DICOM INTERNATIONALDICOM INTERNATIONALCONFERENCE & SEMINARApril 8-10, 2008 Chengdu, China

Keeping up with DICOM

Kevin O’Donnell

Toshiba Medical Systems

DICOM is not Static

• DICOM first published in 1993

• Extended regularly to meet theexpanding needs of Medical Imaging:- Multi-slice CT- 3D Ultrasound- Web-based PACS- USB Memory Sticks- Clinical Measurements- Radiation Dose Reporting- Image Registration & Segmentation- Computer Aided Detection/Diagnosis- and many, Many More . . .

DICOM Supplements

1013

8

4

9 10

25

15

47

2

#of

NewSupps

94/95 96/97 98 99 00 01/02 03 04/05 06 07 08…

Working Year

• WG-14 – Security

• WG-15 – Mammo & CAD

• WG-16 – MR

• WG-17 – 3D

• WG-18 – Clinical Trials

• WG-19 – Dermatology

• WG-20 – Integration (HL7)

• WG-21 – CT

• WG-22 – Dentistry

• WG-23 – App. Hosting

• WG-24 – Surgery

• WG-25 – Veterinary

• WG-26 – Pathology

• WG-1 – Cardiac/Vascular

• WG-2 – X-Ray & Angio

• WG-3 – Nuclear Medicine

• WG-4 – Compression

• WG-5 – Exchange Media

• WG-6 – Base Standard

• WG-7 – Radiotherapy

• WG-8 – Structured Report

• WG-9 – Ophthalmology

• WG-10 – Strategic Advisory

• WG-11 – Display

• WG-12 – Ultrasound

• WG-13 – Visible Light

DICOM Working Groups

DICOM Change Process

• Supplements for major changes– Extend Standard by adding new object types, new services, etc.

(i.e. New SOP Classes)– About 10 / year– Developed by Working Groups– Require Work Item approved by DICOM Standards Committee

• Change Proposals for minor corrections– About 100 / year – Anybody can submit– Backward Compatibility: Avoid changes that break existing implementations– Vendors responsible for monitoring final text change proposals

• Consolidated edition published every year– Most recently, January 2008– Available free at DICOM web site

DICOM Change Process

Development of a Supplement :• Work Item Proposal

– Reviewed / Approved by DICOM Standards Committee

• Working Drafts– Developed by Working Groups

• Public Comment– Reviewed / Approved by DICOM WG-6– Published for 45-day Comment Period

• Letter Ballot– Reviewed / Approved by DICOM WG-6– Voted on by DICOM Members

• Final Text / Standard– Finalized by DICOM WG-6– Effective immediately; Incorporated during next publication

• …typically a 1-2 year process

Maintaining Compatibility

Extension vs. Versioning

• DICOM is a family of SOP Classes– It’s just “DICOM”; Not DICOM 3.0, 3.1, etc.– Conformance is to SOP Classes, not to a ‘version’ of the Standard– New SOP Classes are added; Old SOP Classes don’t change– Most applications continue to support older SOP Classes when supporting new ones

• Association Negotiation– Software can determine if two systems are compatible– Happens each time two DICOM systems open an association (connection)– They negotiate which SOP Classes will be used, and how (e.g. Transfer Syntax)– Based on what each system supports and/or prefers

• DICOM Conformance Statement (DCS):– Humans can determine if two systems are compatible – When purchasing, compare the new system to your currently installed systems

“This product supports this list of SOP Classes; here are some details about how the SOP Classes have been implemented and how the system behaves when it uses them”

Some Recent Additions to DICOM

Enhanced Objects

• “2nd Generation” objects for most modalities– Common approach to Multi-frame, multi-dimension objects– New Attributes (Private->Public)

• Acquisition details, Clinical details– New SOPs for CT, MR, XA/XRF, 3D-XR, PET, OCT, 3D-US

• Benefits– Convenient handling of 1000+ slice studies– Faster transfers (orders of magnitude)– Advanced structure for faster, advanced display– Support for modern/advanced protocols

