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 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 Segmentation IOD (2006) 3-D spatial map BINARY – bitmap FRACTIONAL – probability or occupancy Surface Segmentation IOD (2008) Mesh representation for structure surface ? Missing contour? Missing image slice? Disjoint structures? Interior void

DICOM 2nd 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, RaySearch, Varian, and others). 44 revisions of the draft supplement between 2006 and reviews by DICOM WG-6 (Base Standard) beginning in 2009 DICOM Second Generation Radiotherapy 5

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 2nd Gen RT Supplements

DICOM 2 nd 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

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 Radiotherapy8

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 Second Generation Radiotherapy 10 DICOM RT Plan Prescription Fractionation Beams Patient Setup

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 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 …

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

CV Combination Example: CV defined as a logical combination of other CVs DICOM Second Generation Radiotherapy16

RT Segment Annotation “Wrapper” around existing DICOM segmentation objects o Segmentation (3D volume) o Surface Segmentation (3D mesh surface) o RT Structure Set (Contours - 1 st Gen ) Provides RT-specific information for segmented conceptual volumes Segmentation Image Surface Segmentation Image RT Structure Set 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 AttributeTagValue >Segmented Property Category Code Sequence (0062,0003)(SRT, T-D000A, Anatomical Structure) >Segmented Property Type Code Sequence (0062,000F)(CODESCHEME1, Lung_R, Right Lung) >Alternate Segmented Property Type Code Sequence (30xx,134E)(CODESCHEME2, Lung_Ipsi, Ipsi-lateral Lung) >>Purpose of Alternate Segmented Property Type Code Sequence (30xx,134F)(CODESCHEME3, CT1234, Clinical Trial Protocol 1234) AttributeTagValue >Segmented Property Category Code Sequence (0062,0003)(99SUP147, S147050, RT Target) >Segmented Property Type Code Sequence (0062,000F)(CODESCHEME1, CTV, Clinical Target Volume) >Alternate Segmented Property Type Code Sequence (30xx,134E)(CODESCHEME2, CTV_5400, CTV 5400 cGy) >>Purpose of Alternate Segmented Property Type Code Sequence (30xx,134F)(CODESCHEME3, CT1234, Clinical Trial Protocol 1234) [DICOM Supp. 147 PC Draft 1, p. 55]

RT Segment Annotation Properties Concept Name VMUnits Relative Mass Density 1Percent Relative Electron Density 1Ratio Effective Z 1no units Effective Z per A 1Ratio Relative Linear Stopping Power 1Ratio Linear Cell Kill Factor 1Ratio Quadratic Cell Kill Factor 1Ratio High Dose Fraction Linear Cell Kill Factor 1Ratio Half-time for Tissue Repair 1Second High Dose Fraction Transition Dose 1Gray Elemental Composition Atomic Number 1-nno units [DICOM Supp. 147, PC_Draft1, p. 85] Segment Property Codes in Sup 147 (extensible)

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 (CP1287) 1 st Gen RT Structure Set2 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 Ulrich Busch Chairman DICOM WG-07 Christof Schadt Vice-Chair DICOM WG-07 DICOM Second Generation Radiotherapy 25

Links NEMA DICOM Page Participate in DICOM DICOM Standard Status 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