Radiation doses in pediatric radiology: influence of regulations and standards.

The benefits of x-ray examinations contribute to the quality of modern medicine; however the risk of using x-rays, a carcinogen, has always been a concern. This concern is heightened for pediatric patients, who have a much greater sensitivity to the carcinogenic effects of radiation than adults. The principle of as low as reasonably achievable, or ALARA, is essential for minimizing the radiation dose patients receive, especially for pediatric patients. In order to keep radiation doses ALARA, one must know the dose patients receive. The determination of radiation dose in a standard way is therefore necessary so that these doses can be compared with practice, and for meaningful comparison against voluntary standards. In extreme situations, where public health needs may require mandatory standards, or regulations, the quantitative measurement and calculation of radiation dose becomes essential. How some radiation dose metrics and standards have evolved, including the value of different metrics such as entrance air kerma, organ dose, and effective dose will be presented. Recent pediatric x-ray studies, whether or not dedicated pediatric equipment is necessary, and recent initiatives by the Food and Drug Administration for pediatric population will be discussed.

Results of a nationwide survey of chest radiography: comparison with results of a previous study.

PURPOSE: To provide public health information by means of measurement of the radiation exposures that patients undergoing chest radiography would receive and to compare the results with those of a similar previous survey. MATERIALS AND METHODS: Surveyed facilities were randomly selected from each state. Patient exposure was evaluated along with film processing, half-value layer, and image quality. Additional information obtained concerned type of equipment, facility work load, radiographic technique, screen-film system, and grid type. RESULTS: Mean entrance air kerma in all facilities was 141 microGy (16.1 mR). Mean kilovoltage in all facilities was 101 kV. In 1994, 140 (90%) of 156 hospitals (vs 71% in 1984) and 92 (58%; nearly double the percentage in 1984) of 159 nonhospital sites were using grids. Scoring with the imaging test tool resulted in a mean spatial resolution of 2.3 cycles per millimeter, and a mean low-contrast sensitivity of about 3%. Two hundred fifty-three (80%) of 315 facilities surveyed were processing film at minimum acceptable performance levels. CONCLUSION: Mean entrance air kerma for all facilities did not substantially change. Although increased grid usage would lead to the expectation of higher measured exposures, this was offset by an increase in the use of faster screen-film combinations.

Radiographic trends of dental offices and dental schools.

BACKGROUND: A survey of private practice facilities in the United States that perform dental radiography was conducted in 1993 and repeated in dental schools in 1995-1996. METHODS: Both surveys were conducted as part of the Nationwide Evaluation of X-ray Trends, or NEXT, survey program. A representative sample of dental facilities from each participating state were surveyed, and data on patient radiation exposure, radiographic technique, film-image quality, film-processing quality and darkroom fog were collected. RESULTS: The authors found that dental schools use E-speed film more frequently than do private practice facilities. The use of E-speed film and better film processing by dental schools resulted in lower patient radiation exposures without sacrificing image quality. The authors also found that dental school darkrooms had lower ambient fog levels than did those of private practice facilities. CONCLUSIONS: The distribution for the 1993 NEXT survey facilities was greater than that observed for dental schools for radiation exposure, film-processing quality and darkroom fog. Dental schools, in general, had better film quality and lower radiation exposures than did private practice facilities. PRACTICE IMPLICATIONS: Facilities need to emphasize better quality processing and the use of E-speed film to reduce patient exposure and improve image quality.

Mammography in the 1990s: the United States and Canada.

PURPOSE: To evaluate trends in mammography quality before and after the implementation of the Mammography Quality Standards Act (MQSA) of 1992 and to compare technical data collected in the United States with corresponding data obtained from the first survey of mammography facilities conducted in 1994-1995 in Canada. MATERIALS AND METHODS: Data from MQSA inspections conducted in 1995-1997 were analyzed and compared with survey data on U.S. mammography facilities acquired before the MQSA. Technical indicators of mammography quality such as radiation dose phantom image score, film processing, and darkroom fog were analyzed. RESULTS: In the United States, phantom image scores, along with other technical measures of performance such as film processing, darkroom fog, and x-ray beam quality, have improved continuously since 1985. The U.S. mean glandular dose has increased to 1.6 mGy compared with the Canadian dose of 1.1 mGy. The mean total phantom image score with artifact subtraction was 11.1 in Canada in 1994-1995 and 11.8 in the U.S. in 1997. CONCLUSION: Mammography quality is better today than it has been at any other time in the United States. With the exception of radiation dose. Canadian technical measures of performance are comparable to measures before MQSA in the United States.

Patient dosimetry activities in the United States: the nationwide evaluation of X-ray trends (NEXT) and tissue dose handbooks.

In the United States the Food and Drug Administration (FDA) in collaboration with the Conference of Radiation Control Program Directors (CRCPD) and state and local government agencies surveys clinical facilities about X-ray system air kerma and ancillary data related to patient dosimetry for a variety of diagnostic X-ray examinations. The survey program is known as the Nationwide Evaluation of X-ray Trends (NEXT). The survey utilizes reference patient-equivalent phantoms in the collection of comprehensive technical information. With knowledge of the skin-entrance air kerma, specific tissue doses can be calculated. An overview of NEXT and previously published FDA tissue dose handbooks for diagnostic X-ray examinations is presented.

