No abstract

The validation shows that the image quality of a digital mammography image obtained with a particular system can be degraded, in terms of noise magnitude and color, sharpness, and contrast to account for differences in the detector and antiscatter grid. Potentially, this is a powerful tool for observer studies, as a range of image qualities can be examined by modifying an image set obtained at a single (better) image quality thus removing the patient variability when comparing systems.

Pharyngeal videofluoroscopy (VTF) is a well-recognized technique for investigating and assessing swallowing disorders. There is, however, a paucity of data available regarding the radiation dose to patients during such procedures, but there is general concern that fluorographic imaging modalities are associated with significant radiation exposure. We have recorded the dose received by 23 patients undergoing VTF in our department using a Dose-Area Product (DAP) Meter and have used the data to calculate the effective dose to the patients. The mean effective dose is 0.4 mSv (range 0.027-1.1) which compares favorably with the effective doses associated with other common radiological procedures. We therefore conclude that the radiation detriment associated with pharyngeal VTF is well within acceptable levels.

While patient entrance surface dose rate is an important indicator of dose performance for fluoroscopic units, there has been no standardized approach to measuring this. Since results are strongly dependent on the type of phantom used and the relative positions of the X-ray tube, intensifier and phantom, comparisons of the performance for different units are difficult to make. This document sets out a protocol for making these measurements using a standard phantom and standard configurations for different types of X-ray unit Values of dose rates which might be expected are given.

Currently photostimulable phosphor computed radiography (PPCR) promises to be the digital X-ray image acquisition technology of choice for classical radiography (i.e. X-ray examinations of natural anatomy). For the last two years we have been carrying out a physical evaluation of modern PPCR technology and some of our findings relevant to general radiographic applications are reviewed here. Topics covered include the function of the auto-reader system and the reliability of image reproduction, the radiation exposure requirement and physical image quality. The latter is based upon both objective and subjective measures of image quality. These studies have yielded a favourable comparison of the image quality of modern PPCR technology with that of medium-speed and fast radiographic screen-film combinations. The major advantages of PPCR appear to be the maintenance of high imaging efficiency (DQE) over a much wider range of signal levels than film and consistent image acquisition and presentation independent of exposure level. In general radiographic applications no major limitations due to the comparatively modest limiting spatial resolution of PPCR [maximum limiting resolution = 5 line-pair mm-1] have been experienced. Digital image enhancement is a central element of PPCR image reproduction. The authors believe that advances in image enhancement algorithms remain a potential area for further improving the presented quality of PPCR images.