# Presentation: 543057

## Radiation Dosimetry in X-Ray Computed Tomography (CT):

**Standardization and Regulation**
- Stanley H. Stern, Ph.D.
- Center for Devices and Radiological Health
- Food and Drug Administration
- presented to the
*Technical Electronic Products Radiation Safety Standards Committee*
- Rockville, Maryland
- May 17, 2001

## Purpose

- FDA activities and current thinking about recent CT developments
- _radiological practice_
- excess dose to pediatric patients—*ongoing*
- interventional applications (perfusion studies, CT fluoroscopy)—*coming*
- _rapid technological change_
- multi-slice helical scanning—*here and now*
- adaptive x-ray tube current modulation—*on the horizon*
- _revision of industry consensus standards_—*imminent*?
- nomenclature
- dose-index display
- _guidance and regulation_
- EU quality assurance criteria/ICRP reference levels—*current/prospective*
- ACR/AAPM reference levels—*prospective*
- Amendments to FDA performance standard for CT—***?***

## Pediatric CT Dose

_*American Journal of Roentgenology*_1-4
- Common practice for pediatric patients:
**no re-adjustment** of CT scanner parameters previously used for adults 
- needlessly excessive radiation to smaller, thinner patients!
- Practical solution:
- Reduce x-ray tube current according to the patient weight 
**no loss** of diagnostic or interventional efficacy!
_*American College of Radiology*_
*ACR Bulletin*5 alerted radiologists
*ACR* CT Facility Accreditation Program
- will evaluate ability to minimize radiation, produce high-quality scans
- Current *ACR* standard6 for thoracic CT 
*increased* table increment or **pitch**, low mA, partial scans, short scan times

## Current FDA Activities in CT

- _Nationwide Evaluation of X-Ray Trends (__*NEXT*__) '00- '01 CT Survey_7-9
**Q:** Dedicated techniques (e.g., filter, kVp, mA, scan time) for pediatric patients ?
**A:** Preliminary returns, 34 States 
**43%** of 157 facilities use dedicated pediatric technique
- _CDRH recommendations, reviews: reference values, consensus stds._
- ICRP draft,* Managing Patient Dose in Computed Tomography* (12/00)
- IEC draft 60601-2-44 Ed. 2, *Safety of X-Ray Equipment for CT* (4/01)
- AAPM draft, *Task Group on Reference Values for Diagnostic X-Ray Examinations* (11/00)
- ICRP draft,* Diagnostic Reference Levels in Medical Imaging* (07/01)
- _Handbook of Patient Tissue Doses from CT Examinations_10
- _Research_11
- dose indices and related parameters for single- and multi-slice **helical CT**

## References

- 1. Lee F. Rogers, “From the Editor’s Notebook. Taking Care of Children: Check Out the Parameters Used for Helical CT,” *AJR* Vol. 176, p. 287, February 2001.
- 2. David J. Brenner, Carl D. Elliston, Eric J. Hall, and Walter E. Berdon, “Estimate Risks of Radiation-Induced Fatal Cancer from Pediatric CT,” *AJR* Vol. 176, pp. 289-296, February 2001.
- 3. Anne Paterson, Donald P. Frush, and Lane F. Donnelly, “Helical CT of the Body: Are Settings Adjusted for Pediatric Patients?” *AJR* Vol. 176, pp. 297-301, February 2001.
- 4. Lane F. Donnelly  et al., “Perspective. Minimizing Radiation Dose for Pediatric Body Applications of Single-Detector Helical CT: Strategies at a Large Children’s Hospital,” *AJR* Vol. 176, pp. 303-306, February 2001.
- 5. “One Size Does Not Fit All: Reducing Risks from Pediatric CT,” *ACR Bulletin*, Vol. 57, Issue 2, pp. 20-23, February 2001.
- 6. Eric N. Faerber et al., *ACR Standard for the Performance of Pediatric and Adult Computed Tomography*, American College of Radiology, 1995 (Res. 1), amended 1995 (Res. 24, 53), revised 1998 (Res. 4), effective 1/1/1999.

## 7. Stanley H. Stern, “NEXT 2000: Survey of Computed Tomography (CT) Practice, Workload, Dose,” talk presented at (1) the meeting of the Technical Electronic Products Radiation Safety Standards Committee (FDA Advisory Committee), Rockville, Maryland, June 21, 2000, http://www.fda.gov/ohrms/dockets/ac/00/transcripts/3624t1c.pdf, (pp. 234-258), http://www.fda.gov/ohrms/dockets/ac/00/backgrd/3624b1h.pdf; http://www.fda.gov/ohrms/dockets/ac/00/backgrd/3624b1i.ppt; (2) CDRH Science Grand Rounds, Rockville, Maryland, September 28, 2000.

- 8. Stanley H. Stern, David C. Spelic, and Richard V. Kaczmarek, *NEXT 2000 Protocol for Survey of Computed Tomography (CT)*, December 18, 2000, Conference of Radiation Control Program Directors, Inc. (in press for web publication).
- 9. Stanley H. Stern, Richard V. Kaczmarek, David C. Spelic, and Orhan H. Suleiman, "Nationwide Evaluation of X-Ray Trends (*NEXT*) 2000-2001 Survey of Patient Radiation Exposure from Computed Tomography (CT) Examinations in the United States," abstract submitted for poster presentation at the *87th Scientific Assembly and Annual Meeting of the Radiological Society of North America* (RSNA 2001), Chicago, November 25-30, 2001.

## 10. Stanley H. Stern and Jung Ok Yoon, "Development of a Handbook of Patient Tissue Doses for X-ray  Computed Tomographic Examinations," poster TU-FXH-72 presented at the 2000 World Congress on Medical Physics and Biomedical Engineering, Chicago, July 25, 2000.

- 11. Robert M. Gagne, Stanley H. Stern, Thomas B. Shope, and Henry H. Knox, "Dose Descriptor for Computed Tomography:  Single-Slice Axial Scanning and Beyond," abstract submitted for poster presentation at the *87th Scientific Assembly and Annual Meeting of the Radiological Society of North America* (RSNA 2001), Chicago, November 25-30, 2001.