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501 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Question |
Answer
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Hint
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When one item increases and the other decreases, they are ____ related?
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Inversely
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When one item increases and the other increases, they are ____ related?
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Directly
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2 numbers that when multiplied equal 1
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Reciprocal
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Write 1,000,000 in scientific notation
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1x10^6
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Write 0.000000124 in scientific notation
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1.24x10^ -7
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Giga
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G, 10^9, billion
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Mega
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M, 10^6, million
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Kilo
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k, 10^3, thousand
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Hecto
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h, 10^2, hundred
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Deca
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da, 10^1, ten
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Deci
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d, 10^ -1, one-tenth
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Centi
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c, 10^ -2, hundredth
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Milli
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m, 10^ -3, thousandth
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Micro
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u, 10^ -6, millionth
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Nano
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n, 10^ -9, billionth
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Tissue in which sound travels through?
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Media
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What different forms of waves exist?
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Heat, sound, magnetic, and light
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What is it called when molecules are squeezed together?
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Compression
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What is it called when molecules are stretched apart?
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Rarefraction
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What are sound waves?
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Mechanical waves in which particles in the medium move
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When particles move in a direction that is perpendicular to the direction a wave is moving, it is what?
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Transverse wave
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When particles move in a direction parallel to the direction a wave is moving, it is what?
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Longitudinal wave
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What type of waves are sound waves?
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Mechanical and longitudinal
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What are acoustic propogation properties?
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Effects of a medium on a sound wave
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What are the 3 acoustic variables?
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Pressure, density, distance (particle motion)
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What is pressure? Units?
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Concentration of force in an area. Pascals (pa)
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What is density? Units?
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Concentration of mass in a volume. kg/cm^3
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What is distance? Units?
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Measure of particle motion. mm, cm, km, etc.
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When 2 waves' peaks occur at the same time and location, they are ___ waves?
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In-Phase
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When 2 waves' peaks occur at different times and locations, they are ___ waves?
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Out-of-Phase
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What happens when multiple waves arrive at a location at the same time and combine to form a single wave?
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Interference
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In-Phase waves create ___ interference?
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Constructive-- when the combination of waves is larger that each of its' components
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Out-of-Phase waves create ___ interference?
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Destructive-- when the combination of waves is smaller than one of its' components
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Waves of different frequencies create ___ interference?
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Both constructive and destructive
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What are the 7 acoustic parameters?
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Period, frequency, wavelength, propogation speed, amplitude, power, and intensity
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The time it takes a wave to complete one cycle? Units?
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Period. us, s, etc.
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What are typical values of period in ultrasound?
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0.1 to 0.5 us
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What determines period? Is it adjustable by the sonographer?
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Sound source only. No
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The number of cycles per second? Units?
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Frequency. Hz, kHz, MHz
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What are typical values of frequency in ultrasound?
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2 to 10 MHz
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What determines frequency? Is it adjustable by the sonographer?
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Sound source only. No
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What is the relationship between period and frequency?
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Reciprocal. T= 1/f f= 1/T
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Distance or length of one complete cycle? Units?
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Wavelength. mm, cm, etc.
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What are typical values of wavelength in ultrasound?
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0.15 to 0.8 mm
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What determines wavelength? Is it adjustable by the sonographer?
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Sound source AND medium. No
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What is the relationship between wavelength and frequency?
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wavelength= 1.54mm/us/f
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What wavelength and frequency are needed to make good images?
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Short wavelength, high frequency
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What is the distance a sound wave travels through a medium in one second? Units?
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Propogation speed. m/s, mm/us, etc.
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What is the formula for propogation speed?
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speed (c)= f x wavelength
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What are typical values of propogation speed in ultrasound?
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500 m/s to 4,000 m/s-- depending on the tissue
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What determines propogation speed? Is it adjustable by the sonographer?
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Medium only. No
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Difference between maximum/minimum value and the average value? Units?
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Amplitude. dB, Pa, g/cm^3
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Difference between maximum and minimum values?
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Peak-to-Peak amplitude
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What are typical values of amplitude in ultrasound?
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1MPa to 3 MPa
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What determines amplitude? Is it adjustable by the sonographer?
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Sound source only. Yes
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The rate of energy transfer? Units?
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Power. watts
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What determines power? Is it adjustable by the sonographer?
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Sound source only. Yes
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Concentration of energy in a sound beam? Units?
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Intensity. w/cm^2
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What are typical values of intensity in ultrasound?
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0.01 to 300 w/cm^2
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What determines intensity? Is it adjustable by the sonographer?
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Sound source only. Yes
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What is the relationship between intensity, power, and amplitude?
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Intensity α Power Intensity α Amplitude^2 Power α Amplitude^2
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What is the range of audible sound?
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20 Hz to 20,000 Hz (20 kHz)
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What is sound that is below the threshold of human hearing?
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Infrasound
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What is sound that is above the threshold of human hearing?
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Ultrasound
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What is the relationship between propogation speed, density, and stiffness?
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Stiffness increases, speed increases Density increases, speed decreases
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List the speed of sound in the following objects in decreasing order: liquid, gas, solid
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Solid, liquid, gas
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What uses short pulses of acoustic energy to create images?
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Pulsed wave ultrasound
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What are the two components of pulsed wave ultrasound?
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On-time and off-time
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What are the 5 parameters of pulsed wave ultrasound?
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Pulse duration, pulse repetition period, pulse repetition frequency, duty factor, spatial pulse length
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The actual time from the start of a pulse to the end of that pulse? Units?
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Pulse duration. us, ms, etc.
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What are typical values of pulse duration in ultrasound?
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0.3 to 2 us
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What determines pulse duration? Is it adjustable by the sonographer?
