> 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/multi-modality-imaging-pet-ct-and-spect-ct.md).

# Multi-modality Imaging: PET, CT and SPECT, CT

There are very few imaging procedures which are truly *multi-modality* procedures. Two procedures are usually conducted in parallel, rather than as one. Positron emission tomography with computed tomography (PET/CT) and Single photon emission computed tomography with computed tomography (SPECT/CT), however, are produced by one piece of equipment, possibly by a single technician, but with multiple imaging energies.

## Positron emission tomography with computed tomography

* FSN: Positron emission tomography with computed tomography of X (procedure)
* PT: PET CT of X
* SYN: Positron emission tomography with computed tomography of X
  * For example,
    * 16554361000119106 | Positron emission tomography with computed tomography of brain (procedure)|
      * FSN: Positron emission tomography with computed tomography of brain (procedure)
      * PT: PET CT of brain
      * SYN: Positron emission tomography with computed tomography of brain

## Single photon emission computed tomography with computed tomography

* FSN: Single photon emission computed tomography with computed tomography of X (procedure)
* PT: Single photon emission computed tomography with computed tomography of X
* SYN: SPECT CT of X
  * For example,
    * 16534151000119105 | Single photon emission computed tomography with computed tomography of liver (procedure)|
      * FSN: Single photon emission computed tomography with computed tomography of liver (procedure)
      * PT: Single photon emission computed tomography with computed tomography of liver
      * SYN: SPECT CT of liver

<a href="https://docs.google.com/forms/d/e/1FAIpQLScTmbZIf0UEQwYDkY27EEWBkaiYkHSbR0_9DmFrMLXoQLyL7Q/viewform?usp=pp_url&#x26;entry.1767247133=SCT+Editorial+Guide&#x26;entry.670899847=Multi-modality%20Imaging%3A%20PET%2C%20CT%20and%20SPECT%2C%20CT" class="button primary">Provide Feedback</a>


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.

Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:

```
GET https://docs.snomed.org/snomed-ct-specifications/snomed-ct-editorial-guide/readme/authoring/domain-specific-modeling/procedure/index-1/index/multi-modality-imaging-pet-ct-and-spect-ct.md?ask=<question>&goal=<user_goal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.