Sonography is used in hospitals to image body parts to aid in the diagnosis of various conditions. Ultrasound is done under the scope of radiology, but it is unique from other imaging modalities because it does not use ionizing radiation, which can have harmful effects on the body.
Non-Ionizing Radiation
Since ultrasound uses a different type of radiation--sound waves--it sees the body differently than other imaging modalities. X-rays, which are used in the traditional X-ray picture and in computed tomography (CT), form images based on the reaction of the X-rays to the different densities of the tissues. Sonograms are based on the speed and intensity of the sound waves returning from different body structures. For this reason, it is safer than an X-ray, and sonograms can take a different look at a particular structure.
Women's Health
Ultrasound is a useful tool in obstetrics and gynecology. It has no known ill effects on the human body, so it is the most commonly used imaging modality for obstetric ultrasound. It is used to evaluate the uterus and ovaries because X-rays could negatively affect fertility. Ultrasound is also used to compliment mammography. Mammograms are formed by the reaction of X-rays to the different densities of breast tissue. Ultrasound confirms if a mass seen on mammography is cystic or solid and if there is any blood flow in the mass.
Pediatrics
X-ray can be harmful to the sensitive, developing tissue of children. For this reason, ultrasound is a valuable imaging modality for the diagnosis of many conditions in children. Since children are less likely to have fat, significant amounts of bowel gas and scarring, ultrasound often produces clear images of the abdomen. The liver and spleen often are imaged and may be enlarged if lymphoma is suspected.
Doppler
The velocity of blood is evaluated using Doppler ultrasound. Doppler is also used to produce an image showing the direction of blood flow by assigning each direction a different color. It examines the carotid arteries in patients who have either had a stroke or who are suspected to be at risk for stroke. Doppler also is used to evaluate the arm and leg arteries and veins for plague and blood clots, respectively.
Surgical Procedures
Ultrasound is used as a guide for various surgical procedures. Breast and thyroid biopsies are often done under ultrasound guidance. Other parts of the body may be biopsied, as well, including the liver and lymph nodes. Ultrasound also may be used for PICC line insertions. A PICC line is the insertion of a catheter into a vein for the frequent administration of medication. Ultrasound may be used for other surgical procedures under the discretion of the radiologist or other physician.
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