DICOM Second Generation Radiotherapy Objects Part 1 Supplement
DICOM Second Generation Radiotherapy Objects Part 1 Supplement 147: Physician Intent and Segment Annotation Presentation to AAPM TG-263 Walter Bosch, D. Sc. Dec. 19, 2014
What is DICOM RT? • Development of DICOM RT Information Objects started in January, 1995 • Radiotherapy Information Objects (Supp 11, Final Text June 1997) • • RT Structure Set – image segmentation RT Plan – beam/source geometry and dosimetry RT Image – projection image in beam geometry RT Dose – dose matrix and DVHs • Radiotherapy Treatment Record (Supp 29, Final Text May 1999) • RT Beams Treatment Record • RT Brachy Treatment Record • RT Treatment Summary Record • Radiotherapy Extensions for Ion Therapy (Supp 102, Final Text Mar 2006) • RT Ion Plan • RT Ion Beams Treatment Record • • Complete DICOM RT datasets (CT, Structure Set, Dose) were exported from commercial TPS starting in 2003. Since July 1, 2013, DICOM has been the required format for all NRG RT clinical trial data submissions.
Pain Points in 1 st Gen RT • No easy way to add support for new treatment technologies, e. g. , helical tomotherapy, robotic arm, multi-axial, etc. • Incompatible with new DICOM multi-frame CT, MR (2000) and segmentation information objects (2006) • Inadequate support for RT prescription (TP workflow) • RT Plan, RT Dose objects are “overloaded”, i. e. , have multiple uses o RT Plan represents EBRT, Brachy o RT Dose represents DVHs, dose grids, iso-dose curves o Many optional attributes – difficult to assess conformance • Large composite objects o Any change requires a new instance. o Difficult to manage revisions and approvals DICOM Second Generation Radiotherapy 3
Image Segmentation RT Structure Set IOD • Stacked, polygonal contours – difficulty with gaps, interior voids Missing contour? Missing image slice? Disjoint structures? ? Interior void Segmentation IOD (2006) • 3 -D spatial map • BINARY – bitmap • FRACTIONAL – probability or occupancy Surface Segmentation IOD (2008) • Mesh representation for structure surface
DICOM 2 nd Generation RT • Work on 2 nd generation RT objects began in 2006 in DICOM Working Group 7 (includes regular industry members from Accuray, Brainlab, Elekta, IBA, Mevion, Philips, Ray. Search, Varian, and others). • 44 revisions of the draft supplement between 2006 and 2014. • 11 reviews by DICOM WG-6 (Base Standard) beginning in 2009 DICOM Second Generation Radiotherapy 5
2 nd Gen RT Supplements 2 nd Generation DICOM RT Development (2) • Draft Supplement 147 Version 42 (July 2014) was 280 pages long (largest DICOM supplement ever submitted) • Decision at the July 2014 DICOM WG-7 meeting to split the 2 nd Generation RT Supplement into six pieces: Supp 147 – Prescription and Segment Annotation – To be released for PUBLIC COMMENT in Feb 2015 Supp 175 – C-Arm (Photon and Electron) Radiations and Radiation Sets Supp 176 – New RT Radiations (Tomo, Multiple Fixed Sources, Robotic, Multi-Axial) Supp 177 – Dose Objects (Image, Histogram, Samples) Supp 178 – RT Course (information objects, clinical status) Supp 179 – RT Explanatory Material
DICOM 2 nd Generation • Reorganized “radiation” objects separate modalityindependent from modalityspecific information – Minimize optional attributes – Extensible to new treatment modalities • Conceptual volumes link multiple instances of the same structure over time • Support for new and improved image and segmentation objects • New Physician Intent object for treatment planning workflow
RT Process Perspective • 1 st Generation: Focus primarily on the Treatment Planning System • 2 nd Generation: Now supports a broader, more dynamic view of the complete Treatment Workflow DICOM Second Generation Radiotherapy 8
Supplement 147 – Prescription and Segment Annotation DICOM Second Generation Radiotherapy 9
DICOM RT Plan Issues • Prescription cannot exist outside an RT Plan object • Limited capability for expressing dosimetric objectives DICOM RT Plan Prescription Fractionation Beams Patient Setup DICOM Second Generation Radiotherapy 10
RT Physician Intent Contains the following parts: • Physician Intent • Mostly free-text definition of the physician‘s intent based on a diagnosis • Prescription • Actual prescription parameters • Treatment Phase Intent • Specifies time structure of intended treatment delivery • Exists outside of the RT Plan • Supports real-world Prescription workflow DICOM Second Generation Radiotherapy 11
RT Physician Intent Attributes • • • Treatment Intent • Dosimetric objectives (per Anatomy) Physician Intent Narrative – Maximum dose RT Protocol Code – Minimum dose RT Diagnosis Code – Maximum mean dose Diagnostic Image Set – Minimum mean dose Prior Dose Information – Maximum percent volume at dose General Prescription Notes – Minimum percent volume at dose Intended Delivery Duration – Maximum absolute volume at dose Number of Fractions – Minimum absolute volume at dose – Minimum surface dose Fractionation Description – Maximum surface dose Treatment Technique Description … RT Procedure Technique Code
Conceptual Volume • Abstract identification of a region of interest • May or may not be associated with one or more image segmentations • May be a logical combination of other Conceptual Volumes • A Conceptual Volume UID links instances of the same conceptual volume • Prior to segmentation (for prescription) • During segmentation and treatment planning • Across treatment fractions (e. g. , for segmentation of daily CBCT) • For adaptive re-planning
Conceptual Volumes Example Use Case 1. A target volume is identified in a prescription (RT Physician Intent object) and assigned a Conceptual Volume Unique Identifier (UID). 2. Segmentation of the target (ROI) on planning CT is linked to the prescription via its Conceptual Volume UID. 3. In an IGRT/adaptive workflow, the target volume is segmented on multiple CBCTs (or MRIs). Corresponding structures on each verification image are associated via their Conceptual Volume UIDs.
