure)|
    * FSN: Computed tomography of knee with contrast (procedure)
    * PT: CT of knee with contrast
    * SYN: Computed tomography of knee with contrast

The descriptions for all procedure concepts that use contrast must explicitly state ‘with contrast.’ All procedures that use contrast, including 420040002 |Fluoroscopic angiography with contrast (procedure)| and all subtypes, must include the attribute 424361007 |Using substance (attribute)| and a value of 385420005 |Contrast media (substance)| or a subtype in the role group.

Where the value for the method imaging action is 278110001 |Radiographic imaging - action (qualifier value)| or a subtype, the value for 424361007 |Using substance (attribute)| must be 419098001 |Radiographic imaging contrast media (substance)| or a subtype to denote the radio-opaque nature of the substance.

* Exception: procedures which specify negative contrast which is non-radio-opaque

{% hint style="info" %}
This guidance should be applied to new content, the process of updating existing content will be carried out as time and resources permit.
{% endhint %}

It is unnecessary to add the word *media* to contrast.

It is agreed that the linking word to associate the contrast use with the procedure is *with* - not *for,* *or,* etc.

{% hint style="warning" %}
**Contrast**

Additional concept detail is required when it is necessary to know the more precise nature of contrast (e.g. iodinated with various osmolalities, barium, or gas).
{% endhint %}

## Imaging without contrast

Although considered a negation, this term is used in clinical records. *Without contrast* imaging procedures are acceptable.

For example,

* 566341000119106 | Computed tomography of ankle without contrast (procedure)|
  * FSN: Computed tomography of ankle without contrast (procedure)
  * PT: CT of ankle without contrast
  * SYN: Computed tomography of ankle without contrast

## Unacceptable concept qualification

*With and without* and *With or without* imaging concepts are not acceptable due to ambiguity. Two concepts should be used to express these separately.

<a href="https://docs.google.com/forms/d/e/1FAIpQLScTmbZIf0UEQwYDkY27EEWBkaiYkHSbR0_9DmFrMLXoQLyL7Q/viewform?usp=pp_url&#x26;entry.1767247133=SCT+Editorial+Guide&#x26;entry.670899847=Contrast%20for%20Imaging" class="button primary">Provide Feedback</a>


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