B J Conway

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.

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.

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).

Energy and rate dependence of diagnostic x ray exposure meters

Variations in x-ray exposure measurements among a variety of contemporary diagnostic exposure meters are investigated. Variations may result from systematic errors due to calibration, beam-quality dependence and exposure-rate dependence. It is concluded that the majority of general purpose diagnostic meters will agree to within 10% of each other if exposure rates are below 1.3 mC kg-1S-1 of air (5 R s-1) and beam qualities are typical for general purpose radiology, excluding mammography. For exposure rates comparable to those in barium enema radiography the variations can range up to 25% or more. Variations up to 40% were observed among general purpose exposure meters at mammographic beam qualities. In the mammographic range, mammographic (thin window) exposure meters varied by no more than 2%.

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.

Results Of A Six-State Pilot Study To Collect Exposure, Technique And Processing Data In Chest Radiography

The routine measurement of exposures for a reference dimension patient in diagnostic radiology is regarded as an important part of an effective quality assurance program. The most frequent radiologic examination conducted in the United States is chest radiography. If manual techniques are used to conduct the exam, the procedure for measuring exposure to the reference patient is straight-forward. However, if automatic exposure controlled (AEC) techniques are used, a patient-equivalent chest phantom must be employed to reproducibly attenuate the x-ray beam. This is of particular importance if exposures are to be compared among AEC systems with different entrance x-ray spectra. Exposure monitoring is just part of the quality assurance story. Radiographic techniques, filtration, scatter reduction, film/screen use, and film processing performance (among other factors) must also be assessed, in order to effectively evaluate and modify these exposures so that they provide appropriate image quality. The first four factors are relatively easy to determine through measurement or documentation. Poor processor performance, potentially a major cause of abnormally high patient exposure, is more difficult to assess. We have designed, constructed and tested a Lucite/aluminum patient-equivalent attenuation chest phantom (LucAl) to use in the estimation of standard posteroanterior (22-23 cm) patient exposures for both manual and AEC chest systems. A sensitometric procedure that can be used to assess relative processor performance has also been developed. This paper describes these two procedures and their use in a six-State pilot study to monitor and evaluate exposure, technique and processor data in chest radiography. Results from approximately 200 chest systems will be summarized.