Duplex imaging Health Dictionary

See MRI.... magnetic resonance imaging

See MRI.... magnetic resonance imaging(mri)

Techniques for providing pictures that show the structure or function of bones. X-ray images are the most commonly used technique for diagnosing fractures and injuries. More detailed information is provided by tomography, CT scanning, or MRI, which can show tumours

cavities; it may be red or yellow. Red bone marrow is present in all bones at birth and is the factory for most of the blood cells. During the teens, red bone marrow is gradually replaced in some bones by less active yellow marrow. In adults, red marrow is confined chiefly to the spine, sternum, (breastbone), ribs, pelvis (hip-bones), scapulae (shoulderblades), clavicles (collarbones), and bones of the skull.

Stem cells within the red marrow are stimulated to form blood cells by the hormone erythropoietin.

Yellow marrow is composed mainly of connective tissue and fat.

If the body needs to increase its rate of blood formation, some of the yellow marrow will be replaced by red.

Sometimes marrow fails to produce sufficient numbers of normal blood cells, as occurs in aplastic anaemia (see anaemia, aplastic) or when marrow has been displaced by tumour cells.

In other cases, marrow may overproduce certain blood cells, as occurs in polycythaemia and leukaemia.... bone imaging

Techniques that provide pictures of the brain; they are used to detect injury or disease and include X-rays, angiography, CT scanning, MRI, PET (positron emission tomography) scanning, and SPECT (single photon emission ). X-ray films can show changes in the skull caused by a fracture or, rarely, by a brain tumour or aneurysm. Angiography shows up the blood vessels in the brain, and is used to investigate subarachnoid haemorrhage, aneurysms, abnormalities of the blood vessels, and other circulatory disorders.

scanning gives images of the brain substance; it gives clear pictures of the ventricles (fluid-filled cavities) and can reveal tumours, blood clots, strokes, aneurysms, and abscesses. is especially helpful in showing tumours of the posterior fossa (back of the skull). and scanning are specialized forms of radionuclide scanning that use small amounts of radioactive material to give information about brain function as well as structure. They enable

blood flow and metabolic activity in the brain to be measured.

Ultrasound scanning is used only in premature or very young babies since ultrasound waves cannot penetrate the bones of a mature skull.... brain imaging

Techniques that provide images of heart structure. Imaging is used to detect disease or abnormalities. A chest X-ray, the simplest and most widely used method of heart imaging, shows heart size and shape, and the presence of abnormal calcification. Pulmonary oedema and engorgement of the vessels connecting the heart and lungs are also usually detectable.

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Echocardiography is useful for investigating congenital heart defects and abnormalities of the valves or heart wall. An ultrasound technique using the Doppler effect allows measurement of blood flow through valves. Radionuclide scanning and CT scanning provide information about the efficiency of heart function. Angiography may be used to show the heart chambers and to assess the condition of the coronary arteries and valves. High-quality images of the heart can be obtained by MRI.... heart imaging

See barium X-ray examinations.... intestinal imaging

Techniques for visualizing the kidneys, usually performed for diagnosis. Ultrasound scanning can be used to identify kidney enlargement, a cyst or tumour, and the site of any blockage. Conventional X-rays show the outline of the kidneys and most kidney stones. Intravenous urography shows the internal anatomy of the kidney and ureters. Angiography is used to image blood circulation through the kidneys. CT scanning and MRI provide detailed cross-sectional images and can show abscesses or tumours. Two types of radionuclide scanning are used for the kidney: DMSA and DTPA scanning. DMSA is a substance given by intravenous injection that binds to cells in the kidney tubule, giving a single, static picture of the kidneys. DTPA, also given intravenously, is filtered in the kidneys and passes out in the urine. Pictures taken at intervals record its passage through the urinary tract and show kidney function. ... kidney imaging

Techniques that produce images of the liver, gallbladder, bile ducts, and blood vessels supplying the liver, to aid the detection of disease.

