June 2014 Bjoern.Nolte@siemens.com

Here are the summary notes from the latest DICOM Working Group 6 Meeting (WG-06).

A selection out of the 30 DICOM Working Groups are meeting and harmonizing their content with WG-06 on up to five occasions per year.

Progress in new DICOM supplements (new chapters to the standard) is reflected. Further change proposals (bug fixes in the standard) are shown in their maturity groups (CPacks).

Planar MPR Volumetric Presentation State

Sup 156 Revisit planned for September 2014
Stays in public comment state

This supplement introduces the Planar MPR Volumetric Presentation State object to the standard.

The goal is to be able to present the same or close to the same volume view on imaging data (XA-3D, MR, CT enhanced objects and others) with a general volumetric presentation state object regardless of computing and displaying system and vendor. The supplement is the first of a series of supplements. The first one focuses on MPR.

The use of frame of reference was being discussed as ambiguous. This was also reflected in the public comment phase and its comments. This area will be made more clean with a set of change proposals, addressing the shortcomings (E.g. CP1319).

The reason behind a presentation state came up as not well addressed within the supplement. Working group 11 will define an appropriate context group. Further it was made clear that the class of non-rigid transformations would need an additional SOP class. This is currently not in the scope. Also RAW data was discussed not to be in the current scope.

A discussion took place on distinctions between image properties. The outcome was to add appropriate values for categories of images. The aspects being discussed were; regular and uneven sampling, equidistant intervals between slices.

It was articulated to come up with clear definitions of important concepts, such as thin and slab. There are some excellent illustrations added in this area.

The comments from the public comment phase have been incorporated in the latest iteration of the supplement.

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Server Options for RESTful Services

Sup 170 Revisit planned for September 2014 Letter ballot comments are requested

This supplement introduces Server Options for RESTful Services.

It covers the client discovering which server DICOM RESTful services are available and which options are supported on the server e.g.:

  • Supported services
  • Supported transfer syntaxes and media types
  • Supported accept header values
  • Supported query parameters
A client makes an HTTP request and receives and objects describing the server capabilities (similar to info in the conformance statement).

As a comparison: For normal non DICOM WebServices, WSDL has become a standard.

The supplement has been revised to have coherent encoding of attributes. Content encoding compression will not be mandatory as DICOM toolkits may or may not support compression.

A full example has been added to make it easier to comprehend the new concepts in this supplement. Further an illustrative mapping to JSON and example snippets have also been added to help the implementers.

The outspoken aim with the supplement is to follow the HTTP RFCs as close as possible.

The supplement was voted as ready for Letter Ballot.

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Unified Procedure Step RESTful Services

Sup 171 Revisit planned for September 2014 Public comments are requested

This Supplement defines a set of Representational State Transfer (REST) Services for interfacing with the Unified Procedure Step Services. This could be implemented as a proxy to an existing UPS service or as a web service interacting directly with a Workflow Manager.

A main discussion topic was how a server will handle both classic DIMSE and the new HTTP Restful communication and how this is described. The guidance was to update and keep the older UPS supplement in sync with this newer one. This has the implication that there will be no additional new table for work item search keys in this new supplement.

The mechanism for changing the UPS state was debated. It is still an open issue if this shall be accomplished by using the message body or by using query parameters. An advantage of having them in the body is encryption possibilities.

The supplement was voted as ready for Public Comment.

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Dual Energy

Sup MultiEnergy Revisit planned for September 2014

This supplement introduces Multi-Energy CT Imaging.

This includes: CT multi-energy imaging techniques (including scanning, reconstruction, processing) where the scanner utilizes multiple energies from the X-Ray beam spectrum, as opposite to the conventional CT imaging, when a single (accumulated) X-Ray spectrum is used.

The presenter concluded that this supplement will cover a new kind of images. The initial step is to categorize which images and use cases are to be covered. The first attempt is to stick to current IODs.

A longer discussion took place on original versus derived as the category for dual energy images. Opinions voiced during the discussion were; Leave it to the vendor, if there are more than one acquisition then categorize as derived, if the image comes out of a reconstruction then it is original if not then it is derived. If the image has been changed after the initial creation, then it is derived.

The distinction of where the reconstruction happens, on the modality or the work station, might also be important for the original and derived destinction.

The topic was not exhausted in the meeting.

It was agreed that the series description shall be used to indicate how the image was created.

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Ophthalmic Photography

Sup 173 Revisit planned for September 2014

This supplement introduces a SOP Class to enable anatomically correct measurements on wide field ophthalmic photography 8-bit and 16 bit images. Vendors have implemented new technology which enables the acquisition of OP images using wide field fundus photography. Since the back of the eye is approximately a concave sphere, taking a very wide field image of it introduces large error in any attempt to measure a lesion in that image (the error is very large when using a single value for the DICOM Pixel Spacing Attribute.). Therefore, DICOM WG 9 (Ophthalmology) has determined that a new Information Object Definition (IOD) is necessary to adequately represent wide field fundus photography.

A longer discussion took place on how to find an acceptable solution to the distortion problem of projecting from 3D to 2D. There are important attributes to help the applications on this: Actual length and interpolation type for example. The goal is to store enough information to be able to do accurate measurements on the image during post processing.

The images can get very large. 36 MByte per image has been seen during current testing. A detailed walk through of the image module was part of the session. The topics of coordinate systems and IACME algorithms were touched upon.

