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507 Cards in this Set
- Front
- Back
Sound is a ____ wave and must travel in a ____.
|
mechanical, medium
|
|
Sound waves are ____ waves.
|
longitudinal
|
|
The effects of the medium on the sound wave are the ____ ____ ____.
|
acoustic propagation properties
|
|
What are the 3 acoustic variables?
|
pressure, density and distance
|
|
What is the unit for pressure?
|
pascals
|
|
What is the unit for density?
|
kg/cm3
|
|
The characteristics of a sound wave are the ____ ____.
|
acoustic parameters
|
|
What are the 7 acoustic parameters?
|
period, frequency, amplitude, power, intensity, wavelength & propagation speed
|
|
What is the source?
|
the US system & transducer
|
|
The ____ is the medium.
|
tissue
|
|
Transverse waves are ____ to the direction the wave propagates.
|
perpendicular
|
|
T or F. With longitudinal waves, the particles move in the same direction the wave propagates.
|
TRUE
|
|
What are in phase waves?
|
the peaks (max) occur at the same time and the troughs (min) occur at the same time
|
|
A combination of in phase waves forming one BIGGER wave is ____ ____.
|
constructive interference
|
|
With constructive interference there is more _____.
|
amplitude
|
|
What are out of phase waves?
|
when the peaks occur at different times
|
|
A combination of out of phase waves forming one SMALLER wave is known as ____ ____.
|
destructive interference
|
|
With destructive interference there is less _____.
|
amplitude
|
|
When frequencies of the waves differ than what type of interference occurs?
|
both constructive and destructive interference occurs
|
|
The time it takes a wave to vibrate a single cycle (start of one to the start of another) is the ____.
|
period
|
|
Period is determined by the ____ only.
|
source
|
|
The number of events that occur in a specific duration of time (# of cycles/sec) is the _____.
|
frequency
|
|
Frequency is determined by the ____ only.
|
source
|
|
Infrasound (below hearing) is less than ____ Hz.
|
20
|
|
What is the range for audible sound?
|
b/t 20 Hz and 20 KHz
|
|
The frequency for ultrasound is greater than ____.
|
20 KHz
|
|
Period and frequency are ____ related.
|
inversely
|
|
If frequency increases, the period ____.
|
decreases
|
|
The bigness of a wave which can have any acoustic unit is the ____.
|
amplitude
|
|
Amplitude is determined by the ____ and can be altered on the machine.
|
source
|
|
Amplitude ____ as it goes through the body.
|
decreases
|
|
Since amplitude decreases as it goes through the body it depends on the ____ & the ____.
|
source & the medium
|
|
How is amplitude measured?
|
from middle value to max or middle value to min
|
|
What is the peak to peak amplitude?
|
the difference b/t the max and min
|
|
T or F. Peak to peak amplitude is twice the normal amplitude.
|
TRUE
|
|
The rate of energy transfered or work performed is the ____.
|
power
|
|
Power is determined by the ____ and can be changed on the machine.
|
source
|
|
When power increases, amplitude ____.
|
increases
|
|
Power is proportional to ____ ____.
|
amplitude squared
|
|
Power ____ as it goes through the body.
|
decreases
|
|
The concentration of energy in a sound beam is the ____.
|
intensity
|
|
What does the intensity depend on?
|
depends on the power in the beam & area
|
|
Intensity is determined by the ____ and can be changed.
|
source
|
|
What is the unit for intensity?
|
watt/cm2 (w/cm2)
|
|
If intensity increases than amplitude is ____ as well as ____.
|
increased, power
|
|
Intensity is proportional to ____.
|
power
|
|
If power is doubled than intensity is ____.
|
doubled
|
|
Intensity is proportional to ____.
|
amplitude squared
|
|
If amplitude is doubled than intensity is increased ____ times.
|
4
|
|
The distance/length of one complete cycle is the _____.
|
wavelengthq
|
|
T or F. The wavelength can't be changed.
|
TRUE
|
|
What determines the wavelength?
|
it is determined by both the source & medium
|
|
The ____ is the only parameter determined by both the source & the medium.
|
wavelength
|
|
Wavelength and frequency are ____ related.
|
inversely
|
|
How do you find wavelength?
|
divide 1.54/frequency (MHz)
|
|
If frequency increases, wavelength ____.
|
decreases
|
|
T or F. Wavelength is an important factor of image quality.
|
TRUE
|
|
Short wavelength = ____ quality images.
|
higher/better
|
|
A ____ frequency makes a shorter wavelength, which makes the picture look like what?
|
higher, better images
|
|
The distance sound travels in a medium in one second is the ____ ____.
|
propagation speed (can't be changed)
|
|
The propagation speed depends on and is determined by ONLY the ____.
|
medium
|
|
T or F. All sound, regardless of frequency, travels @ the same speed thru any specific medium.
|
TRUE (so if you have a 3 MHz or 4 MHz they both travel the same speed thru bone)
|
|
The speed of sound through tissue is:
|
1,540 m/s, 1.54 mm/us,
|
|
Speed of sound is slowest through ____ and fastest through ____.
|
air, bone
|
|
Speed= ____ x ____.
|
frequency X wavelength
|
|
What are 2 characteristics of a medium that affect speed of sound?
|
density & stiffness
|
|
The weight of a material is the ____.
|
density
|
|
Stiffness & speed are ____ related.
|
directly
|
|
Density & speed are ____ related.
|
inversely
|
|
Speed travels faster w/ ____ density objects.
|
low
|
|
Pulsed ultrasound has a ____ time and a ____ time.
|
transmit (talking), and receive (listening)
|
|
The actual time from the start of a pulse to the end of a pulse is the ____ time.
