Module 4

How many Hertz are there in 4 MHz?

4,000,000 Hz.

Which form of attenuation is due to the sound wave not continuing on the path that the ultrasound unit thinks it's going? Refraction Amplitude Reflection Absorption

Refraction

All of the following are assumptions that the ultrasound unit makes EXCEPT: Ultrasound waves are traveling through tissue at 1.54 mm/µs. Ultrasound travels in a straight path. All interfaces are encountered at an oblique angle. The sonographer made proper adjustments.

All interfaces are encountered at an oblique angle.

Which of the following describes what the frequency of an ultrasound transducer is best? A representation of how compressed tissue becomes when encountering a sound wave How frequently the ultrasound unit sends out a pulse. The speed at which a sound wave moves through tissue The amount of time over which one cycle takes place

How frequently the ultrasound unit sends out a pulse.

What can we say about the transmitted sound beam for two adjacent media (specular interface) that have the same sound velocities?

The transmitted angle is the same as the incident angle

Which attenuation process results in increased tissue heat?

absorption

Which of the following are types of attenuation? (Select all that apply) Reflection Transmission Absorption Scattering Viscosity Wavelength Artifact Refraction

absorption, reflection, refraction, scattering

Which of these will cause an increase in the amount of sound wave absorption? An increase in depth A decrease in viscosity Normal incidence A decrease in frequency

an increase in depth

Suppose that the propagation velocity of Medium 2 is 1300 m / sec and the propagation velocity of Medium 1 is 1200 m / sec. For an incident angle is 30°, is the refracted angle toward or away from normal?

away from normal

The positive half of a pressure wave corresponds to

compression

Absorption is defined as

conversion of mechanical energy to heat

If the propagation velocity of Medium 1 is equal to the propagation velocity of Medium 2, the transmitted sound beam angle at the interface will: refract away from normal incidence equal the incident beam angle refract towards normal incidence

equal the incident beam angle

true or false: The sonographer cannot make adjustments that may eliminate artifacts.

false

true or false: Wavelength is directly proportional to frequency and indirectly proportional to propagation speed.

false

Of the following choices, refraction requires which of the following factors? perpendicular incidence medium 1 velocity > medium 2 velocity media velocity differences acoustic impedance differences

media velocity differences

the acoustic variable that has the greatest effect on sonographic imaging is_____________________

particle motion

Which type of attenuation is responsible for the grainy appearance of organ tissue? Absorption Scattering Refraction Reflection

scattering

More sound energy is _______________than is ______________.

transmitted, reflected

A ________________ wave is NOT the type of wave that constitutes medical ultrasound.

transverse

true or false: Not all types of ultrasound are performed using the same type of transducer.

true

true or false: When sound waves return from the body they are converted into electrical signals.

true

Which of the following changes depending on what function the sonographer is asking the ultrasound unit to perform? ultrasound unit dashboard brightness ultrasound unit touchscreen ultrasound unit monitor

ultrasound touchscreen

If the speed of a wave is decreased, what is the effect on the wavelength?

waveform shortens

Which term describes the distance of one cycle for a wave?

wavelength