Colour flow ultrasound imaging Health Dictionary

See VISION – Defective colour vision.... colour blindness

Ultrasound, or ultrasonic, waves comprise very-high-frequency sound waves above 20,000 Hz that the human ear cannot hear. Ultrasound is widely used for diagnosis and also for some treatments. In OBSTETRICS, ultrasound can assess the stage of pregnancy and detect abnormalities in the FETUS (see below). It is a valuable adjunct in the investigation of diseases in the bladder, kidneys, liver, ovaries, pancreas and brain (for more information on these organs and their diseases, see under separate entries); it also detects thromboses (clots) in blood vessels and enables their extent to be assessed. A non-invasive technique that does not need ionising radiation, ultrasound is quick, versatile and relatively inexpensive, with scans being done in any plane of the body. There is little danger to the patient or operator: unlike, for example, XRAYS, ultrasound investigations can be repeated as needed. A contrast medium is not required. Its reliability is dependent upon the skill of the operator.

Ultrasound is replacing ISOTOPE scanning in many situations, and also RADIOGRAPHY. Ultrasound of the liver can separate medical from surgical JAUNDICE in approximately 97 per cent of patients; it is very accurate in detecting and de?ning cystic lesions of the liver, but is less accurate with solid lesions – and yet will detect 85 per cent of secondary deposits (this is less than COMPUTED TOMOGRAPHY [CT] scanning). It is very accurate in detecting gall-stones (see GALL-BLADDER, DISEASES OF) and more accurate than the oral cholecystogram. It is useful as a screening test for pancreatic disease and can di?erentiate carcinoma of the pancreas from chronic pancreatitis with 85 per cent accuracy.

Ultrasound is the ?rst investigation indicated in patients presenting with renal failure, as it can quickly determine the size and shape of the kidney and whether there is any obstruction to the URETER. It is very sensitive to the presence of dilatation of the renal tract and will detect space-occupying lesions, di?erentiating cysts and tumours. It can detect also obstruction of the ureter due to renal stones by showing dilatations of the collecting system and the presence of the calculus. Adrenal (see ADRENAL GLANDS) tumours can be demonstrated by ultrasound, although it is less accurate than CT scanning.

The procedure is now the ?rst test for suspected aortic ANEURYSM and it can also show the presence of clot and delineate the true and false lumen. It is good at demonstrating subphrenic and subhepatic abscesses (see ABSCESS) and will show most intra-abdominal abscesses; CT scanning is however better for the retroperitoneal region. It has a major application in thyroid nodules as it can di?erentiate cystic from solid lesions and show the multiple lesions characteristic of the nodular GOITRE (see also THYROID GLAND, DISEASES OF). It cannot differentiate between a follicular adenoma and a carcinoma, as both these tumours are solid; nor can it demonstrate normal parathyroid glands. However, it can identify adenomas provided that they are more than 6 mm in diameter. Finally, ultrasound can di?erentiate masses in the SCROTUM into testicular and appendicular, and it can demonstrate impalpable testicular tumours. This is important as 15 per cent of testicular tumours metastasise whilst they are still impalpable.

Ultrasonic waves are one of the constituents in the shock treatment of certain types of gallstones and CALCULI in the urinary tract (see LITHOTRIPSY). They are also being used in the treatment of MENIÈRE’S DISEASE and of bruises and strains. In this ?eld of physiotherapy, ultrasonic therapy is proving of particular value in the treatment of acute injuries of soft tissue. If in such cases it is used immediately after the injury, or as soon as possible thereafter, prompt recovery is facilitated. For this reason it is being widely used in the treatment of sports injuries (see also SPORTS MEDICINE). The sound waves stimulate the healing process in damaged tissue.

Doppler ultrasound is a technique which shows the presence of vascular disease in the carotid and peripheral vessels, as it can detect the reduced blood ?ow through narrowed vessels.

Ultrasound in obstetrics Ultrasound has particular applications in obstetrics. A fetus can be seen with ultrasound from the seventh week of pregnancy, and the fetal heart can be demonstrated at this stage. Multiple pregnancy can also be diagnosed at this time by the demonstration of more than one gestation sac containing a viable fetus. A routine obstetric scan is usually performed between the 16th and 18th week of pregnancy when the fetus is easily demonstrated and most photogenic. The fetus can be measured to assess the gestational age, and the anatomy can also be checked. Intra-uterine growth retardation is much more reliably diagnosed by ultrasound than by clinical assessment. The site of the placenta can also be recorded and multiple pregnancies will be diagnosed at this stage. Fetal movements and even the heartbeat can be seen. A second scan is often done between the 32nd and 34th weeks to assess the position, size and growth rate of the baby. The resolution of equipment now available enables pre-natal diagnosis of a wide range of structural abnormalities to be diagnosed. SPINA BIFIDA, HYDROCEPHALUS and ANENCEPHALY are probably the most important, but other anomalies such as multicystic kidney, achondroplasia and certain congenital cardiac anomalies can also be identi?ed. Fetal gender can be determined from 20 weeks of gestation. Ultrasound is also useful as guidance for AMNIOCENTESIS.