|
talking
|
|
Pulse duration is determined by the ____ only.
|
source
|
|
PD= ____ X ____
|
PD= # of cycles x period
|
|
PD= ____ X ____.
|
PD= # of cycles/frequency
|
|
What is pulse duration directly proportional to?
|
the # of cycles in the pulse and the period
|
|
The pulse duration is inversely proportional to the ____.
|
frequency
|
|
What type of pulses are desirable for US imaging?
|
shorter duration pulses
|
|
The distance that a pulse occupies from start to end of a pulse is the ____ ____ ____.
|
spatial pulse length
|
|
The spatial pulse length is determined by both the ____ & the ____ and can't be changed.
|
source & medium
|
|
SPL = ____ X ____.
|
SPL= # of cycles X wavelength
|
|
What is SPL directly proportional to?
|
the # of cycles in the pulse & wavelength
|
|
SPL is ____ related to frequency.
|
inversely
|
|
What is the pulse repetition period (PRP)?
|
time from the start of one pulse to the start of another
|
|
PRP includes one ____ ____ and one ____ ____.
|
transmitting time, listening time
|
|
PRP is determined by the ____ only but also depends on ____ ____.
|
source, imaging depth
|
|
T or F. PRP is unrelated to period.
|
TRUE
|
|
As depth of view increases (imaging deeper), the PRP ____.
|
increases
|
|
The PRP decreases with ____ imaging.
|
shallow
|
|
With deeper imaging there is a ____ listening time.
|
longer/higher
|
|
The number of pulses that an US system transmits into the body each second is the ____.
|
PRF -pulse repetition frequency
|
|
The PRF is determined by the ____ only but also depends on the ____ ____.
|
source, maximum depth
|
|
With shallow imaging, the PRF is ____.
|
increased
|
|
There is a decreased PRF with ____ imaging.
|
deeper
|
|
T or F. PRF is unrelated to frequency.
|
TRUE
|
|
PRP and PRF are ____ related.
|
inversely
|
|
So PRP X PRF=?
|
1, PRP times PRF equals 1
|
|
The percentage of fraction of the time the system is transmitting a pulse is the ____ ____.
|
duty factor
|
|
The duty factor for continuous sound is ____ because why?
|
100% or 1.0 because it is always listening!
|
|
What is the equation for duty factor?
|
DF= PD / PRP X 100
|
|
Duty factor is determined by the ____ only.
|
source
|
|
The max value of duty factor is ____ and only occurs with ____ sound.
|
100%, continuous
|
|
The min value for duty factor is ____ and only occurs when the transducer is ____.
|
0%, silent
|
|
The typical duty factor is ____ because the system spends most time ____.
|
0.2%, listening
|
|
As the images are deeper, the duty factor ____.
|
decreases
|
|
The duty factor is increased w/ ____ imaging.
|
shallower
|
|
The units for intensity are ____.
|
watts/cm2
|
|
What is the intensities from largest to smallest?
|
SPTP-->SPPA-->SPTA-->SATA
|
|
When pulsed & continuous have the same SPTP than the ____ has the higher SPTA.
|
continuous
|
|
With continous wave, the pulse & temporal averages are the ____.
|
same
|
|
Sound weakening as it travels thru the body is known as ____.
|
attenuation
|
|
Sound returned to the system is strengthened or ____.
|
amplified
|
|
With is a logarithm (log)?
|
how many 10's are multiplied to create the original number?
|
|
An example of a logarithm is:
|
100 = 10 X 10
So, the log of 100 is 2 because two 10's are used |
|
Decibels are ____ and reports ____ ____.
|
logarithmic, relative changes
|
|
2 Intensities are required to use decibels:
|
the reference (starting level) and the actual level at the time of measurement
|
|
Positive decibels are ____ in strength and get ____.
|
increasing, larger
|
|
When a wave's intensity doubles, the relative change is ____.
|
+ 3 dB
|
|
When the intensity increases 10-fold the relative change is ____.
|
+ 10 dB
|
|
When the intensity is reduced to 1/2 its original value, the relative change is ____.
|
- 3 dB
|
|
When the instensity is reduced to 1/10 its original value, the relative change is ____.
|
- 10 dB
|
|
What is attenuation?
|
a decrease in intensity, power and amplitude
|
|
What 2 factors determine attenuation?
|
path length and the frequency of sound
|
|
The further sound travels, the ____ the attenuation and the ____ the beam is.
|
greater, weaker
|
|
T or F. Distance and attenuation are directly related
|
TRUE
|
|
What 3 processes contribute to attenuation?
|
reflection, scattering, and absorption
|
|
Portion of a wave's energy may reflect back causing the continuing portion going forward to weaken. This is called ____.
|
reflection
|
|
Random redirection of sound in many directions is known as ____.
|
scattering
|
|
When ultrasonic energy is converted into another form it is known as ____.
|
absorption
|
|
What are the 2 forms of reflection?
|
specular reflection & diffuse reflection
|
|
When the surface of a boundary is smooth, sound is reflected in only 1 direction and is ____ reflection.
|
specular
|
|
When the boundary is irregular, sound radiates in more than 1 direction and is called ____ reflection.
|
diffuse
|
|
Diffuse reflection is also known as ____ and has a ____ strength than specular reflection.
|
backscatter, lower
|
|
What occurs when the tissue interface is = to or less than the wavelength of the incident sound beam?
|
scattering
|
|
What type of transducers have more scattering?
|
higher frequency transducers
|
|
Scattering is directly related to ____.
|
frequency
|
|
A special form of scattering that occurs when the structures dimensions are much smaller than the beam's wavelength is:
|
rayleigh scattering
|
|
Rayleigh scattering redirects sound waves ____ in all directions.
