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					                                                                Chairman: David Murray Ph.D.
Working Group 07                                                    TomoTherapy Incorporated
(Radiation Therapy                                       
                                                        Vice Chairman: Bruce Curran, ME, MS
Objects)                                                 University of Michigan Medical Center

DICOM                                  Secretariat: National Electrical Manufacturers Assoc.
                                                             1300 North 17th Street, Suite 1847
                                                  Rosslyn, VA 22209
Digital Imaging and                                        Secretary: Stephen Vastagh, NEMA
Communications in Medicine                                    

MEETING:                           DICOM WORKING GROUP 7 – RT OBJECTS

DATE AND TIME:                     July 28-29, 2005

PLACE:                             Roosevelt Hotel
                                   Seattle, WA


AAPM, U. of MI                            Bruce Curran
Calypso Medical Systems                   Steve Phillips
Computerized Medical Systems              Jim Percy
Elekta                                    Hans Sethi
Elekta                                    Mike Ullrich
IMPAC Medical Systems/Elekta              Scot Hogan
IMPAC Medical Systems/Elekta              Stuart Swerdloff +
ITC-ATC / Washington Univ. St. Louis      Walter Bosch
Loma Linda Univ. Med. Ctr.                Michael Moyers
Nucletron                                 Jaap Pijpelink
Philips Medical Systems                   Mark Pepelea
RCET-ATC / U. of Florida                  Vincent Frouhar
Siemens Medical Solutions                 Johannes Stahl
Siemens Medical Solutions                 Brian Fredericksen
Tomotherapy                               Dave Murray
Tomotherapy                               Bob Philbin
Varian Medical Systems                    Uli Busch

NASI, NOMOS Division           Jeff Szuhay
Prowess                        Rex Kerr


DICOM WG-07 RT Objects                                                           Page             128
July 28-29, 2005
NEMA Staff                                   Stephen Vastagh

+ July 28 only

Presiding officer:                           Dave Murray, Chairman
Secretary:                                   Stephen Vastagh


The Chair welcomed members; self-introductions followed. The Agenda was approved.


Stephen Vastagh reviewed the NEMA antitrust meeting rules.

3.     MINUTES

The last meeting was held April 27-29, 2005 at NEMA. The minutes were approved as published.


The Chair’s report dated March 29, 2005 was presented. There were no comments.


The WG-07 Strategy Document was last updated on May 4, 2005. There were no revisions made.
(Note: the statement may be found on the DICOM web site.)

6.     IHE-RO

Stuart discussed in general the IHE activity. To summarize:
    DICOM codifies how things can be done
    IHE-RO specifies how things shall be done to claim compliance with IHE-RO


Scot updated progress. S-102 went for letter ballot on July 1; ballot ends August 19.


No progress currently – Walter will report back when status changes.


Dave Murray introduced the topic and summarized work to date. Stuart Swerdloff presented his work
on use of General Purpose Worklist. Johannes Stahl also presented a similar approach:

Machine-centric (baseline) model

DICOM WG-07 RT Objects                                                              Page     129
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Question: Should the UID of the Delivery Request IODs be sent in the PPS list, or should there be a
C-FIND-REQ and C-FIND-RESP or similar to get the Delivery Request? Answer: No, use the
standard GP worklist approach. For example, a machine could get the schedule (SPS list), prefetch
all related/referenced objects, for each patient at treatment time refetch just the current SPS, check
referenced UIDs against the cached information, refetch any referenced objects that have changed.
This means that the issue does not need to be directly addressed in Supplement 74, but could be
defined in an IHE profile, for example.

Question: In machine-centric model, should a treatment SPS be sent that covers all beams, or
should there be one SPS per beam? Answer: A single SPS will specify all beams in the session.
Multiple updates could be sent notifying delivery on a per-beam basis.

Note: A number of manufacturers at WG-07 expressed interest in accelerating workflow
implementations to a time before the proposed 2007 IHE-RO demo. In this case, a connectathon for
testing these objects could be held under the auspices of NEMA, or at the same time as the 2006
IHE-RO connectathon (prior to ASTRO).