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Echocardiography Report

Sup 169 Revisit planned for September 2014
Public comments are requested

This supplement introduces an SR template called Simplified Adult Echocardiography Report IOD to the standard. It provides similar content to that of TID 5200 while addressing details that were the source of interoperability issues; in particular, varying degrees and patterns of pre- and post-coordination, multiple codes for the same concept and numerous optional descriptive modifiers.

A conformance section will be supplied with content. The structure is defined in fig. A.x-1.

A discussion took place on pre-coordinated and post-coordinated measurements. These concepts have a central place in this supplement.

Pre-coordinated data entails defining concepts such that they are comprised of multiple terms with a very specific definition (think: Severe Left Knee Pain). Post-coordinated data involves creating granular individual concepts that are then grouped together to create responses to questions, with each concept otherwise not making sense on its own (think: Severe + Left + Knee + Pain).

It was observed that LOINC has all the necessary modifiers for pre-coordinated grouping.

A clinical clarification was made during the discussions: Systole indicating the whole heart beat period and End Systole being the value at the end time point.

A rational for the main use cases will be added before the supplement is sent out for Public Comment.

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Parametric Map Storage

Sup 172 Revisit planned for September 2014
Public comments are requested

This supplement defines use cases and storage of information related to quantitative parametric maps. In general, the term "parametric map" is loosely used to referred to any derived image whose pixel values have a quantitative meaning (e.g., CT HU versus arbitrary MR signal intensity).

Examples of parametric maps include

  • parameters of pharmacokinetic models, such as Ktrans of the Tofts model used in DCE-MRI
  • regional cerebral blood volume (RCBV) or flow (RCBF) used in perfusion CT
  • normalized values based on body size, such as SUVbw used in PET
  • diffusion parameters such as Apparent Diffusion Coefficient (ADC) used in MR DWI

SUV and ADC, have been in widespread use already. This supplement has the following additional goals to define:
  • Additional attributes, modules, acquisition context, code sets and scaling functions that may optionally used to extend existing imageIODs
  • A new IOD to address the need for encoding some parametric maps with floating point "pixels"
  • The basic encoding mechanism changes needed to support floating point "pixels"

    The IOD defined in this supplement uses the enhanced multi-frame encoding. The initial presentation of this supplement introduced an interesting new possibility to DICOM. Pixel Data is now extended with Float Pixel Data and Double Pixel Data. Of special interest is the image pixel module in the supplement. Here restrictions on attributes have been added for floating point values.

    The supplement was voted as ready for Public Comment.

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  • 2nd Gen RT

    Sup 147 Revisit planned for September 2014

    This supplement describes the second generation of radiotherapy objects. A new generation of radiotherapy objects was needed to address workflow management, the enhanced multiframe paradigm, the newer model of having different types of data to be stored in separate IODs. New powerful approaches in DICOM are used: e.g. 3D segmentation, mesh representation, rigid and deformable registrations.
    A discussion took place on the meaning of number ordering of radiation sets within the Treatment RT radiation set reference sequence. It was clarified that the number ordering is used for versioning. Higher numbers reflect that radiations took place later in time.

    The topic of RT Physician Intent and its relation to prescription was scrutinized. It will be clarified if this relation should be 1-n or not.

    The supplement is in a draft state and will be revisited in September.

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    Reports using HL7 CDA

    Sup 155 Revisit planned for September 2014

    This Supplement introduces a new mechanism for specifying templates for imaging reports. Such reports are intended to be encoded using the HL7 Clinical Document Architecture Release 2 (CDAr2, or simply CDA) Standard.

    The goals of this supplement are: To create a new a family of imaging reports. Initially there will be templates for radiology reports, aligned with RSNA RadLex and Reporting Initiative. Primarily the reports will be narrative with some discrete data. The reports are planned to evolve to containing more and more discrete data: Diagnostic and screening; evolving to interventional, cardiac, anatomic path and further.

    This Supplement introduces a new mechanism for specifying templates for imaging reports. These reports are intended to be encoded using the HL7 Clinical Document Architecture Release 2 (CDAr2, or simply CDA) Standard.

    It is the purpose of this Supplement to support current and evolving practice. This Supplement therefore focuses on primarily narrative text reports, but also supports incorporation of discrete data and image references.

    This Supplement defines the CDA format structures and technical constraints, i.e., templates, for documents, sections, and entries to be used in imaging report instances. These report instance templates are thus a set of conformance criteria for such report instances.

    The content of the supplement was presented by an informal walk through. The question of mandatory versus non-mandatory attributes came up along with a more fundamental discussion on how meaningful certain attributes are at all in the report. The supplement remains in an early draft state.

    It was reflected that the radiology community wants the content to be DICOM like and not being aligned to HL7. The question came up how well this supplement should fit the DICOM model. Currently the audience, consumer and implementor audience is the CDA implementors (HL7) and not the DICOM toolkit vendors.

    The supplement is in a draft state.

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    CPack 76

    WG-06 approved Final Text in June 2014

    CPack 77

    WG-06 approved for Letter Ballot (CPack-77) Candidates to go into final text in September 2014

    CPack 78 candidates

    In the Voting Packet for the September WG-06 meeting Considered for approval in the next Letter Ballot (CPack-78)
    Clicking on one specific Change Proposal above will take to that actual content.

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