Ultrasound Flashcards
How fast does ultrasound propagate through soft tissue?
a. 343 m/sec
b. 1,540 m/sec
c. 3,051 m/sec
d. 4,892 m/sec
B. 1,540 m/sec
_____ forms the peak of the sound wave.
Compression (a region of high pressure)
______ forms the trough of the sound wave.
rarefaction (a region of low pressure)
A sound is simply a ______ that travels in a longitudinal wave.
pressure wave ( a form of mechanical energy)
Frequency is a measure of _______
pitch.
Frequency tells us how many
cycles occur in a given period of time
________ is the distance between two identical points on adjacent cycles.
Wavelength
______ frequencies produce shorter wavelengths, and _____ frequencies produce longer wavelengths
higher; lower
______ represents the sound’s loudness
Amplitude
Sound propagates through _____ at 343 m/sec and ____ at 3,000-5,000 m/sec
air; bone
Frequency is expressed in
hertz or cycles per second
When no medium is present (such as in a vacuum or outer space), there can
be no sound
Which concept BEST explains why lead zirconate titanate is commonly used in ultrasound transducers?
a. echolocation
b. doppler effect
c. Snell’s law
d. Piezoelectric effect
D. Piezoelectric effect
What is echolocation?
the use of sound and echoes to determine where objects are located in space.
A piezoelectric material can transduce
electric energy to mechanical energy and vice versa
The piezoelectrical material used by modern ultrasound transducers is called
lead zirconate titanate
What is the primary determinant of the vertical placement of each illuminated pixel on the ultrasound monitor?
a. time delay
b. resolution
c. acoustic impedance
d. doppler effect
A. time delay
the vertical placement of each dot is determined by how long it takes for the echo to return to the transducer (time delay)
The horizontal placement of each dot is determined by
the particular crystal that receives the returning echo
The vertical placement of each dot is determined by
how long it takes for the echo to return to the transducer (time delay)
The ultrasound transducer emits ultrasound waves into the body at a fixed rate, and then it listens
for echoes between each pulse- a process that repeats many times each second
______ produces high amplitude echos
Hyperechoic
_______ appear as dark shades of grey
hypoechoic
________does not produce echos
Anechoic
The brightness of each dot is determined by the
amplitude of the returning signal
______ describes a tissue’s ability to transmit or reflect sound waves in the context of the surrounding tissues
Echogenicity
______ structures appear bright
Hyperechoic
examples- bone
____ produce weak (low amplitude) echoes
Hypoechoic
examples include solid organs, liver, skin, adipose, cartilage
_____ appear black
anechoic
Vascular structures appear as
black circles in short-axis and black tubes in long-axis
______ pulsate, ______ do not
arteries; veins
Peripheral nerves near the neuraxis tend to appear _________, but distal peripheral nerves are _______
anechoic; hyperechoic (white) with a characteristic honeycomb appearance
Which process describes a sound wave that bounces off a tissue boundary that has a different acoustic impedance?
a. absorption
b. reflection
c. scatter
d. refraction
b. reflection
______ is the process where a sound wave bounces off a tissue boundary of differing acoustic impedance
reflection
_________ occurs as the ultrasound waves are lost to the body as heat
absorption
______ occurs when the ultrasound wave encounters an object smaller than the wave
scatter
________ is the bending of ultrasound wave that encounters a tissue boundary at an oblique angle
refraction
Resolution is the ability to see
two separate things as two separate things
The three types of resolution are
axial, lateral, and elevational
Ultrasound waves leaving the transducer tend to
converge before diverging beyond a certain point
they don’t travel in a straight line
The _____ is the region where the beam is the narrowest
focal zone
The region between the transducer and the focal zone is called the ______
near zone (Fresnel zone)
The region beyond the focal zone is called the
far zone (Fraunhofer zone)
Examples of attenuation include
absorption, reflection, scatter, and refraction
A _____ view looks at a structure in cross-section, while a _____ view looks at a structure along its length.
short-axis; long-axis
As a sound wave propagates through the body, its strength naturally_____ and some of the sound waves never return to the transducer. These factors conspire to
decreases; reduce image quality through a process called attenuation
Lower frequency transducers allows us to see_____________
Deeper inside the body but we sacrifice image resolution
The array configuration describes the
Arrangement of piezoelectric crystals inside the ultrasound transducer
The linear array transducer has a flat footprint that contains piezoelectric crystals arranged
In parallel
The curvilinear array transducer has a convex footprint with the arrangement of piezoelectric crystals inside
Following suit
A ____________ is very narrow in the near field and fans out with increasing depth
Phased array transducer
Describe the frequency range, imaging depth, & application examples for a high frequency array US transducer
> 10 MHz, <3 cm below skin,
Interscalene, supraclavicular, axillary, forearm, ankle, wrist, femoral, ankle, superficial blood vessels
Describe the frequency range, imaging depth, & application examples for A medium frequency array transducer
5-10 MHz, 3-6 cm below skin,
Infraclavicular, sciatic, popliteal, deeper blood vessels
Describe the frequency range, imaging depth, & application examples for a low frequency array transducer
> 6 cm below skin,