Action items: 1) Dave Murray to update Supplement 74 by adding an introductory section showing
the general use of Supplement 74 IODs, to allow a novice reader to understand the context in which
Supplement 74 will be used. Dave will circulate for review to Scot, Brian, Jaap, Uli, Johannes,
Stuart. 2) Johannes will update his sequence diagrams following discussions.

External Verification Extension

WG-07 favors use of N-SET and N-GET to achieve external verification (along the lines of the
original DTMI proposal, but with roles reversed), rather than use of work-list to achieve this purpose.
In this approach, these additional steps are inserted between the initial LOAD workflow steps and
the TREAT workflow steps:

      Before delivery on beam sequence items, the TDS issues an N-CREATE-REQUEST
       containing UIDs of the RT Plan, delivery request object, etc. The TMS issues an N-CREATE-
       RESPONSE indicating that the delivery can continue, with the UID of the normalized
       Treatment Verification Session Object. Alternatively, the TMS would detect an issue (such as
       an expired Delivery Request object), and indicate this to the TDS in a return code.

      Before each beam sequence item, the delivery machine would issue an N-SET-REQUEST
       command to set the values of the various machine values, including setting the “Tx Delivery
       Status” attribute to “NOT-STARTED” or similar . The verification system returns an N-SET-
       RESPONSE. There may be multiple N-SET-REQUESTs as the treatment machine changes
       status (e.g. the couch moves, and the N-SET-REQUEST contains the new couch position). If
       the TMS considers that the treatment is not ready, it returns “NOT_VERIFIED” in the “Tx
       Verification Status” of the N_SET-RESPONSE.

      When the verification system determines that the treatment is OK to proceed, it sets the “Tx
       Verification Status” to “VERIFIED” or similar in the N-SET-RESPONSE. If the verification
       detects a problem in the N-SET-REQUEST but considers that the problem could be
       overridden, it provides an interface to override the problem, and then returns the “VERIFIED”
       status in the N-SET-RESPONSE. Note: The TMS could echo the verification information to
       external systems (such as gating systems), and use input from those systems when deciding
       to set the “VERIFIED” status.

DICOM WG-07 RT Objects                                                               Page          130
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        Note: At any time, an N-GET-REQUEST may be issued by the TDS to determine if treatment
         can go ahead. The TMS responds with and N-GET-RESPONSE indicating a value of
         “VERIFIED” or “NOT_VERIFIED” in the “Tx Verification Status” This would typically be used
         when the TDS considers that setup is complete, but has not received a VERIFIED response
         because the TMS if waiting for an unknown interlock (such as an external positioning device)
         to be closed. The TDS can proceed when it gets either VERIFIED or VERIFIED_OVR via the

        During delivery, the delivery device may send an N-SET-REQUEST with updated machine
         values, including a “Tx Delivery Status” of “BEAM_ON” or similar. If the TDS and TMS have
         agreed (outside the scope of DICOM) to implement verification during beam-on, the TMS
         could use the information contained in these updates to stop treatment, or if the update is
         coming from a 3rd-party device such as a gating camera. This is not precluded by the current
         approach, but is not addressed explicitly either. In any case, a N-SET-RESPONSE is

        When the beam delivery is complete, the TDS sends an N-SET-REQUEST with a value of
         “TERMINATED” or similar in the “Tx Delivery Status”, and receives an N-SET-RESPONSE.

Supplement 74

The content in Supplement 74 required to support the above approaches consists of two IODs: A
composite “Treatment Delivery Request” object for use in the workflow steps, and a “Treatment
Verification Session” normalized object to support the external verification mode. A “Treatment
Verification SOP” service must also be defined to support the verification messaging.

ACTION:            Scot will draft the content of the N-SET and N-GET messages, for review at the
                   ASTRO DICOM meeting.