CV Example Diagnostic CT Physician Intent: Prescribe 50 Gy to the tumor. CV I “Tumor“ RTStruct. Set 1 - ROI 1, “GTV“ RTStruct. Set 2 - ROI 4, “Target“ RTStruct. Set 3 -ROI 2, “Target“ Planning CT CBCT 1 CBCT 2 Day 10 Day 20 15
CV Combination Example: CV defined as a logical combination of other CVs DICOM Second Generation Radiotherapy 16
RT Segment Annotation • “Wrapper” around existing DICOM segmentation objects o Segmentation (3 D volume) o Surface Segmentation (3 D mesh surface) o RT Structure Set (Contours - 1 st Gen ) • Provides RT-specific information for segmented conceptual volumes RT Segment Annotation Segmentation Surface Segmentation RT Structure Set Image
RT Segment Annotation • RT Segment Annotation provides RT-specific information o Segmented Property Category Code: {Anatomic Structure, Target, Fixation Device, …} o Segmented Property Type Code: Standard Identifier Code o Alternate Segmented Property Type Code: Alternate Identifier Code o Purpose of Alternate Segmented Property Type Code: e. g. , clinical trial, registry, analysis workflow, etc. o Segment Properties: Physical and biological properties of ROI o Recommended display (grayscale value, color, opacity)
RT Segment Annotation Category Codes • Baseline RT Segment Annotation Category Codes (extensible)
RT Segment Annotation Segmented Property Type Code • Segmented Property Type Code provides a standardized ROI identifier • Baseline codes for RT Targets in Sup 147 (extensible)
Segmented Property Type Code Examples Attribute >Segmented Property Category Code Sequence >Segmented Property Type Code Sequence >Alternate Segmented Property Type Code Sequence >>Purpose of Alternate Segmented Property Type Code Sequence Tag Value (0062, 0003) (SRT, T-D 000 A, Anatomical Structure) (0062, 000 F) (CODESCHEME 1, Lung_R, Right Lung) (30 xx, 134 E) (CODESCHEME 2, Lung_Ipsi, Ipsi-lateral Lung) (30 xx, 134 F) (CODESCHEME 3, CT 1234, Clinical Trial Protocol 1234) Tag Value (0062, 0003) (99 SUP 147, S 147050, RT Target) (0062, 000 F) (CODESCHEME 1, CTV, Clinical Target Volume) (30 xx, 134 E) (CODESCHEME 2, CTV_5400, CTV 5400 c. Gy) (30 xx, 134 F) (CODESCHEME 3, CT 1234, Clinical Trial Protocol 1234) [DICOM Supp. 147 PC Draft 1, p. 55]
RT Segment Annotation Properties Segment Property Codes in Sup 147 (extensible) VM Units 1 Percent Relative Electron Density 1 Ratio Effective Z 1 no units Effective Z per A 1 Ratio Relative Linear Stopping Power 1 Ratio Linear Cell Kill Factor 1 Ratio Quadratic Cell Kill Factor 1 Ratio High Dose Fraction Linear Cell Kill Factor 1 Ratio Half-time for Tissue Repair 1 Second High Dose Fraction Transition Dose 1 Gray 1 -n no units Concept Name Relative Mass Density Elemental Composition Atomic Number [DICOM Supp. 147, PC_Draft 1, p. 85]
RT Segment Annotation Codes Mappings in 1 st Gen RT • RT Segment Annotation codes have also been added to the 1 st Gen RT Structure Set information object (CP 1287) 1 st Gen RT Structure Set 2 nd Gen RT Segment Annotation Segmented Property Category Code Sequence RT ROI Identification Code Sequence Segmented Property Type Code Sequence Additional RT ROI Identification Code Sequence Alternate Segmented Property Type Code Sequence Purpose of Additional RT ROI Identification Code Sequence Purpose of Alternate Segmented Property Type Code Sequence
Next steps • Sup 147 Public Comment – expected Feb 2015 • Additional 2 nd Gen RT DICOM Supplements Supp 175 – C-Arm (Photon and Electron) Radiations and Radiation Sets Supp 176 – New RT Radiations (Tomo, Multiple Fixed Sources, Robotic, Multi-Axial) Supp 177 – Dose Objects (Image, Histogram, Samples) Supp 178 – RT Course (information objects, clinical status) Supp 179 – RT Explanatory Material DICOM Second Generation Radiotherapy 24
Contacts Stephen Vastagh DICOM Secretary NEMA/MITA svastagh@medicalimaging. org Ulrich Busch Chairman DICOM WG-07 ulrich. busch@varian. com Christof Schadt Vice-Chair DICOM WG-07 christof. schadt@brainlab. com DICOM Second Generation Radiotherapy 25
Links • NEMA DICOM Page http: //dicom. nema. org • Participate in DICOM http: //dicomconference. org/contact/participation-in-dicomactivities/ • DICOM Standard Status http: //www. dclunie. com/dicom-status/status. html DICOM Second Generation Radiotherapy 26
Thanks to • • Ulrich Busch (Varian), Chair WG-7 Christof Schadt (Brainlab), Vice-chair WG-7 Chris Pauer (Accuray), Co-chair IHE-RO TC Jim Percy (Elekta) Mike Courtney (Philips) Mark Pepelea (Philips) Bruce Rakes (Mevion) DICOM Second Generation Radiotherapy 27
Questions? DICOM Second Generation Radiotherapy 28
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