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
| Code | Name | Description |
|---|---|---|
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 2D image. Structured Reports, Presentation States, waveforms, and RT objects all use the modality framework:
| Code | Name | Description |
|---|---|---|
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
| Code | Name | Description |
|---|---|---|
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)