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Sound source only. No
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What is the formula for pulse duration?
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PD= # of cycles x period PD= # of cycles/f
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The distance that a pulse occupies from the start of a pulse to the end of that pulse? Units?
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Spatial pulse length
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What determines SPL? Is it adjustable by the sonographer?
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Sound source AND medium. No
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What is the formula for SPL?
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SPL= # cycles x wavelength
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Time from the start of one pulse to the start of the next pulse? Units?
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Pulse repetition period. us
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What determines PRP? Is it adjustable by the sonographer?
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Sound source and imaging depth. Yes-- by adjusting the depth, you adjust the listening time
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When imaging depth increases, PRP ___?
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Increases
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The number of pulses that an ultrasound system transmits into the body each second? Units?
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Pulse repetition frequency. Hz
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What are typical values of PRF?
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1,000 to 10,000 Hz
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What determines PRF? Is it adjustable by the sonographer?
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Sound source and depth of view. Yes-- it can be adjusted by adjusting the imaging depth
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When depth increases, PRF ___?
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Decreases
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The percentage of time that a system is transmitting a pulse? Units?
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Duty factor. Unitless
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What are typical values of duty factor in ultrasound?
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0.2 to 0.5 %
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What determines duty factor? Is it adjustable by the sonographer?
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Sound source and depth of view. Yes-- it can be adjusted by adjusting the imaging depth
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What is the formula for duty factor?
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DF= PD/PRP x 100%
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When PRP increases, duty factor ___?
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Decreases
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What does shallow imaging provide?
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Less listening, short PRP, high PRF, high DF
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What does deep imaging provide?
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More listening, long PRP, low PRF, low DF
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What are effects of a sound wave on tissue?
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Bioeffects
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What are the 5 types of intensities?
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Spatial, peak, average, temporal, pulsed
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The beam's intensity at the location where it is maximum?
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Spatial peak intensity
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The average intensity across the beam's entire cross-sectional area?
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Spatial average intensity
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The intensity of the beam at the moment in time of its maximum value?
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Temporal peak intensity
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The average intensity during the most intense half-cycle?
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Intensity max
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The average intensity during the pulse duration?
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Pulse average intensity
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The average intensity during the entire PRP- both transmit and receive times
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Temporal average intensity
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List the following intensities in decreasing order: SPTA, SATA, Imax, SPTP, SPPA
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SPTP, Imax, SPPA, SPTA, SATA
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Which intensity is most important when it comes to bioeffects?
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SPTA
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What is the log of 1,000?
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3-- Hint: count the number of zeros
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Units that measure relative changes?
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Decibels, dB
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What is the change in decibels when intensity doubles?
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+3 dB. When it is halved, the change is -3 dB
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What is the change in decibels when intensity increases by 10?
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+10 dB. When it is reduced by a factor of 10, the change is -10 dB
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What is the change in dB if a sound beam's intensity is increased by a factor of 100?
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+20 dB
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Decrease in intensity, power, and amplitude of a sound wave as it travels? Units?
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Attenuation. dB
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What 2 factors does attenuation depend on?
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Distance and frequency
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What are the 3 components of attenuation?
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Absorbtion, scattering, reflection
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Put the following in decreasing order of attenuation: lung/bone, air, water, soft tissue
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Air, lung/bone, soft tissue, water
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Does attenuation increase with a high or low frequency?
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High frequency
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Which has more attenuation: a 3 MHz sound beam that travels 10 cm, or a 5 MHz sound beam that travels 10 cm?
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The 5 MHz sound beam
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A sound beam attenuates 5 dB in one medium, and 7 dB in a second medium. What is the total attenuation?
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12 dB
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What occurs when sound energy strikes a boundary between two media and some returns to the transducer?
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Reflection
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Specular reflections occur at what angle?
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90 degrees
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A disorganized type of reflection is ___?
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Diffuse reflection or backscatter
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What occurs when a boundary between two media has irregularities?
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Scattering
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What happens if a reflector is much smaller than the wavelength of the sound beam?
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Rayleigh scattering-- sound is uniformly diverted in all directions
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What is the relationship between Rayleigh scattering and frequency?
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Rayleigh scattering is related to frequency^4
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What is the attenuation coefficient?
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The amount of attenuation per centimeter
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How are attenuation coefficient and path length related?
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They aren't: attenuation coefficient doesn't change when path length changes
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How are attenuation, path length, and attenuation coefficient related?
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Total attenuation= path length x attenuation coefficient
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What is the attenuation coefficient in soft tissue?
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0.5 dB/cm / MHz
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What is the unit for impedance?
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Rayls (Z)
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What are the typical values of impedance in ultrasound?
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1.25 to 1.75 Mrayls
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What is the formula for impedance?
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Impedance= density x propogation speed
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If two media have the same propogation speed but different densities, which will have a higher impedance?
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The media with the higher density
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What is the angle of incidence?
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The angle at which the sound beam is hitting a media
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What does PORN stand for?
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Normal incidence-- perpendicular, orthogonal, right angle, ninety degrees
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What is oblique incidence?
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Anything other than 90 degrees
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The intensity of the sound wave at the instant prior to striking a boundary?
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Incident intensity
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The portion of intensity that, after striking a boundary, changes direction and returns back from where it came?
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Reflected intensity
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The portion of intensity that continues in the same general direction after striking a boundary?
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Transmitted intensity
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How are incident, reflected, and transmitted intensities related?
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Incident intensity= Reflected intensity + Transmitted intensity
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What is the Intensity Reflection Coefficient?
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The percentage of intensity that bounces back when the sound strikes a boundary
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What is the Intensity Transmission Coefficient?
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The percentage of intensity that is allowed to pass through when the beam reaches a boundary between two media
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What percent of energy is reflected at a soft tissue boundary between different biologic media?
