final review from canvas file Flashcards
(100 cards)
1
Q
Which is larger macro or micro
A
macro means bigger
2
Q
symbol for millions
A
mega
3
Q
symbol for millionths
A
micro
4
Q
symbol for hundreds
A
hecto
5
Q
symbol for hundreths
A
centi
6
Q
a frequency of 15,000 hz is
A
audible sound
7
Q
if power in a wave is halved the intensity is reduced to
A
half
8
Q
if the amplitude of a wave is increased 3 times, the intensity is increased by
A
9 times
9
Q
propagations speed is determined by
A
medium
10
Q
propagations speed increases as frequency increases or decreases
A
false
not realated
11
Q
how many intensities are needed to calculate decibels
A
two
12
Q
path length increases what happens to the attenuation
A
increases
13
Q
which is lower spatial peak or spatial average intensity
A
spatial average
14
Q
in addition to location in a beam, intensities also vary with
A
time
15
Q
the most important intensity in soft tissue is
A
SPTA
16
Q
duty factor is a unitless number between
A
0 and 1
17
Q
intensities may be reported in various ways in respect to
A
time and space
18
Q
duty factor for a pulsed ultrasound system is typically
A
0.2%
19
Q
beam intensity is the same at different depths and lateral locations
true/false
A
FALSE
20
Q
at a particular depth the center of a beam is more intense than the edges
true/false
A
TRUE
21
Q
temporal peak is the maximum intensity in
A
time
22
Q
3 MHz is how many Hz
A
3 million
23
Q
how much bigger is a billion than a million
A
1000
24
Q
what are the units of a wavelength
A
mm
25
what are the units of frequency
Hz
26
what are the units of intensity
w/cm^2
27
what are the units of propagatoin speed
m/s
28
what are the units of period
us
29
what is determined by sound source
period
frequency
amplitude
power
intensity
30
if the intensity is the same while the power is doubled what happens to the beam area
increases
31
sound beam travels a total of 10cm in 2 sec. What is the speed of sound in this medium
5 cm/sec
32
what term describes the time from the start of a pulse to the end of the pulse
pulse duration
33
PRF is the recipricol of
PRP
34
dB is a mathmatical representatoin with a \_\_\_\_\_\_\_\_\_\_scale
logarithmic
35
rayleigh scattering is related to
frequency^4
36
which media has the greatest attentuatoin and slowest speed
Air
37
what mathmatically describes the physics of refraction
snells law sin (tran)/ sin(inc)= speed 2/speed 1
38
two PZT crystals are made from the same material. The thicker will have a pulse transducer with
lower frequency and slower speed
39
when PZT exceeds the curie point the PZT
depolarizes
40
PZT is also known as
crystal, active element, ceramic
41
what reduces the ringing in a transducer
backing material
42
mathmatically the Q factor is the frequency divided by the
bandwidth
43
imaging transducers are also referred to as
pulsed wave transducer
44
what type of crystal will produce sound with the lowest freq
thick and slow
45
the damping material in the transducer improves the systems what resolution
axial
46
if the electrical excitation volt is 6MHz then the output freq of a CW transducer is
6 MHz
47
the impedance of a transducer active element is 19Mrayls, and the impedance of the skin is 14Mrayls. What is an acceptable impedance for the matching layer
anything between 14 and 19 Mrayls
48
which transducer component is a thin barrier of cork or rubber that isolates or uncouples the internal components from the case
acoustic insulator
49
what is the purpose of the backing material in an imaging transducer
reduce ringing and improve axial resolution
50
what creates the beam with deepest focus
large diameter and high freq
51
how are freq and near zone length related
directly, lower freq shorter near zone
52
what crystal creates the least divergence
large diameter higher freq
53
what creates the most divergence
small diameter
lower frequency
54
what determines the freq of sound created by a pulsed transducer
thickness and speed of the PZT
55
what determines the spread of a sound beam in the far field
diameter of crystal and frequncy
56
frequency does not change, if the diameter of the new PZT increases what happens to the wavelength
no change
57
imaging to greater depths requires the listeing time to
increases
58
when reporting a beams intensity the maximum is referred to as
SPTP
59
