Ultrasonic Imaging

Ultrasound is sound with a frequency greater than the upper limit of human hearing (greater than 20 kHz). Acoustic frequencies between 16 kHz and 1 GHz are referred to as ultrasound. In industrial settings we call it “Ultrasonic”.

figure 1: Frequency range of the sound

Many insects have good ultrasonic hearing and most of these are nocturnal insects listening for echolocating bats. This includes many groups of moths, beetles, praying mantids and lacewings. Toothed whales, including dolphins can hear ultrasound and use such sounds in their navigational system to orient and capture prey.

figure 2: ultrasound used by a fish to catch the prey

Properties of ultrasonic waves

• They have a high energy content.
• Just like ordinary sound waves, ultrasonic waves get reflected, refracted and absorbed.
• They can be transmitted over large distances with no appreciable loss of energy.
• If an arrangement is made to from stationary waves of ultrasonic in a liquid, it serves as a diffraction grating. It is called an acoustic grating.
• They produce intense heating effect when passed through a substance.

How ultrasound uses for imaging

The ultrasound imaging is used to determine the development of health and to determine the sex of unborn babies in the womb. Ultrasound images are generated using the following procedure

1. The ultrasound system transmits a high frequency sound pulse into the body usually 1 to 5 MHz

2. The sound wave travel through the body and hit a boundary between tissues.

3. Some of the waves are reflected back to the probe and relayed to the computer.

4. The machine calculates the distance from probe to the tissue boundaries by using the speed of the sound and the time required for each echo’s to return.

5. The system displays the distances and intensities of the echoes on the screen, forming a two dimensional image.

figure 3: how ultrasound system transmits a pulse and echo it

Domains which are used Ultrasonic imaging

In hospitals (Medical ultrasound)

Also known as diagnostic sonography or ultrasonography. This is a diagnostic imaging technique based on the application of ultrasound. It is used to see internal body structures such as tendons, muscles, joints, vessels and internal organs. Its aim is often find source of disease or to exclude any pathology. The practice of examining pregnant women using ultrasound is called obstetric ultrasound, and is widely used.

figure 4: Development of a pregnancy using ultrasound as an image source

figure 5: Foetus feet

                    figure 6: Thyroids             figure 7: Muscle layers showing lesion

Contributed by

APN Group

R.M.D.N.R Somarathna

H.M.A.R Wijayathilake

H.K.U Poornima

Team Alpha

Vision Group

K Ushamini

S pratheeshan

Z.M Humam