|
equally
|
|
An example of rayleigh scattering is ____.
|
RBC's
|
|
T or F. Rayleigh scattering is proportional to frequency to the 4th power.
|
TRUE
|
|
When frequency doubles, rayleigh scattering is increased by ____ times.
|
16
|
|
What is directly related to frequency?
|
absorption
|
|
The number of dB's of attenuation that occurs when sound travels 1 cm is the ____ ____.
|
attenuation coefficient
|
|
T or F. The value of the A.C. does not change when path length changes.
|
TRUE
|
|
If the A.C. is 2 dB/cm and sound travels a depth of 5 cm, than what would be the total attenuation?
|
10 dB
|
|
In soft tissue, the A.C. and the frequency are ____ ____.
|
directly related
|
|
The attenuation coefficient is one-half of the ____ in soft tissue.
|
frequency
|
|
Attenuation formula
|
A.C. (db/cm) = frequency (MHz)/2
|
|
Attenuation Coeffecient =
|
0.5 dB/cm / MHz
|
|
Attenuation in air is extremely ____.
|
high
|
|
Attenuation in water is ____.
|
low
|
|
The distance that sound travels in a tissue that reduces the intensity of sound to 1/2 its original value is:
|
half-value layer thickness
|
|
The half-value layer thickness is the ____ of tissue at ____ of attenuation.
|
depth, 3dB
|
|
Half value layer thickness is AKA:
|
depth of penetration
|
|
The half-value layer thickness depends on what 2 factors?
|
the medium and the frequency of sound
|
|
A high frequency sound wave with high attenuation equals a ____ half value layer thickness.
|
thin
|
|
Low frequency with low attenuation creates a ____ half value layer thickness.
|
thick
|
|
Acoustic resistance to sound traveling in a medium is the ____.
|
impedance
|
|
What is an important tissue property that influences the amount of reflection?
|
the impedance
|
|
What are the units of impedance?
|
RAYLS
|
|
The equation for impedance is:
|
Density x speed = impedance
|
|
The angle at which the wave strikes the boundary is the angle of ____.
|
incidence
|
|
What are the 3 types of angles?
|
acute- less than 90 degrees
right- 90 degrees obtuse- greater than 90 degrees |
|
Angles w/ any measure other than 90 degrees is ____.
|
oblique
|
|
Normal incidence occurs at exactly ____ degrees.
|
90
|
|
Oblique incidence occurs at any angle other than ____.
|
90 degrees
|
|
What are the units of intensity?
|
w/cm2
|
|
A sound waves intensity B4 it strikes a boundary is the ____ intensity.
|
incident
|
|
The intensity after striking a boundary that returns back in the direction it came is the ____ intensity.
|
reflected
|
|
The intensity after striking a boundary that continues forward in the same direction it was traveling is the ____ intensity.
|
transmitted
|
|
Incident intensity=
|
reflected + transmitted
|
|
The % of intensity that bounces back when a sound beam strikes the boundary is the ____ ____ ____.
|
intensity reflection coefficient (IRC)
|
|
The IRC is ____ between 2 soft tissues.
|
small (less than 1%)
|
|
There is a greater % of the IRC between soft tissue and ___ or ___.
|
bone or air
|
|
The % of intensity that passes in the forward direction is the ____ ____ ____.
|
intensity transmission coefficient (ITC)
|
|
The ITC is usually ____ or greater in soft tissues.
|
99%
|
|
There is a ____ % of the ITC between soft tissue and bone or air.
|
smaller
|
|
IRC + ITC =
|
100%
|
|
With normal incidence, reflection occurs only if the media on either side of the boundary have different _____.
|
impedances
|
|
T or F. NO reflection will occur if the 2 media have identical impedances.
|
TRUE
|
|
If the impedances are slightly different than what will occur?
|
a small reflection
|
|
If the impedances are substantially different than what will occur?
|
a large reflection
|
|
What is the equation of the IRC?
|
IRC%= z2 - z1/z2 + z1 squared times 100
|
|
What is the equation of the ITC?
|
ITC%= transmitted/incident times 100
or 1- IRC |
|
T or F. You cannot judge reflection & transmission w/ oblique incidence.
|
TRUE
|
|
What are the 2 principles for reflection w/ oblique incidence?
|
conservation of energy and reflection angle equals the incident angle
|
|
The angle of ____ = the angle of ____ with oblique incidence.
|
incidence, reflection
|
|
The reflection co + the transmitted co = ____.
|
100%
|
|
The bending or change of direction of the transmitted intensity w/ oblique incidence is ____.
|
refraction
|
|
Refraction is a change in direction and occurs only if 2 conditions are satisfied. What are these 2 conditions?
|
1) with oblique incidence and 2) that the propagation speeds of the 2 media are different
|
|
The physics of refraction are defined by ____ ____.
|
snell's law
|
|
If the 2 speeds of the incidence & transmitted media are identical than no ____ will occur and the angles will be ____.
|
refraction, equal
|
|
The transmission angle will be greater than the ____ angle when the speed of media 2 is ____ than media 1.
|
incident, greater
|
|
Snell's Law=
|
equation:
|
|
The transmission angle will be less than the incident angle when the speed of medium 2 is ____ than medium 1.
|
less
|
|
The elapsed time from pulse creation to pulse reception is the:
|
go-return time or time-of-flight time
|
|
The go-return / time-of-flight time is directly related to the ____.
|
depth
|
|
Shallow imaging has a ___ go return/ time-of-flight time.
|
brief
|
|
Deep imaging has a ____ go-return/ time-of-flight time.
|
longer
|
|
What is the equation for depth?
