Ultrasound
Introduction
Ultrasound imaging - also known as sonography - uses sound waves to produce images of organs, vessels and tissues in the
body. During an ultrasound examination, a small, hand-held transducer is placed in contact with the patient's body. It emits inaudible, high-frequency sound waves that pass through the body, sending back "echoes" as they bounce off organs, vessel walls and tissues. Special computer equipment then converts these echoes into an image.
Ultrasound imaging has many applications. It is ideal for imaging the heart and the blood vessels. It can evaluate heart wall, chamber and valve motion, as well as blood flow within the heart and blood vessels. It may be used to detect breast cysts or gallstones and to examine the prostate and to examine the liver, kidneys, pancreas, spleen, colon and urinary bladder for tumors, inflammation, stones or cysts. The use of ultrasound is expanding into the field of sports medicine as an effective way to detect ligament, tendon and nerve injuries. Ultrasound also can be used to guide needle placement for biopsies, and to guide the drainage of cysts or fluid collections in the abdomen or chest that occur with some illnesses.
Because ultrasound uses sound waves instead of radiation to create images, it is a safe form of fetal imaging. It is used in obstetrics to assess fetal well-being, determine fetal position, diagnose multiple gestations (twins, triplets, etc.), determine a delivery date and rule out ectopic pregnancy. If the fetus is old enough and positioned correctly, a baby's sex also can be determined. Ultrasound also plays a significant role in the evaluation and treatment of infertility.
In addition to its diagnostic imaging capabilities, ultrasound also is sometimes used in therapeutic applications to help treat soft tissue injuries. The discussion contained here, however, is confined to medical imaging.
Patient Preparation
Depending upon the body part being examined, you may be advised to drink water before your ultrasound examination, because sound waves travel more easily through fluid. You also may be advised to avoid drinking carbonated beverages before the examination because the air bubbles may interfere with the image.
You should wear comfortable clothing on the day of your examination. You may or may not be asked to put on a hospital gown, depending upon the procedure.
Before the exam begins, a sonographer will explain the procedure to you, ask questions about your health, ask why your physician requested the exam, and answer any questions you might have. A sonographer is a skilled medical professional who has received specialized education in the areas of anatomy, patient care, imaging techniques and ultrasound procedures.
During the Examination
Total examination time can range from less than 30 minutes to more than an hour, depending upon the part of the body being examined.
The sonographer will position you on the examination table and apply a special lotion to your skin directly above the area being studied. The lotion is odorless, harmless and water-soluble. It acts as a conductor, making it easier for sound waves to travel into the underlying anatomy. After the lotion is applied, the sonographer will move a device called a transducer over the lotion-covered skin. The transducer sends out sound waves and receives echoes. These echoes are relayed to a computer for processing and displayed on a monitor as a picture for the sonographer to view. Selected pictures will be saved on paper, film, videotape or in a computerized format to be reviewed by the supervising physician.
During the procedure, you will feel light pressure from the transducer being moved over your skin. The sonographer may ask you to change the position of your body or to hold your breath for a few seconds so that certain images can be obtained.
When the exam is complete, your ultrasound scans will be given to a radiologist - a physician who specializes in the diagnostic interpretation of medical images. Other physicians who may obtain additional training and read ultrasound exams include obstetricians, gynecologists, cardiologists, vascular surgeons, oncologists and urologists.
Other Types of Ultrasound Procedures
Echocardiography uses ultrasound to take "moving pictures" of the heart. During an echocardiography examination, you will be hooked up to an electrocardiogram unit (ECG) that monitors the timing of events in the heart. The ECG leads will be attached to your chest with small adhesive patches and wires. The sonographer will spread gel on your chest and then move the ultrasound transducer over your chest wall or upper abdomen to obtain images of your heart. To evaluate the heart's response to stress, you might also be asked to perform a series of exercises that elevate your heart rate. Another echocardiography examination will be performed while your heart rate is elevated.
Doppler ultrasound is a special application of ultrasound that detects moving objects, such as blood flow. With Doppler ultrasound, physicians can examine the amount, direction and speed of blood flowing to the brain or coursing through the heart, vessels or other organs.
Although the ultrasound transducer usually is placed on the outside of the body, on the surface of the skin, a few examinations require that the transducer be placed inside the body to obtain the highest quality images. Some types of gynecological and obstetric examinations, for example, require that the transducer be placed inside the vagina. These examinations, called endovaginal or transvaginal procedures, use a special type of transducer designed for maximum image quality and minimum patient discomfort.
During a transesophageal echocardiogram, the transducer is threaded down a patient's throat into his or her esophagus. Placement of the transducer in the esophagus permits the sonographer to obtain clear images of specific areas of the heart.
A rectal transducer is used for ultrasound examinations of the prostate. This procedure may be used to acquire a tissue sample (biopsy) from areas of the prostate.
Post-examination Information
After your ultrasound images have been reviewed by a radiologist, your personal physician will receive a report of the findings. Your physician then will advise you of the results and discuss what further procedures, if any, are needed.
There are no known side effects or after effects from ultrasound imaging, and it is not necessary to take any special precautions following your examination.
Please remember that the material presented here is for informational purposes only. If you have specific questions about a medical imaging procedure, contact your physician or the radiology department of the institution where your test will be performed.
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