Definitions Flashcards
SOUND: All waves carry ______ from one location to another
Energy
Acoustic propagation properties
the effects of the _____ upon the sound wave
MEDIUM
Compressions: areas of _______ pressure/density
Rarefactions: areas of _______ pressure/density
Compressions= INCREASED
Rarefactions= DECREASED
Sound= __________, longitudinal wave
MECHANICAL
Sound travels in a _______ line
STRAIGHT
List the 3 Acoustic variables
PRESSURE, DENSITY, DISTANCE
Transverse wave= particles move in a ___________ direction
Longitudinal wave= Particles move ____and _______ in the ______ direction
Perpendicular= transverse
Back & forth, Same direction= longitudinal
Acoustic parameters= describe the _______ of a particular sound wave
Features
Period= the time required to complete a ______ cycle
Single
UNCHANGED
Frequency= number of certain _____ that occur in a particular time duration
-UNCHANGED
Events
Audible sound is between __ Hz to 20,000 Hz yes heard
Ultrasound= greater than
Infrasound = less than 20 Hz; frequency too low
20
List the 3 bigness parameters (can be changed)
Power, Amplitude, Intensity
PAI
Amplitude= the difference between the average value and the ________ value of the acoustic variable
DB
Maximum value
Power= the _____ work is performed. Rate of energy transfer.
-Watts
-Sound source
-decreases as sound travels
-changed
Power is proportional to the waves amplitude squared
Rate
When the amplitude is tripled, the power is increased by the factor of _____
3x3=
9
When the amplitude is halved, power is decreased by a factor of _____
4 ; quartered !
When the amplitude is doubled, power is increased by a factor of
4; quadrupled
2x2=4
Intensity= the __________ of energy in a sound beam.
Beams power divided by area
INTENSITY= Power/Beam Area
Watts/cm2
Changed
Intensity is a key parameter for _____
Intensity is NOT UNIFORM across a sound beam
Concentration
Bioeffects
Wavelength= _______ or distance of a single cycle.
-mm
-BOTH MEDIUM/SOURCE
-UNCHANGED
0.1-0.8
WAVELENGTH= SPEED/FREQUENCY
L=C/F
LENGTH
Higher frequency= ________ wavelength
Lower frequency = ________ wavelength
Higher= Shorter
Lower= Longer
Speed= rate that sound travels through medium
-mm/us
-MEDIUM ONLY
-UNCHANGED
1,540
Sound = slow medium= ____ wavelength
Sound = fast medium= ________ wavelength
Slow= short
Fast = long
Gas is _______
Solid is ______
Gas = slower
Solid= faster
Air 330 =
Slowest
Bone= 2,000-40000
Fastest
Stiffness and speed = _____ direction
-bulk modulus
Density and speed= _____ direction
-compressibility/elasticity
Stiffness = same
Density = opposite
Interference= _____ waves overlap at the same location, and at the same time and combine into a single new wave
Two waves
Constructive interference (IN-PHASE) = amplitude of the new, combined wave is _________ then the original two waves.
Deconstructive interference(OUT-OF-PHASE) = amplitude of the new wave is _____than original wave
GREATER
Less than
In diagnostic imaging, short _____ acoustic energy are required to create an atomic images
CW CANNOT CREATE IMAGES!
A pulse= collection of cycles that travel together
Pulses
Pulse duration= start of one pulse to the end of that pulse
-“______” time/TALKING TIME
-time
-sound source
PD= PERIOD x # of cycles
-UNCHANGED
2-4 cycles
Actual time
SPL= spatial pulse length= distance or _____ from start to the end of one pulse
-PD& SPL= directly related
-BOTH MEDIUM/SOURCE
-UNCHANGED
-SPL affects _______ resolution
Shorter pulses= ______ quality images
SPL= WAVELENGTH X # OF CYCLES
Length
Axial resolution
Higher quality
PRP= time from the START of one pulse to the START of the NEXT pulse.
