Analogue Image: From 1 Different Sources
a traditional X-ray image on film that is in shades that range smoothly from black to white with no appreciable steps from one shade of grey to the next (see grey scale). Analogue images can be converted to digital format (see digitization) for manipulation and storage by computers and other electronic devices.
A synthetically produced agent with the same properties as LUTEINISING HORMONERELEASING HORMONE (LHRH).... lhrh analogue
A person’s perception of the different parts of his or her own body.... body image
n. an impression of an image that is registered by the brain for a brief moment after an object is removed from in front of the eye, or after the eye is closed. A positive afterimage, which lasts a few seconds, retains the colour and brightness of the original image; the more common negative afterimage lasts longer and has colours and brightness that are complementary to the original.... after-image
n. a drug that differs in minor ways in molecular structure from its parent compound. Examples are *calcipotriol (an analogue of vitamin D), *betahistine (an analogue of histamine), and the *gonadorelin analogues. Useful analogues of existing drugs are either more potent or cause fewer side-effects. *Carboplatin and *oxaliplatin, for example, are less toxic analogues of *cisplatin.... analogue
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
see gonadorelin analogue.... gnrh analogue
(GnRH analogue, LHRH analogue) any one of a group of analogues of *gonadotrophin-releasing hormone (gonadorelin), which stimulates release of the gonadotrophins luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary gland. They are more powerful than the naturally occurring hormone, initially increasing the secretion of gonadotrophins by the pituitary: this acts to block the hormone receptors and to inhibit the release of further gonadotrophins, which suppresses production of oestrogens and androgens. Gonadorelin analogues include *buserelin, *goserelin, leuprorelin, and triptorelin. They are used in the treatment of endometriosis, fibroids, and some types of infertility. GnRH analogues are also used in the treatment of advanced prostate cancer. After causing an initial rise in plasma testosterone for approximately ten days the level then falls to the same low level as that achieved by castration. Because the initial flare in testosterone may cause an acute enlargement of the cancer, *anti-androgens are given usually for the first two weeks following the first injection of the gonadorelin analogue.... gonadorelin analogue
(IGRT) the process of imaging during a course of radiation treatment to verify the internal position of the target in comparison to the initial planning scan. This enables adjustment of *treatment fields to improve coverage and allows the use of smaller treatment volumes. The possible methods for IGRT include cone beam CT, *tomotherapy, *cyberknife, and ultrasound and kilovoltage X-rays of implanted fiducial markers.... image-guided radiotherapy
see computer-assisted surgery.... image-guided surgery
n. the production of vivid mental representations by the normal processes of thought. Eidetic imagery, more common in children than adults, is the production of images of exceptional clarity, which may be recalled long after being first experienced.... imagery
see 3-D magnetic imager.... magnetic imager
an electronic image taken during radiotherapy treatment to verify the position of radiation beams.... portal image
an instrument that harnesses magnetic technology to give a virtual image of an endoscope during colonoscopy. It aids steering and minimalizes looping of the endoscope. An external antenna tracks the magnetic field generated by coils built inside the endoscope, enabling real-time 3D imaging of this instrument. Trade name: ScopeGuide.... 3-d magnetic imager
an electronic device that provides a TV image from an X-ray source. The X-rays strike a fluorescent screen after passing through the patient, giving off electrons, which are accelerated using an electron lens before striking a second fluorescent screen, which is usually attached to a video camera. The acceleration of the electrons amplifies the signal from the original image, giving a brighter picture, so that the radiation dose can be reduced. Images can be taken from the camera to be observed in real time on a video monitor or, using a brief higher-dose exposure, to provide a more detailed static image (see digital spot imaging).... image intensifier
Health Encyclopedia