The RT Delivery Request IOD Module Table and associated new modules are shown below.                    RT Delivery Request IOD Module Table
                         Table — RT DELIVERY REQUEST IOD MODULES
       IE               Module                     Reference            Usage
       Patient          Patient                     C.7.1.1               M
                        Clinical Trial Subject         C.7.1.3                   U
       Study            General Study                  C.7.2.1                   M
                        Patient Study                  C.7.2.2                   U
                        Clinical Trial Study           C.7.2.3                   U
       Series           RT Series                      C.8.8.1                   M
                        Clinical Trial Series          C.7.3.2                   U
       Equipment        General Equipment              C.7.5.1                   M
       Treatment        RT Delivery Information       C.8.8.aa                   M

DICOM WG-07 RT Objects                                                                Page          131
July 28-29, 2005
        Delivery     Setup Verification                             U
                     Procedure Information
                     SOP Common                        C.12.1                         M

1.1.2     C.8.8.aa            RT Delivery Information Module
           Attribute Name                Tag     Type                 Description
Current Fraction Number              (3008,0022)   1  The index of the fraction that shall be
                                                      delivered or completed in this session.
Delivery Session Notes                  (3011,xxxx)       3      Text description of any additional
                                                                 information to be specified to the operator
                                                                 delivering the treatment.
Delivery Resumption Sequence            (3011,xxxx)       3      Sequence referencing one or more RT
                                                                 Beams Treatment Record or RT Brachy
                                                                 Treatment Record objects containing
                                                                 record(s) of a previous partial delivery
                                                                 sessions for this fraction.
>Include ‘SOP Instance Reference Macro’ Table C.17-3
>More stuff telling how to resume
Referenced Delivery Plan Sequence       (3011,xxxx)       1      Sequence referencing one or more RT
                                                                 Plan objects containing the planned
                                                                 treatment parameters for this fraction.
>Include ‘SOP Instance Reference Macro’ Table C.17-3
>Delivery Fraction Group Sequence       (3011,xxxx)       1      Indicates which fraction group(s) of the
                                                                 referenced plan should be treated in the
                                                                 treatment session.
>>Referenced Fraction Group Number     (300C,0022)        1
>>Delivery Referenced Beam              (3011,xxxx)       3
>>>Referenced Beam Number              (300C,0006)        1


WG-07 discussed the relationship between Worklist and implementation of DICOM. In general, it
was considered that Worklist provides the most effective solution, and Q/R is essentially a “fallback”
solution for sites where workflow is not managed. WG-07 has previously recommended a list of
query keys etc to IHE-RO, and IHE-RO may or may not choose to define a profile for an IHE-RO
demo. No further work from WG-07 is required at this time.


CP490 (not 590 as stated in agenda): In the note or CP490, VL, SC, and RT Images are mentioned,
but not CT Images (which would be used for cone-beam setup, for example). However, the wording
of the CP does not explicitly exclude use of other modalities, and the CP will be left unchanged.

CP576_02 (Motion Synchronization): Reviewed by WG-07, with format and conditions substantially
modified. Dave Murray has updated the template used and placed in a “ReadyForWG6” folder

DICOM WG-07 RT Objects                                                                     Page             132
July 28-29, 2005
(version 3). Vincent commented that additional information such as the “lung volume fraction” is
required for gating from 4D images. WG-07 discussed this and decided not to encode these
parameters at this stage.

CP577_03 (Delivered Meterset Clarification): WG-07 reviewed and made some format and
grammatical changes, and converted the note to normative text. Dave Murray added to
“ReadyForWG6” folder.

CP578_02 (Pixel Intensity Relationship): Some format changes were made. Dave Murray added to
“ReadyForWG6” folder.


12.1 RT_CPBeamDepthForRadCalc_03.doc: WG-07 reviewed the document and added SSD and
made some editorial changes. Jim will return to CMS and Lifeline to confirm that this revised
proposal addresses the issue.

12.2 CP553_02 (RT Patient Positioner): Reviewed by WG-07. Attribute condition removed,
cosmetic corrections made, and additional information added in rationale. Ready for presentation to
WG6. Dave Murray has added to “ReadyForWG6” folder.