-listening time
-PRP & depth= directly related
-CHANGED
-PRP is determined by_____
Depth
PRF= number of _____ created by the system in one second
-Hz
-SOURCE
-CHANGED
-PRF& DF= directly related ++
PRF &PRP= INVERSELY R (-)(+)
-PRF determined by_____
-PRF IS NOT RELATED TO ______
Pulses
Depth
Not related to Frequency
Shallow image = _____ PRF
Deeper image= ______ PRF
Higher
Lower
Duty factor = ________ or fraction of time that the system transmits sound
-UNITLESS
-SOURCE
-CHANGED
-small value, less than ____%
CW= 100%
Little talking, lots of _______
Percentage
1%
Lots talking
Shallow image= ______ DF
DEEEPER IMAGE=_____ DF
Higher
Lower
Spatial: an ultrasound team does not have the same intensity at different ________ within the beam
-DISTANCE/SPACE
LOCATION
Temporal= pulsed ultrasound does not have same intensity at different ________
ALL TIME
TIMES
SPTP= ________ value
SATA= _____ value
SPTA= ______
Highest
Lowest
Bio effects
3dB= ____ bigger
-3dB= ______
One quarter=
2x
One half
-6dB
The relative change in a sound beams intensity is measured in
dB
Attenuation= DECREASE in ______ of sound wave
The further sound travels, the ____ attenuation
SPEED & ATTENUATION = ______!
STRENGTH
MORE
Unrelated
List the 3 components of Attenuation
- Absorption-most important
- Scattering
- Reflection
Less attenuation =
_____ distance
_____ frequency
Less A= shorter D, lower F
More attenuation=
______ distance
______ frequency
Longer distance
Higher frequency
Air is much much ____ attenuation than in soft tissue
AIR=MORE
Lung & bone= _____ than soft tissue
More
Water is much much _____ than in soft tissue
Water= Less
In soft tissue, LOWER frequency = _____attenuation
-PENETRATE FURTHER
Less
T/F?
Air»>Bone & lung» soft tissue» water
True
REFLECTION: occurs when propagating sound energy STRIKES a boundary between two media and _____ returns to the transducer
Some
SPECULAR reflection: reflections from a _______ reflector (MIRROR) & return in _____ direction
-wavelength is much smaller
Strikes boundary at 90 degrees
-VESSEL WALL
SPECULAR = SMOOTH mirror
Strongest reflections are produced ______ incidence -90 degrees
Strongest = NORMAL incidence
DIFFUSE/Backscatter= reflection of sound generally back towards the transducer, but in ______ directions
-disorganized
-ROUGH BOUNDARY
-Same size as wavelength
Multiple directions
Scattering: RANDOM
_____ frequency = more scatter
Higher frequency = more scatter
Rayleigh Scattering: ______
Scatter
Attenuation coefficient= ONE-HALF THE FREQUENCY
0.5db/cm/MHz
Remains the same no matter how far
Frequency & attenuation coefficient= _______ related
DIRECTLY RELATED
IMPEDANCE number associated with a _______
-RAYLS= Z
-CALCULATED/not measured
Impedance = DENSITY x SPEED
MEDIUM
Incident intensity= intensity of a sound wave, _____ to striking a boundary
Reflected intensity= ________ striking a boundary, changes direction, and returns back from where it came
Transmitted intensity= after striking a boundary, continues on in the same general direction that it was originally traveling
Incident intensity = reflected, intensity + transmit it, intensity
Before= incident
AFTER striking = reflected
Intensity, reflection, coefficient IRC= ________ the intensity that bounces ______ when the sound strikes a boundary
Intensity, transmission coefficient ITC= ________ of the incident intensity, that, ______ striking a boundary, continues on the same general direction
IRC + ITC= 100%
IRC= Percentage ; bounces back
ITC= percentage; after
Snell’s Law= describes the physics of _________
Refraction
REFRACTION= transmission with a ______ (like Beckham)
-________ in direction as sound transmits from one medium to another
Requires:
________ incidence
_________ speeds
BEND
Transmits
-oblique incidence
-Different speeds
Time-of-flight= time needed for a pulse to travel to, and from the transducer in the reflector
When time of flight is measured, we can determine reflector _____
Depth
13 microsecond rule = every 13 us of go-return time means reflector is __cm deeper in body
1 cm
Piezoelectric effect= property of certain materials to create a _______ when PRESSURE IS APPLIED or when material is mechanically _______.