• e.g. in CT/MR: cardiac, gating, perfusion, diffusion, angio, fluoro, multi-stack spine, spectroscopy, functional imaging, color, raw data, …

Pixel dataDimension dataPer-frame headerFixed Header

N Objects, N Headers

N Frames, One Header

Multiframe Architecture

UsingSingle FrameObjects

UsingMulti-FrameObjects

Unified Procedure Step (UPS)

Addresses more advanced Workflow needs:

• Adds “Push Workflow” & “Create Workitem”– Request another system to add item to worklist

• Simplifies Implementation– General Purpose Worklist had N:M relation of SPS:PPS– State diagram was very complex– Unified PS contains details of both requested task & performed task

• Adds “Cancel Request” – Lets systems request (and monitor) cancellation of a task

• Improves Status/Result Monitoring– Getting PPS was awkward; required configuration and forwarding

• 4 SOP Classes operating on 1 IOD– UPS Push, UPS Pull, UPS Watch, UPS Event

Unified Procedure Step (UPS)

Other Interesting Features:– Allows Push, Pull, and Watch Workflows– Subscription-based Monitoring– Task Locking by performer– Deletion Locking by watchers– Allows Sub-contracting

Likely Applications• Radiotherapy

– Sup. 74 (Radiotherapy Worklists) is based on UPS– Automates worklists, verification steps, and beam delivery instructions– Now in Trial Implementation with IHE-RO

• Softcopy Display Management– Sup. 124 plans to use UPS push workflow and monitoring features

• Not intended to obsolete Modality Worklist– MWL has large install base and works well for most situations

Registration

• New SOP Classes– Rigid Registration Storage– Deformable Registration Storage

• Records one or both of:– Transformations to map one or more data sets

(e.g. images) into the space of another data set– Fiducials used for the registration

• Example use:– Modality or workstation spatially registers two datasets– Registration object is stored to the PACS– Display station retrieves and applies the transformation;

displays fused images

Segmentation

• New SOP Classes– Segmentation Image Storage

• Based on Pixels / Voxels• Binary (1-bit/pixel) or fractional

(probability or occupancy)– Surface Segmentation Storage

• Based on 3D Mesh

• May record multiple segments representing:– Tissue type, organ surface, etc.

• Example use:– Workstation analyzes images; segments tumor– Segmentation object is stored to the PACS– Display station retrieves/displays segmentation;

perhaps for surgical planning

Dose Reporting

• New SOP Class– X-Ray Radiation Dose SR Storage– Templates for Projection X-Ray,

Mammo & CT

• Records individual Irradiation Events– Does not depend on creation of digital images– Can be correlated with images for dose mapping– Driven by work of IEC and Euratom

• IHE now working to facilitate deployment

• Example Use:– Modality stores Dose Reports to PACS– Dose Monitoring system retrieves reports and generates weekly

analysis of departmental dose; monitors compliance with policies

How can you keep up?

dicom.nema.org

• Download the current issue of the Standard (free)– Both PDF and Word– Both normal and “Diff” version (showing changes from previous issue)

• Monitor and Implement CPs (Change Items)– Keep your product current

• Review New Supplements– Current documents are visible at all stages of the process– http://www.dclunie.com/dicom-status/status.html

• Review the DICOM Strategy Document– Activity reports from all Working Groups

• Attend the next DICOM International Conference and Seminar– Stay tuned!

How can you contribute!

• Ask questions/discuss on the DICOM Newsgroup– http://groups.google.com/group/comp.protocols.dicom

• Submit Change Proposals– if you find a gap, error, inconsistency or confusing text– mailto:hclark@medicalimaging.org

• Respond to Supplements released for Public Comment– Feedback is particularly welcome during Public Comment period– http://www.dclunie.com/dicom-status/status.html

• Join DICOM– Membership categories for users, vendors and national bodies– mailto:hclark@medicalimaging.org

• Participate in the DICOM Standards Committee and Working Groups– Submit new Work Item proposals– Help develop new Supplements