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Ultrasound technology in general and Doppler ultrasound in particular has come a long way. The first quantitatively accurate Doppler ultrasound instruments became available in the 1980s and since then there has been continuous improvement in instrumentation and therefore quality of diagnostic images and thereby improving medical outcomes. It is the safest, lowest cost and simplest way to evaluate blood vessels. The use of [url=http://www.sandvikfw.net/shopuk.php]hollister outlet sale[/url] ultrasound in medical imaging is ubiquitous in the healthcare setting. The use of Doppler ultrasound which is a subset of diagnostic ultrasound imaging has also risen invariably. Ultrasound imaging utilizes reflected sound waves to produce diagnostic images of the relevant organs and structures in the body including vessels, joints and muscles. Ultrasound generally refers to the frequencies above [url=http://www.rtnagel.com/airjordan.php]jordan pas cher[/url] the audible range of human hearing. This is generally thought to about 20Khz. Frequencies used in diagnostic ultrasound imaging are generally between 2 [url=http://www.1855sacramento.com/moncler.php]moncler sito ufficiale[/url] MHz and 8Mhz. A computer converts these frequencies or sound waves into two dimensional black and white moving pictures on your computer screen. Doppler ultrasound however, uses the reflected sound waves in the evaluation of moving structures like blood vessels in the body. It is usually ordered to check blood flow in the major arteries and veins.
The basis of Doppler ultrasound is what is [url=http://www.mxitcms.com/tiffany/]tiffany outlet[/url] known as the Doppler Effect. It is named for Austrian physicist Christian Doppler who theorized it in 1842. It [url=http://www.1855sacramento.com/woolrich.php]woolrich[/url] states that the reflected waves from a moving object will undergo a change in frequency. For example when [url=http://www.thehygienerevolution.com/barbour.php]barbour[/url] a vehicle [url=http://www.maximoupgrade.com/hot.php]hollister[/url] with a siren moves toward an observer the frequency received by the observer is higher than that emitted from the siren and this is also the case as the source of the siren moves away. The magnitude and direction of this change is able to provide information about the moving object. In the medical realm, the [url=http://www.thehygienerevolution.com/barbour.php]barbour paris[/url] movement of blood cells causes changes in the pitch of reflected sound waves from the Doppler ultrasound machine. This hand-held machine is known as a transducer and is lightly applied on the skin over a blood vessel. Information from the reflected sound waves is then processed by a computer into two dimensional color images and graphs as well.
There are various benefits of Doppler ultrasound. First and foremost, Doppler ultrasound is the only ultrasound examination that can be used to evaluate blood vessels in a noninvasive manner. It also a fairly straightforward and can be easily performed in a doctor's office. Studies have shown that Doppler ultrasound can be effective in high-risk pregnancies in reducing caesarian [url=http://www.mquin.com/saclancel.php]lancel[/url] sections and the number who may die because of this. When Doppler ultrasound is used to evaluate blood flow in the unborn fetus, medics can decide which high risk pregnancies need assistance during delivery and those that can be delivered unassisted. Doppler ultrasound instrumentation is also relatively inexpensive compare to other methods of diagnostic imaging evaluation like CT scans and conventional x-ray machines. Certainly it is more portable than the aforementioned methods (Science Daily 2010). However, just like any other imaging technique in diagnostic.
Depth ambiguity is one of the limitations of Doppler ultrasound. Reflections deep in [url=http://www.1855sacramento.com/moncler.php]moncler outlet[/url] the [url=http://www.mnfruit.com/doudounemoncler.php]moncler[/url] field of view or area being examined may arrive at the transducer after the next pulse [url=http://www.mnfruit.com/doudounemoncler.php]moncler pas cher[/url] has been emitted. Deep Doppler shifts may therefore record in an area where there is no flow. This may occur with low frequency transducer but is usually not a clinical issue because tissue usually attenuates the beam sufficiently causing shifts to go below depiction threshold.

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