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Advancements in DICOM RT Generation 2: Segment Annotation

Explore the evolution of DICOM RT objects, challenges of 1st Gen RT, and features of 2nd Gen RT focusing on segment annotation and physician intent. Learn about the new structures, like the RT Structure Set IOD and Surface Segmentation IOD. Follow the development journey from drafting Supplement 147 Version 42 to the split of the 2nd Generation RT Supplement into innovative segments. Discover the enhanced capabilities for treatment workflow and physician intent in radiotherapy. Semantic attributes for physician intent defined with flexible parameters and real-world prescription workflows.

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Advancements in DICOM RT Generation 2: Segment Annotation

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  1. 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

  2. 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.

  3. Pain Points in 1st 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 • RT Plan represents EBRT, Brachy • RT Dose represents DVHs, dose grids, iso-dose curves • Many optional attributes – difficult to assess conformance • Large composite objects • Any change requires a new instance. • Difficult to manage revisions and approvals DICOM Second Generation Radiotherapy

  4. Image Segmentation • RT Structure Set IOD • Stacked, polygonal contours – difficulty with gaps, interior voids • Segmentation IOD (2006) • 3-D spatial map • BINARY – bitmap • FRACTIONAL – probability or occupancy • Surface Segmentation IOD (2008) • Mesh representation for structure surface Interior void Missing contour? Missing image slice? Disjoint structures? ?

  5. DICOM 2nd Generation RT • Work on 2nd generation RT objects began in 2006 in DICOM Working Group 7(includes regular industry members from Accuray, Brainlab, Elekta, IBA, Mevion, Philips, RaySearch, 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

  6. 2nd Generation DICOM RT Development (2) 2nd Gen RT Supplements • 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 2nd 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

  7. DICOM 2nd Generation • Reorganized “radiation” objects separate modality-independent from modality-specific 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

  8. RT Process Perspective • 1st Generation: Focus primarily on the Treatment Planning System • 2nd Generation: Now supports a broader, more dynamic view of the complete Treatment Workflow DICOM Second Generation Radiotherapy

  9. Supplement 147 – Prescription and Segment Annotation DICOM Second Generation Radiotherapy

  10. DICOM RT Plan Issues DICOM RT Plan • Prescription cannot exist outside an RT Plan object • Limited capability for expressing dosimetric objectives Prescription Fractionation Beams Patient Setup DICOM Second Generation Radiotherapy

  11. 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

  12. RT Physician IntentAttributes • Treatment Intent • Physician Intent Narrative • RT Protocol Code • RT Diagnosis Code • Diagnostic Image Set • Prior Dose Information • General Prescription Notes • Intended Delivery Duration • Number of Fractions • Fractionation Description • Treatment Technique Description • RT Procedure Technique Code • Dosimetric objectives (per Anatomy) • Maximum dose • Minimum dose • Maximum mean dose • Minimum mean dose • Maximum percent volume at dose • Minimum percent volume at dose • Maximum absolute volume at dose • Minimum absolute volume at dose • Minimum surface dose • Maximum surface dose …

  13. 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

  14. Conceptual Volumes • Example Use Case • A target volume is identified in a prescription (RT Physician Intent object) and assigned a Conceptual Volume Unique Identifier (UID). • Segmentation of the target (ROI) on planning CT is linked to the prescription via its Conceptual Volume UID. • 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.

  15. CV Example Diagnostic CT CV I “Tumor“ Physician Intent: Prescribe 50Gy to the tumor. RTStructSet 1 - ROI 1, “GTV“ RTStructSet 2 - ROI 4, “Target“ • RTStructSet 3 • ROI 2, • “Target“ Planning CT CBCT 1 CBCT 2 Day 10 Day 20

  16. CV Combination • Example: • CV defined as a logical combination of other CVs DICOM Second Generation Radiotherapy

  17. RT Segment Annotation RT Segment Annotation • “Wrapper” around existing DICOM segmentation objects • Segmentation (3D volume) • Surface Segmentation (3D mesh surface) • RT Structure Set (Contours - 1st Gen ) • Provides RT-specific information for segmented conceptual volumes Segmentation Surface Segmentation RT Structure Set Image Image Image

  18. RT Segment Annotation • RT Segment Annotation provides RT-specific information • Segmented Property Category Code: {Anatomic Structure, Target, Fixation Device, …} • Segmented Property Type Code: Standard Identifier Code • Alternate Segmented Property Type Code: Alternate Identifier Code • Purpose of Alternate Segmented Property Type Code: e.g., clinical trial, registry, analysis workflow, etc. • Segment Properties: Physical and biological properties of ROI • Recommended display (grayscale value, color, opacity)

  19. RT Segment AnnotationCategory Codes • Baseline RT Segment Annotation Category Codes (extensible)

  20. RT Segment AnnotationSegmented Property Type Code • Segmented Property Type Code provides a standardized ROI identifier • Baseline codes for RT Targets in Sup 147 (extensible)

  21. Segmented Property Type Code Examples [DICOM Supp. 147 PC Draft 1, p. 55]

  22. RT Segment Annotation Properties Segment Property Codes in Sup 147 (extensible) [DICOM Supp. 147, PC_Draft1, p. 85]

  23. RT Segment Annotation CodesMappings in 1st Gen RT • RT Segment Annotation codes have also been added to the 1st Gen RT Structure Set information object (CP1287)

  24. Next steps • Sup 147 Public Comment – expected Feb 2015 • Additional 2nd 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

  25. 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

  26. Links • NEMA DICOM Page http://dicom.nema.org • Participate in DICOM http://dicomconference.org/ • DICOM Standard Status http://www.dclunie.com/dicom-status/status.html DICOM Second Generation Radiotherapy

  27. 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

  28. Questions? DICOM Second Generation Radiotherapy

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