-change shape
VOLTAGE
DEFORMED
Piezoelectric materials:
Synthetic = PTZ= lead ______ titanate
Natural= quartz, tourmaline
Zirconate
Curie temperature = PZT heated 360-680
-PZT is _________
DESTROYED
PZT IS DEPOLARIZED
Active element=
-CERAMIC, PZT, CRYSTAL
it is ____ wavelength THICK
Active element = 1/2 wavelength THICK
Case= protects the _______ components from damage and insulates the patient from electrical shock
Internal
Matching layer= IMPEDANCE between those of the SKIN and the ACTIVE ELEMENT _________ transmission between the active element and skin.
________ wavelength thick
INCREASE
Matching layer = ONE-Quarter wavelength thick
Damping/Backing material= REDUCES “________”
Material is bonded to active element
Short pulses create more accurate images
Made from :
Continuous wave transducers do not require damping material
Damping= reduce RINGING
Epoxy resin
Bandwidth = RANGE of _______
between the highest and lowest frequency emitted from the transducer
Imaging probes are _____ bandwidth or broadband
FREQUENCIES, WIDE
Quality factor= ______ number related to DAMPING
Low-Q= ______ & _____ bandwidth (imaging pulsed transducers)
High-Q= _______ & ______ bandwidth (CW & therapeutic transducers)
UNITLESS number
LOW Q= DAMPING/WIDE
HIGH Q= NO DAMPING/ NARROW
CW transducers:
sound frequency= ______ frequency
Electrical frequency
Pulsed transducers:
the main or ______ frequency of sound from a pulsed transducers, determined by two characteristics of the Crystal:
1.
2.
Higher frequency =
____ crystal
____ PZT
Lower Frequency =
____ crystal
____ PZT
Pulsed transducers
Center
1. THICKNESS
2. SPEED of PZT material
High F=
THIN crystal
FAST PZT
LOW frequency=
THICK
SLOW PZT
Beam width= as sound travels width of beam changes
-starts out SAME SIZE as transducer _____ or APERTURE
-gets ______ until it reaches smallest diameter then beam diverges
Diameter
Narrower
Near zone/FRESNEL = region in between the transducer and the _______.
-sound beams _______ in the near zone
Far zone/FRAUNHOFER=
region, deeper than the focus, ________ the Near field
-Sound beams
________ in far zone
FOCUS; CONVERGE
Beyond, DIVERGE
More divergence =
_______ diameter active element
_______ frequency
_______ beam in far field
_______ Lateral resolution
More divergence =
SMALL D
LOW FREQ
WIDE BEAM
DEGRADED LATERAL
Diffraction pattern= __-shaped also called ________ wavelet. When produced by a _____ source, with a size near the wave length of the sound, waves will diverge in the shape as they propagate.
Diffraction = V-SHAPED
HUYGENS WAVELET
Huygens’s Principle= _______ shape
-tiny sound source
Result of ________ & destructive interference
Hourglass shape
Constructive
Axial resolution= ability to distinguish two structures that are close to each other, _____to _____, PARALLEL to, or ALONG the beams main axis
Better axial resolution = ______ pulses
-UNCHANGED
mm,cm
AXIAL R= SPL/2
Front to back, parallel
SHORTER PULSES
Axial vs lateral
Yup
Mechanical scanning
-one disc shaped element (coin)
-moved by a ______
-oscillating crystal or mirror
-CONVENTIONAL/______ : curvature of PZT focuses beam at specific depth
-FAN SHAPED
-Scanline spread apart, creating ____ at greater depths
Motor
Fixed
Gaps
Phased arrays: adjustable focus or _____-focus
-_________ STEERED
-sector shaped
Phase delays
-steering can become erratic
Multi focus
Electronically steered
Poor steering
Contrast resolution= visualizing a ______ of gray shade in an image.
