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The horizontal axis, or x-axis - ANSRuns side to side The vertical axis, or y-axis - ANSRuns up and down Unrelated - ANSTwo items that are not associated Related or Proportional - ANSTwo items that are associated or affiliated However, the relationship between the items does not have to be specified Directly related or Directly proportional - ANSTwo items that are associated such that when one item increases, the other increases Inversely related or inversely proportional - ANSTwo items are associated such that when one item increases, the other decreases Reciprocal Relationship - ANSWhen two numbers with a reciprocal relationship are multiplied together, the result is one Reciprocal numbers are inverse because when one increases, the other decreases For a numerical answer to a question to be comprehensive, it requires a - ANSUnit "Increase by a factor" means - ANSTo multiply by that number "Decrease by a factor" means - ANSTo divide by that number Scientific or engineering notation is a shorthand manner to represent what types of numbers?
- ANSVery large or very small numbers A number in scientific notation form with a positive exponent has a value - ANSGreater than 10 A number in scientific notation form with an exponent of zero has a value - ANSBetween 1 and 10 A number in scientific notation form with a negative exponent has a value - ANSLess than 1 10 ⌃ 9 - ANSPrefix: giga Symbol: G Meaning: billion 10 ⌃ 6 - ANSPrefix: mega Symbol: M Meaning: million 10 ⌃ 3 - ANSPrefix: kilo Symbol: k Meaning: thousand 10 ⌃ 2 - ANSPrefix: hecto Symbol: h Meaning: hundred 10 ⌃ 1 - ANSPrefix: deca Symbol: da Meaning: ten 10 ⌃- 1 - ANSPrefix: deci Symbol: d
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Meaning: tenth 10 ⌃- 2 - ANSPrefix: centi Symbol: c Meaning: hundredth 10 ⌃- 3 - ANSPrefix: milli Symbol: m Meaning: thousandth 10^- 6 - ANSPrefix: micro Symbol: μ Meaning: millionth 10^- 9 - ANSPrefix: nano Symbol: n Meaning: billionth List all these metric terms in increasing order: A. mega B. micro C. milli D. hecto E. deca F. deci - ANSmicro, milli, deci, deca, hecto, mega List all these metric terms in decreasing order: A. nano B. canti C. giga D. kilo E. hecto F. micro - ANSgiga, kilo,hecto, centi, micro, nano Sound pulses travel through biologic tissue, or ______. - ANSMedia All waves carry _____ from one location to another. - ANSEnergy Sound is a __________ wave in which particles in the medium move. - ANSMechanical Sound cannot travel through a ______; it must travel through a ______. - ANSVacuum, medium What does compressed mean? - ANSSqueezed together What does rarefied mean? - ANSStretched apart Sound travels in a ________ line. - ANSStraight Sound waves are ____________ waves. - ANSLongitudinal What is the propagation speed dependent on? - ANSThe medium Are there any biologic effects on tissue? - ANSNo Sound waves are identified by - ANSOscillations in acoustic variables
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What is period? And what is it determined by? - ANSThe time it takes a wave to vibrate a single cycle, or the time from start of a cycle to the start of the next cycle It is determined by the source What is frequency? And what is it determined by? - ANSThe number of cycles that occurs in one second Determined by the sound source only 1 cycle/second = - ANS1 Hertz If the frequency of a sound wave is less than _____, it is below the threshold of human hearing and cannot be heard. These are defined as ____________. - ANS20 Hz, infrasonic Audible sound waves that humans can hear are frequencies between _______________________. - ANS20 Hz and 20,000 Hz What is ultrasound's frequency? - ANSGreater than 20,000 Hz or 20 kHz Why is frequency important in diagnostic sonography? - ANSIt affects penetration and image quality Period and frequency are __________ related to each other. - ANSInversely When two reciprocal parameters are multiplied together, the result is: - ANS What three parameters describe the size, or magnitude, or strength of a sound wave? - ANSAmplitude, power, intensity What is Amplitude? - ANSThe "bigness" of a wave. It is the difference between the maximum value and the average or undisturbed value of an acoustic variable Also the difference between the minimum value and the average value of the acoustic variable What is Amplitude determined by? And is it adjustable? - ANSInitially, amplitude is determined only by the sound source, however amplitude decreases as sound propagates through the body (attenuation) Yes, a control on ultrasound systems allows the sonographer to alter initial amplitude What is the difference between amplitude and peak-to-peak amplitude? - ANSAmplitude is measured from the middle value to the maximum value. Peak-to-peak amplitude is the difference between maximum and minimum values of an acoustic variable Peak-to-peak is twice the value of the amplitude What is power? - ANSThe rate of energy transfer or the rate at which work is performed. Power, like amplitude, describes the "bigness" of the wave What is power determined by? And can it be changed? - ANSDetermined by the sound source only It CAN be changed How are amplitude and power related? - ANSBoth describe the size, or magnitude of a wave. When power increases, so does amplitude Power is proportional to... - ANSamplitude^ What is intensity? - ANSThe concentration of energy in a sound beam Intensity = Power/area
