Ultrasound

 

What is ultrasound and how does the procedure work?

Ultrasound (US), also called sonography, is a method of dynamically imaging the human body through the use of high-frequency sound waves. A microphone-like instrument (transducer) is scanned over the skin. Gel is placed on the skin to improve the contact of the transducer to the area being examined. The sound waves are recorded and displayed as a real-time visual image. US can be used to examine many parts of the body including the abdomen, pelvis and blood vessels, as well as the fetus during pregnancy. Because no ionizing radiation (x-ray) is involved, ultrasound is an extremely safe imaging modality. The procedure is painless and generally takes about 30 to 45 minutes to complete.

Ultrasound imaging is based on the same principles involved in the sonar used by bats or ships at sea. As the sound passes through the body, echoes are produced that can be used to identify how far away an object is, how large it is, its shape and its consistency (fluid, solid or mixed). The ultrasound transducer functions as both a generator of sound (like a speaker) and a detector (like a microphone). When the transducer is pressed against the skin it directs inaudible, high-frequency sound waves into the body. As the sound echoes from the body’s fluids and tissues the transducer records the strength and character of the reflected waves. These echoes are instantly measured and displayed by a computer, which in turn creates a real-time picture on the monitor. The "live" images of the examination are usually recorded on videotape but one or more frames of the moving picture may be "frozen" to capture a still image.

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What are the common uses of ultrasound? 

As a diagnostic tool, ultrasound has a wide variety of uses in medicine, including:

• Imaging of veins and arteries to see and evaluate blockages to blood flow

• Examining many of the body's internal organs, including the heart, liver, gallbladder, spleen, pancreas, kidneys and bladder

• Examining the neck to help diagnose thyroid abnormalities

• Monitoring fetal development and accessing fetal abnormalities

• Determining the cause of pelvic pain, abnormal bleeding and other menstrual problems

• Investigating uterine abnormalities in women who experience infertility or multiple miscarriages

• Imaging the breast and to guide biopsy in breast cancer

• Evaluating the prostate

• Determining the source of pain, swelling or infection in many parts of the body

• Assessing organ damage following illness

• Revealing the shape, texture and composition of tumors and cysts

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What are the benefits of ultrasound?

Ultrasound imaging offers these benefits:

• Provides a simple, painless and noninvasive imaging method for viewing structures within the body

• Uses no ionizing radiation (x-rays) and is the preferred image modality for diagnosis and monitoring of pregnant women and their unborn infants

• Produces real-time imaging, making it a good tool for guiding minimally invasive procedures such as needle biopsies

• Visualizes structure, movement and live function in the body's organs and blood vessels

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Is ultrasound safe? 

Since ultrasound emits no x-rays, it is very safe. There are no known risks or side effects associated with diagnostic ultrasound.

 

What are the limitations of ultrasound imaging?

Ultrasound has difficulty penetrating bone and therefore can only see the outer surface of bony structures and not what lies within. For visualization of bone, other imaging modalities such as magnetic resonance imaging (MRI) may be selected. Because ultrasound waves do not pass through air, an evaluation of the stomach, small intestine and large intestine may be limited. Intestinal gas may also prevent visualization of deeper structures such as the pancreas and aorta. Obese patients are also more difficult to image because tissue attenuates (weakens) the sound waves as they pass deeper into the body.

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