HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text (PDF) All Versions of this Article: 2352020016v1 235/2/354    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Gray, J. E. Search for Related Content PubMed PubMed Citation Articles by Gray, J. E.

Reference Values for Diagnostic Radiology: Application and Impact¹

¹ From Landauer, 2 Science Rd, Glenwood, IL 60425 (J.E.G.); Baylor College of Medicine, Houston, Tex (B.R.A.); American College of Radiology, Reston, Va (P.F.B.); University of Western Ontario, London, Ontario, Canada (B.B.H.); University of New Mexico, Albuquerque, NM (F.A.M.); Upstate Medical Physics, Victor, NY (R.J.P.); Mayo Clinic and Foundation, Rochester, Minn (B.A.S.); Children’s Hospital, Boston, Mass (K.J.S.); Food and Drug Administration, Rockville, Md (O.H.S.); and Sunnybrook Health Science Centre, Toronto, Ontario, Canada (M.J.Y.). Received February 1, 2002; revision requested March 25; final revision received July 8, 2004; accepted August 4. Address correspondence to J.E.G. (e-mail: jgray@landauerinc.com).
^{2 2}Consultants to the Task Group and the organizations they represent are listed in the Acknowledgments.

	ABSTRACT

TOP ABSTRACT INTRODUCTION NEED FOR RVs DEFINITION OF RVs EUROPEAN AND OTHER EXPERIENCE ADOPTION OF RVs BY... SELECTION OF RVs IMPACT ON THE PRACTICE... SUMMARY REFERENCES

 
Reference values (RVs) are recommended by the American Association of Physicists in Medicine for four radiographic projections, computed tomography, fluoroscopy, and dental radiography. RVs are used to compare radiation doses from individual pieces of radiographic equipment with doses from similar equipment assessed in national surveys. RVs recommended by the American Association of Physicists in Medicine have been developed from the Nationwide Evaluation of X-ray Trends survey performed by the state radiation protection agencies with the cooperation and support of the U.S. Food and Drug Administration, the Conference of Radiation Control Program Directors, and the American College of Radiology. The RVs selected by the American Association of Physicists in Medicine represent, approximately, the 80th percentile of the survey distributions. Consequently, equipment exceeding the RVs is using higher radiation doses than is 80% of the equipment in the surveys. Radiation doses for specific projections, with standard phantoms, should be measured annually, as recommended by the American College of Radiology. When the RVs are exceeded, the medical physicist should investigate the cause and determine, in cooperation with the responsible radiologist, whether these doses are justified or the imaging system should be optimized to reduce patient radiation doses. RVs are a useful tool for comparing patient radiation doses at institutions throughout the United States and for providing information about radiographic equipment performance.

© RSNA, 2005

	INTRODUCTION

TOP ABSTRACT INTRODUCTION NEED FOR RVs DEFINITION OF RVs EUROPEAN AND OTHER EXPERIENCE ADOPTION OF RVs BY... SELECTION OF RVs IMPACT ON THE PRACTICE... SUMMARY REFERENCES

 
Reference values (RVs), or reference levels, were first discussed by the International Commission on Radiological Protection (1). More recently, the International Commission on Radiological Protection has recommended the use of RVs (2).

Quoting from Radiological Protection and Safety in Medicine, International Commission on Radiological Protection publication no. 73 (2):

(100) The Commission now recommends the use of diagnostic reference levels for patients. These levels, which are a form of investigation level, apply to an easily measured quantity, usually the absorbed dose in air, or in a tissue equivalent material at the surface of a simple standard phantom or representative patient... . [T]he diagnostic reference level will be intended for use as a simple test for identifying situations where the level of patient dose or administered activity is unusually high. If it is found that procedures are consistently causing the relevant diagnostic reference level to be exceeded, there should be a local review of procedures and the equipment in order to determine whether the protection has been adequately optimized. If not, measures aimed at reduction of doses should be taken.

(101) Diagnostic reference levels are supplements to professional judgment and do not provide a dividing line between good and bad medicine. It is inappropriate to use them for regulatory or commercial purposes.

(102) Diagnostic reference levels apply to medical exposure, not to occupational and public exposure. Thus, they have no link to dose limits or constraints. Ideally, they should be the result of a generic optimization of protection. In practice, this is unrealistically difficult and it is simplest to choose the initial values as a percentile point on the observed distribution of doses to patients. The values should be selected by professional medical bodies and reviewed at intervals that represent a compromise between the necessary stability and the long-term changes in the observed dose distributions. The selected values will be specific to a country or region.