In gynaecology, POLYCYSTIC OVARY SYNDROME can readily be detected as well as FIBROID and ovarian cysts. Ultrasound can monitor follicular growth when patients are being treated with infertility drugs. It is also useful in detecting ECTOPIC PREGNANCY. (See also PREGNANCY AND LABOUR.)... ultrasound

A device that measures the rate at which an individual can expel air from the LUNGS. This is an indication of the reserve in the capacity of the lungs. Narrowed airways (bronchospasm) slow the rate at which air can be expelled; the peak ?ow meter can assess the severity of the condition. ASTHMA causes bronchospasm and the device can measure the e?ectiveness of treatment with BRONCHODILATOR drugs; this should be done regularly to monitor the progress of the disease.... peak flow meter

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

The ability to see different parts of the colour spectrum. Light perceived by the human eye consists of electromagnetic radiation (energy waves) with a spectrum of different wavelengths

between about 400 and 700 nanometres. Different wavelengths produce sensations of violet, indigo, blue, green, yellow, orange, and red when they fall on the retina and stimulate nerve signals, which are processed in the brain.

As light falls on the retina, it strikes light-sensitive cells called rods and cones. The rods can detect all visible light, but only the cones can distinguish colour. There are 3 types of cones: red-sensitive, blue-sensitive, and green-sensitive. Each responds more strongly to a particular part of the light spectrum. Because the cones are most concentrated in a central area of the retina called the fovea, colour vision is most accurate for objects viewed directly and is poor at the edges of vision. When light hits a cone, it causes the cone to emit an electrical signal, which passes to the brain via the optic nerve. Colour perception requires a minimum level of light, below which everything is seen as shades of grey. (See also colour vision deficiency; eye; perception; vision.)... colour vision

See barium X-ray examinations.... intestinal 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

The use of ultrasound to treat soft-tissue injuries (such as injuries to ligaments, muscles, and tendons). Ultrasound treatment reduces inflammation and speeds up healing. It is thought to work by improving blood flow in tissues under the skin.... ultrasound treatment

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

Any abnormality in colour vision that causes difficulty distinguishing between certain colours. Total absence of colour vision (monochromatism) is rare. The most common types of colour vision deficiency are reduced discrimination of red and green. Most cases of red and green colour vision deficiency are caused by defects in the light-sensitive cells in the retina. These defects are usually inherited, although occasionally defects are caused by retinal or optic nerve diseases or injury. The inherited defects tend to be sex-linked (see genetic disorders), which means that the majority of sufferers are male. A person with a severe green deficiency has difficulty distinguishing oranges, greens, browns, and pale reds. In severe red deficiency, all reds appear dull. A much rarer deficiency in which blue cannot be distinguished may be inherited or may be due to degeneration of the retina or optic nerve.... colour vision deficiency

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

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

A diagnostic technique in which very high frequency sound waves are passed into the body and the reflected echoes analysed to build a picture of the internal organs or of a fetus in the uterus. The procedure is painless and considered safe.Ultrasonic waves are emitted by a transducer, which is placed on the skin over the part of the body to be viewed. The transducer contains a crystal that converts an electric current into sound waves. These pass readily through soft tissues and fluids, making this procedure useful for examining fluid-filled or soft organs.

One of the most common uses of ultrasound is to view the uterus and fetus, at any time during pregnancy, but often at 18–20 weeks. The age, size, and growth rate of the fetus can be determined; multiple pregnancies detected; and certain problems, such as neural tube defects, diagnosed. Scans may be taken early in pregnancy if problems, such as an ectopic pregnancy, are suspected.

Ultrasound scanning can also be used in newborn babies to examine the brain through a gap in the skull (for example, to investigate hydrocephalus). Ultrasound can help to diagnose disorders such as cirrhosis, gallstones, hydronephrosis, and pancreatitis, as well as problems in the thyroid gland, breasts, bladder, testes, ovaries, spleen, and eyes. The technique is also used during needle biopsy to help guide the needle.Doppler ultrasound is a modified form of ultrasound that uses the Doppler effect to investigate moving objects.

