This page describes how to configure a DICOM store to exportDICOM instance metadata to a BigQuery table whenever one of thefollowing occurs:

• You store a DICOM instance using theStore transaction or byimporting DICOM objects from a Cloud Storage bucket.
• You delete a DICOM instance using aDeletion request.
• Youchange the storage class of a DICOM instance.

Streaming DICOM metadata to a BigQuery table synchronizes the tablewith your DICOM data so you can run complex queries on the latest version ofyour DICOM store.

Before you begin

Before you configure your DICOM store, complete the following

Set BigQuery permissions

Before streaming DICOM metadata to BigQuery, you must grantthe required permissions to theCloud Healthcare Service Agentservice account. For more information, seeDICOM store BigQuery permissions.

Learn to export DICOM metadata to BigQuery

Before configuring streaming, understand how toexport DICOM metadata to BigQuery.

Configure the DICOM store

To enable streaming to BigQuery, configure theStreamConfigobject in your DICOM store. In theStreamConfig object, set theBigQueryDestinationobject to a fully qualified BigQuery table URI as a DICOMinstance metadata destination.

You can specify up to five BigQuery destinations ascomma-separated JSON objects.

Deleting DICOM instances in a DICOM store doesn't delete the BigQueryrows containing the metadata for those instances.

{  'streamConfigs': [{     'bigqueryDestination': {      'tableUri': 'bq://PROJECT_ID.BIGQUERY_DATASET_ID.BIGQUERY_TABLE_ID'     }  }]}

cat > request.json<< 'EOF'{  'streamConfigs': [{     'bigqueryDestination': {      'tableUri': 'bq://PROJECT_ID.BIGQUERY_DATASET_ID.BIGQUERY_TABLE_ID'     }  }]}EOF

curl -X PATCH \
     -H "Authorization: Bearer $(gcloud auth print-access-token)" \
     -H "Content-Type: application/json; charset=utf-8" \
     -d @request.json \
     "https://healthcare.googleapis.com/v1/projects/PROJECT_ID/locations/LOCATION/datasets/DATASET_ID/dicomStores/DICOM_STORE_ID?updateMask=streamConfigs"

@'{  'streamConfigs': [{     'bigqueryDestination': {      'tableUri': 'bq://PROJECT_ID.BIGQUERY_DATASET_ID.BIGQUERY_TABLE_ID'     }  }]}'@  | Out-File -FilePath request.json -Encoding utf8

$cred = gcloud auth print-access-token
$headers = @{ "Authorization" = "Bearer $cred" }

Invoke-WebRequest `
    -Method PATCH `
    -Headers $headers `
    -ContentType: "application/json; charset=utf-8" `
    -InFile request.json `
    -Uri "https://healthcare.googleapis.com/v1/projects/PROJECT_ID/locations/LOCATION/datasets/DATASET_ID/dicomStores/DICOM_STORE_ID?updateMask=streamConfigs" | Select-Object -Expand Content

{  "name": "projects/PROJECT_ID/locations/LOCATION/datasets/DATASET_ID/dicomStores/DICOM_STORE_ID",  "streamConfigs": [    {      "bigqueryDestination": {        "tableUri": "bq://PROJECT_ID.BIGQUERY_DATASET_ID.BIGQUERY_TABLE_ID"      }    }  ]}

Deletion metadata

In previous Cloud Healthcare API versions, DICOM instance metadata was onlyexported to BigQuery when a DICOM instance was inserted into a DICOMstore. When writing metadata for deletions was added,two new columns, namedType andLastUpdated, were added to the generatedtable containing the DICOM metadata.

Any metadata in the table that existed before the introduction of deletionmetadata has aNULL value for these columns. ANULL is the lowest value andappears last when sorting by descending order.

Generated BigQuery view

When you insert or delete a DICOM instance in a DICOM store, the configuredBigQuery table is updated.

If aview of the table doesn't exist,the view is created. Otherwise, the view is updated.

Limitations and additional behavior

Some DICOM tags might be missing from the exported metadata. If so, the missingtags are added to a separate column namedDroppedTags.TagName in thedestination BigQuery table.

Tags will be missing for one of the following reasons:

• The DICOM tag is an unsupported VR listed inExcluded VRs.
• The DICOM tag approximately exceeds 1 MB.
• The number of columns in the destination BigQuery table exceeds themaximum number of columns.When exporting DICOM metadata to a BigQuery table exceeds thecolumn limit, DICOM tags that don't match an existing column are added totheDroppedTags.Name column. If theDroppedTags column can't be added,the DICOM tags are dropped without a notification and a warning log isgenerated. For more information, seeTroubleshooting DICOM streaming requests for viewing logs.

Incorporate deletion metadata into an existing table

Thegenerated view's behaviour depends on whether its basetable contains metadata added before thedeletion metadatafeature was introduced.

Suppose a BigQuery table contains DICOM metadata from beforedeletion metadata was supported, and then the following occurs:

1. You insert a DICOM instance into a DICOM store.
2. You delete the DICOM instance from the DICOM store.
3. You edit the tags of the original DICOM instance, and insert the modifiedDICOM instance into the DICOM store.

Because the BigQuery table contained the original metadata beforedeletion metadata was supported, the original DICOM instance and its editedversion have the same studies, series, and instanceunique identifiers (UID). The generated view might containeither the original DICOM instance or the most recent DICOM instance. WithouttheLastUpdated column, the view can't identify which DICOM instance is newer.

To ensure you're querying the most recent DICOM instance metadata, do one of thefollowing:

• Query the base table instead of the view. Ensure the query searches for the updated tags in the edited DICOM instance.

• Delete the existing table containing DICOM metadata, and then recreate itbyexporting the DICOM metadata to BigQuery manually.The recreated table contains theLastUpdated column.

  This option removes historical streaming metadata, but ensures that the tablecontains theLastUpdated column with valid values.

Troubleshoot DICOM streaming requests

If errors occur during a DICOM export metadata to BigQueryrequest, the errors are logged toCloud Logging. For moreinformation, seeViewing error logs in Cloud Logging.

To filter streaming DICOM metadata error logs in the Google Cloud console, complete the following steps:

1. Go to theLogs explorer page.

   Go to Logs explorer

2. In theQuery field, enter the following query:

   logName="healthcare.googleapis.com%2Fdicom_stream"

3. ClickRun query.

   Any error logs are displayed in theQuery results section.