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Monitoring Radiation Exposure (2011 Update): Standards, Tools and IHE REM

Monitoring Radiation Exposure (2011 Update): Standards, Tools and IHE REM. Kevin O’Donnell Toshiba Medical Research Institute Michael F. McNitt-Gray, PhD, DABR, FAAPM Professor, Department of Radiology Director, Biomedical Physics Graduate Program David Geffen School of Medicine at UCLA.

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Monitoring Radiation Exposure (2011 Update): Standards, Tools and IHE REM

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  1. Monitoring Radiation Exposure (2011 Update): Standards, Tools and IHE REM Kevin O’Donnell Toshiba Medical Research Institute Michael F. McNitt-Gray, PhD, DABR, FAAPMProfessor, Department of Radiology Director, Biomedical Physics Graduate Program David Geffen School of Medicine at UCLA 1

  2. Disclosures • K.O. : • Employee, Toshiba Corporation   • M.M-G: • Institutional research agreement, Siemens AG • Recipient research support Siemens AG • Instructor, Medical Technology Management Institute . 2

  3. Learning Objectives • 1) Understand integration challenges involved in Monitoring Radiation Exposure. • 2) Learn about capturing dose information with the DICOM Radiation Dose SR (RDSR) standard. • 3) Learn about managing RDSR objects with the IHE Radiation Exposure Monitoring (REM) Profile. • 4) Learn how data such as "CT dose screens" from legacy systems can be ported into RDSR. • 5) Learn about pre-scan dose pop-ups on the CT console defined by the MITA Dose Check standard and recent AAPM guidance on their use. • 6) Learn how to specify the above features when purchasing and integrating Radiology Systems. • 7) Learn about components of a dose management program such as protocol optimization, dose QA programs and participation in the ACR Dose Registry. 3

  4. Outline • CT Dose Definitions – MMG • IHE REM, DICOM RDSR and Standards – KO • How to use dose information in practice - MMG 4

  5. CT –Specific Dose Definitions • Computed Tomography Dose Index (CTDI) & its cousins • CTDI100 • CTDIw- weighted • CTDIvol • Dose Length Product (DLP) • Dose Reports

  6. CTDI • CTDI is an Index • CTDI is dose in a phantom • CTDI has LOTs of good uses: • It is a good measure of scanner output • It is a good index when comparing protocols and technical parameter settings • It is a very good indicator of how scanner output is being adjusted with patient size (think peds protocols) 6

  7. CTDI • But CTDI has some limitations (we said it was an index) • Ex: CTDI is not a direct measure of patient dose • (more on that later) 7

  8. CTDI Phantoms • Body (32 cm diam), Head (16 cm diam) • Holes in center and at 1 cm below surface

  9. CTDI – defined • CTDI Does Represent: • Average dose in a phantom • along the z direction • at a givenpoint (x,y) in the scan plane • over thecentral scan of a series of scans • when the series consists of alarge number of scansseparated by the nominal beam width (contiguous scanning)

  10. CTDI100 • CTDI100 Measurements are done: • In Both Head and Body Phantoms with 100 mm ion chamber • At isocenter and at least one peripheral position in each phantom 20 mGy Some typical CTDI100 values 60 mGy 20 20 10 60 60 60 60 20 Head Body

  11. CTDIw • CTDIw is a weighted average of center and peripheral CTDI100 to arrive at a single descriptor • CTDIw = (1/3)CTDI100,center + (2/3)CTDI100,peripheral

  12. CTDI vol • Calculated, not measured directly • Based on CTDIw, but accounts for pitch • CTDIvol = CTDIw/ Pitch

  13. CTDIvol in Context of AEC • When Tube current modulation is used: • CTDIvol reported is based on the average mA used throughout the scan

  14. Scan where Tube Current Modulation was used Blue Curve Represents actual instantaneous mA Red Curve Represents avg mA for each image Yellow Curve Represents avg mA over entire scan Overall avg is used for CTDIvol reported in Dose Report

  15. DLP – defined • Dose Length Product is: • CTDIvol* length of scan (in mGy*cm) • Found in most “Dose Reports” • Includes any overscan (extra scanning for helical scans)

  16. CTDIvol and DLP • CTDIvol is reported on the scanner and in dose reports • CTDIvol is Dose to one of two phantoms • (16 or 32 cm diameter) • CTDIvol is a good descriptor of scanner output • And can be a good indicator of how output is adjusted for patient size • Think peds protocols here. • Larger patients SHOULD have a larger CTDIvol

  17. Standards & Tools 17

  18. Headers & Screen Shots • Useful but limited • Missing details • Not machine-readable • Duplication issue • Size issue 18

