Related Essays

  • Sound Wave Test Paper

    Sound Wave Test Date ______ Name _________________________________________________ 8th ChQu ______ Quiz ______ Act___...

  • Comparing Kinetic And Mechanical Waves

    “A transverse wave that involves the transfer of electric and magnetic energy (Don Buckley, 2011)” they are made of vibrating magnetic and e...

  • Ultrasound

    Sound is a wave that travels in a straight line and requires a medium. Frequency and wavelength are related by the speed of sound in the medium with (v=fλ). ...

  • Energy Word Bank: Scientific Model

    Transverse wave A wave where the vibrations of particles travel 90° to the direction of energy transfer Compression waves (also known as a ‘longitudinal wa...

  • Nt1310 Unit 9 Lab Report

    Rebecca McKenney Astronomy 101 Mrs. Alburg 25 March 2017 Chapter 2 Review Questions 1. For each of the following wavelength, state whether it is in the r...

  • Sound Waves Research Paper

    Transverse waves are where the vibration is at 90 degrees to the motion of the waves. On the other hand, sound waves work in a completely different way.

  • Radiation Capstone Case Study

    Therefore when two sound waves of equal frequency travel simultaneously in a medium in the same direction then at some idea both waves produce compression th...

  • Quiz Questions On Chemistry

    ______ atomic number? _______ How many electrons does carbon have? _______ neutrons? _______

  • Analyse The Value Of Voltages In Generation, Transmission And Distribution?

    Analyse the values of voltages in generation, transmission and distribution? Task 4 (D1) Electricity has greatly evolved from what it once was, to be fit...

  • Test 1-3: Unit Used To Measure Electrical Flow?

    8. _________________ used to measure electrical pressure.? 9. __________________ any opposition to electrical flow? 10,_________________ anything that can...

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

Card Range To Study

through

image

Play button

image

Play button

image

Progress

1/507

Click to flip

Use LEFT and RIGHT arrow keys to navigate between flashcards;

Use UP and DOWN arrow keys to flip the card;

H to show hint;

A reads text to speech;

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