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College of Applied Medical Sciences

Dept. of Radiological Sciences

RAD 312 Ultrasound Physics                              

 

Sample Test and Answers (1)

A)     Fill in the blanks:

1. Human being cannot hear sound with frequencies more than …20000………Hz.

2. The speed of sound in soft tissue is …1540 m/s………

3. Rough surfaces cause sound to ……scatter…….. rather than be reflected.

4. U/S is attenuated in tissues by: …absorption… , …scatter…., and …reflection…..

5. When U/S is absorbed in a medium it is converted into …heat……….

6. The power of U/S passing through unit area perpendicular to the direction of propagation is known as …intensity……

7. The speed of sound in air is …330 m/s…………..

8. If an U/S beam with a frequency of 2MHz has a speed of 1000 m/s in a certain medium. Another beam with a frequency of 4MHz passing through the same medium should have a speed of …1000 ….. m/s.

9.  1µs = …1/1000000……… s

10. The wavelength of an U/S beam with a frequency of 3.5MHz is …0.4mm………….

B)     Indicate whether the statements are True or False:

1. For 1MHz U/S beam, the average attenuation coefficient in soft tissue is 70 dB/m …………………………….. (  F  )

2. The frequency of sound is the number of cycles/second, and its unit is the Hz. ……………………………………( T )

3. When the difference in acoustic impedance between two tissues is small, the degree of reflection of U/S will be large ……………………………………………………(F)

4. High frequency U/S beam gives better resolution ……………………………………………………….( T )

5. Attenuation of an U/S beam in a medium is inversely related to its frequency …..………………………………….( F )

6. The wave length = the speed of sound X the frequency ……………………………………………………(F)

7. One MHz = 1000,000 KHz …………………( F )

8. As the frequency of U/S increases the period of the wave decreases …………………………………………….( T )

9. In diagnostic U/S, as the frequency increases the acoustic impedance also increases …………………………….( F )

10. Attenuation = Path length X Attenuation coefficient ………………………………………………………(  T )C)     Draw a figure showing two waves with different frequencies. Indicate the wavelength and the amplitude in each wave.

-         (See the power point slide)

D)     Draw a curve showing the effect of using different frequencies on the penetration ability of an U/S beam.

-         (See the power point slide)

 

 

 
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