We wish to emphasize that reference levels or RVs are a voluntary tool to be used by professional colleagues in evaluation of the exposure levels used in their practices. If a facility exceeds an RV, then that facility, in consultation with a medical physicist, should voluntarily investigate the reason for the higher exposure levels and determine whether it is possible to reduce the exposures without sacrificing image quality. If, in light of the particular practice, the radiologist believes these higher levels are justified, then they are considered acceptable.

RVs do not provide a dividing line between the acceptable and unacceptable practice of radiology. For that reason, RVs should not be used in any way for regulatory purposes. They represent a radiation exposure level that, if exceeded, triggers a voluntary investigation into the cause of the higher exposures.

	NEED FOR RVs

TOP ABSTRACT INTRODUCTION NEED FOR RVs DEFINITION OF RVs EUROPEAN AND OTHER EXPERIENCE ADOPTION OF RVs BY... SELECTION OF RVs IMPACT ON THE PRACTICE... SUMMARY REFERENCES

 
The Nationwide Evaluation of X-ray Trends survey of the Food and Drug Administration has been measuring radiation exposures since 1973 (3–6). There has been no active effort, however, by any professional organization to use the information provided by the Food and Drug Administration to establish guidelines for patient radiation exposures. These data clearly show that there is substantial room for improvement, that is, for exposure reductions. The ratios of the maximum to minimum exposures measured in the Nationwide Evaluation of X-ray Trends survey (Table 1) range from 8.8 to as high as 126.7. These ratios are compared with a ratio of 3.6 for mammography. One must ask the following question: Is it really justified for one facility to use an exposure that is 10, 20, or 126 times greater than that used by another facility to produce a radiographic image?

	DEFINITION OF RVs

TOP ABSTRACT INTRODUCTION NEED FOR RVs DEFINITION OF RVs EUROPEAN AND OTHER EXPERIENCE ADOPTION OF RVs BY... SELECTION OF RVs IMPACT ON THE PRACTICE... SUMMARY REFERENCES

A discussion and the actual adult RVs are presented in this report as an introduction to the topic for the medical imaging community in North America. The phantoms and measurement techniques used for the survey data on which the RVs are based are described in the literature (3–7). In addition, details as to measurement techniques, adult phantoms, and methods for reduction of radiation exposure will be provided in a report that is now in preparation from the American Association of Physicists in Medicine Task Group on Reference Values for Diagnostic X-ray Examinations.

	EUROPEAN AND OTHER EXPERIENCE

TOP ABSTRACT INTRODUCTION NEED FOR RVs DEFINITION OF RVs EUROPEAN AND OTHER EXPERIENCE ADOPTION OF RVs BY... SELECTION OF RVs IMPACT ON THE PRACTICE... SUMMARY REFERENCES

 
The European experience with RVs has been encouraging. The European community has published reference values and image quality criteria for a broad range of radiographic projections, and these are being applied throughout Europe (8–11). The National Radiological Protection Board of Great Britain and the Royal College of Radiologists have developed RVs for common diagnostic radiographic projections. A follow-up study showed a 30% decrease in patient exposures for these radiographic projections in England in a 10-year period (12). In its publication for the international radiation protection community, the International Atomic Energy Agency included guidance levels that were based on worldwide data (13). The Conference of Radiation Control Program Directors already has provided guidance in regard to radiation exposure levels, and some states have included maximum exposure levels in their radiation control programs (14).

	ADOPTION OF RVs BY THE AMERICAN COLLEGE OF RADIOLOGY

TOP ABSTRACT INTRODUCTION NEED FOR RVs DEFINITION OF RVs EUROPEAN AND OTHER EXPERIENCE ADOPTION OF RVs BY... SELECTION OF RVs IMPACT ON THE PRACTICE... SUMMARY REFERENCES

 
The concept of RVs was first presented to the Board of Chancellors and Council Steering Committee of the American College of Radiology in early 1997 by the Commission on Medical Physics. The American College of Radiology believes that it is important to implement RVs for the improvement of patient care and to demonstrate its commitment in regard to patient safety and image quality to third-party payers (insurance companies) and to the public. The responsibility for further development was given to the Commission on Standards and Accreditation. During their meeting in January of 1999, the Board of Chancellors and the Council Steering Committee voted to incorporate RVs into the accreditation programs and appropriate standards beginning with the cycle of three new accreditation programs for CT, interventional radiology, and fluoroscopy. These accreditation programs include the measurement of typical patient exposures with patient-simulating phantoms. Exposure data collected during the accreditation process will be available to help the American Association of Physicists in Medicine refine the RVs in the future.

