| 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) |
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| 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) |
| malignant melanoma: gallium imaging | <radiology> Greater than50% sensitivity for primary and metastatic sites: 73% sensitivity if lesion is greater than 2 cm, 17% sensitivity if less than 2 cm, see: gallium: indications malignant melanoma (12 Dec 1998) |
| gated blood pool imaging | Radionuclide ventriculography where scintigraphic data is acquired during repeated cardiac cycles at specific times in the cycle, using an electrocardiographic synchroniser or gating device. Analysis of right ventricular function is difficult with this technique; that is best evaluated by first-pass ventriculography (ventriculography, first-pass). (12 Dec 1998) |
| ratio imaging fluorescence microscopy | <procedure> A method of measurement of intracellular pH or intracellular calcium levels, using a fluorescent probe molecule (see fura-2), in which the two different excitation wavelengths are used and the emitted light levels compared. If emission at one wavelength is sensitive to the intracellular ion level and emission at the other wavelength is not, then standardisation for intracellular probe concentration, efficiency of light collection, inactivation of probe and thickness of cytoplasm can all be performed automatically. (17 Dec 1997) |
| ventilation/perfusion lung imaging | <radiology> See: ventilation agents, perfusion agents, Biello-Siegel criteria (12 Dec 1998) |
| phantoms, imaging | Devices or objects in various imaging techniques used to visualise or enhance visualization by simulating conditions encountered in the procedure. Phantoms are used very often in procedures employing or measuring x-irradiation or radioactive material to evaluate performance. Phantoms often have properties similar to human tissue. Water demonstrates absorbing properties similar to normal tissue, hence water-filled phantoms are used to map radiation levels. Phantoms are used also as teaching aids to simulate real conditions with X-ray or ultrasonic machines. (12 Dec 1998) |
| myocardial infarct imaging | <radiology> Tc-99m pyrophosphate (PYP) 20 mCi, peak abnormality 2-3 days, often falsely negative before 2 days, abnormal for 7-10 days, mechanism: calcium influx into ischemic cells, PYP incorporated into crystalline structure, analogous to hydroxyapatite see: nuclear cardiology (12 Dec 1998) |
| myocardial perfusion imaging | <radiology> (thallium scanning) thallium (Tl) 201, acts as potassium analog, dose 2.0 - 3.0 mCi at peak exercise, 4% of injected dose reaches myocardium, imaging: exercise (1-5 min), redistribution (3-4 hrs), views: anterior, LAO 45', left lateral, interpretation: normal, reversible abnormalitymost likely to be exercise-induced ischemia, nonreversible abnormalitymost likely to be prior myocardial infarction, reverse redistribution most likely to be normal areas wash out faster, lung activity most likely to be LV failure during exercise see also: dipyridamole test, nuclear cardiology (12 Dec 1998) |
| hepatobiliary imaging | <radiology> The hepatobiliary scan (Tc-99m DISIDA or MBF) is the initial procedure of choice to diagnose acute cholecystitis., Sensitivity 95% False negatives: acalculous cholecystitis, Specificity 95% False positives: non-fasting state, alcoholism, parenteral nutrition (TPN), acute pancreatitis, recent narcotic use, hepatocellular disease (12 Dec 1998) |
| high-resolution imaging | <technique> High Resolution Electron Microscopy is phase contrast microscopy of the atomic structure of materials. In most crystalline inorganic materials and a number of polymeric materials HREM allows the imaging of individual atomic columns. The images can frequently be interpreted in terms of the projected crystal potential, although it is often necessary to match the experimental images with those calculated from multislice algorithms. Allows direct measurement of lattice parameters, inspection of individual defects and grain orientation. (05 Aug 1998) |
| secondary electron imaging | <microscopy> Production of secondary electrons is very topography related. Due to their low energy, 5eV, only secondaries that are very near the surface (less than 10nm) can exit the sample and be examined. Any changes in topography in the sample that are larger than this sampling depth will change the yield of secondaries due to collection efficiencies. Collection of these electrons is aided by using a collector in conjunction with the secondary electron detector. The collector is a grid or mesh with a +100V potential applied to it which is placed in front of the detector, attracting the negatively charged secondary electrons to it which then pass through the grid-holes and into the detector to be counted. When a Secondary Electrons collide with the solid-state saemiconductor detector an 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. (05 Aug 1998) |
| neoplasm: gallium imaging | <radiology> Useful: Hodgkin disease and histiocytic form of NHL poor sensitivity below the diaphragm, Burkitt lymphoma: almost 100% sensitivity, hepatoma: 90% sensitivity, melanoma: 90% sensitivity, leukaemia possibly useful: NHL: good for large and mediastinal lesions, nodal metastases from seminoma and embryonal cell carcinoma: 87% sensitivity, non-small cell lung CA: 85% sensitive not useful: head and neck, GI (especially adenocarcinoma), breast, gynaecological, kiddie tumours see: gallium: indications (12 Dec 1998) |
| nuclear 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) |
| dark field imaging | <microscopy> Using a single diffracted beam to form the image in a transmission electron microscope. This causes all regions of the specimen not of the same crystal structure and orientation as the region which produced the diffracted beam to be represented as very dark in the final image, allowing phase differentiation visually in the transmission electron microscope. (05 Aug 1998) |