DICOM Anniversary Conference

Experience Using DICOM-RTObjects for Clinical Trials QA

Walter R. Bosch, D.Sc., John W. Matthews, D.Sc.,

Vincent A. Frouhar, Ph.D., Jatinder R. Palta, Ph.D.,

James A. Purdy, Ph.D.

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NCI Advanced Technology QA Consortium

• Members• Image-guided Therapy Center (ITC)

• J. Purdy, W. Bosch, J. Matthews, Wm. Straube, J. Michalski

• Resource Center for Emerging Technologies (RCET)• J. Palta, V. Frouhar, J. Dempsey

• Radiological Physics Center (RPC)• G. Ibbott, D. Followill

• Radiation Therapy Oncology Group (RTOG)• E. Martin, R. Lustig

• Quality Assurance Review Center (QARC)• T.J. FitzGerald, M. Urie, K. Ulin

• Support• NIH U24 grant CA81647, “Advanced Technology QA Center”

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NCI Advanced-Technology QA Consortium• History

• Created in 2002 (in its current form) by NCI to support QA for advanced technology clinical trials (P.I.: J.A. Purdy, Ph.D.)

• Builds on a decade of experience in supporting QA for clinical trials involving 3DCRT and IMRT

• Mission

• Develop appropriate and uniform QA procedures and criteria

• Facilitate sharing of developmental and QA resources for digital data submission and review

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Dose-Response Modeling in Radiotherapy

• Fundamental trade-off: • deliver tumoricidal dose to a target

• avoid injury to radiosensitive normal tissues (“organs at risk”)

• Normal-tissue tolerance doses in current use are based on simple point doses and do not account for dose-volume effects.

• Correlating volumetric doses with clinical outcomes is expected to yield better dose-response models for normal tissue.

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Digital Data for Advanced-Technology Clinical Trials in Radiotherapy

• Primary data (volumetric dosimetry)• Volumetric Image (CT)

• Structure Set: GTV, CTV, PTV, OAR

• 3-D Dose Distribution (including fractionation information)

• Secondary data (QA of primary data)• Treatment Plan Specification

• Dose-Volume Histograms

• Digital Simulator and Portal Images

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Digital Data Submission for Advanced-Technology Clinical Trials

• Treatment planning data are stored in proprietary formats.

• For meaningful exchange of information, we need a common data representation and interchange format.

• RTOG Data Exchange Format• Based on AAPM Report 10

• Used to exchange of treatment planning data in RTOG advanced technology protocols, starting in 1994.

• Over 1600 protocol data sets submitted to date.

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RTOG Advanced-Technology ProtocolsRTOG

Protocol Site StatusApproved

Institutions

Accrued

Cases*

9406 Prostate Ph I/II Closed 53 1084

9311 Lung Ph I/II Closed 26 180

9803 Brain (GBM) Ph I/II Closed 46 210

H-0022 Oropharynx IMRT Ph I/II Open 13 25

H-0225 Nasopharynx IMRT Ph II Open 13 2

L-0117 Lung Ph I/II Open 34 14

P-0126 Prostate Ph III Open 79 146

P-0232 Prostate Brachytherapy Ph III Open 5 0

BR-0319 Breast Ph I/II Open 8/15 0 0

* as of 9/16/2003

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Why Use DICOM to Represent Radiotherapy Treatment Planning Information?

• Broadly-based industry standard

• Support for current and future imaging and treatment modalities• PET

• Functional MRI

• External beam IMRT

• HDR brachytherapy

• Heavy-particle therapy

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History of the DICOM RT Objects

• November 1994 – DICOM Ad Hoc Committee on Radiotherapy Objects met at RSNA

• June 1997 – Supplement 11 approved• RT Structure Set• RT Plan• RT Dose• RT Image

• May 1999 – Supplement 29 approved• RT Treatment Record

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DICOM RT Objects Needed for Advanced Technology Clinical Trials• A participant must submit a complete, protocol-

compliant data set: CT Image (MR Image, US Image), RT Structure Set, RT Dose, RT Plan, and RT Image.

• Many clinical implementations support only a subset of the RT objects. Typical external-beam TPS:

• Only recently have commercial treatment planning systems begun to export this complete set of objects.

TreatmentPlanningSystem

CT Image

RT Structure SetRT Plan

RT Plan

RT Image

MR Image

IMPORT EXPORT

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Special Requirements for DICOM Attributes for Clinical Trials

• Type 3 attributes may not be present.• Not meaningful in all applications• Incompletely specified objects at early stages of the

planning process

• Special requirements for attributes values, e.g.,• RT Plan Geometry (300A,000C) must be PATIENT.• CT and MR images must have square pixels.

• The ATC Fileset Reader application Conformance Statement (http://itc.wustl.edu) lists required attributes and special requirements for attribute values.

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RT Dose Object Implementation Issues

• Single, multi-frame dose object vs. many, planar dose objects

• Grid Frame Offset Vector• Absolute axial coordinate of dose grid

plane• Relative “offset” of dose grid plane from

Image Position (Patient) attribute value.

• 32-bit Dose Values• Byte-order and word-order issues

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Maintaining Consistent Object Linkage• DICOM RT objects reference each other.

• Structure Set references images (Frame of Reference)

• Plan references Structure Set

• References are important for automated import.

• Submission software should check that references are correct and complete.

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Clinical Trials Identification

• Data for a clinical patient must be de-identified and associated with a clinical trial subject.

• DICOM Supplement 70 (Jan. 2003) introduces Clinical Trials ID modules which include 10 new attributes that can be added to any DICOM object to identify• Clinical trial sponsor

• Clinical trial protocol

• Clinical trial subject

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Submission of DICOM Data to the ATC

• Part-10 Filesets (currently supported)• CD-R media

• FTP to ITC server (like RTOG Data Exchange)

• ATC Submission System (in development)• Push DICOM data to WebSys client program

(DICOM Storage SCP) on local PC

• Replace patient ID with clinical trials ID

• Perform secure upload to ATC server

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Credentialing for Participation in Advanced Technology Clinical Trials

• Institutions must pass a “dry run” (benchmark) test by submitting a protocol-compliant data set to the ATC.

• Treatment planning systems are said to be “ATC compliant” when a complete data set received from a real, clinical user is judged to be protocol-compliant.

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Institutions Credentialed for RTOG Protocols using DICOM RT

Protocol# Institutions Credentialed*

P-0232 Prostate brachytherapy 5

H-0022 Head-neck IMRT 1

P-0126 Prostate 3DCRT 1

* as of 9/16/2003

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ATC Efforts to Support DICOM Implementation for Clinical Trials

• DICOM Implementers’ Technical Workshops • March 16-17, 2001

• March 16, 2002

• May 3, 2003

• Spring 2004

• Assistance in evaluating compliance of data sets

• Feedback to implementers via the web-based Remote Review Tool

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Remote Review Tool• CT Images (zoom,

window/level)• Structure contours

(review, editing)• Iso-dose contours• Interactive DVH• Point-dose display

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Conclusions

• Advanced-technology clinical trials are attempting to correlate volumetric dosimetry information with clinical outcomes.• Expected to yield improved dose-response models.

• Requires volumetric digital data

• The DICOM RT objects are becoming a viable option for submission of data in these studies.

• ATC compliant treatment planning systems are listed on the ITC website http://itc.wustl.edu . (ATC website coming in Fall, 2003.)