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DICOM-RT Objects for Clinical Trials QA

Learn about the use of DICOM-RT objects in clinical trials quality assurance for radiotherapy treatment planning. Explore the history, benefits, and implementation issues of using DICOM in advanced technology trials.

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DICOM-RT Objects for Clinical Trials QA

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  1. DICOM Anniversary ConferenceExperience 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.

  2. 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” Bosch – DICOM Anniversary Conf. 2003

  3. 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 Bosch – DICOM Anniversary Conf. 2003

  4. 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. Bosch – DICOM Anniversary Conf. 2003

  5. 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 Bosch – DICOM Anniversary Conf. 2003

  6. 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. Bosch – DICOM Anniversary Conf. 2003

  7. RTOG Advanced-Technology Protocols * as of 9/16/2003 Bosch – DICOM Anniversary Conf. 2003

  8. 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 Bosch – DICOM Anniversary Conf. 2003

  9. 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 Bosch – DICOM Anniversary Conf. 2003

  10. IMPORT EXPORT CT Image Treatment Planning System RT Plan MR Image RT Structure Set RT Image RT Plan 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. Bosch – DICOM Anniversary Conf. 2003

  11. 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. Bosch – DICOM Anniversary Conf. 2003

  12. 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 Bosch – DICOM Anniversary Conf. 2003

  13. 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. Bosch – DICOM Anniversary Conf. 2003

  14. Clinical Trials Identification • Data for a clinical patientmust 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 Bosch – DICOM Anniversary Conf. 2003

  15. 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 Bosch – DICOM Anniversary Conf. 2003

  16. 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. Bosch – DICOM Anniversary Conf. 2003

  17. Institutions Credentialed for RTOG Protocols using DICOM RT * as of 9/16/2003 Bosch – DICOM Anniversary Conf. 2003

  18. 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 Bosch – DICOM Anniversary Conf. 2003

  19. Remote Review Tool • CT Images (zoom, window/level) • Structure contours (review, editing) • Iso-dose contours • Interactive DVH • Point-dose display Bosch – DICOM Anniversary Conf. 2003

  20. 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.) Bosch – DICOM Anniversary Conf. 2003

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