March 17 20:31 2019 Print This Article

Ultrasound is a method of examining tissues deep inside the body by means of high-frequency sound waves. Ultrasound waves bounce off tissues at different rates according to the density of the tissue. The waves are generated by a small device called a transducer, which is held or moved over the area tobe examined. The transducer also records the echoes of reflected waves and transmits them to a computer, where they are analysed and converted to an image that can be photographed from the computer screen or printed out, interpretation of the image allows tissues of different density to be distinguished from one another.

Because the sound waves have no known effect on the tissue being examined, the scan can be continued over a period of time to observe the move ment of structures within the body, such as the beating of the heart or the progress of a BIOPSY needle towards its target. Continuous observation under ultrasound is called real-time ultrasound

Ultrasound is used to examine soft tissues and fluids within the body, and can detect tumours, stones, cysts and signs of inflammation. Because the sound waves cannot pass through bone or gas. ultrasound is not used to examine parts surrounded by bone (such as the brain and spinal cord) or containing gas (such as the lungs and parts of the gut). Ultrasound scans can be performed in an out-patient clinic or radiology centre, and are quick and noninvasive. The results are available immediately.

In an ultrasound picture, bone looks white and fluid looks black. In early pregnancy ultrasound can be used to find a normal heartbeat and to measure the baby to see how far along the pregnancy is. Ultrasound can be used to locate objects by means similar to the principle by which radar works. High-frequency acoustic waves reflect from objects, even comparatively small ones, because of the short wavelength. In ultrasonic medical imaging, high-frequency acoustic energy is transmitted into the human body using a set of transducers attached to the skin. Ultrasounds may be performed at any point during pregnancy, and the results are seen immediately on a monitor during the procedure. Because ultrasound gives a continuous picture it is very helpful for guiding a needle to an area deep within the body. A procedure like amniocentesis is performed while watching the needle with ultrasound.

Why the test is performed?

Ultrasound used to:

  • Evaluate flow in blood vessels.
  • To see if there is more than one fetus.
  • Guide the biopsy and treatment of a tumor.
  • Evaluate a fetus.
  • Reveal abnormalities in the scrotum and prostate.
  • To check the physical development of the baby and as, far as possible, make sure there are no abnormalities.

How to prepare for the test?

  • Preparation for the procedure will depend on the body region being examined.
  • You should wear comfortable, loose-fitting clothing for your ultrasound exam.
  • You may be asked to wear a gown during the procedure.


  • Ultrasound imaging uses no ionizing radiation.
  • Ultrasound provides real-time imaging, making it a good tool for guiding minimally invasive procedures such as needle biopsies and needle aspiration of fluid in joints or elsewhere.
  • Ultrasound is usually painless.


  • For standard diagnostic ultrasound there are no known harmful effects on humans.
  • No ionizing radiation exposure is involved.
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