Study your flashcards anywhere!

Download the official Cram app for free >

  • 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

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key

image

Play button

image

Play button

image

Progress

1/218

Click to flip

218 Cards in this Set

  • Front
  • Back
What are the general frequencies used in ultrasound imaging and name a type of exam used for the transducers.
2.0-Cardiac, 3.5-OB/Abdominal, 5.0-Vascular, 7.5-Superficial, 10.0-Small parts
Define bandwith.
The range of frequencies contained within a pulse
What is better Narrow or broad bandwidth?
Broad due to the larger spectrum of frequencies
What is the main pulse that is emitted from the transducer termed?
Operating/Resonance
What is the process that increases the range of frequencies called?
Damping
Define Velocity.
Speed with direction of motion specified
What is velocity determined by?
Density and stiffness
What is the formula for propagation speed?
C=wavelength*Freq
What 2 variables determine the mediums properties?
Stiffness-resistance of a material to compression, and Density-concentration of mass per unit of volume
What is the rule of thumb regarding propagation speed?
Prop speed increase=Stiffness increase=Density decrease
Prop speed decrease=Stiffness decrease=Density increase
What are the ranges for PRF?
1000-10,000Hz
Define PRF.
Number of electrical pulses per second
Describe two types of pulse anatomy?
On time and listening time
What are the 2 formulas for pulse duration?
pd=p*n
pd=n/f
What is the typical range for pulse duration?
.5-3 microseconds
What are the units for duty factor and pulsed ultrasound?
Unitless
What happens to duty factor when PRP increases?
DF decreases
What happens to duty factor when Imaging depth increases?
DF decreases
What happens to duty factor when Pulse duration increases?
DF increases
What happens to duty factor when PRF increases?
DF increases
What are the 2 types of detail resolution?
Axial and Lateral
Define Axial resolution.
The minimum reflector separation necessary to resolve reflectors ALONG a scan line
Define Lateral resolution.
The minimum reflector separation necessary to resolve reflectors ACROSS a scan line
What are the 3 modes of focusing for a mechanical transducer?
Lens, Curved element, Mirrors
Define wavelength.
The length of space over which one cycle occurs
What is the formula for wavelength?
wavelenght=c/f
What 2 things determine a wavelength?
Frequency and propagation speed
What does wavelength influence?
Axial/longitudinal resolution
If frequencyy is doubled what hapens to the wavelength?
It is halved
What are the effects of ultrasound on tissue termed?
Bioeffects
What are the 2 types of bioeffects to mammalian tissue?
Heating and Mechanical
What are the 3 types of mechanical bioeffects?
radation force, steaming, cavitation
What are the units for wavelength?
mm
What are the 2 types of cavitation?
Stable-dosent burst, Transient-Bursts
The level at which signals are not transmitted through an ultrasound receiver is termed what?
Rejection
What is a pulse of ultrasound?
A few cycles of ultrasound
What is the formula for pulsed duration?
pd=n*t
How lung is the typical pulsed duration?
.5-3 microseconds
What is spacial pulse length analogus to?
wavelength
Define beam steering.
Movement of the transducer over the area of interest
What does lateral resolution equal?
Beam diameter
Axial resolution = what?
spl/2
Is the following operator adjustable: compensation and rejection?
Yes
Is the following operator adjustable: amplification and compensation?
yes
Is the following operator adjustable: demodulation and compression
no
Is the following operator adjustable: rejection and amplification?
yes
Define pixel.
Unit which imaging information is divided for storage and display in a digital instrument
Define dead zone.
Distance between the transducer face and the 1st rod, no image, area very close to the transducer
Define Aliasing.
Improper doppler shift information from pulsed wave/color when the doppler shift exceeds the nyquist limit
Define M mode.
B mode presentation of changing reflector position, time, motion, and amplitude
Define B mode
Information displayed as brightness
Define matching layer.
Material attached to the front of a transducer to reduce the reflections at the transducer element
Define damping material.