|
equation=
|
|
For every 13 us (microseconds) of go-return time, the object is ___ cm deeper in soft tissue with a total distance of ___ cms.
|
1 cm, 2 cms
|
|
Example of depth- if a reflector is 2 cm deep, a pulse's time of flight is ____ us (microseconds).
|
26 us
|
|
If a reflector is 3 cm deep the microseconds is ____.
|
39 us
|
|
The time of flight of a sound pulse b/t the transducer & the bottom of the image is the ____.
|
PRP (pulse repitition period)
|
|
What is the PRP directly related to?
|
maximum imaging depth
|
|
Deep imaging has a ____ PRP.
|
long
|
|
Shallow imaging has a ____ PRP.
|
short
|
|
What is the equation for PRP?
|
equation=
|
|
The PRF is ____ related to maximum imaging depth.
|
inversely
|
|
When the depth is shallow the PRF is ____.
|
high
|
|
When the depth is deep, the PRF is ____.
|
low
|
|
What is the equation for PRF?
|
equation =
|
|
What is the axial resolution?
|
the ability of a system to display 2 structures that are close together when the structures are parallel to the sound beams main axis
|
|
Axial resolution is determined by the ____.
|
SPL (spatial pulse length)
|
|
What are the units for axial resolution?
|
units of distance
|
|
What determines the SPL?
|
the sound source & the medium determine SPL
|
|
What type of pulse improve axial resolution?
|
shorter pulses
|
|
Axial resolution is related to ____ ____.
|
pulse duration
|
|
A short pulse duration = a short length which = better ____ ____.
|
axial resolution
|
|
What must you use for axial resolution?
|
LARRD
|
|
What does LARRD stand for?
|
longitudinal, axial, range, radial, depth
|
|
Lower numerical numbers of axial resolution = a shorter ___ which equals better ____ ____.
|
pulse, image quality
|
|
What is the equation for axial resolution?
|
axial res. = SPL/2
|
|
Another equation for axial resolution is:
|
axial res. = wavelength x # of cycles in pulse/2
|
|
In soft tissue, axial resolution =
|
.77 x # of cycles in pulse/ frequency
|
|
A short pulse is created in 2 ways. What are the 2 ways?
|
1. less ringing- fewer cycles in pulse and 2. higher frequency- short wavelength and better axial res.
|
|
Axial resolution is half the ____.
|
SPL
|
|
A device that converts one form of energy into another is a ____.
|
transducer
|
|
What are the 2 functions of a transducer?
|
transmission and reception
|
|
When electrical energy from the system is converted into sound it is ____.
|
transmission
|
|
When the reflected pulse is converted into electricity it is ____.
|
reception
|
|
What is the piezoelectric effect?
|
it describes the property of certain materials to create a voltage when they are mechanically deformed
|
|
Peizo materials change shape when a voltage is applied to them & this is called the ____ ____ ____.
|
reverse piezoelectric effect
|
|
Materials that convert sound into electricity & vice versa are called ____.
|
piezoelectric / ferroelectric
|
|
What is an example of a peizoelectric material found in nature?
|
quartz
|
|
A man-made piezoelectric material frequently used is ____.
|
PZT (& lead zirconate titanate)
|
|
What are the 7 basic components of a transducer?
|
case, electrical shield, acoustic insulator, PZT or active element, wire, matching layer, and backing material / damping element
|
|
How thick is PZT?
|
1/2 wavelength thick
|
|
The ___ ___ is positioned in front of the PZT at the face of the transducer.
|
matching layer
|
|
How thick is the matching layer?
|
1/4 wavelength thick
|
|
What does the matching layer do?
|
increase the efficiency of sound energy transfer b/t the active element & the body, & protects the active element
|
|
The impedance of PZT is ____ times greater than the impedance of ____.
|
20, skin
|
|
SO, the matching layer is designed to increase the % of ____ ____ because higher impedances = more ____.
|
transmitted sound, reflection
|
|
What is the decreasing order of impedance?
|
PZT--->matching layer-->gel-->skin
|
|
The ____ ____ is bonded to the back of the active material (PZT).
|
backing material
|
|
What is the backing material made up of?
|
epoxy resin & tungsten
|
|
What does the backing material (damping element) do?
|
reduces ringing and restricts the extent of PZT deformation
|
|
With backing material, the emitted sound pulse is ____ , creating a ____ duration and length which = better axial resolution.
|
dampened, short
|
|
What are 2 characteristics of the backing/damping material?
|
has a high degree of sound absorption, and the acoustic impedance is similar to PZT
|
|
The range or difference between the highest & lowest frequencies in a pulse is the ____.
|
bandwidth
|
|
What type of frequency moves freely?
|
resonant
|
|
Ultrasound probes are ____ pulse, ____ bandwidth probes.
|
short, wide
|
|
A 3 MHz transducer has frequencies ranging from 1 MHz to 5 MHz. What is the bandwidth?
|
5 MHZ - 1 MHZ = 4 MHZ
|
|
What type of probes create a narrow bandwidth?
|
long duration, continuous probes
|
|
Short duration US probes have a wide ____ & ____.
|
range & bandwidth
|
|
A unitless number related to bandwidth is the ____ ____.
|
quality factor
|
|
What is the equation for quality factor (QF)?
|
QF= main freq./bandwidth
|
|
Wide bandwidth = a ____ quality factor.
|
low
|
|
Narrow bandwidth transducers have a ____ quality factor.
|
high
|
|
EX: A 3 MHz transducer has frequencies ranging from 1 MHz to 5 MHz so the bandwidth is 4 MHz. What is the QF?
|
QF = 3 MHZ (main frequency)/4 MHZ (bandwidth) =0.75
|
|
Low quality factor is created from ____ pulse, ____ bandwidth probes.
