DICOM Architecture Overview

DICOM follows a layered architecture similar to the OSI model, providing a structured approach to medical imaging communication.

Layered Model

Layer Details

Key Components

1. Information Object Definitions (IODs)

IODs define what information can be stored in a DICOM object. Think of them as templates:

Each IOD consists of modules, and each module contains attributes (tags).

2. Service-Object Pair (SOP) Classes

SOP Classes combine an IOD with DIMSE services to define what you can DO with an object:

Common SOP Class UIDs:

3. DIMSE Services

DIMSE (DICOM Message Service Element) defines the operations that can be performed:

4. Transfer Syntaxes

Transfer Syntaxes define how data is encoded at the binary level:

Transfer Syntax Components
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Byte Ordering:
  - Little Endian (most common)
  - Big Endian (legacy)

Value Representation:
  - Explicit VR (recommended)
  - Implicit VR (legacy default)

Compression:
  - Uncompressed
  - JPEG Lossless
  - JPEG 2000
  - RLE

Common Transfer Syntax UIDs:

5. Application Entities (AEs)

AEs are DICOM-enabled applications identified by:

Key AE concepts:

• AE Title: 16-character identifier (e.g., “MY_PACS”)
• SCU (Service Class User): Client role, initiates requests
• SCP (Service Class Provider): Server role, responds to requests
• Association: Connection between two AEs

Architecture in Practice

This architecture ensures that DICOM devices can communicate effectively regardless of manufacturer, as long as they implement the same SOP Classes and support compatible Transfer Syntaxes.