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Less than 1%
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What percent of energy is reflected at an air-tissue interface?
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99%
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What percent of energy is reflected at a bone-tissue interface?
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50%
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Reflection with normal incidence only occurs if the two media have ___ acoustic impedances?
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Different
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What happens with oblique incidence?
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Transmission and reflection may or may not occur
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With oblique incidence, the incident angle and reflection angle are ___?
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Equal
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What is transmission with a bend?
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Refraction
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What two conditions must be present for refraction to occur?
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Oblique incidence and different propogation speeds
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Which law describes the physics of refraction?
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Snell's Law
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What is the formula for Snell's Law?
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sine(t angle)/sine(i angle)= speed 1/speed 2
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If speed 2 is less than speed 1, the transmission angle is ___ than the incident angle
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Less
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If speed 2 is greater than speed 1, the transmission angle is ___ than the incident angle
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Greater
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How fast does sound travel in soft tissue?
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1540 m/sec, 1.54 km/sec
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In soft tissue, it takes sound ___ to travel 1 cm in the body?
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13 us
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If a reflector is 2 cm deep, what is the time-of-flight? What is the total distance traveled?
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26 us, 4 cm
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What converts one form of energy to another?
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Transducer
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A property of certain materials to create a voltage when they are mechanically deformed?
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Piezoelectric effect
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What is the active element in a transducer called?
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PZT
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What does PZT stand for?
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Lead zirconate titanate
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What occurs if PZT is heated to above 680 degrees F?
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Depolarization
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The complete destruction of all living organisms?
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Sterilization
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To reduce or eliminate infectious organisms on an object?
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Disinfection
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What chemical should be used to disinfect transducers?
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Cidex
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How thick is the active element in a transducer?
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1/2 wavelength
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What part of a transducer protects the internal components and insulates the patient from electrical shock?
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Case
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What does the voltage of the system travel through to excite the active elements?
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Wire
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What part of the transducer reduces the difference in impedance between the element and skin?
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Matching layer
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How thick is the matching layer?
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1/4 wavelength
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What is used to reduce the difference in impedance between the matching layer and skin?
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Gel
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What material is bonded to the element to reduce its ringing?
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Damping material
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What is damping material made from?
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Epoxy resin impregnated with tungsten
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What are advantages of damping material?
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Shortens SPL and PD, increases axial resolution
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What are disadvantages of damping material?
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Decreases output power, decreases transducer's sensitivity, increases bandwidth, decreases Q factor
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Why don't CW transducers use damping material?
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They do not create anatomical images
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Range of frequencies emitted from a transducer?
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Bandwidth
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What represents the extent of damping?
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Q factor
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What is the formula for Q factor?
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Q factor= resonant frequency/bandwidth
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Imaging transducers have ___ SPL and PD?
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Short
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Imaging transducers have ___ sensitivity?
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Low
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Imaging transducers have ___ bandwidth?
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Wide
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Imaging transducers have ___ Q factor?
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Low
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Imaging transducers have ___ output power?
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Decreased
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What determines the resonant frequency of pulsed transducers?
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Thickness and propogation speed of the crystal
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What is the formula for a transducer's frequency?
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f= propogation speed/ 2xthickness
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The thinner the element, the ___ the frequency?
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Higher
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The higher the element's propogation speed, the ___ the frequency?
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Higher
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Do narrow or wide beams create better images?
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Narrow
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What are the three zones of a sound beam?
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Near zone, focal zone, far zone
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What is the region between the transducer and the focus?
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Near zone (Fresnel zone)
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What is the region beyond the beam's focus?
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Far zone (Fraunhofer zone)
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What determines where the focal point of a sound beam is?
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The transducer diameter and the frequency
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What creates a shallow focus: ___ diameter, ___ frequency?
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Small diameter, low frequency
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What creates a deep focus: ___ diameter, ___ frequency?
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Large diameter, high frequency
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Small diameter crystals create more or less divergence in the far field?
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More
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High frequency transducers create more or less divergence in the far field?
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Less
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Which gives you better lateral resolution: narrow beams or wide beams?
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Narrow beams
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Which principle explains the hourglass shape of a sound beam?
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Huygen's Principle
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The ability to distinguish 2 structures that are close to each other and parallel to the sound beam?
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Axial resolution
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What does LARRD stand for?
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Longitudinal, axial, radial, range, depth resolution
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Do short or long pulses provide better axial resolution?
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Short pulses
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What is the formula for axial resolution?
|
Axial res= SPL/2
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What is the formula for axial resolution in soft tissue?
|
Axial res= 0.77 x # cycles in pulse/f
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Does axial resolution improve with more or less ringing? High or low frequency?
|
Less ringing, high frequency
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The minimum distance that 2 structures perpendicular to the sound beam can be distinguished?
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Lateral resolution
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What does LATA stand for?
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Lateral, angular, transverse, azimuthal resolution
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Where is lateral resolution the best?
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At the focus or one near zone length from the transducer
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Which is better, axial res or lateral res?
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Axial
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With a high frequency transducer, where is the lateral resolution improved?
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Far field
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What are three methods of focusing?
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Lens, curved element, electronic
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What do the x and y axes on an A-mode display represent?
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x- depth, y- amplitude
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What do the x and z axes on a B-mode display represent?
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x- depth, z- strength
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What do the x and y axes on an M-mode display represent?
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x-time, y- depth
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How many elements does a mechanical transducer contain?