Ultrasound scanning, CT scanning, and MRI are commonly used.

Radionuclide scanning may reveal cysts and tumours and show bile excretion.

X–ray techniques include cholangiography, cholecystography, and ERCP (endoscopic retrograde cholangiopancreatography).

In these procedures, a contrast medium, which is opaque to X-rays, is introduced to show abnormalities in the biliary system.

Angiography reveals the blood vessels in the liver.... liver imaging

Techniques that provide images of the lungs to aid in the diagnosis of disease.

Most lung disorders can be detected by chest X-ray.

CT scanning and MRI play an important role in detecting the presence and spread of lung tumours.

Ultrasound scanning is sometimes used to reveal pleural effusion.

Radioisotope scanning is used to detect evidence of pulmonary embolism.... lung imaging

See barium X-ray examinations.... stomach imaging

see Doppler ultrasound.... colour flow ultrasound imaging

any technique that produces an image in the form of a section through the body with the structures cut across. The main techniques are *ultrasonography, *computerized tomography, *magnetic resonance imaging, and some *nuclear medicine techniques (see positron emission tomography; SPECT scanning). If a series of thin-section images is stacked they can be ‘cut’ through to show other planes or allow reconstruction of three-dimensional images.... cross-sectional imaging

a variant of *diffusion weighted imaging in which both the direction and the amount of diffusion of water molecules in a tissue are coded in the image. This MRI technique can be valuable in linear structures, such as nerves and muscle fibres. In the brain the major tracts and their communications can be studied with this technique (see tractography).... diffusion tensor imaging

a method of creating images by *magnetic resonance imaging that relies on the amount of available space that individual water molecules have to move in, which depends on the local microstructure. Pathological tissues generally are less organized, with more space for diffusion and a higher signal.... diffusion weighted imaging

(DSI) the production of static images using an *image intensifier, usually during a fluoroscopic examination. The images can be stored digitally (see digitization) and either transferred to photographic film or viewed on a TV monitor.... digital spot imaging

(fMRI) a type of *magnetic resonance imaging that measures the increased hemodynamic response seen with neural activity in the brain or spinal cord. fMRI has allowed major advances in brain mapping (i.e. matching sections of the brain with particular behaviours, thoughts, or emotions).... functional magnetic resonance imaging

see co-registration.... fusion imaging

n. (in radiology) the production of images of organs or tissues by a range of techniques. These images are used by physicians in diagnosis and in monitoring the effects of treatment. They can also be used to guide *interventional radiology techniques. See also computerized tomography; magnetic resonance imaging; ultrasonography.... imaging

an emerging area of imaging that exploits recent developments of molecular and cell biology to create new markers. Most molecular imaging uses versions of these markers labelled with radioactive isotopes, which – after administration – are localized in the body and can be detected using such techniques as *positron emission tomography, *SPECT scanning, *magnetic resonance imaging, and optical imaging.... molecular imaging

the rapid acquisition and manipulation of ultrasound information from a scanning probe by electronic circuits to enable images to be produced on TV screens almost instantaneously. The operator can place the scanning probe accurately on the region of interest in order to observe its structure and appreciate moving structures within it (see Doppler ultrasound). Using similar techniques, the instantaneous display of other imaging modalities, such as *computerized tomography scanning and *magnetic resonance imaging, can now be achieved. Real-time imaging is useful in guiding *interventional radiology procedures, for example, allowing a needle to be guided accurately as it is passed into the body. It is also useful for observing dynamic physiological activity.... real-time imaging

a technique to image the parathyroid glands. Technetium is taken up only by the thyroid gland, but thallium is taken up by both the thyroid and parathyroid glands. *Digital subtraction of the two isotopes leaves an image of the parathyroid glands alone. It is an accurate technique (90%) for the identification of adenomas of the parathyroid glands secreting excess hormone.... thallium-technetium isotope subtraction imaging