True or False? Focused sound beams are considered less likely to create bioeffects because the beams will strike fewer gas bubbles that could potentially cavitate. Correct Answer: True. Small gas bubbles, or gaseous nuclei in tissues, serve as sites of cavitation.
Certain studies of bioeffects ...
SPI Physics Exam 2| 615
QUESTIONS| GRADED A
True or False? Focused sound beams are considered less likely to create bioeffects
because the beams will strike fewer gas bubbles that could potentially cavitate.
Correct Answer: True. Small gas bubbles, or gaseous nuclei in tissues, serve as
sites of cavitation.
Certain studies of bioeffects are performed in vitro. What is the meaning of in
vitro?
A) visible in a living organism
B) observations based on experiments
C) discernible in a test tube
D) perceptible in a living human being Correct Answer: C.
Which component of an u/s system exposes a patient to greatest risk?
A) the CRT
B) the electric cord
C) the pulser
D) the transducer Correct Answer: D.
T or F? The AIUM suggests that in vitro research confirming bioeffects is valuable
and valid. their results are significant and should be directly applied to the clinical
arena. Correct Answer: F. It is difficult to assess their direct clinical significance.
Which of the following statements regarding cavitation is true?
A) it has never been observed in any biologic media
B) stable cavitation relates to oscillating bubbles while transient relates to bursting
bubbles
C) it is a nonlethal bioeffect produced in animal experiments
D) waves with peak pressures <100MPa can never induce cavitation Correct
Answer: B
What is epidemiology the study of?
A) large groups
,B) the prevalence of disease
C) acoustic bioeffects on the fetus Correct Answer: B
T or F? One reason focused ultrasound beams with low intensities are less likely to
cause bioeffects is that a focused beam is less efficient in heating a large mass of
tissue to a critical temperature Correct Answer: T
Which of the following u/s beams has a characteristic that is most likely to cause
temperature elevation in soft tissue?
A) strongly focused
B) medium focused
C) unfocused Correct Answer: C
Research has indicated that cavitation_____.
A) never occurs
B) cannot occur with long pulses
C) can be lethal to living things
D) effects are purely theoretical Correct Answer: C
Which component of an u/s system is made of lead zirconate titanate (PZT)
A) matching layer
B) active element
C) damping material
D) scan converter's computer chips Correct Answer: B
T or F? The characteristic impedance of acoustic gel is > the matching layer's
impedance but < the piezoelectric element's impedance. Correct Answer: F
T or F? The piezoelectric crystal of a transducer typically has an impedance higher
than the impedance of skin. Correct Answer: T
Which of the following lists orders the impedance from high to low?
A) skin, gel, matching layer, PZT
B) PZT, gel matching layer, skin
C) gel, PZT, mathching layer, skin
D) PZT, matching layer, gel , skin Correct Answer: D
What is the thickness of the matching layer of a 2 MHz PW transducer?
A) 1.54 mm
B) 0.77 mm
,C) half the wavelength of the sound wave in the PZT
D) 1/4 the wavelength of sound in the matching layer Correct Answer: D
An u/s pulse is traveling in soft tissue. Which of the following is most important in
the determination of the frequency of the sound?
A) the propagation speed of the matching layer
B) the thickness of the backing material
C) the impedance of the matching layer
D) the propagation speed of the active element Correct Answer: D
What is the best estimate of the propagation speed of the ferroelectric element of a
transducer used in a typical diagnostic imaging lab?
A) 1.2 mm/usec
B) 4 m/sec
C) 4 mm/usec
D) 1 km/sec Correct Answer: C
How thick is the active element of a 3 MHz PW transducer?
A) 1.54 mm
B) 0.51 mm
C) half the wavelength of the sound wave in the PZT
D) 1/4 the wavelength of wound in the matching layer Correct Answer: B
T or F? The backing material helps to decrease the duty cycle at a particular PRF
Correct Answer: T
T or F? The backing material decreases the QF Correct Answer: T
T or F? The SPL is decreased with the application of backing material Correct
Answer: T
T or F? The PD is increased as a result of backing material Correct Answer: F
T or F Damping material helps to decrease the PRP at a given depth Correct
Answer: F
Which component of an u/s transducer is made from a slab of epoxy embedded
with tungsten particles?
A) matching layer
B) piezoelectric crystal
, C) damping material
D) computer chips Correct Answer: C
T or F The purpose of the backing material is to shorten the pulses, thereby
creating images with better quality Correct Answer: T
T or F In general, imaging transducers have a lower QF and a wider BW than
therapeutic transducers Correct Answer: T
Which properties of the piez crystal of a CW transducer result in the high emitted
frequency?
A) thin, high prop speed
B) thick, slow speed
C) thin Slow speed
D) none of the above Correct Answer: D
Which properties of the piez crystal result in highest emitted frequency?
A) thin, high speed
B) thick, slow speed
C) thin, slow speed
D) none of the aboves Correct Answer: A
Damping material is secured to piez material during the fabrication of a transducer.
Which of the following is not a consequence of the attachment?
A) BW increases
B) QF decreases
C) sensitivity increases
D) longer transducer case Correct Answer: C
For a disc-shaped PZT crystal producing continuous sound, which design will
create a beam with the shallowest focus?
A) large diameter, low frequency
B) large, high
C) small, low
D) small, high Correct Answer: C
1meter = _____________mm Correct Answer: 1,000
1 cm = __________ mm Correct Answer: 10
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