Reference

DICOM Modalities

Every DICOM study carries a two-letter Modality code in attribute (0008,0060). The code drives routing rules in PACS, filters in worklists, billing codes, and the IOD schema the image must conform to. The authoritative list is PS3.3 Section C.7.3.1.1.1. Below are the modalities you'll actually encounter in production.

Common clinical modalities

Most of these codes are a machine. CT and MR share the same shape: a bore ringed with detectors, and a table that moves the patient through it. The two-letter code in (0008,0060) is how every downstream system learns which one produced the study.
CodeNameDescription
CT Computed Tomography Cross-sectional X-ray imaging. High-volume output: a single CT study can be 500-1,500 images.
MR Magnetic Resonance Multi-parametric soft tissue imaging. Dozens of series per study with wildly different acquisition parameters.
US Ultrasound Real-time sonography: single frames plus multi-frame cine loops.
XA X-Ray Angiography Fluoroscopy with contrast injection, cath lab staple.
MG Mammography Specialized digital X-ray for breast imaging. Tomosynthesis (DBT) is a multi-frame variant.
NM Nuclear Medicine Radiotracer-based imaging: SPECT, bone scans, thyroid uptake.
PT Positron Emission Tomography PET (the standard modality code is PT, not PET, easy to mistype).
RF Radio Fluoroscopy Real-time X-ray, typically GI / GU studies.
DX Digital Radiography Digital X-ray using flat-panel detectors. Replaces classical film.
CR Computed Radiography Digitized X-ray using phosphor plates. Legacy but still widespread.
SC Secondary Capture Screen captures, scanned forms, derived annotations: anything not from a primary modality.

Non-image modalities

Not every DICOM object is a picture. A waveform, a structured report, an RT dose grid: all carry a modality code and travel the same framework, and none of them decode to an image.

Not every DICOM object is a 2D image. Structured Reports, Presentation States, waveforms, and RT objects all use the modality framework:

CodeNameDescription
SR Structured Report Hierarchical structured findings: measurements, diagnoses, key image notes.
PR Presentation State Display-state overlay: window/level, LUTs, annotations saved per user.
RTSTRUCT RT Structure Set Contours for radiation therapy planning.
RTPLAN RT Plan Radiation therapy treatment plan.
RTDOSE RT Dose Radiation therapy dose distribution.
ECG Electrocardiography Waveform storage for ECG traces.

Specialty modalities

Cameras and scopes, not bores. The specialty codes mostly describe small optical instruments rather than the room-sized equipment CT and MR imply, which is why their images arrive with very different geometry and scale.
CodeNameDescription
OCT Optical Coherence Tomography Ophthalmic cross-sectional imaging.
OP Ophthalmic Photography Fundus photography and external eye photography.
XC External-camera Photography Wound photos, dermatology, visible-light captures.
IO Intra-oral Radiography Dental periapical + bitewing X-rays.
PX Panoramic X-Ray Dental panoramic imaging.
OT Other Catch-all for modality types not otherwise specified. Vendors overuse this. Budget for manual review.

Where the modality tag lives in the data

The Modality attribute appears at the Series level: one Modality value per DICOM series. A study's Modalities in Study attribute (0008,0061) aggregates the unique codes across all series, which is what Q/R uses for modality filtering at the study level.

A single DICOM study can contain multiple modalities. A contrast-enhanced PET/CT produces both PT and CT series under one Study Instance UID. Your PACS filter rules need to handle this: querying ModalitiesInStudy=CT will match the study; filtering Modality=CT at the series level will return only the CT series.

Browse: Modality tag (0008,0060) · Modalities in Study (0008,0061)

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