DICOM Anniversary Conference
Experience Using DICOM-RT
Objects 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.
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 Protocols
RTOG
Protocol
Site
Status
Approved
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
Open 8/15
0
0
BR-0319 Breast Ph I/II
* 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, protocolcompliant 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:
IMPORT
CT Image
MR Image
RT Structure Set
RT Plan
EXPORT
Treatment
Planning
System
RT Plan
RT Image
• Only recently have commercial treatment planning
systems begun to export this complete set of objects.
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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 protocolcompliant 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.)
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