a radiological technique that enhances visualization of blood vessels (see angiography). A digitized image is taken before the contrast medium (a ‘mask’) is injected, and this is subtracted by computer from the images taken after contrast injection. Only the blood vessels remain on the image. The technique enables blood-vessel anatomy and blood supply to an organ to be demonstrated more clearly. The quality of the image is very dependent on the patient remaining still, since movement causes severe loss of image (movement *artifact). The technique can also be used in nuclear medicine using two different tracers to look for parathyroid gland tumours.
A radiological technique for detecting osteoporosis (see BONE, DISORDERS OF) in which a beam of X-rays is directed at the bone-area under investigation – normally the spine and hip – and the CALCIUM density measured. If the calcium content is low, preventive treatment can be started to reduce the likelihood of fractures occurring.... quantitative digital radiography
an image made up of *pixels. Each pixel has numbers (digits) to describe its position and shade on the *grey scale. The more shades available, described by the number of computer bits required to store the shade of grey, the more accurately the image represents the original tissue contrast. An 8-bit computer image shows 28 (256) possible shades of grey, close to the maximum the human eye can differentiate. 12-bit (4096 levels of grey) images are of much higher quality and take up more memory. They can be manipulated more easily by computer using image enhancement techniques. Compare analogue image.... digital image
(DR) an alternative to film radiography, by acquiring X-ray images from a large number of individual X-ray detectors on a matrix in a digital format directly. This contrasts with *computerized radiography, in which an *analogue image is taken and then put into a reader to be converted into a *digital image. The technique allows the storage of images and their subsequent retrieval, manipulation, and interpretation using computers (see PACS).... digital radiography
the trading name of the *Health and Social Care Information Centre (HSCIC) since 1 August 2016. It is the national provider of information, data, and IT systems for commissioners, analysts, and clinicians for the National Health Service (England). It also runs the *NHS Choices website.... nhs digital
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