PDI Extensions - Detailed Proposal

1. Proposed Workitem: PDI Extensions

• Proposal Editor: David Clunie
• Profile Editor: David Clunie
• Date: 2008-10-01
• Domain: Radiology (Mammo, NM), Cardiology, Radiation Oncology

Summary

PDI uses uncompressed CDs and these are too small for many studies without awkward disk spanning.

DVD and USB media are already supported in DICOM, demonstrated to be interoperable, and reading and writing hardware is ubiquitous. Lossless and lossy compression are also supported by DICOM.

Vendors are already attempting to satisfy the demands of users by producing DICOM but not IHE PDI compliant media using compression and larger media.

2. The Problem

The existing IHE PDI profile supports CDs only, and does not use compression (lossless or lossy) for radiology images. Modern acquisition techniques often produce single data sets that exceed the available PDI CD capacity, and disk spanning (using multiple CDs for one study) makes them difficult (and slow) to view.

The lack of support by IHE of existing standards for contemporary hardware, larger media of low cost and effective compression schemes creates a "credibility gap" for PDI.

Increasing attention on image sharing and media interoperability demands that PDI make use of contemporary rather than obsolete technology to satisfy users demands.

3. Key Use Cases

Large Studies

A multi-detector CT, or a PET-CT scanner produces a large high resolution set of images, which needs to be sent off site to a referring physician for review on their own PC or importation into another site's PACS. The size of the image set exceeds the capacity of a single CD but would fit on DVD media, with or without lossless compression.

Without importation (which may be slow), the alternative of spanning CDs makes it impossible to view the study in its entirety using the on-board or a pre-installed viewer.

Multiple Studies

For referral to another facility for consultation or treatment, a set of relevant studies for a patient need to be recorded on media. The total size of the studies exceeds the capacity of a single CD.

Longitudinal Record

An ambulatory patient receives successive imaging studies at external imaging center for review by the referring physician, e.g., to monitor the progress of treatment, and the referring physician needs to review the entire set simultaneously from a single piece of media since they have no persistent local storage. Updating a previously finalized CD is difficult if not impossible, but USB memory devices permit the possibility of adding to an existing record.

Review Speed

A referring physician has a finite, usually short, period of time in which to review images, and delay reduces their productivity and effectiveness. The use of higher capacity DVD media, compression to reduce the size of what needs to be read from mechanically slow disks, and memory based media all reduce the time required to review images.

4. Standards & Systems

DICOM already supports larger (DVD) and faster (USB memory) media already, and provides for both lossless and lossy compression as clinically appropriate. Fears of lack of DVD interoperability have been allayed by successful media readability tests performated at the 2008 IHE NA Connectathon.

No PC in recent history has been shipped without both DVD drives and USB connectors.

5. Technical Approach

PDI can easily be extended to support DVD and USB with minimal changes by adding the relevant DICOM Media Application Profiles to PDI.

DICOM contains a family of "General Purpose DVD with Compression Interchange Profiles", which support any of the 120 mm DVD media other than DVD-RAM, including DVD-R, DVD+R, DVD-RW, and DVD+RW. DICOM also contains "General Purpose USB and Flash Memory with Compression Interchange Profiles". There are separate profiles for support of either JPEG lossy and lossless compression, or JPEG 2000 lossy and lossless compression.

IHE could, if perceived as important for interoperability, forbid the use of compression by constraining one of these profiles.

It is currently proposed that DVD and USB be added as separate options to the existing PDI profile, without any phased introduction.

In a future phase, it might be desirable to also add the MPEG DVD profile, but this has little application in the radiology domain and there is little experience with respect to its interoperability, so it is proposed that this be deferred for now.

Existing actors

• Portable Media Creator
• Portable Media Importer
• Image Display
• Report Reader
• Print Composer
• Display (ITI TF)

New actors

• None

Existing transactions

• [RAD-47] Distribute Imaging Information on Media

New transactions (standards used)

• None

Impact on existing integration profiles

• Add a DVD option to PDI
• Add a USB option to PDI

New integration profiles needed

• None

Breakdown of tasks that need to be accomplished

<A list of tasks would be helpful for the technical committee who will have to estimate the effort required to design, review and implement the profile.>

6. Support & Resources

<List groups that have expressed support for the proposal and resources that would be available to accomplish the tasks listed above.>

7. Risks

<List technical or political risks that will need to be considered to successfully field the profile.>

8. Open Issues

<Point out any key issues or design problems. This will be helpful for estimating the amount of work and demonstrates thought has already gone into the candidate profile.>

9. Tech Cmte Evaluation

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Effort Evaluation (as a % of Tech Cmte Bandwidth):

• 35% for ...

Responses to Issues:

See italics in Risk and Open Issue sections

Candidate Editor:

David Clunie