1. Second Generation Radiotherapy Additional RT Treatment Modalities
DICOM
Second Generation Radiotherapy
Supplement 176
Additional RT Treatment Modalities

2. Introduction to Sup 176
Scope and Field of Application Following the definition of the RT Radiation composite IOD for the most common external beam radiation therapy machine (C-Arm Linac), this supplement adds IOD definitions for three external beam radiation therapy machines that do not fit the C-Arm Linac geometry. In this way, the structure of data that is being established for 2nd Generation RT can be maintained while defining the right format of data for these particular machines (RT also needed to do this for RT ION machines in 1st Generation).

3. Rationale for 2nd Gen
General shortcomings of current Radiotherapy Objects
in ‘RT 1st Generation’
Radiotherapy Workflow Representation:
Basically all function points of RT Workflow in one IOD: RT Plan (besides Treatment Recording)
No independent IOD for Prescription
Not suited for adaptive character of today’s radiation therapy processes (1st Generation originated from a model of one-time planning, which is outdated today)
 Hard to use 1st Generation IODs in a dynamic workflow environment
Conclusions:
New set of IODs is needed
Partitioned along the different function points of the workflow
Each object has its dedicated role
Extensible for new treatment techniques, positioning technologies, etc.

4. 1st Generation

5. Specific Issues of 1st Gen
Shortcomings of RT Plan IOD
Over-extended Scope
Treatment parameter definition for treatment delivery: OK
Besides delivery, various other workflow elements are represented in the same object (prescription, positioning etc.)
Prescription: only basic information, and scope of data not defined
Positioning: just basic information, no extensibility No way to cover new technologies (unless extending the RT Plan even further)
Not Extensible for new Treatment Technologies
Unbalanced, historically grown structure:
Photon / Electron Beam and Brachytherapy together in one IOD
Ion Therapy as separate IOD
Three Treatment Record IODs for two plan IODs
No concept how to represent new treatment delivery devices

6. 2nd Gen Overview

7. Sup 176 Content
Sup 175:
Introducing general concepts: see later slides
Concept of RT Radiation Set IOD
Concepts of RT Radiation IODs
Various Payload Concepts like
Control Points
Dose Accumulation
Beam Modifier Macros
Introducing one 2nd Gen RT Radiation IOD for:
conventional Photon / Election C-Arm Linacs
Sup 176:
Introducing three more 2nd Gen RT Radiation IODs for:
Tomotherapeutic Treatment Devices
Multi-Source Treatment Devices
Robotic Treatment Devices
based on Sup 175 Concepts
represents also template for future additions of new RT Radiation IODs for more treatment devices

8. Tomotherapeutic Devices
A.VV.1.6 Tomotherapeutic Radiation IOD
This machine is characterized by its ability to continuously rotate within a covered gantry (like a CT) while the patient is moved through the bore longitudinally by the treatment table top. It uses a binary MLC for modulating the beam and thus its beam limiting device (a Multi-Leaf Collimator or MLC) only has an in or out setting rather than a millimeter position setting.
Device-specific IOD Content:
Photon/Electron radiation type
Multi-revolution Arc Treatment (using 2nd Gen Continuous Angle representation)
Binary MLC
Fractional leaf opening
Couch speed
IEC like Device Geometry

9. Multi-Source Devices A.VV.1.9 Multiple Fixed Source Radiation IOD
This machine is characterized by a fixed mounting of many decaying sources (Cobalt 60, but potentially others as well) in a large, semi hemispherical dome that fits over the patient’ head and neck area. The object defines the source locations, directions and source sizes to use for the desired treatment. The patient is not moved during treatment.
Device-specific IOD Content:
Use of decaying Radiation Sources
Specification of source strength
Grouping of sources
Use of delivery pattern
Time-driven
Spherical Device Geometry

10. Robotic Devices A.VV.1.10 Robotic Radiation IOD
This machine characterized by a small linear accelerator mounted on a robotic arm. There is only one source of radiation but it can be directed from a large number of directions that is no longer constrained by mounting on a C-Arm. These directions are achieved by combinations of gantry and table top angles that are being reported by this object. The beam limiting device of this machine can be a fixed cone size or an MLC.
Device-specific IOD Content:
Photon/Electron radiation type
Path definitions
Definition of treatment along patterns
3D Room Device Geometry
Specification of Source and Target point as 3D coordinates

