book study questions Test2 Flashcards
every 3dB change means that the intensity will:
double
every 10dB change means that the intensity will:
increase 10 times
a reduction in the intensity of a sound beam to 1/2 of its original value is:
-3dB
a reduction in the intensity of a sound beam to 1/4 of its original value is:
-6dB
-10dB means that the intensity is reduced to _____ of its original value
1/10
dB is a mathematical representation with a _____ scale
a. logarithmic and relative
b. division and relative
c. longitudinal and relative
d. logarithmic and absolute
a. logarithmic and relative
we need one intensity to calculate decibels
false
a wave’s intensity is 2mW/cm2
there is a change of +9dB
what is the final intensity?
a. 6mW/cm3, b. 2mW/cm2, c. 16mW/cm2, d. 16µW/cm2
c. 16mW/cm2
if the final intensity of a sound beam is more than the initial intensity, then the gain in dB is:(+or-)
positive-the beam’s intensity is increasing
if the initial intensity of a sound beam is less than the final intensity, then the gain in dB is:(+or-)
positive-the beam’s intensity is increasing
name the 3 components of attenuation
absorption
reflection
scattering
as the path length increases, the attenuation of ultrasound in soft tissue:
increases
attenuation in lung tissue is (less than, greater than, the same as) attenuation in soft tissue
greater than
attenuation in bone is ____ attenuation in soft tissue
greater than
attenuation in air is ____ attenuation in soft tissue
greater than
what are the units of attenuation?
decibels (dB)
in a given medium, attenuation is unrelated to the speed of sound
true-attenuation and propagation speed are unrelated
what is the relationship between ultrasound frequency and the attenuation coefficient in soft tissue
attenuation coefficient in dB per centimeter is approx 1/2 of the ultrasonic frequency in MHz
what are the units of the half-value layer thickness?
distance-centimeters
as frequency decreases, depth of penetration:
increases
as path length increases, the half boundary layer:
remains the same
impedance is associated with:
only the medium
as the path length increases, the attenuation coefficient of ultrasound in soft tissue (decreases, remains the same, increases)
remains the same
acoustic impedance=
_____x_____
density(kg/m3) x propagation speed(m/s)
two media A and B have the same densities
the speed of sound in medium A is 10% higher than in medium B
which has the higher acoustic impedance?
medium A’s acoustic impedance is higher than medium B’s
recall that impedance = speed x density
since both media have identical densities and medium A’s speed is 10% higher, then medium A’s impedance is 10% higher
impedance is important in ____ at boundaries
reflections
which is better to use while examining a carotid artery, a 7.5 or 3.0MHz transducer?
7.5MHz transducer
higher frequency produces better image in a superficial structure
a sound wave with an intensity of 50W/cm2 strikes a boundary and is totally reflected
what is the intensity reflection coefficient?
a. 50w/cm2, b. 25w/cm2, c. 0w/cm2, d. 100%, e. 0
d. 100%
coefficient is a percentage
a sound wave with an intensity of 50W/cm2 strikes a boundary and is totally reflected
what is the reflected intensity?
a. 50w/cm2, b. 25w/cm2, c. 0w/cm2, d. 100%, e. 0
a. 50w/cm2
a pulse of ultrasound is propagating in soft tissue, such as liver
the pulse strikes a boundary with a different soft tissue at normal incidence
what portion of the intensity is reflected back toward the transducer?
why?
a very small percentage of sound is reflected at a boundary between two soft tissues, because the impedances of the two soft tissues are similar
the difference in impedance directly determines the intensity reflection coefficient
sound is traveling in a medium and strikes a boundary with normal incidence
If 63% of the wave’s intensity is reflected back toward the transducer, what percentage is transmitted?
37%
conservation of energy occurs at a boundary
everything must equal 100%
a pulse of ultrasound is propagating in bone and strikes an interface with soft tissue at 90°
a giant reflection is created
from these facts alone, what can be said about the impedance of bone?
soft tissue?
what can be said about the differences between the impedances of bone and soft tissue?
nothing can be said about the impedance of bone or soft tissue based on the info given
because a large reflection was created, the impedances must be different
reflections with normal incidence are created based on the difference in the impedances, not on the actual values of the impedances
sound strikes a boundary between two media orthogonally
although the media are very different, no reflection is created
how can this be?
with normal incidence, reflections occur only when the impedances of the two media at the interface are different
if the two media have the same impedances, no reflection occurs
which of the following does not belong:
a. orthogonal, b. oblique, c. normal, d. perpendicular
b. oblique
all the others mean equal to 90°
sound is traveling from bone to soft tissue
the impedances of the media differ significantly, and 90% of the beam’s intensity is reflected
what percentage of the intensity is transmitted?