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What is intensity determined by? And is it adjustable? - ANSSound Source Yes, it is adjustable How is intensity related to power and amplitude? - ANSIntensity is proportional to power Intensity is proportional to amplitude^ What is the distance or length of one complete cycle called? - ANSWavelength What is wavelength determined by? And is it adjustable? - ANSBoth the medium and source No, it is not adjustable What is the relationship between wavelength and frequency? - ANSAs long as a wave remains in one medium, wavelength and frequency are inversely related As frequency increases, wavelength decreases. The lower the frequency, the longer the wavelength What is the wavelength of 1 MHz sound in soft tissue? - ANS1.54 mm What is the wavelength of other frequency sound waves in soft tissue? - ANSSound with a frequency of 2 MHz has a wavelength of 0.77 mm in soft tissue. 1.54mm/2 = 0.77 mm What is the wavelength equation? - ANSwavelength = (1.54mm/μsec)/(frequency) Why is wavelength important in diagnostic ultrasound? - ANSWavelength plays an important role in image quality Shorter wavelength sound usually produces higher quality images with greater detail (higher frequency) What is the distance that a sound wave travels through a medium in 1 second called? - ANSPropagation Speed What does the speed of sound range from? - ANS500m/s to 4000m/s What is Propagation Speed determined by? And is it adjustable? - ANSThe Medium No, it is not adjustable What is the speed of sound in soft tissue? - ANS1,540 m/s 1.54 mm/μsec 1.54 km/s 1 mile per second What has the slowest propagation speed? And the longest? - ANSSlowest: Lung (Air, Gas) Longest: Bone What is the speed of sound in Blood? - ANS1,560 m/s What is the order for speed of sound from lowest to highest in Water, Metals, and Air? - ANSAir, Water, Metals What determines the speed of sound in that medium? - ANSStiffness, density What describes the ability of an object to resist compression? - ANSStiffness; A stiff material will retain its shape if it is squeezed; whereas a non-stiff material will change its shape How does stiffness affect speed? - ANSStiffness and Speed are directly related As materials become stiffer, the speed of sound in the material increased Non-stiff media are described as... - ANSElastic or compressible
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period power amplitude (initial) - ANSWavelength, frequency, propagation speed, period True or False. A wave with a frequency of 15,000 MHz is ultrasonic. - ANSTrue (any wave
20,000 hertz) True or False. If the amplitude of a wave is increased to 3 times its original value, the intensity in increased by 6 times. - ANSFalse (if we triple amplitude, we increase intensity by a factor of nine) True or False. If the power of a wave is halved ,the intensity is reduced to one-fourth its original value. - ANSFalse (intensity is the power/area, if we halve the power we will halve the intensity) True or False. Propagation Speed increases as Frequency increases. - ANSFalse (frequency is unrelated to speed) Medium 1 has a density of 9 and a stiffness of 6. Medium 2 has a density of 8 and a stiffness of 6. In which medium will sound travel slower? - ANSMedium 1: Since both media have the same stiffness, the medium with the greater density has the lower propagation speed If the power in a beam is 1 watt and the area is 5cm^2, what is the beams intensity? - ANS0. W/cm^ If intensity remains the same while the power had doubled, what has happened to the beam area? - ANSDoubled (if intensity stays the same, whatever happens to power also has to happen to area)
A sound beam travels a total of 10 cm in 2 seconds. What is the speed of the sound? - ANS cm/sec True or False. Propagation speed increases as frequency increases. - ANSFalse True or False. Propagation speed increases as frequency decreases. - ANSFalse True or False. Propagation speed does not change as frequency increases. - ANSTrue (propagation speed and frequency are unrelated) What is the wavelength of a 3 MHz sound in soft tissue? - ANS0.51 mm (wavelength = 1.54mm/frequency in MHz) The effects of sound waves on tissue in the body are called __________. - ANSBioeffects Which of the following are considered acoustic variables? Frequency, density, particle motion, temperature, period, and pressure - ANSDensity, particle motion, and pressure Which of the following are considered acoustic parameters? frequency, density, distance, pressure, and period - ANSFrequency and period The effects of tissue on sound waves are called _________ _________ ____________. - ANSAcoustic Propagation Properties The effects of a medium on an ultrasound wave are called _________ ____________ _________. - ANSAcoustic Propagation Properties
