Sonography

It is also called Ultrasonography. It involves the use of high frequency ultrasonic sound waves to produce images of structures within the human body.

Mechanism

Sonography is based on ultra sound (frequency above 20 KHz). When high frequency sound waves travel forwards, they continue to move until they make contact with an object. Then a certain amount of the sound bounces back.

In medical practice, ultra sound of frequency 1 - 15 MHz in beamed into the human body, and the returning echoes are detected. For clinical examination, the sonographer places a scan head transducer in contact with the area to be scanned. A layer of aqueous gel is applied over the skin to make sure that the sound has an air - free path into the organ. The transducer is move over the part of the body to be examined. The ultrasound waves penetrate the body, strike the organ and reflect back to the surface. The returning sound waves are detected by the transducer which acts as the receiver. The echoes are processed by the computer into a two-dimensional image that appears on screen. The image is called as Sonogram.

Advantages

1) Safer than radiography as there is no exposure to radiation.

2) Non-invasive and painless.

3) Comfortable and inexpensive.

Significance

1) Used to assess foetal growth and detect abnormalities such as spina bifida etc.

2) Useful in diagnosing kidney stones, gall stones, cirrhosis, obstructions in intestine, oviducts, uterus etc.

3) To measure blood flow through the heart, arteries and veins based on a phenomenon known as Doppler Effect.