DICOM INTERNATIONAL CONFERENCE SEMINAR April 8 10 2008

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, Email, WADO)

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

Information Object Definition (IOD): • DICOM Composite objects: For persistent, “permanent” objects using DIMSE-C commands (C-Store, C-Move, CFind…) l Multiple IE’s: relate to DICOM Information Model (Patient-Study-Series-Image…) l Cannot be changed or modified, if so, create a new object with new SOP Instance UID l

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

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)

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

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

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

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

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

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

Query/Retrieve Service class: l Simple Query, NOT a full SQL: l Query: Perform basic image information queries using small set of common key attributes (“FIND”) l Retrieve: Either from remote AE (“GET”), or Xfer from one AE to the other (“MOVE”) l Note: “GET” rarely supported

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

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

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, 000 D) U Modality (0008, 0060) R Series Number (0020, 0011) R Series Instance UID (0020, 000 E) U Instance Number (0020, 0013) R SOP Instance UID (0008, 0018) U

Query/Retrieve Service class: Q/R SOP Classes use: l C-Find: l 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) l SCP provides Response for each match with values of all key fields and requested, known attributes l Can also Cancel if needed

Query/Retrieve Service class: Q/R SOP Classes use: l C-Move: l 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 l C-Move responses with status pending can be issued till all the C-Stores are completed or after each Store (see conf statement) l Can also issue Cancel at any time

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

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 CONFERENCE & SEMINAR April 8 -10, 2008 Chengdu, China Thank you! Herman Oosterwijk: herman@otechimg. com www. otechimg. com