PHYSICS THREE

1. What is the average velocity of ultrasound in soft tissue at 5 MHz?

1540 meter per millisecond

1540 meters per microsecond

1540 meters per nanosecond

1540 meters per second, 1.54 mm/us or 154,000 cm/sec or1.54 km/s

2. Pulse duration

Is the fraction of time that the system is transmitting a pulse

Is the distance that a pulse occupies in space

Is the actual time from the start of a pulse to the end of that pulse

3. Specular reflection occurs when

The frequency is small compared with the wavelength

The object that causes the reflection is small

The reflector surface is smooth as compared with the wavelength

The angle of incidence and the angle of reflection differ by at least 45 degrees

4. The transducer _____________is equal to the ratio of the operatoring frequency to the frequency bandwidth

Frequency

Q factor

Resolution

Polarity

5. Axial resolution

Is improved with the focal zone

Depends on the TCG slope

Is improved with digital scan converters

Depends on the wavelength

6. If the amplitude is doubled the intensity is

Doubled

Halved

Increased 4 times

Unchanged

7. As frequency increases the beam width will

Decrease

Increase

8. The ability to resolve structures lying perpendicular to the axis of the ultrasound beam is called

Lateral resolution

Axial resolution

Depth resolution

Longitudinal resolution

9. Apodization helps reduce

The pulse duration

Attenuation in tissue

Slice thickness

Alters the electrical spke voltages and reduces side lobes

10. The role of sound attentuation in tissue is expressed in terms of

Half value layer

Huygen's principle

Duty factor

Spatial peak

11. The change in direction of an ultrasound beam, when it pases from one medium to another, is which elasticity and density differ from those of the first medium is called

Refraction

Rarefraction

Angulation

Reflection

12. Increasing the PRP

Improves resolution

Increases the maximum depth that can be imaged

Decreases the maximum depth that can be imaged

13. Which of the following will improve both axial and lateral resolution

Short pulse length

Narrow beam length

Increase beam diameter

Increase transducer frequency

14. For a specular reflector

The angle of incidence is equal to the angle of reflection

The angle of incidence is greater than the the angle of reflection

There is no dependence of beam angle

The angle of incidence is less than the angle of reflection

15. Dynamic aperture

Guards the transducer from noise

Reduces beam width changes with depth

Provides a diverging image field

Expands the focal region of single element transducers

16. The near field length of a 5MHz unfocused, single - element transducer will be ____________ than that of 2.5 MHz transducer of the same diameter.

Twice

Equal to

Half

1/4

17. Bandwidth can be increased by

Increasing the quality factor

Increasing the frequency

Increasing the pulse length

Increasing damping

18. The spatial pulse length

Determines penetration depth

Usually decreases with freqency

Is improved with rectification

Determines lateral resolution

19. The comet tail artifact can be seen posterior to an object that has

A much lower acoustic impedance than it surroundings

A much higher acoustic impedance than it surroundings

Either a much lower or a much higher acoustic impedance than it surroundings

The same acoustic impedance as it surroundings

20. The width of an ultrasound beam measured perpendicular to the scanning plane, determines the

Hoziontal distance measurement accuracy

Maximum depth of visualization

Lateral resolution

Slice thickenss

21. The number of ultrasound pulses per second emitted by an ultrasound machine is

Transmit power

Image frame rate

Pulse repetition frequency

Wave frequency

22. Red blodd cells are an example of a

Are smaller than the beams wavelength

Rayleigh scattering redirects beam in all directions

Strong reflector

Mirror reflector

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Physics Three