Exchanging Imaging Data

DICOM INTERNATIONALCONFERENCE & SEMINAR

Oct 9-11, 2010 Rio de Janeiro, Brazil

Exchanging Imaging Data

Cor Loef

Philips

Exchanging Imaging Data

• Objective: This presentation will answer the following question:– What are the types of DICOM objects and

how do we move them around, i.e. over a network as well as on media?

Exchanging Imaging Data

• Agenda– Main Classes of Objects:

Images, Presentation States, Structured Reports, Encapsulated Objects

– Pushing Objects, Pulling Objects, Finding Objects and Retrieving Objects

– DICOM: a Protocol vs a File Format vs a product Internal Data Representation

– Use of Media: CDs, Memory Sticks, Email, WADO

IE’s AttributesModules

Information Object Definition (IOD):

• DICOM Composite Objects:For persistent, “permanent” objects using

DIMSE-C commands (C-Store, C-Move, C-Find…)

Multiple IE’s: relate to DICOM Information Model (Patient-Study-Series-Image…)

Cannot be changed or modified, if so, create a new object with new SOP Instance UID

Information Object Definition (IOD):

Multi-frame Objects:

• Ultrasound Multiframe• Nuclear Medicine• XA and RF• New objects: MR, CT,

PET, XA-XRF (new), X-Ray 3D, US 3D

• VL and Ophthalmology• Any future new objects:

NM (new)

Vector

Structured Reports:

• Same structure as Images:– “main body” contains report and/or other

information (measurements, etc.) instead of pixels

– Same structure for header– Same study information– Modality is “SR”– Has a tree structure

SR example (IHE simple report):

0-n

CONTAINS

HAS OBS CONTEXT

1

CONTAINS

1-n

0-n

INFERRED FROM

Report Text (TEXT)

Image Reference (IMAGE)

Observation Context (See Figure 5.3-5)

1-n

Section Heading (CONTAINER)

Document Title (CONTAINER)

Image Reference (IMAGE)

Measurement (NUM)

0-n

Measurement (NUM)

0-n

HAS OBS CONTEXT

0-1

Observation Context (See Figure 5.3-5)

SR example (Key Image/Object Note KON):

Document Title(CONTAINER)

1 1-n

CONTAINS

HAS OBS CONTEXT

1

Image Reference(IMAGE)

Observation Context(See figure 5.3-5)

Key Image Description(TEXT)

Encapsulated Objects (SC and PDF):

• Some objects are difficult to encode as “native” objects:

• Secondary Capture (SC):– Digitized film, captured video,

scanned documents

• Encapsulated PDF:– typically for bone scans and eye care

(topographic maps)

- Present images (almost) identical on softcopy media in standard manner

- Separation of Stored Image Instances from Display characteristics and changes

- Includes shutters, image annotation, spatial transformation, display annotation

Softcopy Presentation State:

Solution:

- Create Composite object containing the presentation state parameters ONLY (no images)

- Link this Composite object to one or more images (Series, Images)

- Store within same Study; Modality “PR”

- Communicate with regular Storage service (C_Store); Retrieve with Query/Retrieve service

Softcopy Presentation State:

How do we move these objects around?

Pushing, Pulling Objects (Storage SOP Classes),

Finding Objects (Information model/FIND),

Retrieving Objects (Move/Get)

Modality

Information System

Display

Printer

Archive

PACS

Modality Push/PACS Push

DICOM C-Store

Storage Service class:

Transfer composite objects (e.g. images, reports, RT plans, waveforms) from one AE to another

One AE functions as the SCU, the other as SCP

SOP classes use C-Store DIMSE-C service

Information is stored in some medium, accessible for some time

Storage Service class:

(Issue! Might need Storage commitment!)