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How are frequency and period related? - ANSInversely How are amplitude and power related? - ANSDirectly How are amplitude and intensity related? - ANSDirectly How are power and intensity related? - ANSDirectly How are wavelength and intensity related? - ANSUnrelated How are wavelength and frequency related? - ANSInversely How are acoustic velocity and density related? - ANSInversely How are elasticity and speed of sound related? - ANSInversely How are acoustic velocity and compressibility related? - ANSInversely How are stiffness and sound speed related? - ANSDirectly How are frequency and sound speed related? - ANSUnrelated How are frequency and intensity related? - ANSUnrelated How are power and frequency related? - ANSUnrelated What are the five parameters to describe pulsed sound? - ANSPulse duration, pulse repetition period, pulse repetition frequency, duty factor, and spatial pulse length What is pulsed ultrasound? - ANSA pulse of an ultrasound is a collection of cycles that travel together. The entire pulse moves as a single item What are the two components of pulsed ultrasound? - ANSTransmit, talking, or "on" time Receive, listening, or "off" time What is the actual time from the start of pulse to the end of that pulse called? - ANSPulse duration (a single "on" time) What is pulse duration determined by? And can it be adjusted? - ANSSound source, NO Pulse duration (μsec) = - ANS# cycles x period (μsec) or #cycles/frequency (MHz) Pulse duration is directly proportional to ___________. - ANS# cycles in a pulse and to period Pulse duration is ____________ proportional to frequency. - ANSInversely What creates pulses of long duration? - ANSMany cycles in the pulse, and individual cycles with long periods What creates pulses of short duration? - ANSFew cycles in the pulse, and individual cycles with short periods Which type of pulse duration is more desirable in diagnostic imaging? - ANSShorter duration pulses are desirable for imaging because they create images of greater accuracy What is Spatial Pulse Length? - ANSThe distance that a pulse occupies in space from the start to the end of a pulse. What determines Spatial Pulse Length? And is it adjustable? - ANSBoth the source and the medium. No it is not adjustable. Spatial Pulse Length (mm) = - ANS# cycles x wavelength (mm)
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PRP = - ANS1/PRF
imaging depth (cm) x 13 μsec/cm PRF x PRP = - ANS True or False. Two waves can have identical pulse repetition frequencies, even if their pulse repetition periods are different. - ANSFalse (two waves can never have identical PRF's if their pulse repetition periods are different) True or False. Two waves can have identical PRF's, even if their periods are different. - ANSTrue (period and pulse repetition frequency are unrelated) True or False. Two waves can have identical PRF's, even if their frequencies are different. - ANSTrue (frequency and pulse repetition frequency are unrelated) True or False. PRF and pulse repetition period are determined only by the imaging depth. - ANSTrue What is duty factor? - ANSThe percentage or faction of time that the system is transmitting a pulse What is duty factor determined by? And is it adjustable? - ANSSound Source Yes, it is adjustable Duty factor (%) = - ANS(pulse duration/pulse rep. period) x 100 What are the maximum and minimum values for duty factor? - ANSMaximum = 1 or 100% Minimum = 0% Pulse wave ultrasound the duty factor is only _____%. - ANS1 (listening 99% of the time) How does the sonographer change duty factor? - ANSWhen imaging depth is altered. If all the other factors remain unchanged, what happens to the duty factor when the pulse repetition frequency increases? - ANSIncreases If all other factors remain unchanged, what happens to the duty factor when the pulse repetition frequency increases? - ANSDecreases If all other factors remain unchanged, what happens to the duty factor when the pulse repetition period increases? - ANSDecreases If all other factors remain unchanged, what happens to the duty factor when the sonographer uses a new transducer with a longer pulse duration? - ANSIncreases What is the duty factor if the pulse duration is 1 μsec and the pulse repetition period is 1 ms?