RVs will provide the benchmark with which we can compare radiation exposures for all facilities. RVs will assist us as a profession to optimize radiation exposures to our patients.

	SELECTION OF RVs

TOP ABSTRACT INTRODUCTION NEED FOR RVs DEFINITION OF RVs EUROPEAN AND OTHER EXPERIENCE ADOPTION OF RVs BY... SELECTION OF RVs IMPACT ON THE PRACTICE... SUMMARY REFERENCES

 
RVs have been selected by the American Association of Physicists in Medicine Task Group on Reference Values for Diagnostic X-ray Examinations for nine imaging projections or examinations performed with radiography in adults (Table 3). These projections or examinations were selected because they were considered typical of most imaging procedures. In addition, adequate data had to be available for the projections or examinations selected. Mammography was excluded from the list of RVs, since it is within the purview of the Mammography Quality Standards Act, with regulated maximum mean glandular doses of 300 mGy (300 mrad) for a single view.

In a review of the data, it became apparent that the mean or median exposures seemed to be higher than one might expect. It is important to note, however, that survey data represent state-of-the-practice as opposed to state-of-the-art exposures. Most surveys are performed at randomly selected facilities. These include major medical facilities such as teaching hospitals, as well as small hospitals and medical facilities with a single radiographic unit. The data from these diverse facilities are treated similarly and are given the same weight in the survey. Consequently, the radiation exposure data from a teaching hospital at which 100 chest radiographic examinations are performed per day have the same weight as the data from a small hospital at which three such examinations are performed per day. In fact, the data from the small hospitals or medical facilities may overwhelm those from large or teaching institutions, since there are substantially more small facilities than there are major medical facilities with radiographic units. Unfortunately, we have only state-of-the-practice data to evaluate, and this situation represents where we are but not necessarily where we want to be.

RVs for CT were selected on the basis of available survey data. This selection resulted in the use of the central measurement of the CT dose index for studies of the head (6) and peripheral measurement for CT of the body (7). Although other measures may be more descriptive of some doses in CT, it was necessary to use available survey data in the selection of CT RVs. The CT dose index for the head is based on the data from the Nationwide Evaluation of X-ray Trends survey of the Food and Drug Administration; these data were taken from measurements of a representative sample of CT systems throughout the United States (6). The CT dose index for the body was taken from the Commonwealth of Pennsylvania survey of 105 CT scanners, as these were the only survey data in regard to CT of the body that were available at the time. The RVs were selected by using the 75th–80th percentiles of the survey data. This means that at between 20% and 25% of the facilities radiation exposures will exceed the RVs, and radiologists will need to investigate the reasons for their higher exposures. We believe that these levels will have less of an impact on facilities that maintain good quality control and technical support programs, since the data are from state-of-the-practice surveys. It should be stressed that since these RVs are based on state-of-the-practice data, the RVs selected by using the 75th–80th percentiles of the survey distributions will be slightly high, and these higher RVs provide a natural conservative approach to assisting in the management of patient doses.

	IMPACT ON THE PRACTICE OF RADIOLOGY

TOP ABSTRACT INTRODUCTION NEED FOR RVs DEFINITION OF RVs EUROPEAN AND OTHER EXPERIENCE ADOPTION OF RVs BY... SELECTION OF RVs IMPACT ON THE PRACTICE... SUMMARY REFERENCES

 
Image Quality
Radiation exposure levels and image quality go hand in hand. Although the lowering of radiation exposure levels is a laudable goal, it is essential that an image be produced that contains the diagnostic information necessary for making a clinical decision. Ideally, one would like to develop a list of radiographic examinations that includes both RVs and image quality indicators, as has been done by our European colleagues (8–11). The American Association of Physicists in Medicine Task Group, however, concluded that this would be a difficult and controversial task. The Europeans elected to include nonquantitative image quality indicators, such as small round details in the lung, linear and reticular details that extend out to the lung periphery, and visualization of the spinous processes. Although quantitative image quality measures, such as resolution, modulation transfer function, noise, and Wiener spectra (a measure of image quality as a function of spatial frequency), are available, there are few data that link these values with the clinical effectiveness of the images. Ultimately, the radiologist is the individual responsible for image quality and should ensure that the noise levels are low enough to obtain adequate clinical image quality and diagnostic information. The radiologist should not sacrifice diagnostic image quality in order to reduce patient dose beyond a reasonable level.