Material attached to the rear of the transducer to reduce the pulse duration
Define Q factor.
Recriprical of fractional bandwidth
Define Linear array.
Array made of rectangular elements arranged in a line
Define Sequential array.
Array of elements which are activated one at a time
Define Annular array.
Array of crystals arragned in a circular symmetry.
Define frequency spectrum.
The range of doppler shift frequencies present in returning echoes
What is the equation for: Prop speed?
C=
What is the equation for: Intensity formula?
I(mw/cm2)=P(mw)/A(cm2)
What is the equation for: spatial pulse length?
spl=number of cycles*wavelength
What is the equation for: Impedance formula?
Z(rayls)=density*prop speed
What is the equation for: Wavelength?
Wavelength=c/f
What is the equation for: Pulse Duration?
pd=n*t
Define: Comet tail artifacts.
A series of closely spaced reverberation echoes
Define: Grating lobes?
Additional, weaker beams of sound traveling in directions different from the primary beam
Define: Slice thickness.
Also called sectional thickness, Echoes from adjacent tissues filling what should be anechoic
Define: propagation speed artifact.
Occurs when the assumed prop speed is incorrect
Define: refraction.
Change of sound direction on passing from one medium to another
Define: reverberation.
Myltiple reflections
Define: Beam profiler.
Device used to record 3D reflection and amplitude information.
Define: Tissue equivalent phantom.
Device for testing ultrasound characteristics of tissue. Simulates soft tissue
Define: Doppler phantom.
Used to measure doppler
What is the AIUM 100mm test object?
A device that contains rod groups to measure axial and lateral resolution, range accuracy, receiver compensation, dead zone, and thurough registration accuracy
What type of propagation speed errors relate to improper position?
Section thickness, Speckle, Reverberation, Mirror image, range ambiguity, refraction, grating lobes, speed errors
What is a type of imaging that relates to the height of the vertical defection?
A-mode
What is a type of imaging that relates to time and motion?
M-mode
What is a type of imaging that relates to the brightness of the returning echo?
B-mode
Define duty factor?
The fraction of time the pulsed ultrasound is on
What is the typical duty factor in pulsed echo?
.1-1.0
What is the typical duty factor in continuous wave?
100%
Define: Attenuation.
Reductin of power or intensity as sound travels through a medium
What are the units of attenuation?
dB/cm/MHz
What is attenuation coefficient?
The attenuation that occurs with each cm the sound wave travels
What is reduced with attenuation?
Power and intensity
Describe the piezoelectric effect?
When electricity is applied the PZT elements converts the electricity into ultrasound pulses
What is the typical man made crystal used in most transducers today?
Lead Zirconat Titante (PZT)
What is a scan converter?
A device used to reformat echo data into image form for image processing, storage, and display (image memory)
What is the frequency for ultrasound?
> 20,000Hz Greater than audible range
What is infrasound?
<20Hz Less than the audible range
What are the frequencies of audbile sound?
20Hz-20,000Hz
What is sound?
A mechanical longitudinal wave
What is sound made up of?
Compressions and rarerefractions
What parameters can a hydrophone measure?
Amplitude and period; Acoustic pressure output levels, intensities and output indexes
What parameters are measured by radiation force?
PRP, Period, PD, and amplitude
What does in-vivo dentoe?
Within
What does in-vitro dentoe?
Outside
What is a calorimeter?
A device used to measure the amount of conversion of heat
What is a beam profiler?
A device used to record 3D reflection and amplitude information
What are the 3 mechanisms of action for ultrasonid bioeffects?
Heat-Intensity, Radiation force-Exposure time, and Cavitation-mechanical effect to tissue
What type of intensity does heating depend on?
SPTP- Spatial peak Temporal peak
If frequency decreases what happens to the SPL?
It increases
What 2 factors would increase ine intensity of a sound beam?
Increase power, Decrease focusing
What is Q factor?
The recriprical of fractional power
What is optimal Q factor?
Low
Qvalue equals what?
Material prop speed*thickness of the element
WHat factor is the operating crystal dependant on?
Thickness of the element and the mediums prop speed