|
short, wide
|
|
What is PZT created by?
|
polarization
|
|
The temperature at which the PZT is polarized is called the ____ ____.
|
curie temperature (or curie point)
|
|
The loss of PZT properties is called ____.
|
depolarization
|
|
With continuous wave transducers the ____ frequency equals the ____ frequency.
|
electrical, acoustic
|
|
Two characteristics of the active element (PZT) that combine to determine frequency of sound from a pulsed wave transducer:
|
1) speed of sound in the PZT
2) thickness of the PZT |
|
How does the speed of sound in PZT affect frequency?
|
When speed of PZT is fast, the frequency of sound created is higher
|
|
In PW transducers, the speed of sound in the PZT and the frequency of sound are ____ related.
|
directly
|
|
How does the thickness of PZT affect frequency?
|
thinner PZT = higher frequency
|
|
PZT thickness and frequency are ____ related.
|
inversely
|
|
Frequency equation=
|
=
|
|
Thickness of PZT equation=
|
= 1/2 wavelength of sound in the PZT
|
|
Five terms describe the shape & regions of a sound beam. What are they?
|
focus, near zone, focal length, far zone, and focal zone
|
|
The location where the beam diameter is the narrowest is the ____.
|
focus
|
|
For a disc-shaped crystal, the width of the sound beam at the focus is what?
|
it is 1/2 the width of the beam diameter as it leaves the transducer
|
|
The region from the transducer to the focus is the ____ ____.
|
near zone
|
|
What are the other names for the near zone?
|
near field and fresnel zone
|
|
The beam starts to ____ in the near zone.
|
narrow
|
|
The distance from the transducer to the focus is the ____ ____.
|
focal length
|
|
What are other names for the focal length?
|
focal depth and near zone length
|
|
Certain characteristics of the ____ ____ determine the focal length.
|
active element
|
|
The region starting at the focus and extending deeper is the ____ ____.
|
far zone
|
|
Other names for the far zone include:
|
far field & fraunhofer zone
|
|
The beam ____ in the far field.
|
diverges (spreads out)
|
|
The region around the focus where the beam is relatively narrow & image quality is superior is the ____ ____.
|
focal zone
|
|
Better images are seen in the ____ ____.
|
focal zone
|
|
Half of the focal zone is in the ____ ____ and the other half is in the ____ ____.
|
near field, far field
|
|
So the distance from the transducer to the narrowest part of the beam is the ____ ____.
|
focal length/depth (near zone length)
|
|
Adjustable focus systems are called ____ ____.
|
phased array
|
|
With a fixed-focus transducer, what 2 factors determine focal depth/length?
|
transducer diameter and frequency of sound
|
|
An increasing transducer diameter equals a ____ focus.
|
deeper
|
|
Transducer diameter and focal depth are ____ related.
|
directly
|
|
What type of transducers have a deeper focus?
|
higher frequency transducers
|
|
Frequency & focal depth are ____ related.
|
directly
|
|
A small PZT & low frequency equals a ____ focus.
|
shallow
|
|
A large PZT and high frequency equals a ____ focus.
|
deeper
|
|
How does transducer diameter affect beam divergence in the far field?
|
Smaller diameter crystals produce beams that spread out/diverge more in the far field
|
|
Larger diameter crystals equals ____ divergence in the far field.
|
less
|
|
Crystal diameter & beam divergence are ____ related.
|
inversely
|
|
Since large diameter crystals create sound beams that diverge less in the far field, they improve ____ ____ in the far field.
|
lateral resolution
|
|
What type of frequencies diverge/spread more in the far field?
|
lower frequencies
|
|
Frequency & beam divergence are ____ related.
|
inversely
|
|
What type of frequency diverges less in the far field?
|
higher frequency
|
|
Higher frequency sound improves ____ ____ in the far field.
|
lateral resolution
|
|
Sound waves with very small sources that diverge in the shape of a V are ____ waves.
|
spherical
|
|
What makes up the small sources of a spherical wave?
|
huygen's sources
|
|
Inconstistency between large and small sound sources & their beams is defined by the ____ principle.
|
Huygen's
|
|
Large elements are made of millions of tiny sound sources and each of these is a ____ ____ & creates a ____ shape.
|
Huygen's source, V
|
|
The hourglass shape produced by a large crystal is the result of millions of ____ sources interfering ____.
|
Huygen's, constructively
|
|
What type of interference occurs in the areas where the sound beam is absent?
|
destructive interference
|
|
The ability to identify 2 structures that are very close together when the structures are side by side or perpendicular to main axis is:
|
lateral resolution
|
|
Lateral resolution measure the ____ in an image.
|
detail
|
|
So what question does lateral resolution answer?
|
what is the minimum distance 2 structures positioned side by side can be apart & still produce 2 distinct echoes on an US image?
|
|
Lateral resolution with ____ numbers makes better images.
|
smaller
|
|
What determines the lateral resolution?
|
width of the sound beam
|
|
What type of sound beam is ideal for better resolution?
|
narrower
|
|
Since beam diameter varies w/ depth, lateral resolution changes w/ ____.
|
depth
|
|
What is the acronym for lateral resolution?
|
LATA- lateral, angular, transverse, azimuthal
|
|
Lateral resolution is best at the ____.
|
focus (narrowest)
|
|
Lateral resolution (mm) =
|
beam diameter (mm)
|
|
For ultrasound, what type of resolution is better (best) and why?
|
axial resolution because the pulses are shorter
|
|
The numerical value for axial resolution is ____ than lateral resolution.
|
less
|
|
When 2 reflectors/structures are closer side by side than the beam width than what is seen?
