What is an ultrasound?
Ultrasound scanning, also called sonography, is a method of obtaining images from inside the human body through the use of high-frequency sound waves. The sound waves are recorded and displayed as a real-time image. No ionizing radiation is involved in ultrasound imaging. Because ultrasound images are captured in real time, they can show movement of internal tissues and organs, and enable physicians to see blood flow.
Common uses of the procedure
Ultrasound imaging is used extensively for evaluating the kidneys, liver, gallbladder, pancreas, spleen, uterus, ovaries, testicles, thyroid, breast, fetus, blood vessels and much more. Because it 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;
Help physicians determine the source of pain, such as stones in the gallbladder or kidney, cysts on the ovaries, or an inflamed appendix;
Help identify the cause for enlargement of internal organs.
Doppler ultrasound is a special type of ultrasound study that is used in the examination of blood vessels. These images can help the physician see and evaluate:
Blockages to blood flow, such as clots; Build up of plaque inside the vessel; Congenital malformations.
What does the equipment look like?
Ultrasound scanners consist of a console containing a computer and other electronic equipment, 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 sonographer will spread a lubricating gel on your body in the area being examined, and then press the transducer firmly against your skin to obtain images.
The ultrasound image is immediately visible on a nearby screen that looks much like a computer or television monitor. The sonographer watches this screen during the examination.
How is the procedure performed?
You will be positioned on an examination table, and a clear gel will be applied to your body part being imaged to help the transducer make a secure contact with the skin. The sound waves produced by the transducer cannot penetrate air, so the gel helps to eliminate air pockets between the transducer and the skin. The sonographer then presses the transducer firmly against the skin and sweeps it back and forth to image the area of interest.
When the examination is complete, you will be asked to wait in the exam room while the sonographer reviews the images with the radiologist.
What will I experience during the exam?
Ultrasound imaging is easy and painless. There may be varying degrees of discomfort from the pressure as the sonographer guides the transducer over you, especially if you require a full bladder. The exam usually takes between 30 minutes to an hour depending on the exam type.
How does the ultrasound work?
Ultrasound imaging is based on the same principles involved in the sonar used by bats, ships and fishermen. When a sound wave strikes an object, it bounces backward, or echoes. By measuring these echo waves it is possible to determine how far away the object is and its size, shape, consistency (whether the object is solid, filled with fluid, or both) and uniformity.
In medicine, ultrasound is used to detect changes in appearance and function of organs, tissues, or abnormal masses, such as tumors.
In an ultrasound examination, a transducer both sends the sound waves and records the echoing waves. When the transducer is pressed against the skin, it directs a stream of inaudible, high-frequency sound waves into the body. As the sound waves bounce off of internal organs, fluids and tissues, the sensitive microphone in the transducer records tiny changes in the sound’s pitch and direction. These signature waves are instantly measured and displayed by a computer, which in turn creates a real-time picture on the monitor. These live images are usually recorded on videotape and one or more frames of the moving pictures are typically captured as still images.
Doppler ultrasound, a special application of ultrasound, measures the direction and speed of blood cells as they move through vessels. The movement of blood cells causes a change in pitch of the reflected sound waves (Doppler effect). A computer collects and processes the sounds and creates graphs or pictures that represent the flow of blood through the blood vessels.
How should I prepare for the procedure?
You should wear comfortable, loose fitting clothing for your ultrasound 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 the appointment. For others, you may be asked to drink several glasses of water two hours prior to your exam and avoid urinating, so that your bladder is full when scanning begins.
Who interprets the ultrasound?
A radiologist, who is a physician experienced in ultrasound and other imaging examinations, will analyze the images and send a signed report with his/her interpretation to your primary care physician. Your physician’s office will inform you how to obtain the results.