- ANS0. By adjusting the imaging depth, the operator changes the __________________, _______________, and ____________. - ANSPulse repetition period, pulse repetition frequency, and duty factor ____________ is the time from the start of a pulse to the end of that pulse. - ANSPulse duration ____________ is the time from the start of a pulse to the start of the next pulse. - ANSPulse Repetition Period Pulse repetition frequency is the reciprocal of _________. - ANSPulse repetition period
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By changing the image depth, what does the operator also change? - ANSPRF, Duty Factor, and PRP What is the duty factor if the pulse duration is 1 microsecond, and the pulse repetition period is 1 second? - ANSThe duty factor is 0.001 or 10^- 3 (10^-6 divided by 10^-3 = 10^-3 or 0.001) What is the duty factor if the pulse duration is 1 millisecond, and the pulse repetition period is 1 second? - ANSThe duty factor is 0.001 or 0.1% (0.001 divided by 1.0 = 0.001) What is Intensity? - ANSA beam's power divided by its area What is temporal intensity? - ANSRefers to all time, transmit (pulse duration) and receive What is pulsed intensity? - ANSThe average intensity for the pulse duration only What does spatial refer to? - ANSLocation or space. What is the beam's intensity at the location where it is maximum called? - ANSSpatial peak intensity The average intensity across the beam's entire cross-sectional area is called ____________. - ANSSpatial average intensity Spatial peak intensity is always _______ than the spatial average. - ANSHigher The term temporal refers to ______. - ANSTime Measuring the intensity of the beam at the instant in time of its maximal value is called the _________________. - ANSTemporal peak intensity What is SPTP? - ANSMeasured at the location where intensity is maximum (highest value intensity) What is SPPA? - ANSMeasured at the location where intensity is maximum, averaged over the transmit time (pulse duration) What is SPTA? - ANSMeasured at the location where intensity is maximum and averaged over all time, both the transmit and receive times (Used to test for bioeffects) What is SATA? - ANSMeasured over the entire cross-sectional area of the sound beam, and over all time (lowest value intensity) All intensities have units of __________. - ANSW/cm^ What is the number that describes the spread of a beam in space called? - ANSThe Beam Uniformity Coefficient (SP/SA factor) Unitless with a value of 1 or greater What describes the relationship of beam intensities with time? - ANSDuty factor For continuous wave ultrasound, the beam is always "on" and the pulse average and temporal average intensities are ____________. - ANSThe same SPTA = SPPA and SATA = SAPA When pulsed and continuous wave sound beams have the same SPTP intensities, the __________ wave beam has the higher SPTA intensity. - ANSContinuous
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What is diffuse reflection? - ANSWhen a wave reflects off an irregular surface, it radiates in more than one direction (also called backscatter) What are the advantages and disadvantages of diffuse reflection? - ANSAdvantage: interfaces as suboptimal angles to the sound beam can still produce reflections that the transducer will receive Disadvantage: the backscattered reflections will have a lower strength than specular reflections What is scattering? - ANSThe random redirection of sound in many directions Why does scattering happen? - ANSWhen the tissue interface is small; that is, equal to or less than the wavelength of the incident sound beam Scattering is directly related to frequency. Therefore, higher frequency sound beams scatter much ______ than lower frequency beams. - ANSMore What is a special form of scattering that occurs when the structure's dimensions are much smaller than the beam's wavelength? - ANSRayleigh scattering Rayleigh scattering = - ANSFrequency^ When there is a higher frequency, there is ________ pulses, __________ penetration, ________ attenuation, and ___________ resolution. - ANSShorter pulses, less penetration, more attenuation, and better resolution When does absorption occur? - ANSWhen ultrasonic energy is converted into another energy form, such as heat Absorption is __________ related to frequency. - ANSDirectly What is attenuation coefficient? - ANSThe number of decibels of attenuation that occurs when sound travels one centimeter total attenuation (dB) = - ANSAttenuation coefficient (dB/cm) x distance (cm) The attenuation coefficient is ______________ of the frequency in soft tissue. - ANSOne- half In soft tissue: attenuation coefficient (dB/cm) = - ANSFrequency (MHz)/ atten. coef. = 0.5 dB/cm/MHz Air (lung) and Bone have extremely ________ attenuation compared to sift tissue. - ANSHigh Biologic fluids (blood, urine, amniotic fluid) have _____ attenuation. - ANSLow What has the lowest attenuation? - ANSWater What is the half-value layer thickness? - ANSThe distance that sound travels in a tissue that reduces the intensity of sound to one-half its original value What are synonyms of half-value layer? - ANSPenetration depth, depth of penetration, half- boundary layer What does the half-value layer thickness depend on? - ANSThe medium and the frequency of sound
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If there is a thin half-value, there is a _____ frequency sound and a media with _____ attenuation rate. - ANSHigh, high If there is a thick half-value, there is a ____ frequency sound and a media with ____ attenuation rate. - ANSLow, low What is impedance? - ANSThe acoustic resistance to sound traveling in a medium impedance (rayls) = - ANSDensity (kg/m^3) x prop. speed (m/s) What is impedance determined by? - ANSThe medium What is a synonym to impedance? - ANSCharacteristic impedance Name three components of attenuation. - ANSAbsorption, reflection, and scattering As the path length increases, the attenuation of ultrasound in soft tissue __________. - ANSIncreases Attenuation in lung tissue is __________ than attenuation in soft tissue. - ANSGreater Attenuation in bone is __________ than attenuation in soft tissue. - ANSGreater Attenuation in air is ________ than attenuation in soft tissue. - ANSGreater What are the units of attenuation? - ANSdecibels (dB) T or F. In a given medium, attenuation is unrelated to speed of sound. - ANSTrue (attenuation and propagation speed are unrelated) What is the relationship between ultrasound frequency and the attenuation coefficient in soft tissue? - ANSIn soft tissue, the attenuation coefficient in dB per centimeter is approximately one half of ultrasonic frequency in MHz What are the units of the half-value layer thickness? - ANSDistance; centimeters As frequency decreases, depth of penetration _________. - ANSIncreases As path length increases, the half boundary layer __________. - ANSRemains the same Impedance is a characteristic of ___________. - ANSOnly the medium As the path length increases, the attenuation coefficient of ultrasound in soft tissue __________. - ANSRemains the same Acoustic impedance = ________ x _____________. - ANSImpedance = density (kg/m^3) x propagation speed (m/s) Two media A and B have the same densities. The speed of sound in medium A is 10% higher than in medium B. Which medium has the higher acoustic impedance? - ANSMedium A Impedance is important in _______ at boundaries. - ANSReflections Which is better to use while examining a carotid artery., a 7.5 or 3.0 MHz transducer? - ANS7.5 MHz transducer (superficial) What are the three types of angles? - ANSAcute - <90 degrees Right - exactly 90 degrees Obtuse - >90 degrees All angles that do not equal 90 degrees are called _________ angles. - ANSOblique What does normal incidence mean? - ANSThe incident sound beam strikes the boundary at exactly 90 degrees.
