Ultrasound (US) imaging, also called ultrasound scanning or sonography, is a method of "seeing" inside the human body through the use of high-frequency sound waves. These sound waves are outside the range of human hearing. The sound waves are recorded and displayed as a real-time visual image. No ionizing radiation is involved in ultrasound imaging.
US is a useful way of examining many of the body's soft tissues, including the heart, liver, gallbladder, spleen, pancreas, kidneys, blood vessels, breast, and bladder. Because US images are captured in real-time, they can show movement of internal tissues and organs, and enable physicians to see blood flow and heart valve functions. This ability to see in “real time” can help to diagnose a variety of conditions. For example, assessment of heart damage after a heart attack and visualization of a blood clot.
What are some common uses of the procedure?
Millions of expectant parents have seen the first "picture" of their unborn child with pelvic ultrasound examinations of the uterus and fetus. Ultrasound imaging is used extensively for evaluating the eyes, pelvic and abdominal organs, heart, blood vessels, and other soft tissues. US can help a physician determine the source of pain, swelling, or infection in many parts of the body. Because US provides real time images, it can also be used to guide procedures such as needle biopsies, in which a needle is used to sample cells from an organ for laboratory testing. Ultrasound is now being used to image the breasts and to guide biopsy of breast cancer.
Doppler ultrasound is a special technique used to examine blood flow. Doppler images can help the physician to see and evaluate:
- blockages to blood flow, such as clots
- build-up of plaque inside the vessel
- congenital malformation
How should I prepare for the procedure?
You should wear comfortable, loose-fitting clothing for your US exam. Other preparation depends on the type of examination you will have. For some scans, your doctor may instruct you not to eat or drink for as many as 12 hours before your appointment. For others, you may be asked to drink up to six glasses of water two hours prior to your exam and avoid urinating, so that your bladder is full when the scan begins.
What does the equipment look like?
Ultrasound scanners consist of a console containing a computer and electronics, a video display screen and a transducer that is used to scan the body. The transducer is a small hand-held device about the size of a bar of soap, attached to the scanner by a cord. The physician or sonographer spreads a warm, lubricating gel on the area being examined, and then presses the transducer firmly against the skin to obtain images.
The US image is immediately visible on a nearby screen that looks much like a computer or television monitor. The physician or sonographer watches this screen during an examination; often, the patient is able to see it as well.
How does the procedure work?
Ultrasound imaging is based on the same principles involved in the sonar used by bats, ships at sea, and anglers with “fish finders”. 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, how uniform it is, and whether it is cystic or solid.
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 high-frequency sound waves into the body. As the sound echoes from the body's fluids and tissues, the transducer records tiny changes in the pitch and direction of the sound. 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 may be recorded on videotape, but one or more frames of the moving picture may be "frozen" to capture a still image.
How is the procedure performed?
The patient is usually positioned on an examination table. A warm, clear gel is applied to the patient's body in the area to be examined, to help the transducer make secure contact with the skin. The sound waves produced by the transducer cannot penetrate air, so the gel helps eliminate air pockets between the transducer and the skin. The sonographer or radiologist presses the transducer firmly against the skin and sweeps it back and forth to image the area of interest.
When the examination is complete, the patient may be asked to dress and wait while the ultrasound images are reviewed, either on film or on a TV monitor. Often, though, the sonographer or radiologist is able to review the ultrasound images in real time as they are acquired, and the patient can be released immediately.
What will I experience during the procedure?
Ultrasound imaging is painless, fast, and easy. You will lie on your back on an examining table, but you may be asked to roll on your side. The sonographer or doctor will spread some warm gel on your skin and then press the transducer firmly against your body, moving it until the desired images are captured. There may be varying degrees of discomfort from pressure as the technologist guides the transducer over your abdomen, especially if you are required to have a full bladder. The examination usually takes less than 30 minutes.
Who interprets the results and how do I get them?
Our radiologist, will analyze the images and fax a signed report with the interpretation to your personal physician. Your personal physician's office will inform you on how to obtain their results.
What are the benefits of Ultrasounds?
- Ultrasound imaging is a painless, low cost examination.
- Ultrasound is widely available and easy to use.
- US imaging uses no ionizing radiation, and is the preferred image modality for diagnosis and monitoring of pregnant women and their unborn infants.
- Ultrasound provides real-time imaging, making it a good tool for guiding minimally invasive procedures such as needle biopsies.
- US images can visualize movement and live function in the body's organs and blood vessels.
- Ultrasound scanning is painless and noninvasive.
For standard diagnostic ultrasound there are no known harmful effects to humans.
What are the limitations of Ultrasound Imaging?
Ultrasound waves do not reflect clearly from bone or air. For visualization of bone, other imaging modalities should be selected.
What are the limitations of Abdominal Ultrasound Imaging?
Ultrasound has difficulty penetrating bone and therefore can only see the outer surface of bony structures and not what lies within. For visualizing bone or internal structure of certain joints, waves do not reflect clearly from bone or air. For visualization of bones, joints, other imaging modalities, such as CT or MRI should be selected.