Imaging Data Commons

Imaging Data Commons

Overview

Query and download public cancer imaging data from the National Cancer Institute Imaging Data Commons (IDC). No authentication required for data access.

Expected network access: IDC metadata is reachable three ways — a local DuckDB index shipped with the idc-index Python package (no network), or the hosted IDC service over MCP or REST (api.imaging.datacommons.cancer.gov, no authentication). File downloads use public GCS (storage.googleapis.com) and AWS S3 (s3.amazonaws.com) — no authentication required. DICOMweb access uses either the public IDC proxy (proxy.imaging.datacommons.cancer.gov, no auth) or the Google Cloud Healthcare API (healthcare.googleapis.com, requires GCP authentication). Optional BigQuery queries (bigquery.googleapis.com) also require GCP authentication. No credentials or environment variables are accessed by this skill.

Current IDC Data Version: v24 (always verify — see Best Practices)

Choose the access path first. There is no single default: the cheapest correct path depends on the session and the task.

1. Session already has the IDC MCP server? Route discovery and metadata there — see IDC MCP Server.
2. Otherwise, is `idc-index` installed? Run python scripts/check_version.py. If it passes, use idc-index for everything.
3. Not installed, and the task is read-only metadata — counts, attribute values, collection lookups, SQL under 10 000 rows, licenses, citations, viewer URLs? Use the REST API over `curl`; do not install anything. Installing costs ~77 MB of packaged index data plus pandas, pyarrow, and duckdb, which a metadata question does not need. See Data Access Options.
4. Not installed, and the task needs more than metadata — downloading files, pandas or plotting, pydicom/SimpleITK, pathology tiling, results past 10 000 rows, or a version-pinned script the user re-runs? Install idc-index: check_version.py exits non-zero and prints the exact install command for the running interpreter. Prefer a virtual environment, then restart Python.

idc-index (GitHub) is still the most capable path and the only one that moves image bytes; the rule is just not to pay for it before the task calls for it. check_version.py never installs anything itself — it also flags a newer idc-index or skill release when one exists.

Setup for the `idc-index` path:

from idc_index import IDCClient
client = IDCClient()

# Verify IDC data version (should be "v24")
print(f"IDC data version: {client.get_idc_version()}")

Core workflow: query metadata with client.sql_query() → download with client.download_from_selection() → visualize with client.get_viewer_URL(). Python examples below assume this client; Data Access Options has the REST equivalents. For current data scale, run the summary query in references/sql_patterns.md or GET /v3/stats.

IDC MCP Server

IDC operates a hosted MCP server at https://api.imaging.datacommons.cancer.gov/mcp (streamable HTTP, no authentication). Where it is available it complements — it does not replace — the idc-index workflow below.

Identify it by the MCP resource idc://guide, or by three or more of the tool names build_cohort, get_cohort_urls, list_analysis_results, and get_idc_version. Generic names such as run_sql are not evidence on their own. If identification is ambiguous, use idc-index.

If this session has the server, treat it as authoritative for discovery and metadata — IDC version, counts, attribute values, cohort building, metadata SQL — and follow the server's own instructions rather than re-deriving them from this file. Its data version is whatever the server reports: call get_idc_version instead of relying on the version pinned in this file.

Return here for what the server does not do: downloading files, local pandas/notebook analysis, DICOMweb, BigQuery, digital pathology tiling, and reproducible scripts. Hand off by passing SeriesInstanceUIDs from the server to client.download_from_selection(...), and run scripts/check_version.py at that point.

If it is not available, the identical service is reachable with no configuration as a REST API at https://api.imaging.datacommons.cancer.gov/v3 — use it for read-only metadata rather than installing idc-index, per the routing gate in Overview. Suggest connecting the MCP server at most once, only for repeated interactive discovery, and never change the user's configuration yourself.

See references/mcp_guide.md for the tool inventory, handoff patterns, and per-host notes.

When to Use This Skill

• Finding publicly available radiology (CT, MR, PET) or pathology (slide microscopy) images
• Selecting image subsets by cancer type, modality, anatomical site, or other metadata
• Downloading DICOM data from IDC
• Checking data licenses before use in research or commercial applications
• Visualizing medical images in a browser without local DICOM viewer software

Quick Navigation

Inline below: the MCP/REST routing rules, the IDC data model, the index tables and how they join, the core API patterns (query, download, visualize, license, cite), best practices, and troubleshooting.

Reference Guides (load on demand):

IDC Data Model

IDC adds two grouping levels above the standard DICOM hierarchy (Patient → Study → Series → Instance):

• collection_id: Groups patients by disease, modality, or research focus (e.g., tcga_luad, nlst). A patient belongs to exactly one collection.
• analysis_result_id: Identifies derived objects (segmentations, annotations, radiomics features) across one or more original collections. Use it to find AI-generated or expert annotations, while collection_id finds original imaging data (which may itself include deposited annotations).

Key identifiers for queries: | Identifier | Scope | Use for | |------------|-------|---------| | collection_id | Dataset grouping | Filtering by project/study | | PatientID | Patient | Grouping images by patient | | StudyInstanceUID | DICOM study | Grouping of related series, visualization | | SeriesInstanceUID | DICOM series | Grouping of related series, visualization |

Index Tables

The idc-index package provides multiple metadata index tables, accessible via SQL or as pandas DataFrames. The REST API exposes the same tables through GET /tables and POST /sql.