  19. DICOM RDSR Radiation DoseStructured Report Object

  20. DICOM Dose Reports • “SR Objects” – DICOM Structured Reports • Easily ingested (and regurgitated) by PACS • Granularity : “Irradiation Event” • & Accumulated Dose over Study, Series • Templates : • CT, Projection X-Ray (Mammo, Fluoro) • DR/CR (Soon), PET/NM (WIP) • Not yet addressed: RT

  21. Key Measurements • CT Dose • DLP, CTDIvol, kVP, mA, sec • Effective Dose [ Optional; Reference estimation method ] • Projection X-Ray Dose • DAP, Dose@RP, kVP, mA, sec • Fluoro Dose, Fluoro Time • [CR/DR: Exposure Index, Deviation Index] • Mammography Dose • AGD, Entrance Exposure@RP, kVP, mA, sec • Compression, Half Value Layer ftp://medical.nema.org/medical/dicom/2011/11_16pu.pdf

  22. Other Details in Dose SR • Full Patient / Order / Study Details • Unique ID for each Irradiation Event • Equipment ID, Ordering Doc, Performing Tech • Patient Size, Orientation, Anatomy Imaged • Imaging Geometry • X-Ray Filtering & Collimation Details • Anode Target Material • Calibration, Phantom, Dosimeter, Patient Model

  23. some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 Numer 12.2 14.5 9.5 10.9 IHE REM Profile Radiation Exposure Monitoring

  24. IHE in One Slide • IHE helps vendors implement & test functions that span multiple systems • Profiles are implementation guides • how to use existing standards • to address a specific problem scenario • Connectathons are test events • managed testing of Profile implementations • IHE helps users purchase & integrate multi-system solutions • list required IHE Profile support in RFPs

  25. some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 Numer 12.2 14.5 9.5 10.9 IHE Radiation Exposure Monitoring Profile National Registry Outlier: # Performing Phys. Over Target: 12.2% some text: # Numerical Details 12.2 14.5 11.8 7.6 Dose Information Reporter Archive

  26. Using SR Dose Reports • Radiation QA • Periodically Query / Retrieve Reports from Archive • Set policies/standards and flag deviations • Set goals for improvement and track progress • Implement protocol changes and compare difference in dose • Patient Impact Evaluation • e.g. if Patient identified as pregnant post-facto • Dose Mapping • Store data in realtime from Modality to Mapping Workstation

  27. Using SR Dose Reports • National Registries • Anonymize and submit Dose Reports to Registry • Compile Population Risk Estimations • Derive Dose Reference Levels (DRLs) • Provide Site-Site Comparisons • Individual Dose Record • Collect Dose Reports over time • Clinical Trials • Collect Dose together with Images • Demonstrate both improved detection & reduced dose

  28. some text: # Numerical Details 12.2 14.5 11.8 7.6 9.5 10.9 Legacy Dose Extractors

  29. Legacy Extractor • What if you can’t get REM? • Extractors create (partial) REM objects • Based on OCR of dose screens • Based on image header contents • Based on MPPS • Likely incomplete but still useful • Allows use of uniform infrastructure (RDSR) • Current focus: CT, some XA

  30. Example Extractors • Open Source • “Dose Utility” - dclunie.com • by David Clunie (PixelMed) • “Radiance” - radiancedose.com • by Tessa Cook (Hospital of U of Pennsylvania) • “GROK” – dose-grok.sourceforge.net • by Graham Warden (Brigham and Women's Hospital) • Also • “Valkyrie” (considering open source) • by George Shih (Weill-Cornell) • ACR Triad Site Server (included in ACR participation) • by Mythreyi Chatfield (ACR)

  31. ACR DIR DoseIndexRegistry

  32. ACR Dose Index Registry nrdr.acr.org • Open to facilities worldwide • Anonymized data submission • (via IHE REM or legacy extractor) • Provides periodic reports • Dose statistics • Site Comparisons • Modest annual participation fee 33

  33. ACR Activity • Tracking practice • Understand current dose patterns • Provide basis for establishing DRLs • Not tracking patient/longitudinal • Procedure Naming Issue • Comparison requires consistent naming • Local consistency vs National consistency • ACR maps to Radlex Playbook 34

  34. MITA XR-25 Dose Notification Predicted DLP (981 mGy-cm) Exceeds Threshold … CTDoseCheck

  35. MITA CT Dose Check Initiative • Goals • Enhance dose awareness (CTDI/DLP) • Help to avoid excessive radiation events • Provide data to sites for QA • MITA has published the standard (XR-25)* Manufacturers worked to ensure • Uniformity • Speed of implementation • Breadth of deployment *Available at: http://www.nema.org/stds/xr25.cfm

  36. Dose Notification • Pop-up message • Notifies technologist that dose for the current scan element will exceed a trigger value • Tech may: • confirm and proceed, or • go back and adjust scan parameters • System records audit trail • Predicted dose, Notification value, Date/time, diagnostic reason, etc. • Clinical sites set values that will trigger a notification • Can set DLP and/or CTDIvol values for each scan element e.g. head without contrast • Defined by the clinical site for their patient population