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One
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What shape is the crystal in a mechanical scanner?
|
Circular and disc-shaped, like a coin
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What type of focusing do mechanical transducers use?
|
Conventional or fixed- by using a curved element or acoustic lens
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What shape is the image that a mechcanical transducer makes?
|
Fan or sector shape
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If the crystal in a mechanical transducer is defective, what happens to the image?
|
Entire image is destroyed
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What is a transducer array?
|
A collection of active elements in a single transducer-- a single slab of PZT is cut into separate pieces
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What are the 2 types of linear array transducers?
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Linear sequential, linear phased
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What shape are the elements arranged in an annular array?
|
In rings with a common center (bull's eye)
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How are the elements in a curvilinear transducer arranged?
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In an arc
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What are 2 types of curvilinear arrays?
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Convex switched, convex phased
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What is the difference between sequential arrays and phased arrays?
|
Sequential arrays use fixed focusing. Phased arrays use electronic focusing
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How does a sequential array work?
|
5-10 elements are fired at exactly the same time and the sound wavelets combine to form one beam. Then the next group is fired
|
|
|
|
What image shape is produced by a linear transducer?
|
Rectangular
|
|
|
|
How does a phased array work?
|
A collection of pulses are delivered to all of the transducer's elements in various patterns
|
|
|
|
What electrical pattern affects steering?
|
Slope
|
|
|
|
What electrical pattern affects focusing?
|
Curve
|
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|
If the electrical slope goes down from left to right, which direction will the beam be steered?
|
Upward from left to right
|
|
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|
If an electrical slope is going upward from left to right, which way will the beam be steered?
|
Downward from left to right
|
|
|
|
Will the beam be focused with a convex firing pattern?
|
No-- a defocused or divergent beam will be created
|
|
|
|
Which part of the transducer is responsible for steering and focusing?
|
Beam former
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|
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|
What type of focusing is provided by an annular phased array transducer?
|
Electronic focusing in all planes at all depths
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|
|
|
What image shape is produced by a curved array transducer?
|
Blunted sector
|
|
|
|
What component is a form of electronic receive focusing?
|
Dynamic aperture
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|
|
|
What type of transducer creates 3D ultrasound images?
|
2-dimensional array
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|
Which transducer allows focusing in the plane of the beam width and improves elevational resolution?
|
1 1/2 dimensional array
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|
|
|
What transducer combines linear sequential and linear array technologies?
|
Vector array
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|
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|
Seeing different shades of gray in an image is ___ resolution?
|
Contrast
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|
|
|
Seeing detail in an image is ___ resolution?
|
Spatial
|
|
|
|
Resolution pertaining to time?
|
Temporal resolution
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|
The number of images produced per second is what?
|
Frame rate
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|
What 2 factors determine frame rate?
|
Imaging depth, number of pulses per frame (propogation speed of sound in medium)
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|
What are 4 factors that affect temporal resolution?
|
Imaging depth, # of pulses per scan line, sector size, line density
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|
Shallow image depth= ___ frame rate?
|
High
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|
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|
Deep image depth= ___ temporal resolution?
|
Decreased
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|
If imaging depth is doubled, what happens to frame rate?
|
It is halved
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|
Which has better temporal resolution: single focus or multi-focus transducers?
|
Single focus
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|
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|
Wide image sector= ___ frame rate?
|
Low
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|
Narrow image sector= ___ temporal resolution?
|
Increased
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High line density= ___ frame rate?
|
Low
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|
How are spatial resolution and temporal resolution related?
|
The better spatial resolution is, the worse temporal resolution is
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|
When a frame is created in 1/10th of a second, what is the frame rate?
|
10 Hz
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|
When a frame is created in .02 seconds, what is the frame rate?
|
50 Hz (Hint: 0.02= 1/50)
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|
|
|
What are the 6 components of an ultrasound system?
|
Master synchronizer, transducer, pulser, receiver, display, storage
|
|
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|
What component of an ultrasound system communicates with all of the individual components?
|
Master synchronizer
|
|
|
|
What part of a US system converts energy?
|
Transducer
|
|
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|
During transmission, a transducer converts ___ energy into ___ energy
|
Electrical, acoustic
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|
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|
During reception, a transducer converts ___ energy into ___ energy
|
Acoustic, electrical
|
|
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|
What component of a US system controls the electrical signals sent to the transducer?
|
Pulser
|
|
|
|
What component of a US system determines the PRF, PRP, and pulse amplitude?
|
Pulser
|
|
|
|
What component of a US system processes the electric signal received by the transducer?
|
Receiver
|
|
|
|
What component of a US system produces a picture on an appropriate display?
|
Receiver
|
|
|
|
What component of a US system presents the processed data for interpretation?
|
Display
|
|
|
|
What are devices that are used to permanently archive US data?
|
Storage devices
|
|
|
|
What voltage is produced by the pulser to excite the PZT?
|
10 to 500 volts
|
|
|
|
What happens to an image when output power is increased?
|
The brightness of the entire image increases
|
|
|
|
High quality images are created when the signal-to-noise ratio is ___?
|
High
|
|
|
|
Does increasing transducer output improve or degrade the signal-to-noise ratio?
|
Improve
|
|
|
|
What are the 5 functions of the receiver?
|
Amplification, compensation, compression, demodulation, reject
|
|
|
|
What is another name for amplification?
|
Gain
|
|
|
|
What happens to the signal-to-noise ratio when gain is increased?
|
Nothing-- signal-to-noise ratio remains unchanged when gain levels change
|
|
|
|
What is another name for compensation?
|
TGC-- time gain compensation
|
|
|
|
With a high frequency transducer, is more or less TGC needed?
|
More
|
|
|
|
Reducing the total range of signals is what?
|
Compression
|
|
|
|
Compression ___ the number of shades of gray in an image?
|
Reduces
|
|
|
|
If a signal with an initial dynamic range of 120 dB is compressed by 35 dB, what is the dynamic range of the compressed signal?