Investigation of High Exposures
The direct impact of the RVs on radiology will be the need for about 20%–25% of facilities to perform radiographic examinations to investigate the reason for their higher radiation exposure levels. The medical physicist should compare the measured radiation exposures at the facility with the RVs as part of the annual monitoring recommended by the American College of Radiology (18). As noted before, however, many facilities will probably be small facilities that lack technical support and not major medical centers or hospitals. Radiologists at these facilities must be encouraged to seek appropriate help from medical physicists to review and reduce the exposure levels. Most important, RVs provide reliable benchmark data for comparison with the radiation exposure levels from every radiographic facility in the United States. Although RVs are provided for nine projections or examinations, it will only be necessary to measure and to compare radiation exposures for, at most, five projections in a room where radiography or fluoroscopy is performed and two types of examinations in a CT suite. For automatic exposure control systems, the measurements should be made with the appropriate phantom (preferably one that includes a measure of image quality) and geometry (without backscatter for all examinations but CT), as opposed to being based on estimates provided by the technologists with regard to the techniques used and the calculations made by the medical physicist. The approach for manual exposure control systems would be similar, but the technique would be selected from the technique chart for a patient of specified thickness.

X-ray Tube Life
One potential impact of the RVs and the reduction of patient radiation exposures is on x-ray tube life. It may be possible to increase x-ray tube life by reducing radiation exposures, in the same way that the life of a conventional light bulb is extended if it is used less frequently or at a lower voltage or current level. There are no data in the literature, however, to support this assumption.

	SUMMARY

TOP ABSTRACT INTRODUCTION NEED FOR RVs DEFINITION OF RVs EUROPEAN AND OTHER EXPERIENCE ADOPTION OF RVs BY... SELECTION OF RVs IMPACT ON THE PRACTICE... SUMMARY REFERENCES

 
RVs provide a means for radiologists and medical physicists in the medical imaging community to compare radiation exposure levels at their facilities with those at facilities across the nation, while they bear in mind that the comparative data are state-of-the-practice data as opposed to state-of-the-art data. As imaging professionals, we should also ensure that our medical imaging equipment and practices are optimized and that they provide the necessary diagnostic information with exposures that are as low as reasonably achievable.

	ACKNOWLEDGMENTS

 
Consultants to the American Association of Physicists in Medicine Task Group on Reference Values for Diagnostic X-ray Examinations and the organizations they represent include the following: E. Stephen Amis, Jr, MD, American College of Radiology; John K. Crowe, MD, American Roentgen Ray Society; Fred A. Mettler, Jr, MD, National Council on Radiation Protection and Measurements; Michael Odlaug, MPH, Conference of Radiation Control Program Directors; Keith Faulkner, PhD, National Health Service Breast Screening Programme, Newcastle upon Tyne, England; Donald McLean, PhD, Cumberland College of Health Sciences, Sydney, Australia; and Detlev Richter, PhD, Siemens Medical Systems, Erlangen, Germany.

	FOOTNOTES

 
Abbreviation: RV = reference value

Authors stated no financial relationship to disclose.

	REFERENCES

TOP ABSTRACT INTRODUCTION NEED FOR RVs DEFINITION OF RVs EUROPEAN AND OTHER EXPERIENCE ADOPTION OF RVs BY... SELECTION OF RVs IMPACT ON THE PRACTICE... SUMMARY REFERENCES

 

