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Improving Quality Assurance in CT Stanley H. Stern, Ph.D. Stanley.Stern@FDA.HHS

Improving Quality Assurance in CT Stanley H. Stern, Ph.D. Stanley.Stern@FDA.HHS.gov U.S. Food and Drug Administration Center for Devices and Radiological Health Office of Communications, Education, and Radiation Programs Division of Mammography Quality and Radiation Programs

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Improving Quality Assurance in CT Stanley H. Stern, Ph.D. Stanley.Stern@FDA.HHS

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  1. Improving Quality Assurance in CT Stanley H. Stern, Ph.D. Stanley.Stern@FDA.HHS.gov U.S. Food and Drug Administration Center for Devices and Radiological Health Office of Communications, Education, and Radiation Programs Division of Mammography Quality and Radiation Programs Radiation Programs Branch MITA CT Stakeholders’ Meeting at RSNA, Chicago, November 30, 2009

  2. Example of QA Problem • From public sources, it appears that... • In an 18-month interval • Cedars-Sinai Medical Center (CSMC), using GE equipment, unknowingly exposed 260 patients to eight times the facility’s normal radiation dose during CT brain perfusion for diagnosis and treatment of stroke.1,2 • CSMC CT brain perfusion: maximum direct-irradiation dose3 • Before Feb 2008 ~ 0.5 Gy • Feb 2008 – Aug 2009 ~ 4 Gy • Acute radiation-induced injuries • Temporary epilation in 80 patients, many with erythema • In 50 patients: eye lenses directly irradiated  risk for cataracts1,2,4 Improving QA in CT

  3. What Epilation Looks Like5 St. Marianna University School of Medicine Kanagawa, Japan Temporary hair loss (lasting 51 days) in 53-year old woman with subarachnoid hemorrhage. Hair loss was observed on day 37 after the first of four CT perfusion exams and two digital subtraction angiography exams within 15 days of admission to the hospital. Improving QA in CT

  4. Contributing Factors at CSMC • Change in brain-perfusion protocol4,6 • Apparently, misunderstanding of functions of some machine parameter selections and default settings4,6 • In auto mA mode,7 role of default noise index do not seem to be clear vis-à-vis “manufacturer’s recommended settings”6 • Dose implications of kV selection, multiple rotations in cine mode—factors not mentioned • Meaning, utility of dose indices do not seem to be clear6 • Values not prominently displayed, not related to any alerts • Quantities & units (“mGy,” “mGy-cm”) not construed as standardized or consistent with nomenclature used in training • Seeming lack of QA SOPs for changes to CT protocols6 • Inadequate systems of institutionally directed or coordinated control, review, authorization, documentation, or systematic communication to staff Improving QA in CT

  5. QA Issues: Broad Scope ~ 700,000 U.S. hospital discharges p/a acute cerebrovascular disease8 ~ 150,000 CT brain perfusionexams9 Mean CTDIvol800  200 mGy (N = 6)10 COV 50% Threshold for early, transient erythema ~ 2000 mGy (ref. 11) Threshold for temporary epilation ~ 3000 mGy (ref. 11) Ref. 12 Mean 63  3 mGy COV 52% Median 58 mGy ~ 12,500,000CT routine headexams p/a U.S.13 Improving QA in CT

  6. Bolstering QA: • Informed Perspectives • Radiologists might have caught the problem with a hospital SOP to save the dosage data with the images14 • —Geoffrey Rubin, Stanford University Vice Chief of Staff, Stanford Hospitals and Clinics; Associate Dean for Clinical Affairs, School of Medicine; Associate Director, Cardiovascular Institute; Chief, Department of Radiology Section of Cardiovascular Imaging; Medical Director, Department of Radiology 3D Laboratory15 • CSMC overdoses point to a well-documented need in medicine: multiple backup systems to catch mistakes14 • —Najmedin Meshkati, Professor of Civil/Environmental Engineering and Professor of Industrial & Systems Engineering, University of Southern California; Fellow of the Human Factors and Ergonomics Society16 • Additional safety redundancies in the total care delivery system including the equipment would enhance safety in CT brain perfusion studies and other fast-paced, intense medical procedures6 • —Thomas M. Priselac, President and CEO, Cedars-Sinai Medical Center Improving QA in CT

