Ultrasound, also called ultrasound scanning or sonography, is an imaging method that uses sound waves to create an image of a part of the body. A computer program is used to analyze the echoes of sound waves sent into the body and generates an image on screen.
Unlike mammograms, which use radiation (x-rays), ultrasounds expose the body region of interest to high-frequency sound waves. Ultrasound images are captured in real time; that is, not only do they show the structure of a particular part of the body, but they can also show movement of the body’s internal organs as well as blood flowing through vessels.
How It Works
What instruments are used?
Ultrasound scanners consist of a stand with a computer and electronics, a display screen to show the image, and a hand-held transducer that is used to scan the body. The transducer emits high-frequency sound waves and receives the returning waves (echoes). The computer collects the echoes and creates an image on the screen. In creating the final image, the computer analyzes several characteristics of the returned sound waves:
- Amplitude: strength of the signal
- Frequency: the number of waves received per second
- Time Delay: the time it takes for the signal to return from the targeted region to the transducer
How does ultrasound work?
Ultrasound imaging is based on the same principles of physics that bats use to locate their prey. When the transducer emits a sound wave and it hits an object, the wave bounces off the object. By measuring the echo waves, the computer can determine how far away the object is, its size, shape, uniformity, and consistency (whether the object is solid, fluid-filled, or a mixture).
What To Expect
For most ultrasound exams, the patient lies face-up on the examination table. A clear gel is applied to the area being examined. The gel allows the transducer to have ideal contact with the body by eliminating all air pockets. The physician will then firmly press the transducer against the skin and slowly move it around the area of interest. After the ultrasound scanning is complete, the gel will be wiped off the patient’s skin and the patient can leave.
In some ultrasound exams, physicians insert the transducer inside the body to obtain useful results. In these cases, the transducer is attached to a probe and then placed into one of the body’s openings. For example, a transesophageal echocardiogram is taken by placing the transducer into the esophagus to get an image of the heart. A transrectal ultrasound involves placing the transducer into a man’s rectum to obtain images of the prostate. In a transvaginal ultrasound, the transducer is inserted into a woman’s vagina to view the uterus and ovaries.