Ultrasound imaging uses high-frequency sound waves to produce live pictures of the inside of the body. It involves the use of a small transducer (probe) and ultrasound gel placed directly on the skin. High- frequency sound waves are transmitted from the probe through the gel into the body. The transducer collects the sounds that bounce back and a computer then uses those sound waves to create an image. It is used to help diagnose diseases of the internal organs, to examine a baby in pregnant women, and the brain and hips in infants. It’s also used to help guide biopsies and diagnose heart conditions. Ultrasound is safe, painless, non-invasive, and unlike X-ray and CT scan, does not use ionizing radiation.
Because ultrasound images are captured in real-time, they can show the structure and movement of the body's internal organs, blood flowing through the vessels, as well as fetal movement within the uterus.
Conventional ultrasound displays the images in 2D. Advancements in ultrasound technology include three- dimensional (3-D) ultrasound that formats the sound wave data into 3-D images. Doppler ultrasound is a special technique that allows the radiologist to see and evaluate blood flow through arteries and veins in the abdomen, arms, legs, neck and/or brain (in infants and children) or within various body organs such as the liver or kidneys.
Ultrasound examinations are painless and easily tolerated by most patients.
For most ultrasound exams, you will be positioned lying face-up on an examination bed. The doctor will apply a thin layer of gel on the skin. A detector is then placed on your body to send sound waves to your body to produce images. You may be asked to turn to either side to improve the quality of the images. The examination is usually done within 10 minutes.
There is usually no discomfort apart from mild pressure as the transducer is pressed against the area being examined. Ultrasound exams in which the transducer is inserted into an opening of the body (such as transvaginal scan in female and transrectal scan in male) may produce minimal discomfort.
If a Doppler ultrasound study is performed, you may hear pulse-like sounds that change in pitch as the blood flow is monitored and measured.
After an ultrasound examination, you should be able to resume your normal activities immediately.
Ultrasound waves are disrupted by air or gas; therefore ultrasound is not an ideal imaging technique for air-filled bowel or organs obscured by the bowel. In most cases, barium exams, CT scanning, and MRI are the methods of choice in such a setting.
Ultrasound also has difficulty penetrating bone (except in infants who have more cartilage in their skeletons). For visualizing bones or certain joints, other imaging modalities such as X-ray, CT scan or MRI are typically used.