# PHYSICS QUESTIONS

48 Questions

QUESTIONS

• 1.
The frequency closest to the lower limit of US is
• A.

19,000 kHz

• B.

10,000 MHz

• C.

20,000 msec

• D.

15,000 Hz

• 2.
Put in decreasing order
• A.

Deca, deci, centi, micro

• B.

Deci, deca, centi, micro

• C.

Micro, centi, deca, deci

• D.

Centi, micro, deci, deca

• 3.
Which of the following is determined by the source and the medium?
• A.

Frequency

• B.

Period

• C.

Propagation speed

• D.

Range resolution

• 4.
As a result of _____________ the propagation sped increases
• A.

Increasing stiffness and increasing density

• B.

Increasing stiffness and increasing elasticity

• C.

Decreasing compressibility and decreasing density

• D.

Decreasing stiffness and decreasing density

• 5.
Put in decreasing order of propagation speed.
• A.

Gas, liquid and solid

• B.

Solid liquid and gas

• C.

Liquid gas solid

• 6.
If the frequency of US is increased from 0.77 MHz to 1.54 MHz, what happends to the wavelength?
• A.

Doubles

• B.

Halved

• C.

Remain the same

• D.

4 times greater

• 7.
If the intensity of a sound beam remains unchanged while the beam area is reduced in half, what has happend to the power?
• A.

• B.

Doubled

• C.

Halved

• D.

Unchanged

• 8.
What is the minimum value of the duty factor?
• A.

10.0

• B.

1%

• C.

1.0

• D.

0.0%

• 9.
If a 5MHz sound wave is traveling in the tissues listed below, which will have the longest wavelength?
• A.

Fat

• B.

Air

• C.

Muscle

• D.

Bone

• 10.
As the impedances (z (rayls) = density (kg/m^3) x prop. speed (m/s) or acoustic resistance to sound traveling in a medium, becomes vastly different, the
• A.

Reflection increases

• B.

Transmission increases

• C.

Refraction increases

• D.

Absorption increases

• 11.
With normal incidence, what factors affect refraction of US?
• A.

Propagation speeds

• B.

Frequencies

• C.

Attenuation coefficients

• D.

None of the above

• 12.
The most likely amount of reflection at a boundary between soft tissue is:
• A.

1%

• B.

22%

• C.

34%

• D.

99%

• 13.
How many cm are 60 millimeters
• A.

600

• B.

6

• C.

0.6

• D.

0.006

• 14.
How is range ambiguity artifact eliminated?
• A.

Lower the PRF

• B.

Raise the PRF

• C.

Increase the gain

• D.

Use a lower frequency transducer

• 15.
Under which of the following conditions is lateral resolution improved?
• A.

Decreased beam diameter

• B.

Decreased pulse duration

• C.

Decreased imaging depth

• D.

Decreased pixel size

• E.

Decreased spatial pulse length

• 16.
Which transducer would be best to image superficial structures?
• A.

Small diameter, high frequency

• B.

Small diameter, low frequency

• C.

Large diameter, high frequency

• D.

Large diameter, low frequency

• 17.
If the frame rate increases and the lines per frame is unchanged, what else must happen?
• A.

US speed increases

• B.

Frequency increases

• C.

Depth increases

• D.

Depth decreases

• 18.
TRUE OR FALSEA system which was working well now does not display clear images in the far field.  This may be a problem with the monitor.
• A.

True

• B.

False

• 19.
If the output of an US machine is calibrated in dB and the output is increased by 20 dB, the beam intensity is increased
• A.

100 times

• B.

1,000,000 times

• C.

20 times

• D.

10 times

• 20.
Which of the following will result in the greatest number of shades of grapy in a digital image display?
• A.

Large pixels with many bits/pixel

• B.

Small pixels with few bits/pixel

• C.

Many TV lines per frame

• D.

High contrast

• E.

Narrow dynamic range

• 21.
With good images on the CRT but not on the strip chart recorder, one should
• A.

Increase the gain

• B.

• C.

Check the same converter

• D.

• 22.
Compression is used to
• A.

Decrease the amplitude

• B.

Decrease the range of amplitudes

• C.

Decrease the range of frequencies

• 23.
In which of these biologic tissues will sound waves propagate most quickly?
• A.

Tendon

• B.

Blood

• C.

Lung

• D.

Fat

• E.

Amniotic fluid

• 24.
All of the following statements regarding in-vitro bioeffects are true EXCEPT?
• A.

In vitro bioeffects conclusions are clinically relevant

• B.

In vitro bioeffects are always real

• C.

In vitro bioeffects are vey important

• D.

In vitro bioeffects may not be applicable to clinical settings

• 25.
Which of the following improves signal to noise ratio
• A.

Dynamic range

• B.

Frame averaging

• C.

Gray scale

• D.

Edge enhancement

• E.

• 26.
Under which circumstances is cavitation most likely to occur
• A.