  7. QA Considerations to Reduce Risk - 1 • Targeted Software/Hardware • Default settings corresponding to clinical protocol selected • Weight/size-based triggers for defaulting to automatic exposure control (AEC) mode • Diagnostic referencelevel17(DRL) interlock for each clinical protocol • Manufacturer-provided defaults based on scientific literature • Some protocols: default threshold11 dose value for acute injury (erythema, epilation)18 • DRLs/acute-injury thresholds referenced to displayed values of dose indices • New index to represent directly-irradiated peak skin dose (PSD)19 • Standardized index, accepted metrics, representative actual doses in patients20 • Special modes of operation based on standardized thresholds: compare to SAR in MRI21 • Prominentdisplays, pre- and post-scanning, of dose indices • Technologist alert interlock: dose indices exceeding DRLs or injury thresholds • Radiologist alert: prominently stamped on images and in dose report Improving QA in CT

  8. QA Considerations to Reduce Risk - 2 • Targeted Software/Hardware (cont.) • Interlocks and logs identifying personnel who • Establish, change protocols, change parameters affecting dose • Review and approve new and modified imaging protocols (two individuals) • Operate the equipment • Alerts to technologist and radiologist, records of alerts  EHR • When changes in a protocol affect dose • When examination or procedure is repeated for an individual patient • Repeated-exam doses are tracked in patient record • When protocol selected does not match “appropriateness criteria” indication • Auto DICOM recording dose-index, organ-dose data, other parameters • For each individual patient examination or procedure • Automatic transmission to electronic storage and retrieval systems compatible with trends-tracking and auditing software/programs Improving QA in CT

  9. QA Considerations to Reduce Risk - 3 • Particular Technical Information to Users • Up-to-date image-quality metrics: med phys eval sysperformance22 • New phantom, method for modulation transfer function (MTF) • Noise power spectrum (NPS) as a complementary metric • MTF and NPS facilitate the evaluation of the signal-to-noise ratio (SNR) • Enhanced Training: Docs, Techs, Safety Managers • SOPs: DRLs, protocol control, appropriateness criteria • How to: monitor dose indices; develop, use DRLs; follow up large-dose cases • Promotion of a safety culture of collective responsibility • At installation • On site by applications specialists • In continuing education courses Improving QA in CT

  10. References and Notes 1. Alan Zarembo, “Cedars-Sinai investigated for significant radiation overdoses of 206 patients,” Los Angeles Times, October 10, 2009, http://www.latimes.com/news/local/la-me-cedars-sinai10-2009oct10,0,1920150.story. 2. Nicole Santa Cruz, “Cedars-Sinai finds more patients exposed to excess radiation,” Los Angeles Times, November 9, 2009, http://www.latimes.com/news/local/la-me-cedars10-2009nov10,0,2052232.story. 3. U.S. Food and Drug Administration, Safety Investigation of CT Brain Perfusion Scans: Initial Notification, October 8, 2009, http://www.fda.gov/MedicalDevices/Safety/AlertsandNotices/ucm185898.htm. 4. Alan Zarembo, “Hospital error leads to radiation overdoses,” Los Angeles Times, October 13, 2009, http://www.latimes.com/news/local/la-me-cedars13-2009oct13,0,1200257.story. 5. Yoshimasa Imanishi et al., “Radiation-induced temporary hair loss as a radiation damage only occurring in patients who had the combination of MDCT and DSA,” European Radiology Vol. 15, pp. 41-46, 2005. 6. Thomas M. Priselac, President and CEO, Cedars-Sinai Medical Center, statement of October 15, 2009, published online by the Los Angeles Times. See Alan Zarembo, “Cedars-Sinai head expresses regret for radiation overdoses,” Los Angeles Times, October 16, 2009, http://www.latimes.com/news/local/la-me-cedars16-2009oct16,0,3559559.story. Improving QA in CT

  11. 7. GE Healthcare, AutomA / SmartmA Theory, document 08-10495 01-08, found through a Google search yielding the following URL: http://www.gehealthcare.com/usen/education/tip_app/docs/AutomA-SmartmA%20Theory.pdf; downloaded November 14, 2009. 8. HCUP Nationwide Inpatient Sample, 2007, U.S. Agency for Healthcare Research and Quality, http://hcupnet.ahrq.gov. 9. The annual number of brain perfusion studies is an upper limit, an extrapolation estimated from the ratio of the annualized number of CT brain perfusion studies to all CT studies reported by Cedars-Sinai Medical Center in references 2 and 6: 173/72,000 = 0.0024. The value of this ratio times the total annual number of CT procedures in the U.S. (62.0 million in 2006, reported in ref. 13) yields ~ 150,000 CT brain perfusion studies. 10. Statistics reflect data corresponding to 6 brain perfusion protocols applied to various CT models from the following sources: Yoshimasa Imanishi et al., "Radiation-induced temporary hair loss as a radiation damage only occurring in patients who had the combination of MDCT and DSA," Eur. Radiol. Vol. 15, pp. 41-46, 2005, with Toshiba Aquilion; M Cohnen et al., "Radiation Exposure of Patients in Comprehensive Computed Tomography of the Head in Acute Stroke," AJNR Am. J. Neuroradiol. Vol. 27, pp. 1741-1745, Sep 2006, with Siemens Somatom Sensation 64; Sung Won Youn et al., "Perfusion CT of the Brain Using 40-mm Wide Detector and Toggling Table Technique for Initial Imaging of Acute Stroke," AJR Vol. 191, pp. W120-W126, Sep 2008, with Philips Brilliance 64; Anisa Mnyusiwalla, Richard I. Aviv, and Sean P. Symons, "Radiation dose from multidetector row CT imaging for acute stroke," Neuroradiology Vol. 51, No. 10, pp. 635-640, Oct 2009, with GE LightSpeed VCT. Improving QA in CT