|
85 dB
|
|
|
|
What are the 2 types of demodulation?
|
Rectification and smoothing (enveloping)
|
|
|
|
What affects all low level signals, but doesn't affect bright echoes?
|
Reject
|
|
|
|
What is the order of receiver operations? (Hint: alphabetical order)
|
Amplification, compensation, compression, demodulation, reject
|
|
|
|
Which receiver operation is not adjustable by the sonographer?
|
Demodulation
|
|
|
|
With harmonic imaging, the received frequency is ___ the transmitted frequency?
|
Twice
|
|
|
|
What type of behavior results in harmonic imaging?
|
Non-linear
|
|
|
|
In what type of imaging are positive and negative pulses transmitted down each scan line?
|
Pulse-inversion imaging
|
|
|
|
What are 5 requirements for contrast agents?
|
Safe, long persistence, small enough to pass through capillaries, strong reflector of ultrasound, metabolically inert
|
|
|
|
What is the difference between output power and receiver gain?
|
Output power amplifies signals put into the body. Receiver gain amplifies signals returning from the body.
|
|
|
|
What does ALARA stand for?
|
As low as reasonably achievable
|
|
|
|
How many lines make up an interlaced display?
|
525
|
|
|
|
How does an interlaced display work?
|
The odd field is written first, followed by the even field
|
|
|
|
What type of display presents all the lines in sequence?
|
Progressive scan display
|
|
|
|
Are bistable images high contrast or low contrast?
|
High contrast
|
|
|
|
What word describes the "real world"?
|
Analog
|
|
|
|
What word describes "computer world"?
|
Digital
|
|
|
|
What divides pictures into a 1000x1000 matrix with an electrical storage element?
|
Analog scan converter
|
|
|
|
What are 4 disadvantages of analog scan converters?
|
Image fade, flicker, drift, deterioration
|
|
|
|
What is an advantage of analog scan converters?
|
Excellent spatial resolution
|
|
|
|
What converts image data into numbers which are stored in memory?
|
Digital scan converter
|
|
|
|
What is the smallest element of a digital picture?
|
Pixel
|
|
|
|
The greater the pixel density, the ___ the detail in an image
|
Greater
|
|
|
|
Which provides better spatial resolution: a 1000x1000 display or a 512x512 display?
|
1000x1000
|
|
|
|
What determines the spatial resolution of a CRT (cathode ray tube)?
|
The number of TV lines per frame
|
|
|
|
What is the smallest amount of digital storage?
|
Bit
|
|
|
|
What can the values of a bit be?
|
0 or 1
|
|
|
|
Which provides better contrast resolution: few bits or many bits?
|
Many bits
|
|
|
|
What is a group of 8 bits called?
|
Byte
|
|
|
|
What is a pair of 2 bytes called?
|
Word
|
|
|
|
How many shades of gray can be displayed by 8 bits?
|
256 (Hint: multiply 2 by itself the same number of time as there are bits. 2^8)
|
|
|
|
How many bits are needed to represent 10 shades of gray?
|
4- can represent from 9-16 shades of gray. 3 bits can represent up to 8, and 5 are needed to represent 17
|
|
|
|
How many bits are needed to represent 18 shades of gray?
|
5
|
|
|
|
What is it called when data is manipulated before storage in the scan converter?
|
Preprocessing
|
|
|
|
Can data be changed once pre-processing occurs?
|
No
|
|
|
|
What is it called when data is manipulated after it has been stored in the scan converter?
|
Postprocessing
|
|
|
|
What is needed to change information that is sent and received by the transducer, so that it can be seen on the display?
|
First, it goes through the A-to-D converter, and it needs to come back through the D-to-A converter
|
|
|
|
Describe the order in which information travels through an ultrasound system.
|
Master synchronizer→ pulser→ beam former→ receiver→ scan converter→ display→ image archive
|
|
|
|
Which provides better image detail: read or write magnification?
|
Write magnification
|
|
|
|
Is read magnification pre or postprocessing?
|
Postprocessing
|
|
|
|
What can help improve images by filling in missing information?
|
Fill In Interpolation
|
|
|
|
What happens to the frame rate when fill in interpolation is used?
|
It decreases
|
|
|
|
When scan lines leave the transducer in different directions to improve detail in an image, it is called?
|
Spatial compounding
|
|
|
|
Does a narrow dynamic range provide a high contrast image or a low contrast image?
|
High contrast image
|
|
|
|
Which component of a US system has the greatest dynamic range?
|
Transducer
|
|
|
|
Which component of a US system has the lowest dynamic range?
|
Storage devices
|
|
|
|
A range from 1 volt to 100 volts can be processed accurately by a US system. What is its dynamic range?
|
40 dB (Hint: Divide higher number by lower number. 100/1=100. Count the zeros (2). Each zero=20 dB. 20+20= 40)
|
|
|
|
A US system can process voltages from 1 mV to 10 V. What is the dynamic range?
|
80 dB (10/.001=10,000. 4 zeros. 20+20+20+20= 80)
|
|
|
|
What is the main disadvantage for all magnetic media?
|
It can be disrupted by a strong magnetic field
|
|
|
|
What does PACS stand for?
|
Picture archiving and communications system
|
|
|
|
What does DICOM stand for?
|
Digital imaging and communications in medicine
|
|
|
|
What type of flow moves at a constant speed or velocity?
|
Steady flow
|
|
|
|
What type of flow moves with a variable velocity, and results from cardiac contractions?
|
Pulsatile flow
|
|
|
|
What type of flow moves with a variable velocity, and results from respiration?
|
Phasic flow
|
|
|
|
What type of flow is arterial flow?
|
Pulsatile
|
|
|
|
What type of flow is venous flow?