  37. Dose Alert • Pop-up message • Alerts technologist cumulative dose for current study will exceed a trigger value: • CTDIvol(summed at each patient location) • DLP (summed over the current study) • Tech may: • enter their name, (& a password if configured), confirm and proceed, or • go back and adjust scan parameters • Clinical sites set values that will trigger an alert • Can set DLP and/or CTDIvol values • System must allow at least one global value • System tracks accumulated CTDIvol at each patient location & accumulated DLP • System checks predicted accumulated dose indices when protocols are saved &when scans are ready

  38. Default Values • The FDA has suggested an alert value for CTDIvol of 1000 mGy, • AAPM suggested notification values • Can be changed at local site 39

  39. Audit Trails • Pop-up Overridden? System must record: • Dose Notification • Predicted dose, Notification value, Date/time, Diagnostic reason • Dose Alert • Predicted dose, Alert value, Date/time, Diagnostic reason, Operator name • RDSR has fields to record all these details • May choose to record even if not overridden • Triggers vs DRLs • 75th percentile -> popups on 25% of scans • See AAPM guidance

  40. Implementation Progress • IHE REM • Testing: IHE Connectathon • http://connectathon-results.ihe.net • Product: IHE Integration Statement • http://product-registry.ihe.net • DICOM RDSR • Product: DICOM Conformance Statement • NEMA XR-25 • Vendors commitment; some products already released 41

  41. Takeaway Data Collection • New/recent Modalities • IHE REM / DICOM RDSR to capture dose data • Legacy strategies • Dose extractors to generate RDSR data Analysis • IHE REM – Dose Information Reporter for local analysis • ACR Dose Registry to compare to benchmarks Prevention • CT Dose Check for configurable pre-scan alerts

  42. Things to Implement in Practice • Turn On/Upgrade to get these Informatics Tools • Make sure CTDIvol is displayed on all of your CT scanners • Can be turned off, so make sure • Make sure Patient Protocol pages are sent to PACS • Not always automatically sent to PACS, so make sure • RDSR (may require software upgrade, so check) • MITA’s Dose Check (also may require software upgrade) • Consider joining ACR’s Dose Index Registry 43

  43. Things to Implement in Practice • Review CT protocols • All if possible, but at least top 10 highest dose and/or usage • One key question – Fewer Protocols? Or More Protocols?: • Build a basic protocol that is inclusive and ask techs to adapt (in real time) at scanner • Build protocols for each possible situation and have them listed separately on the scanner (e.g. peds<5kg, peds 6-16 kg, peds> 16kg) • Some combination of these two 44

  44. Things to Implement in Practice • What to review • Review Indications and Requirements for Exam • What do you need to see? What amount of noise can you tolerate? • Technical parameters (kVp, mAs, pitch, etc.) • Examine CTDIvol and DLP values for protocols • Determine number of phases necessary for indication • Are both pre- and post-contrast necessary on all patients? • Are different enhancement phases necessary (arterial/venous)? 45

  45. ACR CT Dose Reference Values • Based Solely on CTDIvol (not DLP) • Two levels: • Reference level and Pass/Fail level • Exam Ref Level Pass/Fail Level • Adult Head* 75 mGy 80 mGy • Adult Abdomen* 25 mGy 30 mGy • Pediatric (5 y/o) Abd* 20 mGy 25 mGy • Pediatric Head* 45 mGy None (yet) • All values pertain to a single phase, NOT cumulative from multi-phase exams • Adult Head, pedsabd and peds head are based on 16 cm phantom

  46. AAPM Protocols • For All Manufacturers • Brain Perfusion already posted on AAPM public website • Coming Soon • Routine Head • Routine Chest • Routine Abdomen • Routine Cardiac • Not Meant to be “optimal”, but a good starting point 47

  47. Things to Implement in Practice • Review Usage • Ex.: Summary Statistics from ACR Dose Index Registry • Use tools to help identify high dose exams and outliers • Understand reasons for high dose values • Large Patient (for Body exams) • Multiple Phases • Ensure Compliance with Protocols 48

  48. Things to Implement in Practice • Reporting Dose in Patient Record and Radiology Reports? • Why are you going to do this? • Required by State Law (e.g. CA)? • It’s “the right thing to do”? 49

  49. Limitations of CTDIvol • Some things you should know before you start reporting dose in patient records • CTDIvol is Dose to one of two phantoms • (16 or 32 cm diameter) • CTDIvol is a good descriptor of scanner output • And can be a good indicator of how output is adjusted for patient size • Think peds protocols here. • Larger patients SHOULD have a larger CTDIvol 50

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