|
only one reflection is seen
|
|
What type of transducers improve both axial and lateral resolution?
|
higher frequency transducers
|
|
Axial resolution is improved w/ high frequency because of the ____ ____.
|
short pulses
|
|
Higher frequency transducers improve ____ resolution because there is less ____ in the far field.
|
lateral, divergence
|
|
Focusing improves ____ resolution by concentrating sound energy in to a ____ beam.
|
lateral, narrower
|
|
What are the 3 methods of focusing?
|
external, internal and phased array
|
|
External focusing is w/ a ____.
|
lens
|
|
Internal focusing is w/ a ____ active element.
|
curved
|
|
Phased array focusing deals w/ the electronics of the ____ ____.
|
ultrasound system
|
|
External and internal focusing are used w/ ____ ____ transducers.
|
single element
|
|
Both external & internal focusing are ____.
|
fixed
|
|
What can't be changed w/ external and internal focusing?
|
the focal depth & the extent of focusing
|
|
What type of fixed focusing is the most common?
|
internal
|
|
Phased-array means ____ & is only used w/ ____ ____ tranducers.
|
adjustable, multi-element
|
|
When a sound beam is focused the beam diameter is the near field & focal zone ____.
|
narrows
|
|
When a sound beam is focused, the focus is moved ____ to the transducer & the length of the near field is ____.
|
closer, reduced
|
|
When a sound beam is focused the beam diameter beyond the focal zone ____, so focusing improves lat. res. in the ____ ___
|
widens, near/focal zone
|
|
Focusing degrades lateral resolution in the ____ field.
|
far
|
|
When a sound beam is focused the size of the focal zone is ____.
|
reduced (smaller)
|
|
What are the 3 types of display modes?
|
Amplitude mode, brightness mode, and motion mode
|
|
A series of upward spikes is called ____ mode.
|
amplitude (A)
|
|
The strong echoes create ____ spikes while the weak echoes create ____ spikes.
|
tall, short
|
|
What represents the x-axis w/ A-mode?
|
reflector depth derived from time of flight
|
|
The y-axis w/ A-mode represents ____ ____.
|
reflection amplitude
|
|
A-mode is accurate in determining the ____ of ____.
|
depth, reflectors
|
|
Lines of dots of varying brightness is known as ____ mode.
|
Brightness (B)
|
|
The brightness of the dot indicates the ____ of the reflection.
|
strength
|
|
The x-axis of B-mode is the ____ ____.
|
reflector depth
|
|
What other axis is used w/ B-mode?
|
the Z-axis (amplitude)
|
|
A group of horizontal wavy lines that represent changing depths of reflecting surfaces is ____ mode.
|
motion (M)
|
|
A line up is ____ to the transducer while a line down is ____ from transducer.
|
closer, further
|
|
A straight line on M-mode represents ____.
|
stationary
|
|
The x-axis for M-mode represents ____.
|
time
|
|
The y-axis from M-mode represents ____ ____.
|
reflector depth (from time of flight)
|
|
The sampling rate of m-mode is ____ and equal to the ____.
|
high, PRF
|
|
Back in the day there was ____ scanning.
|
static
|
|
Static scanning was ____ and there was only ____ frame at a time.
|
slow, 1
|
|
Static scanning couldn't image ____ structures.
|
moving
|
|
What is the most important operational parameter of real-time imaging?
|
frame rate
|
|
The ability of the system to create numerous frames each second is known as the ____ ____.
|
frame rate
|
|
Frame rate is measured in ____ or per ____.
|
hertz, second
|
|
What are the units for frame rate?
|
images per second
|
|
The frame rate is determined by 2 factors. What are they?
|
1- sounds speed in the medium and 2- the depth of imaging
|
|
Speed of sound in soft tissue is ____.
|
1.54 km/s
|
|
In US, what determines the frame rate? (FR)
|
maximum imaging depth
|
|
What is temporal resolution?
|
accuracy in time, the ability to precisely position moving structures from instant to instant
|
|
The temporal resolution is ____ when the system produces many frames per second.
|
excellent
|
|
Temporal resolution is superior with a ____ frame rate.
|
high
|
|
Temporal resolution is determined by the ____ ____.
|
frame rate
|
|
A high frame rate =
|
better temporal resolution
|
|
A low frame rate =
|
poor temporal resolution
|
|
Frame rate & the time for 1 frame are ____ related.
|
inversely
|
|
The time for 1 frame times the frame rate =
|
one
|
|
Ex: When an US system creates an image in 1/10 of a second, the frame rate is :
|
10 frames per second or 10 Hz
|
|
When the time needed to make each image decreases the frame rate ____.
|
increases
|
|
Two sonographer-controlled settings on an US system that determine frame rate are:
|
1- imaging depth and 2- number of pulses in each picture (per frame)
|
|
What type of imaging increases frame rate and improves temporal resolution?
|
shallow imaging
|
|
Deep imaging ____ frame rate and ____ temporal resolution.
|
decreases, degrades
|
|
Imaging depth and frame rate are ____ related.
|
inversely
|
|
The time needed to make a single frame (PRP) times the # of pulses =
|
the time for 1 frame
Ex: 100 x 1/1000 sec = 1/10 sec = 10 Hz |
|
When are higher frame rates possible?
|
higher frame rates are possible when each image is made with fewer pulses
|
|
When each image is made with more pulses, the frame rate is ____.
|
lower
|
|
Pulses per frame & frame rate are ____ related.
|
inversely
|
|
What factors affect the # of pulses needed to creare an image? (3)
|
1- # of pulses per scan line (# of focal points) 2- sector size and 3- lines per angle of sector (line density)
|
|
With multiple focal zones, the # of pulses transmitted down each scan line ____ & the # of pulses needed to make the image ____.
