Doppler ultrasound
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S: FetalMed – https://goo.gl/r2iri5 (last access: 4 December 2017); NYTIMES – https://goo.gl/84xDUF (last access: 4 December 2017); WebMD – https://goo.gl/JE9XCJ (last access: 4 December 2017).

N: 1. – Doppler (pn): Eponym that makes reference to Christian Doppler (1803-1853), an Austrian scientist who, in 1842, explained the effect of relative motion on waves (originally to explain colour changes in binary stars), the Doppler effect.
– ultrasound (n): From the prefix “ultra-“ (borrowed from the Latin ultra, “beyond”) and the term “sound” (Since the late 13th Century. From Old French son “sound”, “musical note”, “voice,” from Latin sonus “sound”, “a noise,” from PIE swon-o-, from root swen- “to sound” source also of Sanskrit svanati “it sounds”, svanah “sound”, “tone”; Latin sonare “to sound”; Old Irish senim “the playing of an instrument”; Old English geswin “music”, “song”, swinsian “to sing”; Old Norse svanr, Old English swan “swan”, properly “the sounding bird”).
2. Non-invasive test that can be used to estimate the blood flow through the blood vessels by bouncing high-frequency sound waves (ultrasound) off circulating red blood cells. The Doppler effect is used to evaluate movement by measuring changes in frequency of the echoes reflected from moving structures.
3. The Doppler effect consists in a change in the observed frequency of a wave, as of sound or light, occurring when the source and observer are in motion relative to each other, with the frequency increasing when the source and observer approach each other and decreasing when they move apart. The motion of the source causes a real shift in frequency of the wave, while the motion of the observer produces only an apparent shift in frequency. It is also called Doppler shift.
4. A Doppler ultrasound may help diagnose many conditions, including: Blood clots, poorly functioning valves in your leg veins, which can cause blood or other fluids to pool in your legs (venous insufficiency); heart valve defects and congenital heart disease; a blocked artery (arterial occlusion); decreased blood circulation into your legs (peripheral artery disease); bulging arteries (aneurysms) and the narrowing of an artery, such as in your neck (carotid artery stenosis).
5. There are three types of Doppler ultrasound:
• Colour Doppler uses a computer to convert Doppler measurements into an array of colours to show the speed and direction of blood flow through a blood vessel.
• Power Doppler is a newer technique that is more sensitive than colour Doppler and capable of providing greater detail of blood flow, especially when blood flow is little or minimal. Power Doppler, however, does not help the radiologist determine the direction of blood flow, which may be important in some situations.
• Spectral Doppler displays blood flow measurements graphically, in terms of the distance travelled per unit of time, rather than as a colour picture. It can also convert blood flow information into a distinctive sound that can be heard with every heartbeat.
6. Benefits of a Doppler ultrasound:
• Non-invasive.
• Generally painless.
• Does not use radiation.
• Can show if you have any blocked arteries in your neck, arms and legs.
• Can show if you have any blood clots in the veins in your legs.
• Can show the amount and speed of blood flow in your veins and arteries.
• Can be used instead of some more invasive procedures.
7. Doctors often use Doppler Ultrasound during pregnancy to check fetal umbilical blood flow; placental blood flow and blood flow in the heart and brain. Using the Doppler Ultrasound results, doctors can determine if restricted blood flow due to sickle cell anaemia, RH sensitization or restricted blood vessels is to blame for fetal abnormalities. Restricted blood flow to the foetus could cause: lower birth weight, reduced size, impaired development.

S: 1. OED – https://goo.gl/NguZF4; https://goo.gl/yjyYm8 (last access: 4 December 2017); Wiktionary – https://goo.gl/DPrHaK (last access: 4 December 2017). 2. MAYO – https://goo.gl/rjyfYc (last access: 4 December 2017); RadiologyInfo – https://goo.gl/Jnqd21 (last access: 4 December 2017). 3. MEDICALDICT – https://goo.gl/vj8AoL (last access: 4 December 2017). 4. MAYO – https://goo.gl/rjyfYc (last access: 4 December 2017). 5. RadiologyInfo – https://goo.gl/UqFGfh (last access: 4 December 2017). 6. HW – https://goo.gl/QjN2pn (last access: 4 December 2017). 7. BabyMed – https://goo.gl/byY9Q6 (last access: 4 December 2017).

SYN: Doppler ultrasonography, Doppler scanning, Doppler.

S: TERMIUM PLUS – http://www.goo.gl/54LdyM (last access: 11 December 2017)

CR: artery, Doppler effect, ultrasonography, vein.