1. International Commission on Radiological Protection. 1990 recommendations of the International Commission on Radiological Protection. ICRP publication no. 60 Oxford, England: Pergamon, 1991.
2. International Commission on Radiological Protection. Radiological protection and safety in medicine. ICRP publication no. 73 Oxford, England: Pergamon, 1996.
3. Conference of Radiation Control Program Directors. Nationwide Evaluation of X-ray Trends (NEXT): tabulation and graphical summary of 1993 dental survey. CRCPD publication no. 96–3 Frankfort, Ky: Conference of Radiation Control Program Directors, 1996.
4. Conference of Radiation Control Program Directors. Nationwide Evaluation of X-ray Trends (NEXT): summary of 1994 chest radiography survey. CRCPD publication no. 98–2 Frankfort, Ky: Conference of Radiation Control Program Directors, 1998.
5. Conference of Radiation Control Program Directors. Nationwide Evaluation of X-ray Trends (NEXT): tabulation and graphical summary of surveys 1984 through 1987. CRCPD publication no. 89–3 Frankfort, Ky: Conference of Radiation Control Program Directors, 1989.
6. Conference of Radiation Control Program Directors. Nationwide Evaluation of X-ray Trends (NEXT): summary of 1990 computed tomography survey and 1991 fluoroscopy survey. CRCPD publication no. 94-2 Frankfort, Ky: Conference of Radiation Control Program Directors, 1994.
7. Winston JP, Angelo DL. The Pennsylvania computerized tomography study. Health Phys 2000; 78 (suppl 2):S67-S71.
8. European Commission. European guidelines on quality criteria for diagnostic radiographic images. Publication EUR 16260 EN Brussels, Belgium: European Commission, 1996.
9. European Commission. European protocol on dosimetry in mammography. Publication EUR 16263 EN Brussels, Belgium: European Commission, 1996.
10. European Commission. European guidelines on quality criteria for diagnostic radiographic images in paediatrics. Publication EUR 16261 EN Brussels, Belgium: European Commission, 1996.
11. European Commission. Quality criteria for computed tomography: working document. Publication EUR 16262 Brussels, Belgium: European Commission, 1997.
12. Hart D, Hillier MC, Wall BF, Shrimpton PC, Bungay D. Doses to patients from medical x-ray examinations in the UK: 1995 review. Publication NRPB-R289 Oxon, England: Chilton, Didcot, 1996.
13. International Atomic Energy Agency. International basic safety standards for protection against ionizing radiation and for the safety of radiation sources. Safety series, no. 115-I Vienna, Austria: International Atomic Energy Agency, 1994.
14. Conference of Radiation Control Program Directors. Average patient exposure-dose guides. CRCPD publication no. 92–4 Frankfort, Ky: Conference of Radiation Control Program Directors, 1992.
15. Radiation protection guidance to federal agencies for diagnostic x rays, 43 Federal Register 4377–4380 1978.
16. Department of Labor and Economic Growth, Family and Health Services, State of Michigan. Patient radiation exposure information. Available at: http://www.michigan.gov/cis/0,1607,7-154-10568_17614_17638-46650–,00.html. Accessed February 8 2005.
17. Burkhart RL. Patient radiation exposure in diagnostic radiology examinations: an overview HHS publication FDA 83–8217. Rockville, Md: Center for Devices and Radiological Health, 1983.
18. ACR technical standard for diagnostic medical physics performance monitoring of radiographic and fluoroscopic equipment. Revised Reston, Va: American College of Radiology, 2001; 729-732.

This article has been cited by other articles:

				W. E. Muhogora, N. A. Ahmed, A. Almosabihi, J. S. Alsuwaidi, A. Beganovic, O. Ciraj-Bjelac, F. K. Kabuya, A. Krisanachinda, M. Milakovic, G. Mukwada, et al. Patient Doses in Radiographic Examinations in 12 Countries in Asia, Africa, and Eastern Europe: Initial Results from IAEA Projects Am. J. Roentgenol., June 1, 2008; 190(6): 1453 - 1461. [Abstract] [Full Text] [PDF]

				L. Lanca, A. Silva, E. Alves, F. Serranheira, and M. Correia EVALUATION OF EXPOSURE PARAMETERS IN PLAIN RADIOGRAPHY: A COMPARATIVE STUDY WITH EUROPEAN GUIDELINES Radiat Prot Dosimetry, April 22, 2008; (2008) ncn144v1. [Abstract] [Full Text] [PDF]

				J.-H. Buhk, E. Elolf, D. Jacob, H.-H. Rustenbeck, A. Mohr, and M. Knauth A Comparison of Angiographic CT and Multisection CT in Lumbar Myelographic Imaging AJNR Am. J. Neuroradiol., March 1, 2008; 29(3): 442 - 446. [Abstract] [Full Text] [PDF]

				P. Bohy, V. de Maertelaer, A. Roquigny, C. Keyzer, D. Tack, and P. A. Gevenois Multidetector CT in Patients Suspected of Having Lumbar Disk Herniation: Comparison of Standard-Dose and Simulated Low-Dose Techniques Radiology, August 1, 2007; 244(2): 524 - 531. [Abstract] [Full Text] [PDF]

				E. Vano, J. M. Fernandez, J. I. Ten, C. Prieto, L. Gonzalez, R. Rodriguez, and H. de Las Heras Transition from Screen-Film to Digital Radiography: Evolution of Patient Radiation Doses at Projection Radiography Radiology, May 1, 2007; 243(2): 461 - 466. [Abstract] [Full Text] [PDF]

				E. SEERAM and P. C. BRENNAN Diagnostic Reference Levels In Radiology. Radiol. Technol., May 1, 2006; 77(5): 373 - 384. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) All Versions of this Article: 2352020016v1 235/2/354    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Gray, J. E. Search for Related Content PubMed PubMed Citation Articles by Gray, J. E.