Portal Image: From 1 Different Sources
an electronic image taken during radiotherapy treatment to verify the position of radiation beams.
Raised blood pressure in the PORTAL VEIN entering the LIVER. This results in increased pressure in the veins of the oesophagus and upper stomach and these grow in size to form varices – dilated tortuous veins. Sometimes these varices rupture, causing bleeding into the oesophagus. The raised pressure also causes ?uid to collect in the abdomen and form ASCITES. The commonest reason for portal hypertension is cirrhosis (?brosis) of the liver (see LIVER, DISEASES OF). THROMBOSIS in the portal vein may also be a cause. Treatment requires the cause to be tackled, but bleeding from ruptured vessels may be stopped by injecting a sclerosant or hardening solution into and around the veins. Sometimes a surgical shunt may be done to divert blood from the portal vein to another blood vessel.... portal hypertension
A vein or collection of veins which ?nish at both ends in a bed of capillary blood vessels. An important example is the hepatic portal system, comprising the portal vein and its tributaries. Blood from the stomach, pancreas, spleen and intestines drains into the veins that join up to comprise the portal vein into the liver, where it branches into sinusoids.... portal system
A person’s perception of the different parts of his or her own body.... body image
This is a type of circulatory bypass used when substances in blood or fluid need to be kept out of the general flow. A portal system begins in capillaries and ends in capillaries, and nothing leaves it undocumented. The hypothalamus sends hormones into the portal system between it and the pituitary, and the pituitary responds to it by secreting its own hormones, but dissolving the hypothalamus ones. Blood that leaves the intestinal tract, spleen, and pancreas (partially) goes into the liver’s portal system and does not leave that organ until it has been thoroughly screened and altered.... portal circulation
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
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.... analogue image
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
(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
adj. 1. relating to the portal vein or system. 2. relating to a porta.... portal
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
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
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