Few gray shades= _____ contrast resolution
many gray shades = ______ contrast resolution
VARIETY
Few gray= poor
Many gray = good
Spatial resolution= DETAIL
affected by _______ & __________ resolution, line ________
(3 things)
Fine detail= ______ spatial resolution
Limited detail= ______ spatial resolution
Axial, lateral, line density
Fine= good
Limited= bad
T/F shallow depth makes frame faster
True
Output, power
when output power is changed, the strength of every transmitted pulse to the ______ changes
-can be changed
-impacts brightness of entire image
Low output power= ______ image
High output power= BRIGHTER IMAGE
Body
Low = darker image
Gain: _________ the strength of all electrical signals in the receiver BEFORE further processing.
-adjusted
-db
-changes brightness 🔅 of entire image! Uniform; identical
Preamplifier alters gain _____ gain is applied
Increases strength
Before
Compensation or TGC= used to create _______ BRIGHTNESS 🔆 from ____ to bottom!
Compensation treats echoes differently, depending upon the depth that which they arise
-Compensation makes an image ______ bright at ALL depths
Higher frequency = ____ compensation because it attenuates more
Low frequency = ______ compensation because it attenuated less
UNIFORM BRIGHTNESS 🔅
TOP TO BOTTOM
Equally
High frequency = more c
Low frequency = less c
Dynamic range= adjust the grayscale range within the image. Allows us to see _____ gray shades and different tissues.
-changes gray scale ______
-adjusted
All
Mapping
Reject= displays ____ level echoes
Eliminates ____level noise!
-only affects low level signals, but does not affect bright echoes
Reject =
Low level
Low level
Pixel= smallest/largest element of a digital picture?
PIXEL= smallest !
Pixel density=
the MORE pixels per inch, the MORE ____ in the image —-spatial resolution
Low pixel density= _____ detail
High pixel density= ____ detail
Detail
Low pixel density = poor detail
High pixel density= good detail
Spatial resolution is related to the number of lines per frame
Few lines= ____ detail
More lines= ____ detail
Few lines= poor
More lines= good
Bit = binary digit 🧡
Smallest amount of storage
A bit is ______
Group of bits assigned to each pixel to store gray scale color
More bits=____ shades of gray
= BETTER CONTRAST RESOLUTION 👍
Few bits= ___ gray shades
Poor contrast
Many shades
Less
Preprocessing= manipulating data before storage in scan ______
-altered forever
Converter
Post processing= after= performed on a _____ image
FROZEN 🥶
Analog to digital converter:
Analog-digital = analog signal display on tv
iPod is a D-A conversion
True
Ultrasound system
Correct
Read magnification = blurry image
-DOES NOT RESCAN, only reads ____ image data!
-__processing (after/frozen)
SAME LINE DENSITY
_____ pixels
Spatial resolution _____ improved
Temporal resolution UNCHANGED
Old images
Post processing
Larger pixels
Not improved
Frequency compounding= divides the reflection into sub-bands of _______ frequency ranges. Images are created from each of sub bands.
Images are averaged, improving signal to noise ratio
-speckle artifact reduced
-detail improved
Smaller
Dynamic aperture=
Form of ________ receive focusing
-varying the number of elements used to receive the reflectors
-minimizes beam width variation
Electronic
Edge enhancement= _______ contrast at a boundary to make image appear sharper/blurry?
-distinguish interfaces
-most useful to emphasize different tissues
-light grays become whiter
-dark grays become darker
EDGE ENHANCEMENT = SHARPER IMAGE
Coded excitation:
creates LONG PULSES that contain complex patterns of frequencies & cycles, called a _______
Takes place in a _____
Improves: _______ resolution (most important) , penetration, _______ resolution, contrast resolution
Code
Pulsed
Axial resolution
Spatial
