Ultrasound Physics Review Final_1 Flashcards

Terms Definitions
tenth
deci
Non specular
Scattering
Narrowing of vessel
Stenosis
greater than 20 kHz
ultrasound
Which prefix equals 10-3?
Milli
LOWER FREQUENCY =?
LONGER WAVELENGTH
23. Attenuation coefficient for soft tissue @ 10MHz is
a. 5dB/cmb. 5dB/mmc. 5dBd. 10dB/cm
Parallel
running along the same axis
Traveling wave of acoustic variables
Sound
WITH OBLIQUE INCIDENCE:
REFLECTION ANGLE=?
INCIDENT ANGLE
HIGHER FREQUENCY = ?
SHORTER WAVELENGTH
Reciprocals
Period and frequency are also what?
12. Attenuation of 3dB corresponds to an intensity ratio of
a. 1.00b. .50c. .25d. .33e. .13
What are the units of attenuation?
dB/cm/MHz
What are the units for: PRP
(ms)
1. When frequency is halved, period is
a. unchanged
b. increased
c. doubled
d. decreased
Acoustic
relating to, involving sound, or typical of sound, hearing or the study of sound
The attenuation os ultrasound propigating through soft tissue is approx what?
0.5 dB/cm/Mhz
Increasing voltage received from the transducer to a level suitable for processing denotes:
amplification
Higher frequencies have a higher attenuation with less depth of penetration:
False or True
true
What system control determines the amount of amplification that occurs in the receiver?
Gain
Relationship between round-trip pulse time,propagation speed, and distance to a reflector
Range equation
Increase in echo amplitude from reflectors that lie behind a weakly attenuating structure
Enhancement
INTENSITY ________ AS SOUND PROPAGATES THROUGH THE BODY.
DECREASES
ANOTHER WORD FOR PIEZOELECTRIC MATERIALS
FERROELECTRIC MATERIAL
T/F
ALL NUMERICAL VALUES SHOULD HAVE CORRESPONDING UNITS.
TRUE
Inversely related
How are wavelength and frequency related?
2-4
What is a typical value for Q-factor?
9. The operation Frequency
a. depends on the transducer’s ring-down timeb. depends on the thickness of the crystalsc. is increased as the crystals diameter is decreasedd. depends on the strength of the pulse
What is reduced with attenuation?
Power and intensity
9. The operation Frequency
a. depends on the transducer’s ring-down time
b. depends on the thickness of the crystals
c. is increased as the crystals diameter is decreased
d. depends on the strength of the pulse
Enhancement
Occurs when the medium through which the sound travels has a lower attenuation rate than soft tissue.
Causes: Low attenuation
High focusing
1. Foreground color (brighter echoes)
2. Results from too little attenuation
3. Parallel to the sound beam
4. Beneath the structure with reduced attenuation
Assumption #5 Intensity of the reflections is related to the scattering charateristics of the tissue.
Which of the following tissues would have the slowest propagation speeds for sound? Fat, Blood, Muscle, Bone or Liver?
Fat
A complete cycle consists of one aompression and one rarefaction. The area of low pressure and density is :
a. compression
b. raefaction
B
Individual transducer elements within a single transducer assembly describe:
channels
(multiple transducer elements with individual wiring and system electronics are termed channels)
The spectrum of frequencies emitted by a pulsed wave transducer is known as what?
Bandwith
What doppler technique does not provide range resolution?
CW doppler
Color flow doppler provides what type of velocity information?
Average/Mean
Which of the following adjustments will increase the duty factor: Increasing receiver gain, Increasing output power, Increasing pulse repitition frequency, Increasing scanning time, or Increasing TGC?
Increasing PRF
Is the following form of information Digital or Analog: Input signal from the analog to digital converter
Analog
An object that scatters sound because of its small size or its surface roughness
Scatterer
Propagation speed that is different from the assumed value
Speed error
Presentation of 2 dimensional, realtime doppler shift info superimposed on a real-time,gray-scale, anatomic cross sectional image. Flow toward and away from transducer are presented as different colors on a display
Color Doppler display
Reflected intensity divided by incident intensity; the fraction of incident intensity reflected
Intensity reflection coefficient
______INTENSITY HAS THE HIGHEST VALUE. ________ INTENSITY HAS THE LOWEST VALUE.
SPTP. SATA
ATTENUATION OF SOUND IN BLOOD IS APPROXIMATELY ________ TO THAT IN SOFT TISSUE.
