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Biomedical subjects

P F Butler

Publications and source records attributed to P F Butler.

8 recordsLinked to original sources
PubMed1985

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.

Animals↗
PubMed1979

The status of film/screen mammography. Results of the BENT study.

Results of the Breast Exposure: Nationwide Trends (BENT) study are presented. In this study, data were collected from 42 states and several other jurisdictions and the number of facilities found to have unusually high or low exposures during mammography was determined. Surveyors trained by representatives of the Bureau of Radiological Health then worked with these facilities to determine the source of the problem and recommend corrective measures. Contrast was found to be reduced by high "inherent" filtration, high kVp, or inappropriate imaging conditions, while resolution was impaired by excessive exposure time, as well as inappropriate imaging conditions. These and other problems are discussed and correlated with image quality.

Humans↗
PubMedDate not supplied

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.

Humans↗
PubMedDate not supplied

A clinical evaluation of contrast-detail analysis for ultrasound images.

We report on the reproducibility of human observers' vanishing detection thresholds for visual targets in contrast-detail (C/D) analysis of ultrasound B-mode images. The images used in this study contain visual targets which are circular cross sections of constant-contrast conical structures in the C/D phantom. The vanishing threshold diameters for these targets vary as a function of the perceived size of the imaged target, target-to-background contrast, image noise content, and reproducibility of the decision levels of human observers for repeated observations. Our study indicates that the determination of absolute vanishing threshold diameter values for several targets of different contrast by human observers yields a high degree of error that is not predicted by existing theoretical assumptions based on a static threshold detector. We find that systematic error is introduced by the observers during the course of the experiment and that the levels of sensitivity of the observers differ widely at all times, and increase the amount of total observer error. These results suggest that, due to the large total observer error, C/D analysis may be impractical in a clinical environment, unless there is access to a team of observers specifically and extensively trained in this task. We suggest that a computer-based observer may be more reliable for the objective performance of contrast-detail analysis as a method for evaluating ultrasound image quality and comparison of imaging systems.

Humans↗
PubMedDate not supplied

MQSA (Mammography Quality Standards Act) update--focusing on quality assurance.

To have uniform national standards, Congress passed the Mammography Quality Standards Act (MQSA) in 1992. Screening and diagnostic facilities must now meet minimum quality standards for personnel, equipment and recordkeeping, and be certified by the FDA, the federal agency designated to implement MQSA. The FDA is responsible for developing final standards, approving accrediting bodies, certifying all mammography facilities in the U.S., evaluating the effectiveness of the program, and implementing sanctions for noncompliant facilities. Congress recognized the urgent need for national mammography standards, but realized that 10,000 mammography facilities could not be certified to meet the regulations before October 1, 1994. President Clinton signed legislation granting the FDA Interim Rule authority and allowing the FDA to adopt existing standards from the ACR, HCFA and state regulations. The Final Rules have significant changes in the Quality Assurance (QA) Sections (900.12 d and e) and indicate where staff must now conduct, document and evaluate the results of QA tests, taking responsibility for establishing and maintaining a QA program that ensures safety, reliability, clarity and accuracy of the mammography services they perform. The Rules also specify the roles of interpreting physicians, medical physicists and quality control technologists. Data indicates that such regulation has improved mammography in the U.S. By January 1997, the Government Accounting Office reported that 1,500 facilities had undergone two rounds of MQSA inspections. During the first year of MQSA, 26 percent had significant violations, while only 10 percent did on the second round.

Accreditation↗
PubMedDate not supplied

Breast exposure: nationwide trends; a mammographic quality assurance program--results to date.

BENT (Breast Exposure: Nationwide Trends), a federal-state sponsored mammographic quality assurance program has demonstrated that unproductive radiation exposure can be reduced by identifying and correcting problems that result in poor image quality. BENT provides clinical personnel with knowledge on the performance of their mammographic system as a basis for possible improvements in image quality and for reductions in patient exposure.

Female↗
PubMedDate not supplied

Simple methods to reduce patient exposure during scoliosis radiography.

Radiation exposure to the breasts of adolescent females can be reduced significantly through the use of one or all of the following methods: fast, rare-earth screen-film combinations; specially designed compensating filters; and breast shielding. The importance of exposure reduction during scoliosis radiography as well as further details on the above described methods are discussed. In addition, the early results of a Center for Devices and Radiological Health study, which recorded exposure and technique data for scoliosis radiography, is presented.

Adolescent↗