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 1990 survey 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

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5 Computed Tomography Since 1990 Technological advances slip rings 11  helical scanning high heat-capacity x-ray tubes 18  CT fluoroscopy e-beam 22 & multi-slice helical CT 23, 24  ultra-fast scanning

6 Computed Tomography Since 1990 (continued) Complexity: many different… clinical applications covering the body 25, 26 various protocols for any particular exam or intervention scanner models, options, and non-standardized terminology 23, 30

7 NEXT 2000 Survey Design 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 kV p, 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 dose 32

8 NEXT 2000 Survey Design 31 (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

Patient Tissue Doses Example 33, 34 using CT Database 32 Normalized Single-Scan Dose vs. Scan Location for GE 8800/9000 Scanners testicles ovaries breasts thyroid lungs marrow

10 Under Development: 33, 34 CT Handbook 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 Approach 35 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