|
increases, increases
|
|
So with multi-focused scanning the frame rate is ____ and temporal resolution is ____.
|
decreased, diminished
|
|
What type of focus has quick frame rate and superior temporal resolution?
|
single focus
|
|
What is the advantage of multiple focal zones?
|
it improves accuracy of individual images
|
|
W/ multiple focuses, each scan line has superior ____ ____ because it narrows in on a wide range of depths.
|
lateral resolution
|
|
When the sector size (field of view) is expanded, the # of pulses required to make an image ____ and temp. res. ____.
|
increases, decreases
|
|
The field of view (sector size) and frame rate are ____ related.
|
inversely
|
|
What type of field of view is great for temporal resolution?
|
a narrow field of view
|
|
Narrow images =
|
higher frame rate
|
|
Wider images =
|
lower frame rate
|
|
Spacing between the sound beams is known as ____ ____.
|
line density
|
|
Far apart lines in a beam are known as ____ ____ density.
|
low line
|
|
Closely placed lines in a beam is known as ____ ____ density.
|
high line
|
|
With high line density (closely spaced), the # of pulses per image ____ and the temporal resolution ____.
|
increases, decreases
|
|
High line density has a high number of ____ and poor ____ ____.
|
pulses, temporal resolution
|
|
Line density & frame rate are ____ related.
|
inversely
|
|
Even though high line density is bad for temporal resolution, what does it improve?
|
it improves the accuracy of the individual images
|
|
With high line density, each image contains more detail known as ____ ____ ____.
|
improved spatial resolution
|
|
High line density = ____ spatial resolution & ____ temporal resolution.
|
great, poor
|
|
Low line density = ____ spatial resolution & ____ temporal resolution.
|
poor, great
|
|
Poor temporal resolution is acceptable when scanning ____ ____.
|
motionless organs (gallbladder)
|
|
So for scanning with poor temporal resolution we can use a ____ focus, ____ density and ____ field of view.
|
multiple, high-line, and wide
|
|
When scanning the fetal heart, ____ ____ is critical because it is a moving structure.
|
temporal resolution
|
|
So for scanning the heart for superior temporal resolution we want a ___ focus, ____ field of view & ____ density.
|
single, narrow, and low-line
|
|
What type of resolution improves w/ multi-focusing?
|
lateral resolution
|
|
What type of resolution improves w/ high-line density?
|
spatial resolution
|
|
What are the 2 major functions of an US system?
|
preparation/transmission & reception
|
|
What are the 6 major components of an US system?
|
transducer, pulser/beam former, receiver, display, storage, master synchronizer
|
|
The ____ creates electrical signals that excite the transducers PZT & create sound beams.
|
pulser
|
|
What does the pulser determine?
|
the amplitude, PRP & PRF
|
|
The pulser functions during ____.
|
transmission
|
|
T or F. The sonographer can change the magnitude of the pulser's electrical voltage (0-500 volts).
|
TRUE
|
|
Changes in pulser voltage modify the ____ of the image.
|
brightness
|
|
When the pulser is set low, the active element (PZT) vibrates gently causing a ____ sound beam.
|
weak
|
|
When the pulser is set low it results in a ____ image.
|
darker
|
|
When a pulser is set high, the PZT vibrates forcefully causing a ____ sound beam & ____ image.
|
strong, brighter
|
|
Low output=
|
too dark
|
|
High output=
|
bright
|
|
What are the different synonyms for pulser voltage?
|
output gain, acoustic power, energy output power
|
|
Lower pulser voltages minimize likelihood of ____ so they are more desirable.
|
bioeffects
|
|
Random and persistant disturbances that obscure clarity of the signal are known as ____.
|
noise
|
|
A comparison of the meaningful signal, compared to the amount of contamination (noise) is known as:
|
signal-to-noise ratio
|
|
When the signal-to-noise ratio is high, the signal is ____ than the noise & the image quality is ____.
|
stronger, better/higher
|
|
When the signal-to-noise ratio is low, the strength of the signal is close to the strength of the ____ & results in ____ image quality.
|
noise, lower/poor
|
|
Noise is more likely when the transducer output is ____.
|
low
|
|
As output power is increased, the signal-to-noise ratio ____ and image quality ____.
|
increases, improves
|
|
What is the most common way to improve (increase) signal-to-noise ratio?
|
increase output power
|
|
PRP & PRF determine the ____ ____ ____.
|
maximum imaging depth
|
|
When the PRP is short, the PRF is ____ and the system spends ____ time listening.
|
high, less
|
|
When the PRP is short & the PRF is high the result is ____ imaging.
|
superficial (shallow)
|
|
When the PRP is long, the PRF is ____ and the systems listens for a ____ time.
|
low, long
|
|
When the PRP is long & the PRF is low the result is ____ imaging.
|
deep
|
|
Part of the transmitter that functions w/ array transducers during transmission & reception is the ____ ____.
|
beam former
|
|
What does the beam former do?
|
it receives the single electrical spike from the pulser & than distributes it to the numerous active elements (its forms the beam!)
|
|
The beam former also adjusts the electrical spike voltages to reduce ____ ____ in a process called ____.
|
lobe artifacts, apodization
|
|
During reception, what does the beam former do?
|
established the correct time delays used in dynamic receive focusing
|
|
The beam former also controls the ____ ____ by varying the # of PZT crystals used during ____.
|
dynamic aperture, reception
|
|
What does dynamic aperture do?
|
changes the # of crystals along the face of the probe that are used to produce a narrow sound beam
|
|
What do the most modern beam formers use?
|
advanced micro processor technology
|
|
Modern beam formers produce signals in ____ format & is known as a ____ beam former.