High frequency and low power

• B.

High intensity and high frequency

• C.

Low intensity and low frequency

• D.

Low frequency and high signal amplitude

• 27.
What is displayed on the y-axis of an m-mode image?
• A.

Time

• B.

Time of flight

• C.

Echo intensity

• D.

Red blood cell velocity

• 28.
An amplifier of an ultrasound system increases the voltage of a signal from 0.0001 to 0.1 volt.  What is the amplification
• A.

60 dB

• B.

30 dB

• C.

1,000 dB

• D.

90 dB

• 29.
The impedances of tissue is 3 x 10^5 rayls and for the PZT crystal is 6 x 10^6 rayls.  What is the best impedance for the matching layer?
• A.

36 x 10^5

• B.

3,600

• C.

10,000

• D.

9.5 x 10 ^5

• E.

9 x 10^4

• 30.
Put in increasing order of propagation speed
• A.

Air bone water

• B.

Bone water air

• C.

Air water bone

• D.

Water air bone

• E.

Bone air water

• 31.
What is propagation speed determined by
• A.

Wavelength

• B.

Intensity and density

• C.

Amplitude

• D.

Density and elasticity

• E.

Density and amplitude

• 32.
If 300,000 cycles occur in a second, what is the wave's frequency?
• A.

3 MHz

• B.

30 kHz

• C.

300 MHz

• D.

3 kHz

• E.

0.3 MHz

• 33.
All of the following will improve temporal resolution EXCEPT
• A.

Increased line density

• B.

Single rather than multi focus

• C.

Higher frame rate

• D.

Shallower depth of view

• E.

Slower speed of sound in a medium

• 34.
What component of a transducer changes electrical to mechanical and mechanical back to electrical engergy?
• A.

PZT

• B.

Transducer

• 35.
What are typical clinical Doppler frequencies
• A.

1 - 10,000 Hz

• B.

1 - 10 MHz

• C.

2 - 1,000 kHz

• D.

40 - 45 kHz

• 36.
What is the actual time that an US machine is creating a pulse?
• A.

Duty factor

• B.

Period

• C.

Pulse period

• D.

Pulse duration

• 37.
What is the significance of gray scale variation in the spectrum of a pulssed wave Doppler display?
• A.

It represents the number of red blood cells creating the reflection

• B.

It represents the velocity of red blood cells

• C.

It represents the speed of red blood cells

• D.

It represents the convergence of red blood cell lamina

• E.

It determines the enseble length

• 38.
What is the production of deformation from voltage called?
• A.

Piezoelectricity

• B.

Impedance

• C.

Cogeneration

• D.

Flux

• 39.
What is the elimination of voltages that do not exceed a certain level?
• A.

Amplification

• B.

Decompensation

• C.

Reject

• D.

Demodulation

• 40.
How many data bits are needed to represent 46 gray shades?
• A.

46

• B.

5

• C.

6

• D.

8

• 41.
Which of the following is associated with cavitation?
• A.

Thermal index

• B.

Snell's Law

• C.

• D.

Mechanical index

• 42.
All of the following are true of normal cavitation EXCEPT:
• A.

Harmful bioeffects are commonly observed

• B.

It is also known as inertial cavitation

• C.

Only a 10% increase in pressure is needed to convert to this from stable cavitation

• D.

Temperatures in the thousands of degreesare created

• E.

It is consistent with shock waves

• 43.
The packet size in color Doppler refers to the number of :
• A.

Pulses per second

• B.

Sample volumes per scan line

• C.

Scan lines per unit area

• D.

Pulse - listen cycles per acoustic scan line

• E.

Pulses required to create one frame

• 44.
A commonly used process for determining direction in a Doppler instrument is
• A.

Zero crossing detection

• B.

Autocorrelation

• C.

• D.

Range gating

• E.

Spectral analysis

• 45.
What is the maximum velocity limit for a 3 MHz CW Doppler unit operating at a depth of 4cm?
• A.

40 cm/s

• B.

200 cm/s

• C.

2.5 m/s

• D.

4 m/s

• E.

None of the above

• 46.
What method is used to steer the color beam with a linear array transducer?
• A.

Mechanical

• B.

Electronic time delays

• C.

Electronic voltage variation

• D.

Apodization

• E.

The color beam cannot be steered with a linear array transducer

• 47.
Increasing the wall filter during Doppler sampling will:
• A.

Increase visibility of low velocity signals

• B.

• C.

Decrease bandwidth

• D.

Reduce display of low frequency shifts

• E.

Reduce aliasing

• 48.
What would be the most likely result from increasing the transmit frequecy of the color Doppler?
• A.

Improve sensitivity to slow flow

• B.

Improved penetration for imaging flow in deep tissues

• C.

Reduced flash artifact obscuring small vessel flow

• D.

Reduced color Doppler aliasing

• E.

Improve visibility of complex flow hemodynamics

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