This can be used to examine the fetal heartbeat and to obtain information about the rate of blood flow in vessels.... ultrasound scanning

a diagnostic technique that utilizes the fact that the frequency of sound or light waves changes when they are reflected from a moving surface (the Doppler effect). It is used to study the flow in blood vessels and the movement of blood in the heart. The frequency detector may be part of an ultrasound imaging probe, which displays an image of the anatomy on a monitor. Simultaneously the Doppler signal from a particular point on the ultrasound image can be displayed superimposed on the anatomical position (duplex imaging). Using electronic techniques, direction and velocity of blood flow can each be allocated different colours and displayed on a colour monitor over the anatomical image (colour flow ultrasound imaging). Power Doppler, a modification of this technique, is more sensitive at detecting flow but does not give information on direction of flow. Doppler ultrasound is a valuable technique to detect vessel thrombosis, such as deep vein thrombosis, and can be safely used in pregnancy without the risk of ionizing radiation. It is extensively used in vascular surgery to assess the status of the blood vessels before surgery, especially in carotid surgery. Doppler measurement of the fetal middle cerebral vessels (MCA Doppler) can predict fetal anaemia as the resistance in these vessels is increased. This noninvasive technique has supplanted serial amniocentesis/fetal cord blood sampling in cases of *haemolytic disease of the newborn. Doppler of other fetal vessels (e.g. the ductus venosus) is used as a screening method for fetal chromosomal and cardiac defects and, later, fetal growth restriction. [C. J. Doppler (1803–53), Austrian physicist]... doppler ultrasound

see Doppler ultrasound.... duplex imaging

a technique in which cells are tagged with a fluorescent dye and then directed single file through a laser beam. The intensity of *fluorescence induced by the laser beam is proportional to the amount of DNA in the cells.... flow cytometry

the fusion of endoscopy with ultrasonography. An ultrasound probe is incorporated into the endoscope in order to deliver highly detailed images from within the body. Endoscopic ultrasound is used predominantly by gastroenterologists, to assess internal structures or organs within the upper gastrointestinal tract, or by respiratory physicians in the assessment of bronchial disease. It may be used for diagnostic purposes, to accurately stage a confirmed diagnosis of cancer or to obtain tissue samples using fine-needle aspiration. Therapeutic indications include drainage of a pancreatic *pseudocyst, the common bile duct, or the pancreatic duct, and coeliac plexus neurolysis, a technique used to deliver pain relief in cases of intractable abdominal pain, usually resulting from chronic pancreatitis.... endoscopic ultrasound

(FFR) a technique used to quantify the severity of a coronary artery narrowing. During *cardiac catheterization, a specialized wire is passed down the coronary artery to measure pressure. The ratio of the pressure measured downstream of the narrowing to the pressure measured upstream is derived (this ratio also applies to coronary flow). When the ratio is below a certain threshold, flow restriction by the narrowing is deemed to be significant and *percutaneous coronary intervention is likely to be beneficial.... fractional flow reserve

(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

an unusual phenomenon in newborn babies characterized by transient red colour changes to half of the body, well demarcated at the midline. It is seen usually 2–5 days after birth and can last from 30 seconds to 20 minutes before fading away. It may recur when the infant is placed on his or her side as the intensity of the erythema appears to be gravity-dependent.... harlequin colour change

see HIFU; ultrasound.... high-intensity focused ultrasound

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

(IVUS) a technique in which a micro *ultrasound transducer is mounted on a catheter, which is then advanced over a guidewire into a blood vessel. IVUS is used to accurately assess the diameter of the blood vessels before any treatment, to assess any internal abnormality within the blood vessels, or to help mark the blood vessel branches during any stent placement.... intravascular ultrasound

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

(PEFR) the maximum rate at which a person can forcibly expel air from the lungs at any time, expressed usually in litres per minute (occasionally in litres per second). A low value can help diagnose asthma in the correct clinical context, and differences between the morning and evening values can also be a feature of poor control of asthma. There is a place for PEFR in the monitoring of acute exacerbations of chronic pulmonary obstructive disease (COPD) but not in the diagnosis of COPD.... peak expiratory flow rate

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

the appearance, on *ultrasonography of a pregnant woman, of a feature suggesting an abnormality in the fetus. Such markers can be classified as major fetal structural abnormalities or minor ultrasound features called soft markers. The latter are usually transient and may resolve spontaneously, but they may indicate the risk of a serious chromosomal abnormality in the fetus. An example is increased nuchal translucency (see nuchal translucency scanning).... ultrasound marker

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