Define: Doppler effect.
Change in frequency caused by motion
Define: Doppler shift.
The difference between the emitted Frequency and the frequency returning from echoes
What is variance mode?
Variance adds green to red to blue progressing from RT to LT across the map for detection of turbulent blood flow
What is the doppler shift formula?
FD=2*fo*v*coso/c
What is snells law?
The relationship between the incidence and transmission angles
What does snells law relate to?
Refraction
How long is the round trip time for each cm of distance traveled in soft tissue?
.13 microseconds
Define: Snell's law.
The relationship between the incidence and transmission angles
Define: Huygen's principle.
Each surface of multiple transducer, diffract producing small waves that join together and form one main energy sound beam
Define: Rayleigh's principle.
Scattering caused by RBC
Define: Poiseulles law.
Mathematical description of the dependence of volume flow rate on pressure, vessel length and radius, and fluid viscoscity
Refraction can only occur if you have what 2 factors?
Oblique incidence, and Different prop speeds
Define: Period.
Time per cycle
Define: PRP.
Time from the beginning of one pulse to the next
Define: PRF.
Number of pulses oer second
What are the units for: Period
(ms)
What are the units for: PRP
(ms)
What are the units for: PRF
(KHz)
Why do we use coupling gel?
To provide a good sound path from the transducer to the skin, eliminating the thin layer of air that would reflect the sound
What does Duplex ultrasound mean?
Ultrasound that combines gray scale with pulsed wave and continuous wave doppler
What type of format, beam steering, and beam focusing does the following have: Linear Array.
Rectangular image, Electronic focusing, Mechanical steering
What type of format, beam steering, and beam focusing does the following have: Curved Array.
Convex image, Electronic focusing, Mechanical steering
What type of format, beam steering, and beam focusing does the following have: Phased array.
Electronic focusing and steering
What type of format, beam steering, and beam focusing does the following have: Annular array.
Sector image, Mechanical steering, Electronic focusing
What type of format, beam steering, and beam focusing does the following have: Single element.
Pie shape image, Mechanical focusing and steering; Lens mirror
Define: Fast Fourier Transform.
Digital computer implementation of a mathematical technique for obtaining a doppler frequency spectrum
Define: Autocorrelation.
Rapid technique used in most color doppler instruments for obtaining mean doppler shift
What are the units for Doppler?
(KHz)
What is the minimum doppler shift?
.26(Khz)
What is frequency shift always related to?
Change in motion
At what velocity is the Doppler shift equal to zero?
<10(cm/sec)
What factors will eliminate ailiasing in Doppler instruments?
Change angle, Shift the baseline, Lower the frequency, Increase PRF, Use CW Doppler
What are the 2 types of color doppler?
B-Dmode
Define: duplex.
Something that combines 2 things
Define: harmonics.
Frequencies that are even or odd multiples of another commonly fundamental/operating frequency; 2nd operating frequency
Why is harmonics used?
Using harmonic frequencies improves the quality of sonographic images
What is 3-D?
2-D slice images presented in plane orientation; commonly used for OB
If the reflector and the source are moving away from each other, what type of Doppler shift will you get?
Negative doppler shift
The dependance on Doppler angle is in the form of a waht?
Cosine
All of the following may be used as units of amplitude except which: Millimeters, Degrees, Pascals, meters per second
m/s
How are the spatial pulse length and the number of cycles in the pulse related?
Directly related
What 2 conditions are necessary for refraction to occur at a boundary between two media?
Different prop speeds and oblique incidence
When red blood cells move away from a transducer, the frequency of the wave returned from the RBC is what?
Less than the emitted frequency
What are the units of impedance?
Rayls
What best describes an angle with a measurement of 133degrees?
Obtuse
The sonographer increases the depth. Which parameter is decreased?
PRF
What is enhancement caused by?
Weakly attenuating structures
Which of the following parameters is determined by the medium: Wavelength, Freq, Period?