10% is transmitted
sound that is traveling in Jell-O passes through an interface at 90° and continues to travel in whipped cream
the impedance of Jell-o and whipped cream are nearly identical
what percentage of the intensity is transmitted?
a. 2%, b. 25%, c. 78%, d. 99%
d. 99%
best choice because the impedances are nearly identical
only a small percentage would reflect
a pulse of ultrasound propagates in soft tissue, such as liver
the pulse strikes a soft tissue-soft tissue interface with oblique incidence
some of the sound energy is transmitted
to what extent is the transmitted beam refracted?
transmitted beam undergoes little to no refraction
transmitted beam is refracted when the incidence is oblique and the propagation speeds are different
a sound pulse travels in medium 1 and strikes an interface with another tissue, medium 2, at 30°
the angle of transmission is 10°
from these facts alone, what can be said about:
the speed of sound in medium 1
the speed of sound in medium 2
the difference between the speeds of media 1 and 2
given only this info, nothing can be said about the speed of sound in medium 1 or 2
because the beam refracted significantly, the speeds of both media are different
a sound pulse travels in medium 1 and strikes an interface with another tissue, medium 2, at 30°
the angle of transmission is 10°
in which medium does sound travel slowest?
sound travels slowest in medium 2
sound travels slower in the second medium when the angle of transmission is less than the angle of incidence
a sound pulse travels in medium 1 and strikes an interface with another tissue, medium 2, at 30°
the angle of transmission is 10°
in which medium is the impedance higher?
with the info provided, it cannot be determined which material has the greater impedance
sound travels in a medium and orthogonally strikes a boundary with a different medium
although sound waves traveling in the media have vastly different speeds, there is no refraction
how can this be?
with normal incidence, refraction cannot occur
refraction only occurs when there are different speeds and oblique incident
a sound wave strikes a boundary with normal incidence
the impedances of the two media are identical
what percentage of the sound wave is refracted?
a. 100%, b. 75%, c. 0%, d. 25%, e. 90%
c. 0%
refraction cannot occur with normal incidence
the impedance of medium 1 is 8 rayls
the propagation speed is 1,450 m/s
the impedance of medium 2 is 6 rayls and the speed is 1,855 km/s
a sound beam strikes the boundary between the media and is both partially transmitted and reflected
the angle of the incident beam is 30°
what is the reflection angle?
30°
the angle of reflection = the angle of incidence
a sound wave is created by a transducer, reflects off an object, and returns to the transducer
the depth of the reflector is 10cm in soft tissue
what is the go-return time?
a. 13µs, b. 1.3µs, c. 65µs, d. 130µs
d. time of flight = depth x 13µs
10cm x 13µs/cm = 130µs
a sound wave is created by a transducer, reflects off an object, and returns to the transducer
the go-return time is 26µs
what is the depth of the reflector?
a. 1cm, b. 2cm, c. 3cm, d. 4cm
b. the reflector depth is 2cm
2cm x 13µs/cm = 26µs
a sound wave is created by a transducer, reflects off an object, and returns to the transducer
the go-return time is 26µs
what is the total distance that the pulse traveled?
a. 1cm, b. 2cm, c. 3cm, d. 4cm
d. total distance traveled is twice the depth of the reflector
the maximum imaging depth (depth of view) during an ultrasound exam is 10cm
the sonographer adjusts the imaging depth to 20cm
what happens to pulse repetition period?
pulse repetition period is DIRECTLY related to imaging depth
when imaging depth doubles, pulse repetition period doubles
the maximum imaging depth during an ultrasound exam is 10cm
the sonographer adjusts the imaging depth to 20cm
what happens to pulse repetition frequency?
pulse repetition frequency is INVERSELY related to imaging depth
when imaging depth doubles, PRF is halved
the imaging depth during an ultrasound exam is 10cm
the sonographer adjusts the imaging depth to 5cm
what happens to pulse repetition period?
pulse repetition period is DIRECTLY related to imaging depth
when the imaging depth is halved, PRP is halved
a sound wave is created by a transducer, reflects off an object, and returns to the transducer
the imaging depth is 10cm in soft tissue
what is the maximum pulse repetition frequency?
a. 7,700, b. 7.7kHz, c. 3,500 Pa, d. 7,700µs
b. only one with correct units
a sound wave is created by a transducer, reflects off an object, and returns to the transducer
the maximum imaging depth is 7.7cm
what is PRF?
a. 7,700Hz, b. 5,000kHz, c. 10,000Hz, d. 100µs
c. 77,000/7.7 = 10,000Hz
a sound wave is created by a tranducer, reflects off an object, and returns to the transducer
the go-return time is 130µs
what is the maximum PRF?
a. 7,700Hz, b. 5,000kHz, c. 10cm, d. 100µs
a. 7,700Hz
