WHAT IS ULTRASOUND IMAGING?
Ultrasound imaging, also known as sonography, uses high-frequency sound waves to see internal organs and systems, as well as blood flowing throughout the body. As the sound waves travel through your body, they reflect off of the body's various internal structures. The ultrasound machine detects the strength, or amplitude, of the reflected sound signal and the amount of time it takes to travel through the body and be reflected back. The machine then uses this information to plot an image.
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The imagery that is produced is like a live video feed and we record snippets of that feed for medical professionals to consult - either in motion or a still image. The imagery produced is not clear like a photograph, but it can provide enough information to help medical professionals diagnose and treat patients. Because ultrasound uses sound waves, it is considered extremely safe and there is no radiation exposure like with X-ray imaging.
WHAT TO EXPECT AT YOUR EXAM
Ultrasound examinations are painless, fast and easily tolerated by most patients.
Depending on the area of the body to be examined, the patient might be asked to change into a hospital gown. For most ultrasound exams, the patient is positioned lying face-up on an examination table that can be tilted or moved. A clear water-based gel is applied to the area of the body being studied to help the transducer make secure contact with the body and eliminate air pockets between the transducer and the skin that can interfere with the sound waves.
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The sonographer (ultrasound technologist) or radiologist then presses the transducer firmly against the skin in various locations, sweeping over the area to be examined or angling the sound beam from a farther location to better see an area of concern.
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A transducer is a handheld microphone-like device, with a smooth surface through which soundwaves are transmitted. The transducer is connected by a cord to the ultrasound equipment. Ultrasound imagery is displayed on a screen. While watching this screen, the ultrasound practitioner will use a keyboard to zoom in, adjust settings, and record imagery and measurements.
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Doppler sonography is captured using the same transducer.
Most ultrasound examinations are completed within an hour.
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Patients should check with their healthcare provider on any preparations requested prior to their exam. Some areas of the body are affected by food in the system and the patient may be asked to refrain from eating or drinking anything for a span of time prior to the exam.
KINDS OF ULTRASOUND IMAGING
Conventional ultrasound displays the images in thin, flat sections of the body. Advancements in ultrasound technology include three-dimensional (3-D) ultrasound that formats the sound wave data into 3-D images.
A Doppler ultrasound study may be part of an ultrasound examination.
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Doppler ultrasound is a special ultrasound technique that evaluates blood flow through a blood vessel, including the body's major arteries and veins in the abdomen, arms, legs and neck.
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There are three types of Doppler ultrasound:
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Color Doppler uses a computer to convert Doppler measurements into an array of colors to visualize the speed and direction of blood flow through a blood vessel.
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Power Doppler is a newer technique that is more sensitive than color 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.
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Instead of displaying Doppler measurements visually, Spectral Doppler displays blood flow measurements graphically, in terms of the distance traveled per unit of time.
BENEFITS OF ULTRASOUND IMAGING
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Most ultrasound scanning is noninvasive (no needles or injections).
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Occasionally, an ultrasound exam may be temporarily uncomfortable, but it is almost never painful.
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Ultrasound is widely available, easy-to-use and less expensive than other imaging methods.
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Ultrasound imaging is extremely safe and does not use any ionizing radiation.
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Ultrasound scanning gives a clear picture of soft tissues that do not show up well on x-ray images.
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Ultrasound is the preferred imaging modality for the diagnosis and monitoring of pregnant women and their unborn babies.
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Ultrasound provides real-time imaging, making it a good tool for guiding minimally invasive procedures such as needle biopsies and needle aspiration.
LIMITATIONS OF ULTRASOUND IMAGING
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Vessels deep in the body are harder to see than superficial vessels. Specialized equipment or other tests such as CT or MRI may be necessary to properly visualize them.
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Smaller vessels are more difficult to image and evaluate than larger vessels.
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Calcifications that occur as a result of atherosclerosis may obstruct the ultrasound beam.
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Sometimes ultrasound cannot differentiate between a blood vessel that is obstructed versus one that is slightly obstructed. Even if there is a very small remaining opening, the weak blood flow produces a sometimes undetectable signal.
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The test is specialized and is best performed by a technologist and physician with experience and interest in vascular ultrasound imaging.
