1. Exchanging Imaging Data
Cor Loef
Philips

2. 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?

3. 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, , WADO

4. Information Object Definition (IOD):
IE’s
Attributes
Modules

5. DICOM Composite Objects:
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

6. Multi-frame Objects:
Vector
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)

7. Same structure as Images:
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

8. SR example (IHE simple report):

9. SR example (Key Image/Object Note KON):

10. 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)

11. Softcopy Presentation State:
- 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 8

12. 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 9

13. How do we move these objects around?
Pushing, Pulling Objects (Storage SOP Classes),
Finding Objects (Information model/FIND),
Retrieving Objects (Move/Get)

14. Modality Push/ PACS Push
Storage Service class:
Information System
Modality Push/ PACS Push
Modality
Display
Printer
Archive
PACS
DICOM C-Store

15. 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
(Issue! Might need Storage commitment!)

16. Query/Retrieve Service class:
Information System
Modality Pull/PACS Pull
SCU/SCP
Display
Printer
Archive
PACS
Modality
DICOM C-Find
DICOM C-Move

17. 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

18. Query/Retrieve Service class:
Note: Most vendors also support a proprietary,
direct protocol
SQL
database
(Informix,
Sybase,
Oracle)
DICOM
I/F

19. Query/Retrieve Service class:
Key Attributes:
U: Unique
R: Required
O: Optional
Image IOD
Pat name
Pat ID
----
Keys

20. Keys for FIND: Patient’s Name (0010,0010) R Patient ID (0010,0020) U
Study Date
(0008,0020) R
Study Time
(0008,0030)
Accession Number
(0008,0050)
Study ID
(0020,0010)
Study Instance UID
(0020,000D) U
Modality
(0008,0060) R
Series Number
(0020,0011)
Series Instance UID
(0020,000E) U
Instance Number
(0020,0013) R
SOP Instance UID
(0008,0018) U

21. Query/Retrieve Service Class:
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

22. 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

23. Protocols, Files, Storage
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, , and web access (WADO)

24. DICOM Media: 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

25. DICOM Media Specifications:
DICOM Application Entity
Basic Dir.
Service / Object Pairs
Part 10
DICOM File Format
Part 11
Media Formats: e.g. File data structures
Part 12
Physical Media: e.g. CD-R; 90 mm MOD, etc.

26. 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.

27. 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

28. Cor Loef: cor.loef@philips.com www.philips.com
Thank you!
Cor Loef: