Ultrasound is a technique that uses sound waves to study the internal parts of the body. High-frequency sound waves (20,000Hz and above), which are beyond the range of normal hearing are transmitted to the area that needs to be studied and the returning echos are recorded. The technical term for ultrasound testing and recording is sonography. It is used widely in every branch of medicine eg. in obstetrics to study the foetus, in cardiology to detect heart damage and in ophthalmology to detect problems related to the eye. Sometimes ultrasound waves may be used to treat joint pains and in lithotripsy (a procedure in which shock waves break up kidney stones, eliminating the need for surgery). Ultrasound has been used in medicine since the Second World War and is recognised as a non-invasive and an inexpensive imaging technique.
How is it done?
In this technique, high frequency sound waves are used to produce an image, representative of the part that needs to be studied. An gel is spread over the skin on the area to be studied. A hand held instrument called a transducer is passed over the surface of interest. It emits high frequency sound waves and collects the reflections from the internal organs. The computer compiles this information into a picture on a video screen and this is simultaneously recorded on a film. After the scanning the gel is wiped off.
What are the uses of ultrsasound?
Ultrasound examinations can be used for a variety of purposes ranging from examinations of the chest, abdomen, blood vessels to evaluation of pregnancy. An ultrasound can be used:
To obtain detailed images of the size and function of the heart. It can also detect abnormalities of the heart valves, infections of the heart (endocarditis), abnormal fluid collections around the heart (pericardial effusions) or to evaluate and monitor heart functions after a heart attack.
To examine the internal structures of the abdomen. Gallstones, kidney problems, tumours, abscess or cysts can be detected in the abdomen or liver.
To evaluate the size, gender, movement and position of the growing baby. Transvaginal ultrasounds help to identify patients at risk of opening of the cervix resulting in a miscarriage, monitoring of foetal heartbeat and identifying any other disorders related to pregnancy.
How do patients prepare for an ultrasound?
The preparation required for an ultrasound is minimal. If internal organs such as the gallbladder are to be examined, patients are asked to avoid eating and drinking for six to eight hours prior to the examination. This is because food causes gallbladder contraction, minimizing the size which would be visible during an ultrasound. In case of an examination of the lower abdomen or during pregnancy it is recommended to have four to six glasses of water one to two hours prior to examination for the purpose of filling the urinary bladder. The extra fluid in the bladder is easy to identify and moves air-filled bowel loops away from the womb so that the baby and womb are more easily seen during the test.
How safe is it?
No harmful effects have so far been noted in the field of diagnostic ultrasound. It is a safe technique and can be repeated as and when required.