Wavelength and Spatial pulse length depend on the sound source and medium
Which of the following contributes most to total attenuation in soft tissue: Absorption, Reflection, Scattering?
Absorption
What are the units of the transmitted intensity of a sound wave?
W/cm2
Which of the following statements is true regarding axial resolution artifiacts: Higher quality images are associated with higher numbers, Axial resolution is reported in units of cm3, Numerically axial resolution equals 1/4 the pulse length, or Too few reflectors appear on the image?
Too few reflectors appear on the image
Which of the following is considered an acoustic variable: Freq, Period, Power, or Pressure?
Pressure
What are the effects of medium upon the ultrasound wave called?
Acoustic propagation properties
What is the acoustic velocity in soft tissue?
1540m/s
What is the power intensity for the following: 0dB, -3dB, -6dB, -9dB?
0=100%, -3=1/2, -6=1/4, -9=1/8
What 3 factors contribute to attenuation?
Absorption, Scattering, and Reflection
What is the formula for impedance?
Density*Prop Speed
if the relative output power of an ultrasound instrument is calibrated in dB and the operator increases the output power by 20dB, what is the beam intensity increased by?
100 times
What is impedance important in?
Reflection at boundries
What is the range of Doppler shifts commonly measured in clinical exams?
-0.01MHz to 0.01MHz
How are the maximum imaging depth and spatial pulse lenght related?
Unrelated
What does the dynamic range of the receiver of an ultrasound instrument refer to?
The range of echo signal amplitudes that can be processed without distortion
Two ultrasound transducers are used to perform Doppler exams on the same patient. The exams are identical except that the transducer frequencies are 5 and 2.5. Which frequency will measure the highest Doppler shift?
5MHz
A sound wave leaves its source and travels through air. The speed of sound in air is 330m/sec. One second later an echo returns to the source. At what distance from the source is the reflector that produced the echo?
D=C/2*Round trip time
165meters
What can be said of the Doppler shift when the sound beam is normally incident to the velocity of the red blood cells?
?
What does the damping material in the transducer do?
Increase the spatial pulse length
A sound wave strikes a boundary between two media at a 60degree angle is called what?
Oblique incidence
What are the units of attenuation?
dB
How are ultrasound frequency and the attenuation coefficient related?
Directly related A.C.=f/2
How are spatial pulse length and pulse duration related?
Directly
What is the formal name for dispertion of a wave in many different direction after striking a small particle?
Rayleigh Scattering
A sound wave that strikes a boundary between two media at a 90degree angle is called?
Orthogonal/Normal incidence
At what angles between the sound beam and the direction of motion will the doppler shift be a maximum?
0 and 180 degrees
What kind of angle is a measurement of 35degrees?
Acute
Negative decibles means the intensity is doing waht?
Decreasing
-10dB means the intensity was reduced how much?
10 times its original value
In order for reflection to occur when sound strikes a border between 2 media, what must be different for the reflection to take place?
Different Impedances
Medium 1 has a density of 9 and a stiffness of 6, Medium 2 has a density of 8 and a stiffness of 6. WHich medium has a lower prop speed?
Medium 1
Snells law is a declaration concerning the behavior of waves during a particular physical process or event. what event is this?
Refraction
What information does the Doppler shift furnish concerning the blood cells that produce it?
Velocity
What is the location where the sound beam reaches its narrowest diameter known as?
The focal zone
An ultrasonic pulse is traveling in soft tissue, which of the following is most important in determining the frequency of the sound contained in the pulse: The prop speed of the transducers matching layer, The thickness of the transducers backing material, The impedance of the transducers matching layer, or The prop speed of the transducers active element?
The thickness of the transducers active element
By changing the imaging depth, which of the following does the operator also change: PRF and PRP, SPL, prop speed, or PD