Nationwide survey of fluoroscopy: radiation dose and image quality.

PURPOSE: To determine the average abdominal entrance air kerma, low-contrast sensitivity, and spatial resolution in upper gastrointestinal tract fluoroscopy in the United States. MATERIALS AND METHODS: A random sample of fluoroscopic facilities was selected to be surveyed for the Nationwide Evaluation of X-ray Trends program. Measurements were performed by using a newly developed fluoroscopic phantom. The surveys were conducted by state radiation control personnel. RESULTS: Average air kerma rates 1 cm above the tabletop, free in air, were 43 mGy/min (n = 340). The rate increased to 64 mGy/min when a 1.6-mm-thick copper filter, which simulated the use of barium contrast medium, was added to increase attenuation. The average entrance air kerma, free in air, for radiographs was 3.4 mGy, and an average of 12 radiographs were obtained per examination. Of 352 facilities surveyed, 306 (87%) were able to resolve wire mesh with 20 or more lines per inch. Of 339 facilities for which percentage contrast could be calculated, 192 (57%) had minimum percentage contrast values of 4% or more. CONCLUSION: Spatial resolution for fluoroscopy is adequate for most of the facilities surveyed, but a substantial proportion of facilities could not visualize low-contrast test objects, which strongly suggests image quality problems.

Radiation protection requirements for medical x-ray film.

Previous darkroom shielding requirements for medical x-ray film-assumed that the film should not be exposed to diagnostic x-ray radiation levels greater than 2 microGy (0.2 mR) for the life of the film. Modern medical x-ray films are much less sensitive to ionizing radiation, with most films showing at least an order of magnitude less sensitivity than previously assumed. Conversely, these same films when loaded in cassettes using modern intensifying screens exhibit an order of magnitude greater sensitivity when these cassettes are exposed to ionizing radiation. These data suggest that protection of modern medical x-ray film, stored in a darkroom, may require less shielding than previously assumed. Conversely, film loaded in a cassette will require greater shielding.

National survey of mammographic facilities in 1985, 1988, and 1992.

PURPOSE: To determine trends in mammography in the United States. MATERIALS AND METHODS: A sample of mammographic facilities was selected for each year of the Nationwide Evaluation of X-ray Trends. The same protocol was followed for the 1985, 1988, and 1992 surveys. Data were collected with use of the same imaging phantom for all three surveys and also with a different phantom in the 1988 and 1992 surveys. RESULTS: Of the 356 facilities surveyed in 1992, 59% claimed to be in compliance with the Health Care Financing Administration (HCFA) mammography requirements, 42% were accredited by the American College of Radiology (ACR), and 23% did not hold credentials from either the HCFA or the ACR. Since 1985, there has been a 34% improvement in acceptable phantom image quality score and a 20% decrease in the mean glandular dose. CONCLUSION: Mammography as practiced today is essentially a screen-film technique. Mammographic phantom image quality has improved considerably. The overall mean glandular dose has decreased primarily because of the elimination of xeroradiography.

Automatic film processing: analysis of 9 years of observations.

A survey method known as the sensitometric technique for the evaluation of processing (STEP) has been used to monitor processing speed of over 2,000 automatic film processors in hospitals, private offices, and mammography facilities since 1981. Analysis of data obtained through this program revealed underprocessing at 33% (76 of 231) of observed hospitals in 1987, 7% (13 of 179) of mammography facilities in 1988, and 42% (101 of 241) of private practices in 1989. Underprocessing at mammography facilities decreased from 18% (25 of 139) in 1985, which was contrary to the trend in hospitals. The consequence of underprocessing is higher radiation exposure and a degradation in film contrast. Evaluation of automatic film processors is a necessary part of any comprehensive evaluation of a diagnostic radiography facility. The STEP procedure was designed only as a field survey test; to ensure optimal conditions for obtainment of diagnostic quality radiographs, facilities should perform quality assurance evaluations of their processing equipment and verify that processing recommendations of manufacturers are being followed.

Radiography of the lumbosacral spine: characteristics of examinations performed in hospitals and other facilities.

A survey of 523 facilities performing radiographic lumbosacral spine examinations was conducted as a part of the Nationwide Evaluation of X-Ray Trends program in 1987 and 1989. Average patient radiation exposure was measured by using a standard phantom developed by the Center for Devices and Radiological Health of the Food and Drug Administration, U.S. Public Health Service. Data pertaining to radiographic equipment, film processing, and radiographic techniques were obtained. The overall average entrance skin air kerma was 3.65 mGy (420 mR). Ninety-eight percent (496 of 506) of observed facilities used a grid, 89% (466 of 523) had tube potentials between 70 and 89 kVp, and 67% (280 of 418) used screen-film systems with a speed of 400. The most important finding is that underprocessing of film remains a major concern. Thirty-three percent (78 of 234) of the hospitals, 25% of the radiologists in private practice (four of 16), 33% of the nonradiologist private practitioners (27 of 82), and 48% (69 of 143) of the chiropractors underprocessed their film.