11. 2nd Gen Radiation IODs
The following slides provides background on the underlying concepts. Those concepts are realized by Sup 175 and re-used in Sup 176

12. General 2nd Gen Goals Main Goals for 2nd Generation RT Radiation IODs
Well-defined Scope for each IOD
Generality versus Specificity
Extensibility (new Treatment Techniques)
Precision, Cleanness, Efficiency
Re-usable Building Blocks
Generalized Geometry

13. Radiation IOD Scope
Scope: Which Content is needed for Treatment Delivery?
 Common Denominator across: Treatment Planning Systems and Treatment Delivery Devices
Content beyond that scope not glued to these IODs, since:
Never satisfies Producers and Consumers
Other dedicated content should have it’s dedicated representation
Has its own lifecycle
 Further Content Scopes benefit from their own dedicated IODs:
RT Prescription -> Physician Intent IOD (Sup 147)
Planning-Specific Information -> Planning Record IOD (Sup nnn)
Positioning Procedural Content -> Instruction and Result IODs (Sup 160)
Status -> Approval IOD (Sup 192)
Workflow -> DICOM Worklist, Key Object Selection IOD
Etc.

14. Generality versus Specificity
Radiation Set IOD
Main Object representing a Radiotherapy Treatment Fraction
Container pointing to all contributions of therapeutic radiation dose (aka ‘Beams’ in old world)
Represents the therapeutic radiation dose
In a generic way
Uses Conceptual Volumes as dose tracking entities
Concept of physical and radiobiological dose addressed
Independent of Treatment Device and Treatment Technique
References RT Radiation IODs of any device
New RT Radiation IODs can be integrated seamlessly
A Radiation Set IOD Instance is the main subject to
Planning
Scheduling
Delivery
Monitoring

15. Extensibility Radiation IOD Technique-independent Modules
Serve as root information container
Represent the therapeutic radiation dose
Generically
Physical and radiobiological dose
QA Support
Technique-specific Modules
Accommodate specific treatment parameters
Uses generic building blocks as applicable by the specific technique
Building Blocks for Beam Elements (Jaws, MLCs, Cones, Wedges, Blocks etc…)
Building Blocks for Beam Parameters (Control Point Framework)

16. Precision, Cleanness Definition of Terms Less Optionality Devices
Fractionation, Fraction, Session, Meterset, Control Point …
Less Optionality
Removal of 1st Generation Variation Hell
Devices
Individual Identification
Class Identification
Delivery Device and Patient Support Device clearly modelled

17. Precision, Efficiency Control Points Angles Energy and Radiation Type
Proven concept kept in place
Optimized value representation: Now only present at value change
No Scaling any more
Angles
Continuous Angles
No Rounding Issues (due to Discontinuities)
E.g. Get rid of one of the worst engineering sins, but still prevailing: Extended Angle Flags
Energy and Radiation Type
Rich model, including Beam Generation Modes (“FFF”, etc.)
Re-usable representation
Room for Delivery Device-specific Mode Information

18. Re-usable Building Blocks
Building Blocks are generic
-> Implementation Efficiency
Invocation of Building Blocks: Specific to Treatment Technique
-> Include only Elements as needed -> Extensible Approach for new Techniques or new Building Blocks
Generic scheme for identification and classification
-> High re-use of ‘header data’
-> Future components will re-use the same structure and only differ in specific payload
Device-Components, Beam Modifiers
Re-usable building blocks (Macros) for:
Beam Limiting Devices (Collimators, MLCs, Cones)
Compensators
Blocks
Wedges
Holder Devices (Trays, Applicators)
Other Modifiers will be added as needed
(e.g. Ion Lateral and Range Spreaders etc.)
Only used in IODs where applicable

19. Re-usable Building Blocks
External Beam:
1st Gen: 11 Pages
2nd Gen: 1 Page

20. Generalized Geometry Generalized Geometric Information
IEC coordinate system where applicable
Other coordinate systems supported
(e.g. Sup 176)
Always based on Frame Of Reference Formalism
Generic registration of Patient FOR to Device FOR
Transformation instead of specific Patient Positioner Parameters
Specific Patient Positioner Parameters are available as annotation available for display of native representation
Decoupled from IEC Drawbacks
Open for new Delivery Devices and Patient Support Devices

21. Generalized Geometry

22. Contacts Ulrich Busch Christof Schadt Chair WG-07
Varian Medical Systems
Christof Schadt
Editor, Vice-Chair WG-07
Brainlab AG