Modality

Information System

Display

Printer

Archive

PACS

Modality Pull/PACS Pull

DICOM C-Find

DICOM C-Move

SCU/SCP

Query/Retrieve Service class:

Simple Query, NOT full SQL:

Query: Basic image information query (“FIND”) using small set of common key attributes

Retrieve: Either from remote AE (“GET”), or Xfer from one AE to the other (“MOVE”)

Note: “GET” rarely supported

Extensions allow retrieval of selected frames of a multi-frame

Query/Retrieve Service class:

SQL

database

(Informix,

Sybase,

Oracle)

DICOM

I/F

Query/Retrieve Service class:

Note: Most vendors also support a proprietary,

direct protocol

Key Attributes:U: UniqueR: RequiredO: Optional

Pat name

Pat ID

----

----

----

Keys

Image IOD

Query/Retrieve Service class:

Keys for FIND:

Patient’s Name (0010,0010) R

Patient ID (0010,0020) U

Study Date (0008,0020) R

Study Time (0008,0030) R

Accession Number (0008,0050) R

Study ID (0020,0010) R

Study Instance UID (0020,000D) U

Modality (0008,0060) R

Series Number (0020,0011) R

Series Instance UID (0020,000E) U

Instance Number (0020,0013) R

SOP Instance UID (0008,0018) U

Q/R SOP Classes use:C-Find:

SCP matches all keys specified in the request against it’s database

May be at Patient, Study, Series or Image level

SCP provides Response for each match containing values for all keys and all requested, known attributes

Can Cancel if needed

Query/Retrieve Service Class:

Q/R SOP Classes use:C-Move:

SCU provides unique key values for needed SOP instances

SCP initiates C-Store(s) as SCU (on a separate Association)

SCP can issue C-Move responses with status pending until all C-Stores are completed or after each Store (see Conformance Statement)

Can issue Cancel at any time

Query/Retrieve Service Class:

Protocols, Files, Storage

• Protocols:– DICOM defines a standard communication protocol

(PDU, TCP/IP, addressing: port #, AE title)

• Files:– DICOM also defines a standard for files on media:

“Part-10 files” = meta information + a SOP instance– Media includes CD, DVD, Memory Sticks, etc.– Part-10 file format is also extended for zip files, email,

and web access (WADO)

DICOM Media:

Service Class Specifications

Information Objects Definitions

Data Set Structure and Encoding - Data Dictionary

Message Exchange File Format

Application Entity

DICOM Upper Layer Service Boundary DICOM Basic File Service Boundary

DICOM Upper Layer

Security Layer

(Optional)

TCP/IP Transport

Layer

Security Layer

(Optional)

Physical Media

and Media File Formats

Network Exchange On-Line Communication

Media Storage Interchange Off-Line Communication

Medical Information Application

• Meta-file header:• Transfer syntax (encoding)• SOP Class• Who generated it• Compliant with standard OS’s

• DICOMDIR required for exchange media

• Index/database of files

DICOM Media Specifications:

DICOM Application Entity

Service / Object PairsBasic Dir.

DICOM File Format

Media Formats: e.g. File data structures

Physical Media: e.g. CD-R; 90 mm MOD, etc.

Par

t 10

Par

t 11

Par

t 12

Protocols, Files, Storage:

• Device Internal Storage:– DICOM defines how images go in/out of device

– DICOM does NOT define how to archive images (there is NO archive standard)

– Some vendors keep images in DICOM format, some pre-process images using a compression method, either standard or proprietary

– Migration of both PACS databases and archives are common when changing releases, vendors, etc.

Conclusion:

• DICOM objects include:– not only images

– but also SR’s, Presentation States, and encapsulated objects

• DICOM images are moved around using:– the DICOM protocol

– the DICOM Part-10 file definition

• There is NO DICOM archiving standard, some archives store “natively”, some do not

DICOM INTERNATIONALCONFERENCE & SEMINAR

Oct 9-11, 2010 Rio de Janeiro, Brazil

Thank you!

Cor Loef:

cor.loef@philips.com

www.philips.com