EQUAL
oblique incidencedifferent propagation speeds
What is necessary for refraction?
stiffness
the ability of an object to resist compression
internal focusing
the most common form of fixed focusing
What is sound made up of?
Compressions and rarerefractions
What are the units of the transmitted intensity of a sound wave?
W/cm2
Define: Doppler shift.
The difference between the emitted Frequency and the frequency returning from echoes
Define: Autocorrelation.
Rapid technique used in most color doppler instruments for obtaining mean doppler shift
13. If a wavelength is 4mm and the frequency is doubled, the wavelength becomes:
a. 1mm
b. 2mm
c. 3mm
d. 2cm
e. 8mm
Rarefaction
The state of wave propagation in which the particles of the medium are stretched farther apart than normal (lower density)
As U/S wave travels through the body, its intensity usually:
a. increases
b. decreases
c. remains the same
B
The mechanical index:
predicts the likelihood of cavitation occurring
What reveals the state of the downstream arterioles:
Diastolic flow
What transducer produces a beam that is symmetrical about the beam axis?
Annular array
True or False: In laminar flow the blood is faster near the vessel walls?
False
The units for the doppler shift are:
a. KHz
b. cm/sec
a. KHz
Which of the following improves when frame rate increases: Lateral reso, Longitudinal reso, temporal reso, spatial reso
temporal reso
Ratio of largest to smallest power that a system can handle; ratio of the largest to smallest intensity of echoes
Dynamic range
Reynolds number above which trubulence occurs
Critical reynolds number
IF THE BOUNDARY BETWEEN TWO MEDIA HAS IRREGULARITIES, THEN THE WAVE MAY BE CHAOTICALLY REDIRECTED IN ALL DIRECTIONS.
SCATTERING
THIS EXPLAINS THE HOURGLASS SHAPE OF AN IMAGING TX'S SOUND BEAM.
HUYGEN'S PRINCIPLE
Period
the time it takes a wave to vibrate a
 single cycle
27. Scattering refers to:
a. bending of the sound beam crossing a boundaryb. conversion of sound to heatc. redirection of a portion of the sound from a boundary beamd. redirection of the sound beam in several directions
What are the units for duty factor and pulsed ultrasound?
Unitless
Define Annular array.
Array of crystals arragned in a circular symmetry.
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,
Partial volume artifact
________ is higher in both bone and in lung compared to soft tissue.
attenuation
What term is used to describe the hyperechoic region region seen below a cyst?
Acoustic enhancement
During reception, diagnostic US transducers convert:
acoustic energy into electrical energy
What means impedance
the resistance that a medium present to sound travel
What is the purpose of subdicing?
To reduce grating lobes
The Nyquest limit is equal to ______ of PRF.
a. 1/4
b. 1/2
c. 3/4
d/ none of the above
b. 1/2
The Number of pulses occuring in one second is reffered to as the:
a. PRP
b. PRF
c. Duty factor
d. Q factor
b. PRP
Proper adjustment of the DGC is approx what?
1 dB/cm/MHz
A line produced on a display that represents ultrasonic echoes returning from the body
Scan lines
NAME 2 ADVANTAGES OF DAMPING MATERIAL.
-SHORTENS SPL, PULSE DURATION
-INCREASES PIC ACCURACY BY IMPROVING AXIAL RESOLUTION.
THE LENGTH OR DISTANCE OF A CYCLE IS KNOWN AS:
WAVELENGTH
WHAT IS THE EQUATION ASSOC. WITH SNELL'S LAW?
SINE(TRANSMISSION ANGLE)/SINE (INCIDENT ANGLE) = PROP SPEED 1/PROP SPEED 2.
epoxy resin impregnanted with tungsten
What is backing material made of?
What are the 3 mechanisms of action for ultrasonid bioeffects?
Heat-Intensity, Radiation force-Exposure time, and Cavitation-mechanical effect to tissue
22. For soft tissue, there is approximately_________ of attenuation per____________ for each MHz
a. 0.5dm, mm
b. 0.5dB, cm
c. 1.0 dB, mm
d. 1.0 dB, cm
While preforming an ultrasound of the thyroid gland, you adjust the acoustic power by -3 dB, what would happen to the intensity?
It would be halved
Pixel interpolation is an imaging technique with the purpose of:
allocating amplitude to missed reflections
(pixel interpolation assigns value to missed pixels based on the intensities of the adjacent pixels)
What is the minimum beam diameter for an unfocused disk transducer?
