Wednesday, July 6, 2011

Ultrasound, Done By Ho Jun Hui

What is Ultrasound?

Ultrasound is something like a sound pressure with a frequency greater than the upper limits of human hearing, The normal limit for a healthy young adult is around 20 kilo hertz, which is around 20,000 hertz.

Ultrasound is like somewhere near the range of 2 mega hertz, which is far much more than the human ear can take, and this is primarily because of a low pass filter in the ear. Humans can hear ultrasound if the Ultrasound waves are fed directly into the skull bone and cochlea through bone conduction without passing through the middle ear.

Basically means that the ultrasound waves actually just by-passes the filter, and uses our bones to conduct the sound to let us hear what is the ultrasound actually is. (For those who do not really understand cochlea and bone conduction)

Ultrasound for medical uses can range from 1 mega hertz to 20 mega hertz. Ultrasound imaging does not use more than 10 mega hertz. As stated above, our human hearing can only hear up to like 20 kilo hertz, 20,000 cycles per second, but 1 mega hertz is like 100,000,0 cycles per second!

The speed of ultrasound does not depend on its frequency. The speed of ultrasound depends on what material or tissue it is traveling in. The mass and spacing of the molecules of the material and the attracting force between the particles of the material all have an effect on the speed of the ultrasound as it passes through. Ultrasound travels faster in dense materials and slower in compressible materials. In soft tissue sound travels at 1500 m/s, in bone about 3400 m/s, and in air 330 m/s.
(Taken from:

So basically this means that no matter how fast the frequency of the ultrasound waves are, it is the matter that is passes through that determines its speed. And as stated above, it can be seen that ultrasound waves do travel at a very fast speed, even though its slowest speed in air is still around 330m/s.

Ultrasound waves are produced by a transducer. A transducer is a device that takes power from one source, converts the energy into another form, and delivers the power to another target. In this case the transducer acts like a loudspeaker and a microphone. The transducer converts electrical signals to ultrasound waves, and picks up the reflected waves converting them back into electrical signals. The electrical signals returned from the transducer are used to form pictures on a television screen.
Attenuation is loss of energy, expressed as change in intensity, as the energy travels through a medium.  Ultrasound intensity is measured in watts per square centimeter.  Decibels are used to express difference between ultrasound intensities.  For example, when ultrasound becomes one hundred times less intense, the attenuation is -20 decibels (dB); when ultrasound is one thousand times less intense, the attenuation is -30 dB.
(Taken from:

The above paragraph is just a bit more technical information, and it is up to your decision to read it or not.
Uses of Ultrasound

One use of ultrasound is ultrasound imaging which can be used for medical purposes.Ultrasound imaging is a noninvasive medical test that helps physicians diagnose and treat medical conditions. It means that there is no foreign objects that is put into the patient’s body, only just scanning and such.

Common Uses Of Ultrasound Imaging

Ultrasound examinations can help to diagnose a variety of conditions and to assess organ damage following illness.
Ultrasound is used to help physicians evaluate symptoms such as:

Ultrasound is a useful way of examining many of the body's internal organs, including but not limited to the:
heart and blood vessels, including the abdominal aorta and its major branches
uterus, ovaries, and unborn child (fetus) in pregnant patients
thyroid and parathyroid glands
scrotum (testicles)

How does the procedure work?
Ultrasound imaging is based on the same principles involved in the sonar used by bats, ships and fishermen. When a sound wave strikes an object, it bounces back, or echoes.

By measuring these echo waves it is possible to determine how far away the object is and its size, shape, and consistency (whether the object is solid, filled with fluid, or both).
In medicine, ultrasound is used to detect changes in appearance of organs, tissues, and vessels or detect abnormal masses, such as tumors.
In an ultrasound examination, a transducer both sends the sound waves and records the echoing waves. When the transducer is pressed against the skin, it directs small pulses of inaudible, high-frequency sound waves into the body. As the sound waves bounce off of internal organs, fluids and tissues, the sensitive microphone in the transducer records tiny changes in the sound's pitch and direction. These signature waves are instantly measured and displayed by a computer, which in turn creates a real-time picture on the monitor. One or more frames of the moving pictures are typically captured as still images.

Taken from:

(Also stated above, the above is mostly the technical terms, which would be hard to understand if just written in own words, again, it is up to you to understand it or not)

But the basic understanding is that ultrasound bounces off waves to a particular organ/tissue in the body and helps create an image in the computer.

This is my basic understanding of ultrasound.

Jun Hui~

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