Radiation Dose Data Management

1. Radiation Dose Data Management IHE Presentation – February 2008 Stephen Balter, Ph.D. Columbia University Medical Center, New York, New York

2. Measurements and documentation When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meager and unsatisfactory kind. Lord Kelvin (1824-1907) 1902 Skiameter of Benoist

3. Purposes and costs • The purpose of any diagnostic procedure is to reduce uncertainty about the patient’s health status. • The purpose of most therapeutic procedures is to stabilize or improve the patient’s health. • There are always associated costs • Money and time • Procedural risks • Often radiation risks

4. Real World Case Range • Patient brought into the emergency room by ambulance after an auto crash with evidence of multi-organ trauma. • PCI in place of coronary bypass surgery. • Screening mammogram. • Employee of a high-tech company visiting a ‘wellness clinic’ for an annual check-up. Offered add-on CT scans ‘as long as you are already on the table’. • Whole body security CT scan (before visiting a prisoner or boarding an aircraft).

5. Past radiation history • Rarely has any influence on the decision to order a diagnostic procedure. • May provide additional help in interpreting the results of a diagnostic procedure. • Can be important in planning therapeutic procedures. • Imaging history is another matter.

6. Historical dose recording • Non regulatory recommendations for dose recording • In some form since early 20th century • FDA Radiation “Passport” (circa 1970) • SIR Standard of practice (2004) • Interventional • FDA Recommendation (1994):Record skin dose and location • IEC 60601-2-43 (2001): KAP and Dose at Reference Point • FDA Regulations (2005): Dose at Reference Point(new fluoroscopic equipment) • DICOM MPPS Report (1996) • Assumes RIS and linkages • EURATOM Directive (1997) • National Dose Recording Regulations • Primarily KAP (Stochastic Risk Concerns) • No formal scheme for recording • Space available in DICOM Headers

7. FDA X-RAY Record Card c 1970

8. NCRP 2008? US Population Dose

9. FDA Poster Child

10. Why capture dose data? • Patient Risk Supervision • Deterministic • Stochastic (not really applicable to an individual patient) • Quality Assurance • Departmental vs. Guidance Levels • Local deviations • Equipment • Operators • CQI process • Regulatory Mandate

11. How much to capture? • Stochastic risk to the population • Collect everything? • Sampling • Deterministic injury potential • Collect data on every procedure where injury is possible • Quality Assurance • Collect everything (for local use)

12. Data elements • Direct dose measurements • Technical settings of equipment • Irradiation geometry • Patient and procedure data

13. Modalities • Radiography, Mammography, and Fluoroscopy • Closed system with digital image capture • Independent image receptor with CR or DR • Film/screen image receptor • Dental Radiography • DR image receptor • Film image receptor • Computed Tomography

14. Fluoroscopy - 2008 • All images via common digital video channel • Feedback loop for Automatic Dose Rate Control (ADRC) • Copper spectral shaping filters • (Flat detector) • IEC 60601-2-43

15. Issues 2008 • DICOM header data usually only exists when digital images are saved. • MPPS report is often an exact mirror of the headers of saved images. • No info usually available • Procedures without any saved images • Procedures partially saved images • Repeated exposures

16. Available dose metrics • Reference Point Air Kerma (Ka,r) • IEC 60601-2-43 (2000) • FDA (2005) • Kerma Area Product (PKA) • IEC 60601-2-43 (2000) • Common in Europe • Fluoroscopy Time ± Number of Images • Skin Dose Maps

17. Analysis using DICOM header or MPPS

18. DICOM-DOSE Project • DICOM Limitations • Data is bound to DICOM digital images. • Little or no data about non-stored images. • DICOM MPPS process needs tight coupling to an informatics system • Project • The need for complete documentation of interventional procedures was presented to the IEC (62b MT38) by DIMOND • Co-developed with DICOM committee • Initial version covers all projection radiography and fluoroscopy (except mammography). • Mammo and CT extensions are foreseen.

19. DD simulation using service log

20. RDSR Outputs • Near Real Time Updated RDSR transmitted over network after each irradiation • Post Procedure Complete RDSR transmitted over network once procedure is marked as complete. • Sneaker Net RDSRs stored in imaging system extracted on storage media and physically carried to AGENT IEC PAS specifies storage of at least 500 RDSRs with or without network connections. • AGENT LOCATIONS PACS, RIS, Independent

21. IEC PAS Overview • Claimed compliance with an IEC standard assures minimum requirements • IEC Compliance Levels Based on maximum expected cumulative Air Kerma at the IEC interventional reference point for any normal use of the equipment 1: Stochastic Risk Only (< 2 Gy expected) 2: Deterministic Injury Conceivable (> 2 Gy) 3: Deterministic Injury Possible (> 7 Gy) Presently a place-holder in the standard Implementation planned when adequate dose-mapping software is available

22. IEC Level 1 Equipment where the estimated maximum cumulative Air Kerma for any examination (study) is expected to be less than two (2) gray (Gy) for all normal uses The defining dose is the cumulative dose for a complete examination at the interventional reference point defined in IEC 60601-2-43 (for equipment capable of measuring Air Kerma at this point or The equipment manufactures estimate of the cumulative dose for a complete examination at the closest point to the X-ray source where the patient’s skin might be placed

23. Not only stored digital images • The RDSR is a DICOM object that is independent of any stored images • Valid RDSRs can be generated by equipment used to produce stored or not-stored analog or digital images • IEC specifies that RDSRs be stored by the imaging equipment (downloaded locally or via a network)

24. Verification of displayed “dose” • Accuracy of display • IEC ± 50% (RPDose &KAP) • FDA ± 35% (RPDose) • Stability usually better • Usually validated at factory • Seldom validated by installers • When verified as part of QAShould be able to maintain ± 20%

25. Generic Cases • Forget-about-it • Regulatory Requirement • All Procedures • Reportable Procedures • Institutional Quality Program • All procedures with subgroups for trending • Out of bounds procedures • Stochastic Risk Estimates • Data from population (complete or sampled) • Individual patient (significant difficulties in validly using data) • Potential Tissue Reaction • All patients at risk • Standards of care • Establish reference (guidance) levels • Monitor radiation load on population and its sources

26. Sources of Data • X-ray producing equipment • Manual data entry • Robotic translation (straw man)

27. Consumers of Data • Quality management • Research community • Generate reference levels • Estimate population risks • Policy makers • Individual providers (potential tissue reactions) • Individual patients ???

28. IHE and data collection issues • Procedure Lexicon • Accuracy of reported procedure names and description • Accuracy of demographic data • Accuracy of dosimetric data • Missing data