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In ___________ incidence, it is complicated to tell whether the sound ill reflect or transmit after striking a boundary. - ANSOblique What two principles always apply to reflection with oblique incidence? - ANSConservation or energy reflection angle = incident angle incident intensity (W/cm^2) = - ANSreflected intensity + transmitted intensity angle of incidence = - ANSangle of reflection If the sound beam bends or changes direction after is strikes an interface at an oblique angle, this is called... - ANSrefraction What is refraction? - ANSa change in direction of wave propagation when traveling from one medium to another. Refraction only occurs if two conditions are satisfied: - ANSoblique incidence (not normal) and propagation speeds of the two media are different What is snell's law? - ANSsin(transmission angle)/sin (incident angle) = speed of Medium 2/speed of Medium 1 Under what conditions will the transmission angle equal the incident angle? - ANSif the two media are the same Under what conditions will the transmission angle be greater than the incident angle? - ANSwhen medium 2 is greater than medium 1 Under what conditions will the transmission angle be less than the incident angle? - ANSwhen medium 2 is less than medium 1 A pulse of ultrasound propagates in soft tissue, such as liver. The pulse strikes a soft tissue - soft tissue interface with oblique incidence. Some of the sound energy is transmitted. To what extent is the transmitted beam refracted? - ANSThe transmitted beam undergoes little to no refraction. A transmitted beam is refracted when the incidence is oblique and the propagation speeds are different. A sound wave strikes a boundary at normal incidence. The impedances of the two media are identical. What percentage of the sound wave is refracted? - ANS0%, refraction cannot occur with normal incidence What property has units of rayls? How is it determined? - ANSImpedance Impedance = density x speed What is the elapsed time from pulse creation to pulse reception called? - ANSgo-return time or time-of-flight The time-of-flight is ________ related to the depth that a sound pulse travels. - ANSdirectly depth (mm) = - ANS1.54 mm/μsec x go-return time (μsec)/ For every _____ μsec of go-return time, the object creating the reflection is 1 centimeter deeper in soft tissue. - ANS
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Since a pulse travels to the reflector and back to the transducer, the total distance that a pulse travels is... - ANStwice the reflector depth A sound wave is created by a transducer, reflects off an object, and returns to that transducer. The depth of the reflector is 10 cm in soft tissue. What is the go-return time? - ANS130 μsec A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The go-return time is 26 μsec. What is the depth of the reflector? - ANS2 cm A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The go-return time is 26 μsec. What is the total distance that the pulse traveled? - ANS4 cm The maximum imaging depth (depth of view) during an ultrasound exam is 10cm. The sonographer adjusts the imaging depth to 20 cm. What happens to pulse repetition period? - ANSit is doubled The maximum imaging depth during an ultrasound exam is 10 cm. The sonographer adjusts the imaging depth to 20 cm. What happens to pulse repetition frequency? - ANSit is halved The imaging depth during an ultrasound exam is 10 cm. The sonographer adjusts the imaging depth to 5 cm. What happens to pulse repetition period? - ANSit is halved A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The imaging depth is 10 cm in soft tissue. What is the maximum pulse repetition frequency? - ANS7.7 kHz A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The maximum imaging depth is 7.7 cm. What is the PRF? - ANS77,000/7.7 = 10,000 Hz A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The go-return time is 130 μsec. What is the maximum PRF? - ANS7,700 Hz. What is axial resolution? - ANSit measures the ability of a system to display two structures that are very close together when the structures are parallel to the sound beam's main axis. What is axial resolution determined by? And is it adjustable? - ANSSPL (shorter pulses improve axial resolution) It is not adjustable because the SPL is fixed. What are the synonyms to axial resolution? - ANSlongitudinal, range, radial, or depth resolution LARRD What is the relationship between the numerical value of the axial resolution and the image quality? - ANSLower numerical values of axial resolution indicate a shorter pulse. Shorter pulses create more accurate images; therefore, the image quality is better with lower numbers. axial resolution (mm) = - ANSspatial pulse length/ or (wavelength (mm) x # cycles in pulse)/