|
digital, digital
|
|
What are the advantages of a digital beam former?
|
you only need software programming for updates, it's extremely stable and versatile
|
|
What is the beam former switch?
|
protects delicate receiver components from the powerful signals that are created for pulse transmission
|
|
What does dynamic aperture do?
|
changes the # of crystals along the face of the probe that are used to produce a narrow sound beam
|
|
What else does the beam former switch do?
|
directs electrical signals from the transducer to the appropriate components w/in the system
|
|
What do the most modern beam formers use?
|
advanced micro processor technology
|
|
What makes up a channel?
|
single PZT active element in the transducer, electronics in the beam former/pulser, & wire that connects them
|
|
Modern beam formers produce signals in ____ format & is known as a ____ beam former.
|
digital, digital
|
|
The # of elements in an array transducer that can be excited simultaneously is determined by the # of ____ in the system.
|
channels
|
|
What are the advantages of a digital beam former?
|
you only need software programming for updates, it's extremely stable and versatile
|
|
How many channels are there typically in a system?
|
32 - 256
|
|
What is the beam former switch?
|
protects delicate receiver components from the powerful signals that are created for pulse transmission
|
|
What is the CRT monitor?
|
TV screen
|
|
What else does the beam former switch do?
|
directs electrical signals from the transducer to the appropriate components w/in the system
|
|
What makes up a channel?
|
single PZT active element in the transducer, electronics in the beam former/pulser, & wire that connects them
|
|
The # of elements in an array transducer that can be excited simultaneously is determined by the # of ____ in the system.
|
channels
|
|
How many channels are there typically in a system?
|
32 - 256
|
|
What is the CRT monitor?
|
TV screen
|
|
What is the order of receiver operations?
|
amplification, compensation, compression, demodulation, and reject
|
|
The amplification is known as the ____ ____.
|
receiver gain
|
|
With amplification, each signal returning from the transducer is made ____, & each signal undergoes an ____ amount of amp.
|
larger, equal
|
|
With amplification, the image is either ____ or ____.
|
brighter or darker
|
|
T or F. All signals in the receiver are affected identically/equally by amplification.
|
TRUE
|
|
The amplification does NOT improve ____ ____.
|
signal-to-noise ratio
|
|
T or F. The amplification alone can't make an image of uniform brightness from top to bottom.
|
TRUE
|
|
Amplification has no ____.
|
bioeffects
|
|
What are the units of amplification?
|
decibels (dB)
|
|
The final signal leaving the receiver is compared to the ____ ____ w/ amplification.
|
initial signal
|
|
What is the typical value of amplification?
|
60 - 100 dB
|
|
The process of improving the quality of a signal before it is amplified is called ____.
|
preamplification
|
|
Where does preamplification occur?
|
close to the active elements w/in the transducer
|
|
Part of the receiver that corrects attenuation as the sound waves travel deeper is called ____.
|
compensation
|
|
Compensation creates an image that is uniformly ____ from top to bottom.
|
bright
|
|
What is another name for compensation?
|
TGC's!
|
|
What are the units for TGC's or compensation?
|
decibels (dB)
|
|
The near gain on the TGC's has a constant amount of ____.
|
compensation
|
|
The depth @ which variable compensation begins is called the ____.
|
delay
|
|
The ____ corrects the effects of increasing attenuation.
|
slope
|
|
The ____ ____ represents the maximum amount of compensation.
|
far gain
|
|
Part of the receiver that keeps an images grayscale content w/in range of detection of the human eye is the _____.
|
Compression (dynamic range or log compression)
|
|
Humans can distinguish ____ shades of gray.
|
20
|
|
What else does the compression do?
|
Keeps the electrical signal levels w/in the accuracy range
|
|
Compression is adjustable and there are 2 types. What are they?
|
One that is integral to the system design & can't be changed, and one that is user adjustable (maps)
|
|
Compression is the _____ _____.
|
Grayscale maps
|
|
A 2 part process that changes electrical signals w/in the receiver into a form more suitable for CRT (tv screen) is the _____.
|
Demodulation
|
|
Demodulation involves ____ which converts all negative voltages into positive ones.
|
Rectification
|
|
T or F. Demodulation can't be adjusted and has no effect on the actual image.
|
TRUE
|
|
What part of the receiver allows the sonographer to control whether low level gray scale info w/in the data will appear on the image?
|
Reject
|
|
Reject is also known as AKA ____ or ____.
|
Threshold or suppresion
|
|
There are 2 types of reject what are they?
|
One that is adjustable and one that is not and built into the system
|
|
What does reject get rid of?
|
Reject gets rid of weak reflections
|
|
What does dynamic frequency tuning do?
|
uses high frequency reflections to create superficial portions of image because high frequency sound has superior axial res.
|
|
How does output power affect image brightness?
|
output power adjusts the strength of the sound pulses sent to the body
|
|
More powerful output power=
|
brighter images
|
|
Output power improves the ____ ____ but receiver gain does not affect it.
|
signal-to-noise ratio
|
|
How does receiver gain (amplification) affect image brightness?
|
amplification alters the strength of voltages in the receiver after reception by the transducer
|
|
Higher amplitude =
|
brighter image
|
|
Lower amplitude=
|
darker image
|
|
T or F. Receiver gain (amplification) does not alter signal-to-noise ratio.
|
TRUE
|
|
Patient exposure to sound energy is affected by alterations in ____ ____ but not ____.
|
output power, amplification
|
|
What is the ALARA principle?
|
As Low As Reasonably Achievable- you must chose the modification that minimizes patient exposure
|
|
If an image is too bright you should first decrease the ____ ____ since decreasing it has no effects.
|
output power
|