|
Phasic
|
|
|
|
What type of flow has parabolic or plug patterns, and is made up of layers that travel at individual speeds?
|
Laminar flow
|
|
|
|
Where is the highest velocity found in laminar flow patterns?
|
In the center
|
|
|
|
What is chaotic flow in many directions and speeds, and varies from instant to instant?
|
Turbulent flow
|
|
|
|
What type of flow is associated with cardiovascular pathology and increased velocities?
|
Turbulent flow
|
|
|
|
What is a unitless number that indicates laminar or turbulent flow?
|
Reynold's number
|
|
|
|
What must Reynold's number be to indicate laminar flow?
|
Less than 1,500
|
|
|
|
What must Reynold's number be to indicate turbulent flow?
|
Greater than 2,000
|
|
|
|
If Reynold's number is between 1,500 and 2,000, what type of flow is there?
|
Unknown
|
|
|
|
If Reynold's number is 2,200, what type of flow is there?
|
Turbulent
|
|
|
|
What type of energy loss is caused by blood sliding across vessel walls?
|
Frictional loss
|
|
|
|
What type of energy loss is caused by fluid sticking to itself?
|
Viscous loss
|
|
|
|
What happens to viscous loss when fluid thickens?
|
It increases
|
|
|
|
What type of energy loss occurs when the velocity of a fluid changes?
|
Intertial loss
|
|
|
|
What is a narrowing or irregularity in a lumen?
|
Stenosis
|
|
|
|
In relevance to a stenosis, where are the highest velocities found?
|
At the point of maximum narrowing
|
|
|
|
What is the hydrostatic pressure when a person is supine?
|
Zero at all locations
|
|
|
|
What is the hydrostatic pressure of the heart when a patient is standing?
|
Zero
|
|
|
|
What is the hydrostatic pressure at the ankle when a person is standing?
|
100 mmHg
|
|
|
|
What is the hydrostatic pressure of the head when a person is standing?
|
-30 mmHg
|
|
|
|
How do you calculate the measured pressure?
|
Actual circulatory pressure+hydrostatic pressure
|
|
|
|
What happens to the diaphragm during inspiration?
|
It presses into the abdomen
|
|
|
|
What happens to the diaphragm during expiration?
|
It presses into the thorax
|
|
|
|
What happens to abdominal pressure during inspiration?
|
It increases
|
|
|
|
What happens to abdominal pressure during expiration?
|
It decreases
|
|
|
|
What happens to venous flow in the legs during inspiration?
|
It decreases
|
|
|
|
What happens to venous return to the heart during inspiration?
|
It increases
|
|
|
|
What happens to venous flow in the legs during expiration?
|
It increases
|
|
|
|
What type of doppler shift happens when blood is flowing toward the transducer?
|
Positive
|
|
|
|
What type of doppler shift happens when blood is flowing away from the transducer?
|
Negative
|
|
|
|
What 3 things is doppler shift directly related to?
|
Reflector speed, incident frequency, cosine of angle
|
|
|
|
What is doppler shift inversely related to?
|
Propogation speed
|
|
|
|
How is doppler shift calculated?
|
2 x reflector speed x incident frequency x cos(angle)/ propogation speed
|
|
|
|
Which type of doppler can detect a shift, but not the direction it is moving?
|
Non directional doppler
|
|
|
|
Which type of doppler can detect positive and negative doppler shifts?
|
Bidirectional doppler
|
|
|
|
How many crystals are used with continuous wave doppler?
|
2
|
|
|
|
What is the main advantage of continuous wave doppler?
|
It can measure very high velocities accurately
|
|
|
|
What is the main disadvantage of continuous wave doppler?
|
Range ambiguity
|
|
|
|
How many crystals are used in pulsed wave doppler?
|
One
|
|
|
|
What is the main advantage of pulsed wave doppler?
|
Range specificity
|
|
|
|
What is the main disadvantage of pulsed wave doppler?
|
Aliasing
|
|
|
|
When imaging and pulsed doppler are used simultaneously, it is called what?
|
Duplex ultrasound
|
|
|
|
What is the doppler frequency at which aliasing occurs called?
|
Nyquist limit
|
|
|
|
What is the equation for the Nyquist limit?
|
PRF/2
|
|
|
|
Is aliasing more likely to occur with high or low frequency transducers?
|
High
|
|
|
|
Name 5 ways to eliminate aliasing
|
1. Adjust scale (PRF) 2. Use a low frequency transducer 3. Use a shallower sample volume 4. Use continuous wave doppler 5. Adjust the baseline
|
|
|
|
What creates less spectral broadening: small or large sample volumes?
|
Small sample volumes
|
|
|
|
If 2 identical doppler exams are performed with 4 and 8 MHz probes, what is the difference in the doppler shifts?
|
The 8 MHz probe will produce doppler shifts that are twice as large as the 4 MHz probe
|
|
|
|
What 2 things determine gray shades on a doppler spectrum?
|
1. Amplitude of reflected signal 2. Number of RBC's
|
|
|
|
What are the best angles to use with doppler?
|
Less than 60 degrees
|
|
|
|
What color will the blood in a vessel be when the doppler angle is 90 degrees?
|
Black
|
|
|
|
If the color on an image matches the color on the top of the map, which direction is the blood flowing?
|
Toward the transducer
|
|
|
|
If the color on an image matches the color on the bottom of the map, which direction is the blood flowing?
|
Away from the transducer
|
|
|
|
What doppler mode has a color map that also varies side-to-side?
|
Variance mode
|
|
|
|
What do colors on the left side of a variance mode color map represent?
|
Laminar flow
|
|
|
|
What do colors on the right side of a variance mode color map represent?
|
Turbulent flow
|
|
|
|
What is color jet size most affected by?
