6
Sample Questions
1.
If the relative output power of an ultrasound instrument is
calibrated in decibels and the operator increases the output
by 20 dB, the beam intensity is increased by
A. five percent.
B. two times.
C. twenty times.
D. one hundred times.
E. one million times.
Question Type:
No Look
Keywords:
intensity, increases
Rephrased question:
Increasing the output by 20 dB,
increases the beam intensity by
Solving the problem:
So the intensity, which is proportional to the power, is increased
by a factor of 100, or one hundred times
(Choice D)
.
2.
Assuming a fixed frequency, what happens if the diameter of
an unfocused circular transducer is increased?
A The distance to the far field is reduced.
B. The beamwidth in the near field is reduced.
C. The beamwidth in the far field is reduced.
D. The ultrasonic wavelength is increased.
E. The sensitivity is reduced.
Question Type:
No Look
Keywords:
diameter, increased
Rephrased question:
Increasing the crystal diameter
causes
Increasing the diameter creates a much deeper focus, and hence, a
narrower beamwidth in the relative far field.
Now find the choice which matches your answer.
Choice A is the opposite of what happens
Choice B is the opposite of what happens
Choice C is true
Choice D is unrelated. The wavelength is determined by
the frequency and the propagation speed,
neither of which change with transducer
diameter.
Choice E is most likely the opposite of what occurs, a
larger diameter crystal is effectively a larger
antenna, and therefore usually more sensitive
(BUT NOT ALWAYS).
3.
Which one of the following sets of properties of a test object or
a phantom is MOST relevant when assessing depth calibration
accuracy?
A. Reflector spacing and reflector reflection coefficient
B. Attenuation in the medium and speed of sound in the
medium
C. Reflector spacing and ultrasonic attenuation in the
medium
D. Reflector reflection coefficient and ultrasonic attenua-
tion in the medium
E. Reflector spacing and speed of sound in the medium
Question Type:
Peek
Keywords:
most, depth, calibration, accuracy
Central concept:
Depth calibration has to do with signals ar-
riving at correct time relative to transmit.
This depends on the depth of the reflector
and the propagation speed.
Now find the choice which matches your answer.
Choice A
is half true, half not. Reflector spacing refers to
depth, but the reflection coefficient determines
echo amplitude, not propagation speed.
Choice B
is half true, half not. Attenuation determines
signal strength, not depth.
Choice C
is also half true, half not. Again attenuation
determines signal strength.
Choice D
is completely false.
Choice E is correct.
4.
From a safety standpoint,which one of the following methods
is BEST?
A. Low transmitter output and high receiver gain
B. High transmitter output and low receiver gain
C. High near gain and low far gain
D. Low near gain and high far gain
E. High reject and high transmitter output
