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This article reviews the design and operation of both flat-panel detector (FPD) and image intensifier fluoroscopy systems. The different components of each imaging chain and their functions are explained and compared. FPD systems have multiple advantages such as a smaller size, extended dynamic range, no spatial distortion, and greater stability. However, FPD systems typically have the same spatial resolution for all fields of view (FOVs) and are prone to ghosting. Image intensifier systems have better spatial resolution with the use of smaller FOVs (magnification modes) and tend to be less expensive. However, the spatial resolution of image intensifier systems is limited by the television system to which they are coupled. Moreover, image intensifier systems are degraded by glare, vignetting, spatial distortions, and defocusing effects. FPD systems do not have these problems. Some recent innovations to fluoroscopy systems include automated filtration, pulsed fluoroscopy, automatic positioning, dose-area product meters, and improved automatic dose rate control programs. Operator-selectable features may affect both the patient radiation dose and image quality; these selectable features include dose level setting, the FOV employed, fluoroscopic pulse rates, geometric factors, display software settings, and methods to reduce the imaging time., (© RSNA, 2011.)

The purpose of this study was to evaluate the use of digital x-ray imaging detectors for the measurement of diagnostic x-ray tube focal spot size using a slit camera. Slit camera images of two focal spots for a radiographic x-ray tube were acquired with direct-exposure film (DF) (as specified by the National Electrical Manufacturers Association [NEMA] Standards Publication No. XR 5, 1992), computed radiography (CR) imaging plates, and an a-Si:H/CsI:Tl-based flat-panel (FP) detector. Images obtained with the CR and the FP were acquired over a broad range of detector entrance exposure levels. The DF slit images were evaluated according to NEMA specifications (visually, using a 7x magnifying glass with reticule) by six medical physicists. Additionally, the DF images were digitized and the focal spot sizes obtained from the digital profiles of the slit. The CR and the FP images were analyzed in a manner similar to the digitized DF images. It took less than 20 minutes for a complete CR or FP measurement of focal spot size in two dimensions. In comparison, a typical DF measurement with visual evaluation takes at least 60 minutes, in our experience. In addition to a great reduction in measurement time achieved by using digital detectors, the tube loading requirements were reduced to approximately 20 mAs compared with approximately 1000 mAs when using the DF technique. The calculated focal spot sizes for CR and FP differed from those of digitized DF by -2.4% to +4.8% (sigma=2.5%), far less than the -16.6% to +9.3% (sigma=8.1%) variability introduced by the visual evaluation of the slit image. In addition, the calculated focal spot sizes for the CR and the FP images maintained a coefficient of variation <1.0% over the broad range of exposure levels. Based upon these results, we conclude that (1) FP and CR detectors yield consistent results in measurements of x-ray tube focal spot sizes, (2) compared to DF, CR and FP significantly reduce measurement time and tube loading requirements, (3) CR and FP readily permit digital profile analysis, thereby eliminating observer error, and (4) unlike DF, CR and FP are independent of exposure level.

Objective: The purpose of this investigation was to describe the extent to which dental schools use materials, equipment, and quality-assurance protocols that reduce radiation exposure to patients., Study Design: Questionnaires soliciting information regarding intraoral and extraoral radiographic practices and quality-assurance procedures were sent to the directors of oral and maxillofacial radiology (OMR) at the 65 schools of dentistry in the United States and Canada., Results: The response rate was 100%. E-speed film is used at 86% of institutions. Direct digital radiography is used at 58% of institutions for intraoral imaging and 11% for extraoral radiography. Other dose-reducing techniques include long source-film distances (88%), rectangular beam limitation (47%), leaded aprons (95% for extraoral films; 85% with thyroid collars for intraoral films), and rare earth intensifying screens (100%). The most commonly used tube potential is 70 kVp (88%). The director of OMR is solely responsible for radiographic policies at approximately 75% of institutions. Regular tests for film fog, speed, and contrast are done at roughly 75% of schools, while over 90% test darkroom lighting and x-ray equipment., Conclusions: Some dose-reducing strategies are commonly used in dental schools, while others have not gained wide acceptance.

The guidelines of the committee on health protection in medical exposure contain, as required by the international commission on radiation protection, the requirement for the determination of values for reference levels for medical exposure, their use, and their fulfillment. Here we discuss the basis for their determination and point out that their control only appears to be meaningful in combination with quality requirements for which parameters are given in the guidelines of the German Medical Chamber and the European Guidelines.

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.

Chest image quality is of three types: image attractiveness, physical measurement, and diagnostic yield measurement. Each is important, but it is the Georgetown group's opinion that it is the improvements in diagnostic yield that can result from the reconstruction of a single set of digital information with different image algorithms, each selected as best for a particular suspected disease, that will drive the conversion from conventional film radiography to storage phosphor plate radiography and that it is a combination of the need for the dissemination of images within hospitals and the desire to view several different reconstructions of chest digital data that will lead to chest radiographic images being interpreted on workstations. In its current form CR has been shown to be equivalent in diagnostic yield to FR. As better reconstruction algorithms are tested and proved, they are expected to demonstrate better diagnostic yield than FR.

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.