|
Color doppler gain
|
|
|
|
What are the 2 advantages of a greater doppler packet size?
|
1. Greater accuracy of velocities 2. Sensitivity to low flows
|
|
|
|
What are the 3 disadvantages of greater doppler packet sizes?
|
1. More time required to acquire information 2. Frame rate is reduced 3. Temporal resolution is reduced
|
|
|
|
Which measures mean velocity: color doppler or spectral doppler?
|
Color doppler
|
|
|
|
Which measures peak velocity: color doppler or spectral doppler?
|
Spectral doppler
|
|
|
|
Which type of color doppler shows flow, but not the direction in which it's moving?
|
Color angio doppler (power doppler, energy doppler)
|
|
|
|
What are the 3 advantages of power doppler?
|
1. Increased sensitivity to low flows 2. Not affected by angles, unless it equals 90 degrees 3. No aliasing
|
|
|
|
What are 3 disadvantages of power doppler?
|
1. No measurement of direction 2. Slower frame rates 3. Susceptible to motion (flash artifact)
|
|
|
|
What type of doppler would you use if you wanted range resolution?
|
Pulsed wave doppler
|
|
|
|
What type of doppler would you use if you wanted to measure very high velocities accurately?
|
CW doppler
|
|
|
|
What type of doppler would you use if you didn't want to have aliasing?
|
CW doppler
|
|
|
|
What type of doppler would you use to show the direction of flow in a vessel?
|
Color doppler
|
|
|
|
What type of doppler would you use if you wanted to show color in vessel with very low velocities?
|
Power doppler
|
|
|
|
What color doppler control would you adjust if you saw aliasing in a vessel?
|
Color scale
|
|
|
|
What is performed in order to extract or identify the individual frequencies making up a complex signal?
|
Spectral analysis
|
|
|
|
What method of spectral analysis is used in pulsed and CW doppler?
|
Fast Fourier Transform (FFT)
|
|
|
|
What method of spectral analysis is used with color doppler?
|
Autocorrelation
|
|
|
|
What are 3 early methods of spectral analysis?
|
1. Zero crossing detection 2. Time interval histograms 3. Chirp z-transforms
|
|
|
|
Can you perform a doppler exam on a patient who is anemic?
|
Yes- doppler exams can be successfully performed regardless of a patient's hematocrit
|
|
|
|
What is the Nyquist limit if the PRF is 5 kHz
|
2.5 kHz
|
|
|
|
If the Nyquist limit is 3,000 Hz, what is the PRF?
|
6,000 Hz
|
|
|
|
What are errors in imaging known as?
|
Artifacts
|
|
|
|
What are 5 causes of artifacts?
|
1. Violation of assumptions 2. Equipment malfunction or design 3. Physics of ultrasound 4. Interpreter error 5. Operator error
|
|
|
|
What are the 6 basic assumptions of imaging systems?
|
1. Sound travels in a straight line 2. Sound travels directly to a reflector and back 3. Sound travels at exactly 1,540 m/s 4. Reflections arise from structures along the beam's main axis 5. Intensity of the reflections is related to scattering characteristics of the tissue 6. Imaging plane is extremely thin
|
|
|
|
Which artifact appears as a ladder or venetian blind?
|
Reverberation
|
|
|
|
What artifact is a result of US "ping-ponging" between 2 reflectors?
|
Reverberation
|
|
|
|
What artifact appears as a single, solid hyperechoic line?
|
Comet Tail or Ring Down
|
|
|
|
What artifact is "merged reverberation"?
|
Comet Tail
|
|
|
|
What artifact occurs when sound hits a structure with high attenuation?
|
Shadowing
|
|
|
|
What artifact is seen with gallstones?
|
Shadowing
|
|
|
|
What artifact appears as an anechoic or hypoechoic line behind a structure?
|
Shadowing
|
|
|
|
What artifact is caused by refraction at the edge of a circular structure?
|
Edge shadow
|
|
|
|
What artifact occurs when sound hits a structure with a low attenuation rate?
|
Enhancement
|
|
|
|
What artifact is seen when sound hits a fluid-filled object?
|
Enhancement
|
|
|
|
What artifact is caused by high intensity in the focal zone?
|
Banding
|
|
|
|
What artifact is caused when sound bounces off of a strong reflector?
|
Mirror image
|
|
|
|
What artifact displays a second copy of a reflector which appears deeper than the true reflector?
|
Mirror image
|
|
|
|
What artifact results in improper depths, or a "step -off" appearance?
|
Propogation speed errors
|
|
|
|
When propogation speed is greater than 1,540 m/s, the reflector will be placed too ___ on the display?
|
Shallow
|
|
|
|
When propogation speed is less than 1,540 m/s, the reflector will be placed too ___ on the display?
|
Deep
|
|
|
|
What happens with refraction artifact?
|
A second copy of the true reflector is displayed next to the true structure
|
|
|
|
How do you get rid of an artifact?
|
Change the view
|
|
|
|
Side lobes are created by what type of transducer?
|
Mechanical
|
|
|
|
Grating lobes are created by what type of transducer?
|
Array
|
|
|
|
A method of reducing grating lobes by dividing each element into even smaller pieces is called what?
|
Subdicing
|
|
|
|
A method of reducing grating lobes by exciting elements closer to the center of the beam with higher voltages is called what?
|
Apodization
|
|
|
|
What artifact occurs when the sound beam has a greater width than the reflector?
|
Slice thickness
|
|
|
|
What artifact is created by interference effects of scattered sound, and makes a grainy appearance?
|
Speckle
|
|
|
|
What artifact is caused when very deep reflections arrive at the transducer after the next pulse was created?
|
Range Ambiguity Artifact
|
|
|
|
How do you cure range ambiguity artifact?
|
Lower the PRF
|
|
|
|
What eliminates low magnitude doppler shifts?
|
Wall filter
|
|
|
|
What is a doppler artifact that appears as a "mirror image"?
|
Cross talk
|
|
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|
What are 2 causes of cross talk?
