DICOM INTERNATIONAL DICOM INTERNATIONAL CONFERENCE & SEMINAR April 8-10, 2008 Chengdu, China Exchanging Imaging Data Herman Oosterwijk Add logo if desired

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 as a Protocol vs a File Format vs a product Internal Data Representation –Use of Media (CDs, Memory Sticks, , WADO)

IE’sAttributesModules 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):

Multiframe objects: Ultrasound Multiframe Nuclear medicine XA and RF New objects (MR, CT) VL and ophthalmology Any future new objects (XA,RF, 3- D,etc) 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):

SR example (Key Image/Object Note-- KON):

Encapsulated Objects (SC and PDF): Some objects are difficult to encode as “native” objects: Secondary Capture (SC): –Digitized film, captured video, 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); stored 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? Push, Pulling Objects (Storage SOP Classes), Finding Objects (Information model/FIND) and Retrieving Objects (Move/Get)

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

Allow composite objects, e.g. images, reports, RT plans, waveforms, to be transferred from one to the other AE One AE functions as the SCU, the other one SCP The SOP classes use the C-Store DIMSE-C service The information is stored in some medium, accessible for some time Storage Service class: (Issue! Might need Storage commitment!)

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

Simple Query, NOT a full SQL: Query: Perform basic image information queries using small set of common key attributes (“FIND”) Retrieve: Either from remote AE (“GET”), or Xfer from one AE to the other (“MOVE”) Note: “GET” rarely supported 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: Unique R: Required O: 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 performs a match of all the keys specified in the identifier of the request against the information it has, depending on level specified (Patient, Study, Series, Image) SCP provides Response for each match with values of all key fields and requested, known attributes Can also Cancel if needed Query/Retrieve Service class:

Q/R SOP Classes use: C-Move: Upon providing unique key values by the SCU, the SCP initiates C-Store for the SOP instances indicated. SCP becomes SCU for Store; requires separate Association C-Move responses with status pending can be issued till all the C-Stores are completed or after each Store (see conf statement) Can also issue Cancel at any time Query/Retrieve Service class:

Protocols, Files, Storage Protocols: –DICOM is a communication standard defining the protocol (PDU, TCP/IP, addressing: port #, AE title) Files: –DICOM ALSO defines a standard for exchanging files on media: encapsulated with “group 2” also known as Part-10 files –Media includes CD, DVD, flash media –The part-10 file format is extended for exchange using s (WADO)

DICOM Media: Meta-file header: Transfer syntax (encoding) SOP Class Who generated it Compliant with standard OS’s DICOMDIR is also required for exchange media

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

Protocols, Files, Storage: Storage: –DICOM does NOT define how to archive images (there is NO archive standard) –Some vendors preserve the images in a DICOM format, some pre-process the 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, and exchanged using the DICOM part-10 file definition There is NO DICOM archiving standard, some archives store natively, some do not

DICOM INTERNATIONAL DICOM INTERNATIONAL CONFERENCE & SEMINAR April 8-10, 2008 Chengdu, China Thank you! Herman Oosterwijk: