September 2014 Bjoern.Nolte@siemens.com

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

WG-06 meets 5 times a year to do technical review and harmonization of the output from the 30 DICOM Working Groups.

Current progress on new DICOM supplements (new chapters to The Standard) is shown below. Also change proposals (bug fixes in The Standard) are shown grouped into voting packages (CPacks).

Planar MPR Volumetric Presentation State

Sup 156 Revisit planned for November 2014
Stays after 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 common instance reference module has been added as mandatory. Presentation LUT shape and presentation LUT sequence were discussed and WG6 advised not to use them. The result of the discussion was that the sequence attribute is removed and the condition for shape is removed.

There was a general discussion on control points, which are specified for an animation curve within the attribute contour data.

A longer presentation was held on the topic "Three inputs for PCS-values (Profile Connection Space) output". See figure Y.6-4 for details.

There was a discussion on how to help users and implementers who are only implementing simple presentation states:

E.g. Simple CT MPR with no color. This would not need to implement all bells and whistles of the supplement. The question came up if there be several IODs from simple to comprehensible? One idea was to define one general SOP class plus two simplified ones. Would we hit the sweet spot with this approach?

Within the volume graphic annotation module, there was a decision to include as literal and reference the clinical context as optional information.

The boundaries for what can be done with graphic layers and graphic types were made more precise. See C.10.7 and C.18.9 and the corresponding references in the supplement for details.

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Server Options for RESTful Services

Sup 170
Final Text

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.

After the presentation and discussion there were very Small changes to defined terms and the supplement was voted to be accepted as Final Text.

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Unified Procedure Step RESTful Services

Sup 171 Revisit planned for November 2014 Sent out for Letter Ballot vote

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 service class provider behavior section has been added with appropriate references on other places in the document.

Actual status update events sent from the SCP to the subscribing SCUs was discussed in detail. Examples have been added to section CC.1:

E.g. Work item instance created, changed or cancelled.

The idea is that notifications contain the same information regardless if DIMSE or HTTP is used.

The web services description in part 18 will be removed from this supplement and handled separately.

The working group performed a line by line walk through of the document.

The supplement was voted to be sent out for Letter Ballot voting.

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Restful rendering

Sup Revisit planned for November 2014

This supplement enables the RESTful Retrieve service to retrieve rendered instances. This is done by adding query parameters to the request URI. These parameters are similar to those already available in the URI and WS Retrieve services.

A client makes an HTTP request with query parameters specifying how the images should shall be rendered and receives a response containing those images as the result.

The open and closed issues were discussed and annotated/updated.

It was decided that there is no preference order for accepting headers as proxies are not necessarily supporting this. Also order of images in response messages are not to be relied on. There are no restrictions to prevent caching. This can also impact order in replies.

From a discussion it was made clear that unknown parameters in the communication shall be ignored and that vendor specific parameters shall be well documented in the corresponding conformance statement.

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Ophthalmic Photography

Sup 173 Revisit planned for Januar 2015
Sent out for public comments

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.

The supplement has four specialized IODs. There are 8bit and 16bit image objects, divided into stereographic projection and 3D coordinate objects.

The usage of the different IODs has been made more precise.

Examples of generating equipment is included: including fundus cameras, slit lamp cameras, scanning laser ophthalmoscopes, stereoscopic cameras, video equipment and digital photographic equipment.

The first method, stereographic, uses the stereographic projection method to represent on-face images of the 3D human retina in 2D on which geometric measurements can be made when the correct mathematical formulae are used.

The second method captures the projection of the wide field 2D Pixel image to 3D (x,y,z) Cartesian coordinates.

It was discussed which depth is necessary for floating point precision: 32bit or 64bit.

A question arose during the meeting addressing the concept of points contra pixels. Points have no area at all but pixels have x and y dimensions.

Sparse sampling was discussed in the context of 2D to 3D data mapping.

The supplement was voted ready for public comments.

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Echocardiography Report

Sup 169 Revisit planned for January 2015
Sent out for Letter Ballot vote

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.

It was noted that it is now a mechanism available to reference IMAGEs and SCOORD structures.

The TID3602 includes height and weight. A discussion took place how this should refer or be duplicated from the DICOM header defined in PS3.3. The guidance is that these values are the same throughout the report.

It was clarified that the time zone module is mandatory and that two measurements have the same semantics if they are in one scope.

TID 5200 is kept as a fallback. It might be retired. The still open discussion on how to support vendor specific information may clarify this point. Currently TID 5200 is a fallback solution when newer TIDs don't cover non core measurements. Working group 12 is planning to prepare example files to illustrate the usage.

A walkthrough of codes was performed in the meeting. The core list of codes were scrutinized. The focus was to find the right level necessary for pre coordination. Loinc codes are still planned to be added.

The supplement was voted to be sent out for Letter Ballot voting.

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Parametric Map Storage

Sup 172 Revisit planned for November 2014
Sent out for Letter Ballot vote

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

After some discussion, it was decided to currently remove large rows and columns for integer pixel data. The primary reasoning was the DICOM limitations of OB/OW/OF/OD 32bit size.

The multiframe dimension module is the most complicated in the supplement. There was a debate if it should be mandatory or not. The main argument for having it as mandatory is to better support the consumer applications and that the appropriate values are known to the creator parametric map application.

As there are no known important use cases for 32bit, this format is not added to the supplement's current state, which supports 16bit and float.

Also Monochrome1 is left out as there is no known use case. If it is needed, it can be handled with the appropriate presentation state.

It was elaborated on how to keep references to other objects e.g. images. The Reference Image functional group macro addresses this. Further there is no explicit semantics for grouping of images beyond the normal series mechanism.

Special values like NaN, +Inf, -Inf are explicitly permitted. The abbreviation NaN in the supplement stands for "Not a Number". Inf stands for infinity.

The floating point image pixel module has been added. This is a substantial change.

It was agreed to separate the float and double float variants within the "floating point image pixel" module into two separate modules. This is to get rid of all the conditions in the text.

The example has been updated to highlight some of the new features, especially:

  • Dimensions, stack and use of Quantity as a dimension
  • Image/Frame Type value 3 of PERFUSION and 4 of KTRANS
  • Study and Series Description and Procedure Code Sequence
  • use of (113066,DCM, "Time Course of Signal") in Derivation Code Sequence, since that seemed to be the best fit for this from the CID 7203 selections (defined as "The image is derived by calculating values based on the time course of signal").

The supplement was voted to be sent out for Letter Ballot voting.

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2nd Gen RT

Sup 147 Revisit planned for November 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.

The supplement for Second Generation Radiotherapyhas been split up in six parts. This will hopefully speed up the standardization process:

  • Sup 147 2nd Gen RT Prescription and Segment Annotation
  • Sup 175 2nd Gen RT C-Arm Radiations
  • Sup 176 2nd Gen RT New RT Radiations
  • Sup 177 2nd Gen RT Dose Objects
  • Sup 178 2nd Gen RT RT Course
  • Sup 179 2nd Gen RT RT Explanatory (Part 17)

It was advised from the WG6 to remove indices with parameters and to only use concrete attributes.

A line by line review of all macros and modules was done.

A revisit is planned for November 2014.

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Reports using HL7 CDA

Sup 155 Revisit planned for January 2015
Sent out for public comments

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.

During the meeting there was a focus on the actual templates.

Open and closed templates were discussed. In open templates, all of the features of the CDA Specification are allowed except as constrained by the templates. By contrast, a closed template specifies everything that is allowed and nothing further may be included.

Imaging report document title is a list which will be extended with further report titles. Examples of the current title areas are: Diagnostic, Interventional, CT, MRI, PET, Thyroid Scan and Bone Density.

There was no clear answer to the discussion on if the append case is handled or not within this supplement.

There was an inconclusive discussion on specific conformance requirements for DICOM part 2 for this supplement.

There were some clarifications on codes reused from other standards.

It was decided that the supplement will be passed through the HL7 public comment process to get a good alignment.

The supplement was voted to go out for public comments in the DICOM community.

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CPack 77

WG-06 approved Final Text in September 2014

CPack 78

WG-06 approved for Letter Ballot (CPack-78) Candidates to go into final text in November 2014
1350 Add WADO-RS as a retrieval mechanism for referenced Instances 1366 Correction of Relationships in Planar and Volumetric ROI Templates 1367 Correct errors in Colon CAD SR IOD Template Figures 1368 Space should be listed in DS and IS VR character repertoire 1369 Relax device identifier constraint in x-ray irradiation event per CP 1065 undone by CP 1077 1370 Conformance Statement Example is Missing Private Creator Value 1371 Length of TM permitted is too long 1372 Add NCI Thesaurus as Coding Scheme 1373 Add Alzheimers Disease PET Radiotracers 1374 Add Zr 89 Monocolonal Antibody PET Radiotracers 1375 Add Various PET Radionuclides and Radiotracers 1376 Add Individual Long Bone Concepts to Anatomic Region and Body Part Examined 1377 Use SNOMED Code for Radiopharmaceutical 1378 Add Anatomic Codes for Fetal Biometry and Pelvic Ultrasound 1379 Add Definitions for all DCM Controlled Terms or Replace with Terms from External Lexicon 1380 Various NM Radionuclides are not list in CID 18. Add them, using DCM codes if necessary for those not in SNOMED or UMLS. 1381 Add term Flat Filter for Filter Types used in Proj. X-Ray 1382 Correct element number in reference to SOP Instance UID 1383 Add external resource URI to MWL 1384 Update values in CID 3722 1385 Add Measurement Laterality to General Ophthalmic Refractive Measurements Module 1386 Addition of Measurement Report Root Template for Planar and Volumetric ROIs 1387 Addition of Quantity Descriptors to Real World Value Maps 1388 Add Real World Value Map Reference to Measurements 1389 Factor Common Descriptions Out of Image Library Entries 1390 Generalize Concepts in Abstract Multi-dimensional Image Model Component Semantics 1391 Addition of Quantity Descriptors for Perfusion and Tracer Kinetic Modelling 1392 Addition of Quantity Descriptors and Measurements for PET 1393 Correct Tag Numbers For BLD Adjusted Positions 1394 Add Radioactive Source Model ID to RT Brachy Application Setups Module 1395 Extend RT Structure Set ROI Color 1396 Clarify Dose Value units for DVH in RT Dose 1397 Multiplicity Structure Classification Code 1398 Add FOR Module to RTSS IOD 1399 Add Effective Wedge Angle 1400 Assign WADO-WS namespace and schema 1401 Clarify meaning of PARTIAL in X-Ray RDSR

CPack 79 candidates

In the Voting Packet for the November WG-06 meeting Considered for approval in the next Letter Ballot (CPack-79)
Clicking on one specific Change Proposal above will take to that actual content.

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