Ultrasound uses sound waves and a computer to create images of internal organs and blood vessels and to monitor many medical conditions, including the progress of pregnancy. A tool called a transducer that emits sound waves is placed over the area of the body being examined. The sound waves bounce off these structures and their echoes are received by the transducer, which then sends the information to a computer. The computer analyzes the information and creates a moving image.
Its most familiar use involves determining the status (including movements) and gender of a fetus. Most obstetricians perform a routine diagnostic ultrasound to look for any abnormalities with either the fetus or the uterus during early pregnancy. Depending on the time of gestation and positioning, the gender may or may not be identified. This procedure is painless and non-invasive.
Diagnostic ultrasound has many other uses, including the evaluation of tumors and bone structure and in interventional radiology.
When is it used?
Ultrasound has a wide range of applications, from adult bone studies to fetal heart rate monitors. It helps clinicians assess the organs and blood vessels in the abdomen (liver, kidneys, spleen, gallbladder, bile ducts, aorta and pancreas). It also helps in evaluating organs in the pelvic area (uterus, ovaries, bladder, and prostate). Ultrasound is frequently used to check for the gestational age of a fetus, as well as any irregularities of the fetus. The breast, thyroid, scrotum or any other soft tissue mass can be assessed using ultrasound, as can arteries and veins in the neck, abdomen and legs. Here are some examples of ultrasound study types and their purpose:
- Doppler ultrasound (to visualize blood flow through a blood vessel).
- Bone sonography (to diagnose osteoporosis).
- Echocardiogram (to view the heart).
- Fetal ultrasound (to view the fetus in pregnancy).
- Ultrasound-guided biopsies.
- Doppler fetal heart rate monitors (to listen to the fetal heart beat).
What happens during the procedure?
A technologist will take you to the exam room, ask you some medical questions, and explain what you can expect during your test. Before your scan, you may change into a gown and be asked to remove all metal and plastic items from the part of your body being examined. A technologist will help you onto the examining table and position you comfortably. A water based gel is applied to the skin over the area to be examined to block any air between the skin and transducer, as well as to eliminate friction on the skin. The technologist then places the transducer over that area. For some pelvic ultrasound exams, the technologist will use a vaginal transducer, which creates clearer images of the organs in your pelvis.
What are the benefits and risks?
Diagnostic ultrasound was put into practice for medical purposes in the 1950s. The ability to use sound waves to reflect an image of body organs and tissues completely changed the practice of radiology. It remains an extremely useful procedure, and we use state-of-the-art technology and rapid digital reporting to provide fast results for every diagnostic study.
There is no ionizing radiation exposure with this procedure; ultrasound has an excellent safety record. We nevertheless practice prudent use of ultrasound, particularly for fetal imaging.