PRP and PRF
Which of the following parameters is affected by the medium: PRP, SPL, DF, or PD
SPL
All of the following are determined solely by the ultrasound machine except which: PD, freq, SPL, or Period?
SPL
How are the maximum imaging depth and PRP related?
Directly related
The sonographer decreases the depth. Which of the following parameter is decreased: PRP, PRF, Resonance Freq, or non of tthem?
PRP
What is the Doppler effect presented when the source and the receiver are moving closer together or further apart?
Frequency shift
Doppler shift produces information about what?
Velocity
At what angle between the sound beam and the direction of motion will the Doppler shift be absent?
90degrees
If a red blood cell is traveling ttoward a transducer, the frequency emitted by the transducer is what compared to the frequency reflected from the RBC?
Less than
In standard Doppler, what is known about the reflected frequency produced by RBCs traveling in a direction away from the transducer: It is in the audible range, It is ultrasonic, Its greater than the transmitted frequency, or its less than the transmitted frequency?
Its ultrasonic
The Doppler shift does not always provide a valid estimate of the speed of the RBCs that produce it because the shit is related to what?
The Cosine of the angle between the direction of the beam and the direction of blood flow
An artifiact produced by interference patterns and resulting in the granular appearance if images is termed what?
Speckle
When creating an ultrasound image, all of the following assumptions are made Except which: Sound travels in a straight line, Sound travels at 1.54mm/microsec, Reflections only arise from structures in the pulses main beam, The sound beam is extremely thin, or All structures create reflections of equal magnitude?
All structures create reflections of equal magnitude is false
You have obtained an ultrasound image that demonstrates refraction of the sound beam, this artifact might be manifested as what?
Lateral displacement of a reflector
Define: Doppler frequency.
The difference between the transmitted and received frequencies
You have placed the Doppler sample volume in a vessel that is 3cm deep. How long will it take the reflected signal to arrive back at the transducer?
39microseconds
You are performing a venous ultrasound exam with a 5MHz linear array transducer using a single focal zone. Where is the thinnest width of the beam in the z-axis
At the point of mechanical focusing
Which of the following statements is true about lateral resolution: It is also called angular, transverse, and depth resolution, It is reported in units of time, It is the same at all depths, or it can be improved by focusing?
It can be improved by focusing is true
All of the following artifacts result in the placement of too many echoes on the image Except which: Shadowing, Reverberation, Mirror image, or Grating lobes?
Shadowing
At what point does ailiasing occur?
When the frequency exceeds 1/2 the PRF
Which of the following artifcat is associated with resonance of a gas bubble: Grating lobes, Comet tail, Acoustic speckle, Ring down, or Refraction?
Ring down ie.-bowel
You are imaging a patient with a thickened gallbladder wall. In what direction can the the wall thickness be measured most accurately?
Perpendicular to the beam axis
What is the source of the enhancement artifact?
Decreased attenuation through a weakly attenuating structure
Which of the following does not result from multiple reflections: Comet tail, Reverberations, Ring down, or Enhancement?
Enhancement
What are the units for measuring the volume of a sphere?
cm3
If you measure the distance around the perimieter of a structure, you are measuring what?
Its circumfrence
You are using a transducer that produces a beam with a very wide slice thickness. Which of the following problems are you most likely to encounter: Increased near field reverberations, Increased side lobes, Decreased penetration, Partial volume artifact, or Increased electrical interference?
Partial volume artifact
What does the range equation describe?
The relationship between round-trip pulse travel time and distance to reflector
Which of the following artifacts commonly fills in small linear vessels: Refraction, Partial volume, Mirror image, Range ambiguity, or multipath artifact?
Partial volume artifact