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Overview of 2000 CT Survey: Practice, Workload, and Radiation Dosimetry

This report presents findings from the 2000 nationwide survey on computed tomography (CT) practices, workloads, and radiation doses, authored by Stanley H. Stern, Ph.D. The survey explores technological and clinical advancements in CT since 1990 and encompasses a comprehensive analysis of CT radiation dosimetry. Conducted by the FDA/CDRH, this assessment involved data collection from 350 clinical facilities to evaluate quality assurance and patient safety in imaging practices, while providing insights into patient-equivalent radiation exposure and emerging trends in diagnostic imaging.

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Overview of 2000 CT Survey: Practice, Workload, and Radiation Dosimetry

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  1. NEXT 2000: Survey of Computed Tomography (CT) • Practice, Workload, Dose • Stanley H. Stern, Ph. D. • FDA/CDRH Office of Health and Industry Programs • Division of Mammography Quality and Radiation Programs • Radiation Programs Branch • presented to the • Technical Electronic Product Radiation Safety Standards Committee • Rockville, Maryland, June 21, 2000* • NEXT program, results • Technological, clinical CT advances since 1990survey • 2000 CT survey design—body and head exams • CT radiation dosimetry • CDRH CT handbook of patient doses • *Complete citations for references are provided with the notes to the presentation.

  2. NEXT: Nationwide Evaluation of X-Ray Trends • Cooperative, State-Federal program • quality assurance and radiological-health research • Administered by Conference of Radiation Control Program Directors (CRCPD) • States annually survey ~350 clinical facilities, various diagnostic modalities • Clinical facilities participate voluntarily • CDRH leads scientific, technical aspects and provides training logistics

  3. NEXT: Nationwide Evaluation of X-Ray Trends • (continued) • Nationally representative data • medical x-ray exposure, image quality, clinical practice/patient dose • Random sampling of facilities in States • Patient-equivalent radiation attenuation phantoms • Annual “snapshot” of U.S. x-ray exposure  feedback to facilities, q/a • Trends emerge from results analyzed over time

  4. Computed Tomography Since 1990 • Technological advances • slip rings11helical scanning12-17 • high heat-capacity x-ray tubes18CT fluoroscopy19-21 • e-beam22 & multi-slice helical CT23, 24ultra-fast scanning

  5. Computed Tomography Since 1990 • (continued) • Complexity: many different… • clinical applications covering the body25, 26 • various protocols for any particular exam or intervention27-29 • scanner models, options, and non-standardized terminology23, 30

  6. NEXT 2000 Survey Design31 • 350 facilities, most frequently used CT system • Two parts for each facility • (I) Surveyor on-site: head exams, adult patients • patient workload • capabilities—helical? CT fluoroscopy (for any exam)? • protocols—axial vs. helical scanning? with contrast media? • techniques • kVp, mA, scan time, number of slices, slice width, table increment, • number of revolutions, table feed, pitch • measurements of exposure, time • central hole of CDRH head phantom  MSAD • surface of CDRH head phantom  skin dose, dose rate • free-in-air on axis of rotation  body-tissue dose32

  7. NEXT 2000 Survey Design31 (continued) • Two parts for each facility • (II) Facility questionnaire: head & body exams, adult patients • types of CT units—non-helical, helical, multi-slice, EBCT • patient workload, • scan protocols—axial vs. helical, contrast vs. no-contrast, • techniques • each broken out by exam category • abdomen & pelvis; head; simple sinus; chest/abdomen/pelvis; exams of the skull:facial bones, orbits; spine; liver; kidneys; pancreas; etc. • quality-assurance • servicing and maintenance arrangements • frequency of medical-physicist testing • frequency of specified tests—noise, reproducibility, resolution, sensitivity, measurement of CTDI, etc. • Spreadsheet data entry  electronic file transmission

  8. Patient Tissue Doses Example33, 34 using CT Database32 Normalized Single-Scan Dose vs. Scan Location for GE 8800/9000 Scanners 0.07 testicles thyroid ovaries breasts marrow lungs 0.00

  9. Under Development:33, 34 • CTHandbook of Normalized Tissue Doses • Objectives • Easy to use by medical physicists and radiologists: • -Look-up doses by exam—one table for each kind of exam • -General applicability—one table for any CT model • To include dosimetry upcoming as well as current technology • -axial, helical, fluoroscopic, multi-slice CT • Would address pediatric exams and fetal dose • Technical Approach35 • Generalize data set of National Radiological Protection Board (NRPB, UK)32 • Scanning regions mapped for ~50 distinct exams • Computed tomography dose index (CTDI) to represent system radiation output

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