| density gradient centrifugation | <technique> High-speed centrifugation inwhich molecules float at a point wheretheir density equals that in a gradient of cesium chloride or sucrose. (12 Jan 1998) |
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| systolic gradient | The difference in pressure during systole between two communicating cardiovascular chambers, e.g., between the left ventricle and aorta in aortic stenosis. (05 Mar 2000) |
| electrochemical gradient | A measure of the tendency of an ion to move passively from one point to another, taking into consideration the differences in its concentration and in the electrical potentials between the two points; commonly expressed as the additional voltage needed to achieve equilibrium. (05 Mar 2000) |
| ficoll gradient | A density gradient of ficoll (synthetic sucrose polymer) in solution, where concentration of the ficoll varies continuously through the solution. It is often used to separate different types of cells from each other during the process of sedimentation. (09 Oct 1997) |
| field gradient | In magnetic resonance imaging, a magnetic field that varies with location, superimposed on the uniform field of the magnet, to alter the resonant frequency of nuclei and allow recovery of their spatial position. Synonym: field gradient. (05 Mar 2000) |
| adrenal imaging | <radiology> Cortex, I-131 iodo-cholesterol, not widely used due to high rad dose and 4-15 day delayed imaging, medulla, search for pheo, MIBG (I-131 meta-iodobenzylguanidine) (12 Dec 1998) |
| adrenal medullary imaging | <investigation, radiology> A nuclear scan that images the adrenal glands after a radioactive tracer is injected into the bloodstream. This test is useful in detecting a pheochromocytoma, particularly if it not within the adrenal gland. (27 Sep 1997) |
| backscattered electron imaging | <microscopy> The production of backscattered electrons from a sample varies directly with the specimen's average atomic number, higher atomic number elements produce more backscattered electrons than lower atomic number ones. Detection of Backscattered Electrons is achieved by using a donut shaped solid state saemiconductor device mounted on the bottom of the objective lens. When Backscattered Electrons strike the detector electron-hole pairs are created which are then counted. This quantity is translated into a pixel intensity and displayed on the CRT, forming the image. By splitting the detector into halves (or quadrants) differences in the signal level on the individual detector segments provide surface topography information. (05 Aug 1998) |
| blood pool imaging | Nuclear medicine study using a radionuclide that is confined to the vascular compartment. (05 Mar 2000) |
| bone: gallium imaging | <radiology> Increased activity in: active osteomyelitis (90% sensitivity: better than Tc-99m MDP), sarcoma, cellulitis, septic arthritis, rheumatoid arthritis, Paget disease, metastases (65% sensitivity: than for bone agents) see: gallium: indications (12 Dec 1998) |
| bright field imaging | <microscopy> An imaging mode in a transmission electron microscopy that uses only unscattered Electrons to form the image. Contrast in such an image is due entirely to mass-thickness variations in amorphous samples, and may include diffraction contrast in crystalline samples. (05 Aug 1998) |
| cardiac blood pool imaging | This noninvasive test uses radioactive tracers to delineate the hearts chambers and major vessels. It may be used to detect a heart attack, heart muscle function and coronary artery disease. The patient receives a radioactive tracer by injection (into a vein) and then the heart is imaged using a gamma camera. The heart is imaged before and after exercise. This test may be used to detect and evaluate atrial septal defect, dilated cardiomyopathy, congestive heart failure, cardiomyopathy, Lyme disease (secondary), mitral stenosis and superior vena cava syndrome. (27 Sep 1997) |
| radionuclide imaging | Process whereby a radionuclide is injected or measured (through tissue) from an external source, and a display is obtained from any one of several rectilinear scanner or gamma camera systems. The image obtained from a moving detector is called a scan, while the image obtained from a stationary camera device is called a scintiphotograph. (12 Dec 1998) |
| Magnetic Resonance Imaging | A special imaging technique used to image internal stuctures of the body, particularly the soft tissues. An MRI image is often superior to a normal X-ray image. It uses the influence of a large magnet to polarize hydrogen atoms in the tissues and then monitors the summation of the spinning energies within living cells. Images are very clear and are particularly good for soft tissue, brain and spinal cord, joints and abdomen. These scans may be used for detecting some cancers or for following their progress. Acronym: MRI (11 Nov 1997) |
| magnetic resonance imaging, cine | A type of imaging technique used primarily in the field of cardiology. By coordinating the fast gradient-echo mri sequence with retrospective ecg-gating, numerous short time frames evenly spaced in the cardiac cycle are produced. These images are laced together in a cinematic display so that wall motion of the ventricles, valve motion, and blood flow patterns in the heart and great vessels can be visualised. (12 Dec 1998) |