# DICOM Radiotherapy Structure Sets

DICOM Radiotherapy Structure Sets (RTSS, or RTSTRUCT) define regions of interest by a set of planar contours. 

RTSS objects can be identified by the `RTSTRUCT` value assigned to the `Modality` attribute, or by `SOPClassUID` = `1.2.840.10008.5.1.4.1.1.481.3`.

If you use the IDC Portal, you can select cases that include RTSTRUCT objects by selecting "Radiotherapy Structure Set" in the "Original" tab, "Modality" section ([filter link](https://portal.imaging.datacommons.cancer.gov/explore/filters/?Modality_op=OR\&Modality=RTSTRUCT)). Here is [a sample study](https://viewer.imaging.datacommons.cancer.gov/viewer/1.3.6.1.4.1.14519.5.2.1.77129820837198295687264213920427872580) that contains an RTSS series.

As always, you get most of the power in exploring IDC metadata when using SQL interface. As an example, the query below will select a random study that contains a RTSTRUCT series, and return a URL to open that study in the viewer:

```sql
# get the viewer URL for a random study that 
#  contains RTSTRUCT modality
SELECT
  ANY_VALUE(CONCAT("https://viewer.imaging.datacommons.cancer.gov/viewer/", StudyInstanceUID)) as viewer_url
FROM
  `bigquery-public-data.idc_current.dicom_all`
WHERE
  StudyInstanceUID IN (
  # select a random DICOM study that includes an RTSTRUCT object
  SELECT
    StudyInstanceUID
  FROM
    `bigquery-public-data.idc_current.dicom_all`
  WHERE
    SOPClassUID = "1.2.840.10008.5.1.4.1.1.481.3"
  ORDER BY
    RAND()
  LIMIT
    1)
```

### Metadata

RTSTRUCT relies on unstructured text in describing the semantics of the individual regions segmented. This information is stored in the `StructureSetROISequence.ROIName` attribute. The following query will return the list of all distinct values of `ROIName` and their frequency.

```sql
SELECT
  structureSetROISequence.ROIName AS ROIName,
  COUNT(DISTINCT(SeriesInstanceUID)) AS ROISeriesCount
FROM
  `bigquery-public-data.idc_current.dicom_all`
CROSS JOIN
  UNNEST (StructureSetROISequence) AS structureSetROISequence
WHERE
  SOPClassUID = "1.2.840.10008.5.1.4.1.1.481.3"
GROUP BY
  ROIName
ORDER BY
  ROISeriesCount DESC
```

### Conversion into alternative representations

We recommend [Plastimatch convert](https://plastimatch.org/plastimatch.html#plastimatch-convert) tool for converting planar contours of the individual structure sets into volumetric representation.


---

# Agent Instructions: Querying This Documentation

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

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://learn.canceridc.dev/dicom/derived-objects/dicom-radiotherapy-structure-sets.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
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.