Average radiation dose in standard CT examinations of the head: results of the 1990 NEXT survey.

In 1990, as part of the Nationwide Evaluation of X-ray Trends (NEXT) program, 252 computed tomographic (CT) systems were evaluated to measure radiation doses associated with standard head CT in adults. The multiple-scan average dose (MSAD) was used as the dose descriptor. For most of the systems, the MSAD at the midpoint on the central axis of a standard dosimetry phantom was between 34 and 55 mGy. Doses were as high as 140 mGy, and dose sometimes varied by a factor of two or more for identical CT units. This range indicates that dose can potentially be reduced by careful selection of standard CT techniques. Users of CT systems should be aware of radiation dose delivered with CT, dose ranges associated with different systems, and doses delivered with their particular unit, which requires that dose performance of CT systems be assessed by means of a protocol that allows comparison of data collected for identical and/or different units.

Tissue doses in the upper gastrointestinal fluoroscopy examination.

A method was developed to estimate tissue doses from the upper gastrointestinal fluoroscopy examination. It involved measuring the technical parameters of the clinical examination, partitioning the dynamic examination into a set of discrete x-ray fields, and generating corresponding tissue does tables with an existing computer program. Knowledge of the radiation exposures associated with each of the fields enabled the calculation of tissue doses for the entire dynamic examination. In this limited sample (eight patients), fluoroscopy times ranged from 108 to 183 seconds. Radiation exposures ranged from 2.3 to 7.2 mC/kg (9.1-28 R), thyroid doses from 0.15 to 3.5 mGy (15-350 mrad), uterine doses from 0.16 to 1.0 mGy (16-100 mrad), lung doses from 0.90 to 4.2 mGy (90-420 mrad), and active bone marrow doses from 0.81 to 5.4 mGy (81-540 mrad).

Mammography in the eighties.

Mammography has experienced the greatest change of any existing radiologic examination in recent years. In 1985, as a part of the Nationwide Evaluation of X-Ray Trends (NEXT) program, a national survey was conducted of a statistically selected sample (n = 232) of facilities performing mammography examinations in the United States. By 1988, the number of mammography facilities in the United States had increased to over 6,400, an increase of over 60% from the 1985 level. To assess the consequence of this expansion as well as the impact of recent technological and other significant developments on mammography, a NEXT survey of mammography facilities was repeated in 1988 (n = 226). Screen-film mammography accounted for 83% of the facilities surveyed in 1988, and dedicated equipment dominated screen-film systems (99%). There was a 26% increase in the overall mean phantom image score, over 45% increase in the use of grids, and 10% increase in mean glandular dose for systems using grids.

Average radiation exposure values for three diagnostic radiographic examinations.

National surveys of more than 600 facilities that performed chest, lumbosacral spine, and abdominal examinations were conducted as a part of the Nationwide Evaluation of X-Ray Trends program. Radiation exposures were measured with use of a set of standard phantoms developed by the Center for Devices and Radiological Health of the Food and Drug Administration, U.S. Public Health Service. X-ray equipment parameters, film processing data, and data regarding techniques used were collected. There were no differences in overall posteroanterior chest exposures between hospitals and private practices. Seventy-six percent of hospitals used grids, compared with 33% of private practices. In general, hospitals favored a high tube voltage technique, and private facilities favored a low tube voltage technique. Forty-one percent of private practices and 17% of hospitals underprocessed their film. Underprocessing in hospitals increased from 17% in 1984 to 33% in 1987. Average exposure values for these examinations may be useful as guidelines in meeting some of the new requirements of the Joint Commission on Accreditation of Healthcare Organizations.

Chest radiography: a survey of techniques and exposure levels currently used.

In diagnostic radiology, the routine measurement of exposure levels for a reference patient is an important part of an effective quality assurance program. In the United States, chest radiography is the most frequent examination and has the lowest exposure level of all radiologic examinations. We estimated the amount of exposure an average patient received from both manual and automatic exposure-controlled radiographic techniques by using a "patient-equivalent" chest phantom during measurements. A densitometric procedure was used to assess processor performance. The mean exposure from 194 chest systems was 20 mR (5.16 X 10(-5) C/kg); the mean film density, 1.38; and the mean processing speed, 108. It is interesting to note that a wide range of radiographic techniques, processing conditions, and screen-film speeds are currently being used. With the information given in our study, investigators can begin to identify the problems that lead to unusual exposure levels and, perhaps, poor image quality.

Radiographic film fog in the darkroom.

One of the most common and yet also most preventable problems in the radiology department is unnecessary darkroom fogging of x-ray film, which can degrade image quality to the extent that the procedure must be repeated. Such problems can be overcome by identifying and eliminating sources of fog, such as incorrect safelight filters, excessive safelight wattage, using too many safelights or placing them too close to the work area, light leaks, and indicator lights on telephones, silver recovery units, timers, or other electrical devices.