  12. 11. Fred A. Mettler et al., “Radiation Injuries after Fluoroscopic Procedures,” Seminars in Ultrasound, CT, and MRI Vol. 23, No. 5, pp. 428-442, October 2002. 12. From data summarized by Stanley H. Stern, Nationwide Evaluation of X-Ray Trends (NEXT) Tabulation and Graphical Summary of 2000 Survey of Computed Tomography, CRCPD Publication E-07-2, (Conference of Radiation Control Program Directors, Inc., Frankfort KY, 2007), http://www.crcpd.org/Pubs/NEXT_docs/NEXT2000-CT.pdf. 13. Benchmark Report CT 2006, (IMV Medical Information Division, Inc., Des Plaines IL, 2006). 14. Alan Zarembo, “Cedars-Sinai radiation overdoses went unseen at several points,” Los Angeles Times, October 14, 2009, http://www.latimes.com/news/local/la-me-cedars-sinai14-2009oct14,0,5065886.story. 15. Stanford University School of Medicine, Profile, “Geoffrey D. Rubin, M.D.,” downloaded November 15, 2009, http://med.stanford.edu/profiles/Geoffrey_Rubin. 16. University of Southern California Viterbi School of Engineering, Aviation Safety & Security, “Dr. Najmedin Meshkati,” January 17, 2007, http://viterbi.usc.edu/aviation/bios/meshkati.htm. 17. See, for example, the following references and citations therein: Joel E. Gray et al., “Reference Values for Diagnostic Radiology: Application and Impact,” Radiology Vol. 235, No. 2, pp. 354-358, May 2005; A.R. Roda, M.C. Lopes, and A.M. Fausto, “Diagnostic Reference Levels in Computer Tomography at IPOCFG, EPE,” World Congress on Medical Physics and Biomedical Engineering, September 7 - 12, 2009, Munich, Germany, IFMBE Proceedings, Vol. 25/III, pp. 26-29, Olaf Dössel and Wolfgang C. Schlegel (Eds.), Springer 2009; R. Treier et al., “Diagnostic Reference Levels in Computed Tomography in Switzerland,” ibid., pp. 146-149. Improving QA in CT

  13. 18. See, for example, S. Balter et al., “A pilot study exploring the possibility of establishing guidance levels in x-ray directed interventional procedures,” Medical Physics Vol. 35, No. 2, pp. 673-680, 2008. 19. See, for example, Donald L. Miller et al., “Radiation Doses in Interventional Radiology Procedures: The RAD-IR Study Part II: Skin Dose,” J. Vasc. Interv. Radiol. Vol. 14, No. 8, pp. 977-990, Aug 2003; and M. Victoria Marx, “The Radiation Dose in Interventional Radiology Study: Knowledge Brings Responsibility,” ibid., pp. 947-951. 20. See, for example, Robert L. Dixon et al., “Comprehensive Methodology for the Evaluation of Radiation Dose in X-ray Computed Tomography,” Report of AAPM Task Group 111 on the future of CT dosimetry, submitted for publication in Medical Physics, 2009. 21. Guidance for Industry:Guidance for the Submission Of Premarket Notifications for Magnetic Resonance Diagnostic Devices, U.S. Dept. Health and Human Services, Food and Drug Administration, Center for Devices and Radiological Health, November 14, 1998, http://www.fda.gov/MedicalDevices/DeviceRegulationandGuidance/GuidanceDocuments/ucm073817.htm. 22. Iacovos S. Kyprianou et al., “Noise and signal detection in digital x-ray detectors using the spatial definition of SNR,” Proc. SPIE Vol. 7258, 725819 (2009); doi:10.1117/12.813843, published online March 14, 2009. Improving QA in CT

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