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NEXT 2000: Survey of Computed Tomography (CT) Practice, Workload, Dose Stanley H. Stern, Ph. D.

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

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NEXT 2000: Survey of Computed Tomography (CT) Practice, Workload, Dose Stanley H. Stern, Ph. D.

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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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