12.3 RT_CPPitchAndRollAngles_02.doc and RT_CPOutOfPlaneImage_02.doc: Pitch and roll
angles were discussed at length. Uli’s proposal inserts the angular movements after the table
translations, and effectively extends IEC 61217 coordinate systems. However, in Supplement 102
(ion therapy) the angular movements occur before the table translations, as was the thinking at that
time. A CP for the ion therapy objects would then be required to bring the implementation into line
with the photon objects.

ACTION:       1) Scot will draft an email communication to WG-06 (to be reviewed by Hans), and it
              will be transmitted to WG-06 by Dave prior to August 19 (the end of the current
              Supplement 102 letter ballot period), seeking WG-06’s advice. The existing pitch and
              roll angle proposal for photons will be submitted to WG-06 at a later date.

ACTION:       2) Uli and Jaap will draft new wording to make the CP conform with the IEC
              coordinate definitions in a separate section.

Note: Out-of-Plane has been renamed Off-Plane for consistency with attributes used in Ion Therapy.

ACTION:       Uli to draft new work item proposal for the IEC coordinate system addition, for
              submittal to IEC SC62C WG1 early October (meeting 16-18 November).

12.4 RT_CPStoppingPwrRatios_01.doc. Link to depth has been removed.

ACTION:       Dave will clean up to make ready for discussion at WG-06.

12.5 RT_CPDeliveryType_01.doc: Nominal Energy Unit needs to be added to RT Plan, and the
note needs to be removed from Nominal Energy. This needs to be added to the CP.


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Uli reported that no significant progress has been made since the last discussion. However, WG-07
discussed the project briefly and concluded that it is orthogonal to the worklist and to Supplement
74, and neither body of work depends upon the other.


BENDING ACTION: Bruce sent a note to WG17, but there is currently no chair for that group.
                    Bruce will enquire again at WG17.
No update was reported.

2     Curve Module
At the last meeting Jaap re-iterated that Nucletron and other companies still use the curve module to
overlay projected contours and user-drawn items on simulator images, DRRs, and port films. WG7
implementors of the curve construct consider that it is limited and should ultimately be replaced by
use of a standalone object.

Jeff Szuhay was to investigate presentation state and structured report and report back to WG7.
(Alternatively, a new standalone object incorporating ROI Contour, or RT Structure Set itself could
be considered.)

3     File Organization (Jeff Szuhay)
Update and discussion.

15.     ZEROCONF

PENDING ACTION:              Jeff was to look at LDAP in Part 17, and potentially draft an email
                             that Dave could send to the WG-06 mailing list.

No update was reported.

16.     CURVE MODULE – no progress

At the last meeting Jaap re-iterated that Nucletron and other companies still use the curve module to
overlay projected contours and user-drawn items on simulator images, DRRs, and port films. WG7
implementers of the curve construct consider that it is limited and should ultimately be replaced by
use of a standalone object.

Jeff Szuhay was to investigate presentation state and structured report and report back to WG7.
(Alternatively, a new standalone object incorporating ROI Contour, or RT Structure Set itself could
be considered.)

No update was reported.

17.     FILE ORGANIZATION – no discussion due to Jeff’s absence.


Fluence maps were approved in RT Image in 2004.

DICOM WG-07 RT Objects                                                              Page         134
July 28-29, 2005
PENDING ACTION: Jeff Szuhay to investigate if presentation state can ultimately be used for RT


Todd Kantchev’s email will be discussed at the ASTRO meeting.

20.       NEXT MEETINGS:

DICOM WG7: October 20 (9:00-17:00) and October 21 (8:30-15:00) after ASTRO (Denver)

IHE-RO Joint Meeting of Planning & Technical Committees on October 19, 7:00-9:00 a.m. (during

WG-06 (For info and planning)

           August 22 – 26, 2005 at NEMA
           October 31 – November 4, 2005 at NEMA


The meeting recessed at 5:00 p.m. on July 28, reconvened at 9:00 a.m. on July 29 and was
adjourned at 3:00 p.m. on July 29.