the highest temporal intensity is
temporal peak
60
units for reporting intensity are
w/cm^2
61
what is measured where intensity is maximum and averaged over time
SPTA
62
which intesity is measureed over the entire cross section of the beam and over all time
SATA
63
what is the same as normal incidence
perpendicular, orthogonal, right angle, 90 degrees
64
intensity of a sound beam just prior to striking a boundry is referred to as
incident intensity
65
the portion of a sound beam that contimnues on after striking a boundry is the
transmitted intensity
66
the percentage of US intensity that is allowed to pass through when the beam reaches a boundry between two media is referred to as
intensity transmission coefficient
67
a sound beam with an intensity of 50 w/cm^2 strikes a boundry and is totally reflected. What is the intensity reflectoin coefficient
100%
68
the intensity reflection coefficient of sound is 99.9% . What percentage is transmitted into the body
0.1%
69
specular reflections arise when the interface is
smooth
70
what do we know about oblique incidence
nothing
71
transmission with a bend is
refraction
72
Snells law describes what physics
refraction
73
sound waves strike a boundry at normal incidence. The impedances of the two are identical. What percentage of the beam is reflected
0%
must be difference in impedance for reflection to occur
74
what processes occur as the ultrasound passes through all media
reflection, scattering and absorption
75
two waves are traveling through a medium and arrive at a location at the same time. What event takes place
interference
76
the percentage of time that a system is transmitting a pulse is referred to as
duty factor
77
a 3MHz beam travels though two media. It attentuates 5 dB in A and 6 dB in B.
What is the total attenuation of the beam
11 dB
78
what is the dominant factor in attenuation
absorption
79
impedance is a characteristic of
acoustic resistance of sound traveling in media
density x propagation speed
80
hertz is a unit used to describe what wave characteristic
frequency
81
a low freq transducer is best at imaging what structures? Deep or shallow
deep
82
The percentage of the US intensity that is allowed to pass through when the beam reaches a boundary between two media is
intensity transmission coefficient
83
what is the best estimate for attenuation coefficient of sound traveling in soft tissue
.5 dB/cm/MHz
84
Attenuation is determined by two factors
path length and freq of sound
85
With longer distances and higher frequencies you have
higher attenuation
86
With shorter distances and lower frequencies you have
lower attentuation
87
Because attenuation means a weakening or a decrease, the dbs must be
negative
88
Which term best describes redirection of sound in many directions
scattering
89
Reflections from a smooth reflector are referred to as
specular
90
When a boundary is rough, reflected sound is disorganized and random, also called
diffuse or backscatter
91
Rayleigh scattering increases dramatically with increasing frequency, which is the relation
frequency 4
92
Acoustic Impedance is equal to
density x propagation speed
93
The time needed for a pulse to travel to and from the transducer and the reflector is called
go return time, time of flight,
94
A sound wave is created by the transducer, reflects off an object and returns to the transducer in 52, what is the reflector depth and total distance traveled
4 cm depth and 8 cm total travel
95
The maximum imaging depth during an ultrasound exam is 5 cm. The sonographer adjusts the depth to 10cm.
What happens to pulse repetition frequency
PRF is halved
96
A sound wave is created by the transducer, reflects off an object, and returns to the transducer. The time of flight is 130 microseconds. What is the maximum PRF
7,700 Hz
97
A sound wave is created by the transducer, reflects off an object, and returns to the transducer. The go return time is 39 microseconds. What is the total distance traveled
6 cm
98
Axial resolution deals with structures that are \_\_\_\_\_\_\_\_\_\_\_to the sound beam
parallel
99
As frequency increases, the numerical value of LARRD resolution
lowers
100
Superior axial resolution is associated with the following
shorter spatial pulse length, shorter pulse duratoin, higher Freq, fewer cycles per pulse, lower numerical values