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What is the case? - ANSthe cylindrical tube, constructed of metal or plastic, that protects the internal components of the transducer from damage. What is the electrical shield? - ANSThin metallic barrier lining the inside of the case. What is acoustic insulator? - ANSA thin barrier of cork or rubber that isolates or "uncouples" the internal components of the transducer from the case. Prevents vibrations in the case from inducing an electrical voltage in the PZT of the transducer. What is the wire? - ANSProvides an electrical connection between PZT and the ultrasound system. What is the matching layer? - ANSincreases the efficiency of sound energy transfer between the active element and the body, and protects the active element What is the backing material (or damping element)? - ANSbonded to the back of the active element, it reduces the "ringing" of the pulse. The matching layer and gel _________ the efficiency of sound transfer between the transducer's PZT and the skin. - ANSincrease How thick are the matching layer and the active element of a basic ultrasound transducer? - ANSThe thickness of the matching layer is one quarter of the wavelength of sound in the matching layer. The thickness of the active element is one-half of the wavelength of sound in the active element. What are the characteristics of damping material? - ANShigh degree of sound absorption, and acoustic impedance similar to PZT. What are additional consequences related to the use of a backing material? - ANSdecreased sensitivity wide bandwidth low quality factor What does decreased sensitivity mean? - ANSthe transducers with damping material are less able to convert low-level sound reflections into meaningful electrical signals during reception. What is bandwidth? - ANSthe range, or difference, between the highest and lowest frequencies in the pulse. Thus, imaging probes are identified as short pulse, wide bandwidth. Long duration events are _______ bandwidth, whereas short duration events are _______ bandwidth. - ANSnarrow, wide quality factor = - ANSmain frequency/bandwidth A shorter pulse has a _________ Q-factor. - ANSlower A longer pulse has a ______ Q-factor. - ANShigher How is PZT created? - ANScreated by exposing the material to a strong electrical field while being heated to a substantial temperature. (polarization) What is the Curie temperature, and what is its importance? - ANSthe temperature that the PZT is polarized is called the Curie temperature or Curie point.
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If the polarized PZT is heated above the Curie temperature, the crystal's piezoelectric properties are destroyed. (depolarized) What is the difference between sterilization and disinfection? Which method is used on transducers? - ANSSterilization is the destruction of all microorganisms by exposure to extreme heat, chemical agents, or radiation. Disinfection is the application of a chemical agent to reduce or eliminate infectious organisms on an object. Ultrasound transducers only require disinfection. Pulse length is ______ related to pulse duration. - ANSdirectly Q-factor is ___________ related to bandwidth. - ANSinversely Pulse duration is __________ related to bandwidth. - ANSinversely T or F. Shorter duration events (such as dampened pulses) are more likely to be wide bandwidth. - ANSTrue. What occurs when a PZT crystal's temperature is elevated above the Curie point? - ANSthe PZT is depolarized In a continuous wave transducer, electrical frequency = - ANSacoustic frequency The frequency of sound emitted by a continuous wave transducer is determined by what? - ANSthe frequency of the electrical signal created by the ultrasound system What characteristics of the active element determine the frequency of sound created by a pulsed wave transducer? - ANSspeed of sound in the PZT and the thickness of the PZT How does the speed of sound in PZT affect frequency? - ANSin a pulsed wave transducer, the speed of sound in PZT and the frequency of sound are directly related. When the speed of sound in PZT is faster, the frequency of sound created by a pulsed wave transducer is higher. How does the thickness or the PZT crystal affect frequency? - ANSFor pulsed wave transducers, thinner active elements create higher frequency sound pulses. PZT thickness and frequency are inversely related. The thickness of the PZT crystal in a pulsed wave transducer is equal to ___________ of the wavelength of sound in the PZT. - ANSone-half frequency (MHz) = - ANSsounds speed in PZT (mm/μsec)/2 x thickness (mm) True or False. The acoustic impedance of the matching layer is approximately the same as the acoustic impedance of skin. - ANSFalse. True or False. Imaging transducers are usually of high rather than low bandwidth. - ANSTrue. True or False. A very high Q factor transducer is used more often in diagnostic imaging transducers than a low Q factor. - ANSFalse. True or False. A pulse with a long pulse duration is likely to have a narrow bandwidth. - ANSTrue. True or False. The damping material in a transducer increases the sensitivity. - ANSFalse. True or False. The damping material in a transducer increases pulse length. - ANSFalse.