1/2x disk diameter
Which one of the following factors is not determined in the doppler equation:
a. doppler angle
b. incident frequency
c. reflertor speed
d. acoustic information
d. acoustic information
The receiver can distinguish harmonic signals from the fundemental signals because of all of the following except:
a. lower intensity
b. higher frequency
c. lower amplitude
d. timing of received signal
d. timiing of received signal
Which of the following adjustments would improve contrast resolution: Increasing # of pixels, Increasing number of scan lines, Increasing number of bits, Increasing number of raster lines, or Decreasing the size of the scan converter matrix?
Increasing the number of bits
WHAT ARE THE THREE COMPONETS OF ATTENUATION?
1. ABSORPTION
2. SCATTERING
3. REFLECTION
1)smooth boundary 90˚ to sound source2)boundaries with irregularities larger than the wavelengthyes
When does specular reflection occur?Is it organized?
What are used to commonly used as materials in the production of modern transducer elements?
Lead Zirconate Titanate (PZT)
What is the frequency for ultrasound?
> 20,000Hz Greater than audible range
If the reflector is 4 cm deep in the body, how many us is that?
52 usecs
While performing a hepatic sonogram on a patient with a fatty liver, you are unable to visualize the posterior right lobe of the liver. Which of the following solutions would be most likely to enable visualization of this area: Decrease dynamic range, Dec
Choose a lower freq transducer
Intensity of a focused sound beam is more uniform in the:
Fraunhofer zone (far field)
Which of the folllowing will not improve axial resolution: Increased Damping, Increased Transducer frequency, Increased bandwith, decreased pulse length, or Increased focusing
Increased focusing improves lateral resolution
The flow of blood through the body is affected by which of the following factors: Density, Size of the vessel, pressure gradient, or all of them
All of them
When compensation is properly adjusted what happens to the image?
Identical reflectors appear on the image similarly
FOCAL DEPTH IS DETERMINED BY 2 FACTORS:
-TRANDUCER DIAMETER
-FREQUENCY OF THE US
What material is attached to the rear face of the transducer elements to reduce the number of cycles in each pulse? Two Names?
1. Damping material2. Backing material
What 2 conditions are necessary for refraction to occur at a boundary between two media?
Different prop speeds and oblique incidence
6 basic assumptions of imaging systems
1. Sound travels in a straight line
2. Sound travels directly to a reflector and back to the transducer
3. Sound travels exactly 1,540 meters/second
4. Reflections arise from the structures positioned along the beams main axis (side lobe and grating lobe)
5.Intensity of the reflections is related to the scatering characterstics of the tissue (shadowing and enhancement)
6. The imaging plane is extremely thin
The Doppler shift is inversely related to the:
propagation speed of the medium
(and directly related to the operating frequency, blood velocity, and Doppler angle.)
What factors are velocity calculations dependant on?
Speed of sound in tissue, Doppler angle, and Transmitted frequency
In US sustems, the range equation is used to determine which of the following: Reflector amplitude, Relfector frequency, Reflector direction, Reflector depth, Reflector size?
Reflector depth (Range = Depth)
WHAT IS THE 13 MICROSECOND RULE?
IN SOFT TISSUE, EVERY 13 MICROSECONDS OF GO-RETURN TIME MEANS THE REFLECTOR IS 1cm DEEPER IN THE BODY.
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
Why is diagnostic US limited in its diagnostic application to the adult brain?
Because the great acoustic impedance mismatch between the cranium and soft tissue causes most of the sound to be reflected at that interface
What is the result of increasing the wall filter during doppler sampling?
Reduce display of low frequency shifts
How is reflector depth determined with pulse wave US?
By the arrival times of the echoes
If focusing increases, the focal zone gets smaller.
What happens to the focal zone when focusing increases?
In soft tissue, the _______ frequency, the _______ the attenuation.
greater, greater. This is why we do not image deep with high freq sound.
What would be the result of inaging the aorta at an angle of 45?
Tha angle of reflection will be oriented away from the transducer resulting in decreased visuaalization of the aorta
In order for a reflected wave to be produced, which of the following conditions must be met at an interface?
a. oblique incident, different sound speeds
b. perpendicular incedent, same sound speeds
c. both of the above conditions produce reflection
a. oblique incident, different sound speeds
WHY DO WE USE GEL IN U/S?
TO REMOVE AIR FROM THE PATH OF ULTRASOUND.
Which of the following digital scan converters would demonstrate the best contrast resolution: 8 bit, 7 bit, 6 bit, 5 bit, or 4 bit?
8 bit (equaks 256 shades of gray in standard US systems
/ 120
Term:
Definition:
Definition:

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