                                          Reported by
                                          Stephen Vastagh, Secretary
                                          August 12, 2005


DICOM WG-07 RT Objects                                                         Page         135
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Appendix A: Updated WG-07 Strategy Document
3.1     WG-07 (Radiotherapy)
Secretariat                         NEMA
Secretary                           Stephen Vastagh, NEMA
Chair                               David Murray, TomoTherapy Incorporated
Vice-Chair                          Bruce Curran, University of Michigan
Date of Last Update:                May 4, 2005

To develop and maintain radiotherapy information objects for the DICOM Standard, and promote their implementation
and acceptance within the industry.

In the next few years, the RT-specific objects in the standard need to be maintained to completely stabilize existing
implementations. Extensions to existing objects have been and will be introduced to accommodate new techniques. Ion
therapy is being addressed with a new IOD. Another major goal is to address how workflow in the RT department can be
enhanced using existing and upcoming DICOM objects and concepts. As the field of radiation therapy advances,
initiatives will be taken such as modeling the evolution of a treatment course (current work), and development of new-
generation objects to support technological advances (future work). Promotion of DICOM in the radiation oncology, via
vendor testing initiatives and demonstrations of interoperability at major trade shows, remains an important part of WG-
07’s work.

Short Term Goals:
A major goal of WG-07 is maintenance of existing RT-specific DICOM objects, correcting issues discovered during
detailed implementation and introducing minor extensions to deal with new techniques and approaches in radiotherapy.
Typically, a number of Change Proposals are awaiting ratification or are under development. There is significant
commercial pressure to standardize DICOM objects for use in Ion Therapy, and the Ion Therapy Subgroup of WG-07 is
very active and Supplement 102 is nearing publication. An RT Treatment Course subgroup of WG-07 has begun work on
enhancing the standard to deal with evolving treatment prescriptions and dynamic plans such as those found in adaptive
therapy. WG-07 is contributing to realization of an IHE-style demonstration (IHE-RO) initiative being organized by
ASTRO, AAPM and other groups.

Current Status:
Supplement 11 (RT Image, RT Structure Set, RT Dose, RT Plan) and Supplement 29 (RT Treatment Record Objects and
Media Support) are part of the DICOM 1999 standard. Work is continuing on Supplement 74 (Utilization of General
Purpose Worklist in Radiotherapy), in conjunction with parallel WG-06 work on Supplement 96. Supplement 102 (Ion
Therapy) is in the public comment phase. Work on RT Treatment Courses has recently been started. Implementation of
the basic radiotherapy DICOM objects is widespread in the industry, and workflow-oriented issues are becoming
increasingly important.

Current Work Items:
A number of Change Proposals are under discussion to correct some errors, clarify wording and introduce some new
concepts as the industry evolves. Work is continuing on Supplement 74 (Utilization of General Purpose Worklist in
Radiotherapy), Supplement 102 (Ion Therapy) is nearing publication, and work on RT Treatment Course extensions is

Implementation of existing standardized objects is well advanced. There is no clearly identifiable risk to achieving short-
term goals. Incorporation of workflow concepts into RT will require implementation of additional DICOM services by

DICOM WG-07 RT Objects                                                                                Page             136
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RT vendors, but it is believed that they are well motivated to do this, especially in the context of the IHE-RO

Challenges and Opportunities:
Smooth incorporation of RT procedures into DICOM workflow concepts, especially General Purpose Worklist, is a
medium-term challenge. Managing evolution of the standard to handle new technologies and techniques is an ongoing

Relationships to Other Standards:
RT objects use IEC-61217 for treatment machine descriptions and ICRU concepts for dosimetry. The DICOM patient-
based coordinate system (Amendment to IEC 61217, 62C/269) also has a well-defined relationship to the IEC Patient
coordinate system. IEC/TR 62266 (“Medical Electrical Equipment - Guidelines for Implementation of DICOM in
Radiotherapy”) is now published. IEC 62274: “Safety of Radiotherapy Record and Verify Systems” will be released by
the IEC in 2005, and WG-07 has been involved in review of this document. WG-07 will continue to be involved in
review of other IEC standards where necessary.

DICOM WG-07 RT Objects                                                                                Page        137
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