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1. Doppler gain set too high 2. Incident angle near 90 degrees
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What is the routine periodic evaluation of a US system to guarantee optimal image quality?
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Quality assurance
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What are 4 things quality assurance requires?
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1. Multiple evaluations of system's components 2. Repairs 3. Preventative maintenance 4. Record keeping
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What are 4 goals of quality assurance?
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1. Proper equipment operation 2. Detect gradual changes 3. Minimize downtime 4. Reduce # of repeat scans
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What are 4 methods of quality assurance?
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1. Test under known, defined conditions 2. Constant instrument settings 3. Use phantom with measurable characteristics 4. Image in identical environment
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Whose duty is it to perform quality assurance?
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Sonographer
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What is used to display the characteristics of the US beams as produced by the transducer?
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Beam profiler
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What speed is used in the AIUM 100mm Test Object?
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1,540 m/s
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What Q.A. device uses strategically located pins to test US machines, and has the same speed of sound as soft tissue?
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AIUM 100mm test object
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Areas of increased pressure or density
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Compressions
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Areas of decreased pressure or density
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Rarefractions
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Propogation speed= ___ x wavelength
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Frequency
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Propogation speed increases with ___ compressibility, and ___ density
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Decreasing, decreasing
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Wavelength in soft tissue= ?
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1.54 mm/us/ frequency
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If the frequency of a US wave is doubled, what happens to the period?
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Halved
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If a wave's amplitude is doubled, what happens to the power?
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Quadrupled
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If an acoustic variable ranges from 55 to 105, what is the amplitude?
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25 (Hint: peak-to-peak amplitude is 105-55= 50. Divide this by 2 to get amplitude)
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If the intensity of a beam remains unchanged, and the area is reduced by half, what is the power?
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Halved
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What is the minimum value for SP/SA factor?
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1
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Which pair of intensities has the same value for CW ultrasound?
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Pulse average and temporal average
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If go-return time is 130 us, what is the reflector depth?
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10 cm
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Is doppler shift the sum, difference, product, or ratio of the incident and reflected intensity?
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Difference
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How is range ambiguity artifact eliminated?
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Lower the PRF
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What device is a small needle with a PZT crystal at the end, that is used to measure pressure in a sound beam?
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Hydrophone
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If an object is on a balance or float, what intensity can be measured?
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SATA
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If a small suspended ball is used, what intensity can be measured?
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SPTA
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What system uses shadowing to measure beam profiles?
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Schlieren
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What uses a schlieren, and can quantify amplitude, period, pulse duration, and PRP?
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Acoustic-optics
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What is a transducer that turns acoustic energy into heat?
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Calorimeter
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What instrument can measure the total power of a US beam?
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Calorimeter
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What device absorbs US, turns it into heat, and measures the change in temperature?
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Thermocouple
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What does in-vivo stand for?
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Living
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What does in-vitro stand for?
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Nonliving (in glass)
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What is the science of identifying characteristics of US that are relevant to its potential for producing bioeffects?
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Dosimetry
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What is the SPTA intensity limit for unfocused US?
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100mW/cm squared
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What is the SPTA intensity limit for focused US?
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1w/cm squared
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Which type of US has the highest output intensity?
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Pulsed doppler
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Which type of US has the lowest output intensity?
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Gray scale imaging
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What are the 2 different study techniques (approach)?
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Mechanistic and empirical
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What study approach uses theoretical analysis?
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Mechanistic
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What study approach identifies "exposure-response" relationship?
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Empirical
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Any exam that causes a temperature elevation greater than ___ is potentially harmful to a fetus?
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41 degrees C
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What is a theoretical calculation related to possible temperature elevation?
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Thermal index
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What does TIS stand for?
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Thermal index in soft tissue
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What does TIB stand for?
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Thermal index assuming bone is at the beam's focus
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What does TIC stand for?
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Thermal index assuming that cranial bone is near the skin surface
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What kind of beams are more likely to cause temperature elevation, focused or unfocused?
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Unfocused
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What are the 2 types of cavitation?
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Stable and transient
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In what type of cavitation do bubbles burst?
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Transient
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In what type of cavitation do bubbles oscillate but not burst?
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Stable
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Where is cavitation most likely seen?
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Lung tissue- due to air
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What type of study requires large numbers of patients?
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Epidemiology
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The best study is ___ and ___
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Prospective and randomized
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What are 3 limits of epidemiologic studies?
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1. Often retrospective 2. Ambiguities 3. Other risk factors
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___ should outweigh the ___
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Benefits, risks
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Where are harmonics created?
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In tissues
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Which transducer is best to image superficial structures: ___ diameter, ___ frequency?
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Small, high
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If line density increases, and frame rate stays the same, what must happen to depth?
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Decreases
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Which receiver operation can't be adjusted by the sonographer?
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Demodulation
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At what location in a sound beam is the SPTA intensity the highest?
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Focal point
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What results in the highest mechanical index: ___ frequency, ___ amplitude?
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Low, high
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Under what circumstance is cavitation most likely to occur: ___ frequency, ___ amplitude?
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Low, high
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If the fundamental frequency is 2.5 MHz, what is the harmonic frequency?
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5 MHz
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What 2 intensities have the same value for CW?
|
Pulse average and temporal average |
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What is the attenuation coefficient of 1 MHz US in soft tissue?
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5 dB/cm
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Which has the closest propogation speed to soft tissue: muscle, fat, bone, air?
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Muscle
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