flywheel-gear-extensions

DICOM QC Checker

Evaluates DICOM QC check results stored in a file’s metadata and tags the file with an aggregate pass/fail status.

Workflow

Upstream, the dicom-qc gear runs quality checks on DICOM files and writes individual check results into the file’s metadata at file.info.qc.dicom-qc. Each check result is a dictionary entry with a state field ("PASS" or "FAIL").

When invoked on the input file, the checker gear:

1. Extracts the dicom-qc metadata from file.info.qc.dicom-qc.
2. Filters out the job_info entry and any non-check entries (values that are not dicts or lack a state field).
3. Determines aggregate status: PASS only if every check result has state == "PASS", otherwise FAIL.
4. Logs each failed or invalid check name at WARNING level.
5. Tags the file with the result using the GearTags mechanism.

If no QC metadata is present, or if metadata contains no valid check results after filtering, the gear logs a warning and exits successfully without modifying tags.

Inputs

Input	Base	Description
api-key	api-key	The account the gear runs as; needs read/write permission on file metadata and tags.
input_file	file	The file to evaluate for DICOM QC check results.

Configuration

Gear configs are defined in manifest.json.

This gear has no additional configuration parameters beyond the standard inputs.

Status Determination

Condition	Overall Status	Behavior
All check results have state “PASS”	PASS	Tag applied
Any check result has state != “PASS”	FAIL	Failed checks logged, tag applied
No QC metadata present	N/A	Warning logged, no tag change
Metadata has only job_info (no check results)	N/A	Warning logged, no tag change

File Metadata and Tagging

After processing, the gear updates the input file’s tags using the GearTags mechanism. See the QC Conventions reference for details on the data models and conventions used.

• Adds dicom-qc-checker-PASS or dicom-qc-checker-FAIL based on the aggregate QC outcome
• Previous status tags for this gear are removed before adding the new one

Expected Metadata Structure

The gear expects metadata at file.info.qc.dicom-qc with this shape:

{
    "job_info": {
        "job_id": "abc123",
        "gear_name": "dicom-qc"
    },
    "slice_count_check": {
        "state": "PASS"
    },
    "orientation_check": {
        "state": "FAIL"
    }
}

Rules for identifying check results:

• Key is not "job_info"
• Value is a dict containing a "state" field

All other entries are silently ignored.

Error Handling

Scenario	Behavior
QC metadata absent or empty	Log warning, exit code 0 (nothing to check)
Metadata contains only job_info	Log warning, exit code 0
File retrieval fails (API error)	Exit code 1

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