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.

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.

Attenuation properties of diagnostic x-ray shielding materials.

Single- and three-phase broad-beam x-ray attenuation data have been obtained using lead, steel, plate glass, gypsum wallboard, lead acrylic, and wood. Tube voltages of 50, 70, 100, 125, and 150 kVp were employed and the resulting curves were compared to transmission data found in the literature. To simplify computation of barrier requirements, all data sets were parametrized by nonlinear least-squares fit to a previously described mathematical model. High attenuation half value layers and the lead equivalence of the alternate materials were also determined.

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.

A survey of fluoroscopic exposure rates: AAPM Task Group No. 11 Report.

Fluoroscopic procedures, in general, result in much higher exposures to patients than do most types of radiographic procedures [National Council on Radiation Protection, Report 100, p. 31 (1989)]. In spite of this, fluoroscopic exposure rates can vary widely between systems, and often for no apparent reason. The charge of AAPM Task Group No. 11 was to evaluate fluoroscopic exposure rates at the entrant surface of the x-ray image intensifier, and to disseminate this information so that medical physicists could compare their own exposure rate measurements with typical values. The measurement protocol was defined for various system configurations. Sheets of copper were used to attenuate the x-ray beam, and the input exposure rate at the image intensifier (at the input mode closest to 23-cm diameter) in the absence of a scattering medium was determined. With 2 mm of copper as x-ray beam filtration, the median fluoroscopic exposure rate at the image intensifier was found to be 16.5 nC/kg/s (64.0 microR/s), with an average kV of 77 and mA of 2.0 (n = 62).

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.

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.

A patient-equivalent attenuation phantom for estimating patient exposures from automatic exposure controlled x-ray examinations of the abdomen and lumbo-sacral spine.

The Joint Commission on Accreditation of Healthcare Organizations requires diagnostic radiology facilities to known the approximate amount of radiation received by an average patient during radiographic examinations at the facility. Automatic exposure controlled (AEC) techniques are used for many of these exams, and a standard patient-equivalent phantom is necessary when estimating patient exposure on such systems. This is of particular importance if exposures are to be compared among AEC systems with different entrance x-ray spectra. We have developed a phantom, LucA1 Abdomen, to facilitate determining the average patient exposure from AEC anteroposterior (AP) abdomen and lumbo-sacral (LS) spine radiography. The phantom is relatively lightweight, transportable, sturdy, and made of readily available inexpensive materials (Lucite and aluminum). It accurately simulates the primary and scatter transmission through the soft tissue and L-4 spinal regions of a patient-equivalent anthropomorphic phantom for x-ray spectra typically used in abdomen/LS spine radiography. A clinical evaluation to verify the patient-equivalence of three commercial anthropomorphic phantoms (Humanoid, Rando, 3-M) and two acrylic/aluminum phantoms (ANSI and LucA1 Abdomen) has been conducted. The design and development of the LucA1 Abdomen phantom and the evaluation of all phantoms is described.

Assessment and comparison of chest radiography techniques in the United States and Sweden.

The United States Center for Devices and Radiological Health and the Swedish National Institute of Radiation Protection started a collaborative project in 1983. The purpose of the project was to test the adequacy and practicability of the United States (US) Nationwide Evaluation of X-ray Trends (NEXT) programme in Sweden. The NEXT protocol for the postero-anterior chest projection was modified and expanded to make it both "statistical" and "investigational" (in the US, NEXT gives mainly "statistical" information). All chest X-ray units in Sweden were surveyed in 1986-87. The project showed that the NEXT programme is applicable to countries other than the United States and provides a standardized protocol that enables intercomparison of the radiological techniques. This paper presents the comparison of the radiological techniques used in Sweden and the United States. The results of the investigational modifications made to the protocol used in Sweden are discussed. Recommendations concerning expansion of the NEXT protocol to include these valuable tools for investigational surveys are presented.

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.

Beam quality independent attenuation phantom for estimating patient exposure from x-ray automatic exposure controlled chest examinations.

The periodic assessment of exposures in diagnostic radiology is an important part of a comprehensive quality assurance program. The most frequent radiologic examination conducted in the United States is chest radiography. Automatic exposure controlled (AEC) techniques are often used for this exam, and a standard patient-equivalent chest phantom is useful when estimating patient exposures on such systems. This is of particular importance if exposures are to be compared among AEC systems with different entrance x-ray spectra. Such a phantom has been developed to facilitate surveys of the average patient exposure from AEC posteroanterior chest radiography. The phantom is relatively lightweight and easily transportable, sturdy and made of readily available and relatively inexpensive materials (Lucite and aluminum). It accurately simulates the primary and scatter transmission through the lung-field regions of a patient-equivalent anthropomorphic phantom for x-ray spectra typically used in chest radiography. A clinical evaluation has been conducted to verify the patient equivalence of the phantom. Measurements of patient entrance skin exposure were obtained for a large number of patients on a variety of x-ray systems operated in the AEC mode using one or both lung-field detectors. Comparison of these data with exposure estimates derived from the phantom indicate that the phantom attenuates the x-ray beam in such a way that it can be employed to accurately and consistently estimate the mean exposure of the average patient under a variety of radiographic conditions. The design, development, and evaluation of the patient-equivalent attenuation phantom is described.