ARDMS- SPI QUIZ QUESTIONS WITH COMPLETE SOLUTIONS Latest Updates 2024 Latest Updates 2024, Exams of Nursing

Download ARDMS- SPI QUIZ QUESTIONS WITH COMPLETE SOLUTIONS Latest Updates 2024 Latest Updates 2024 and more Exams Nursing in PDF only on Docsity! 1 ARDMS- SPI QUIZ QUESTIONS WITH COMPLETE SOLUTIONS Latest Updates 2024 Latest Updates 2024 The horizontal axis, or x-axis CORRECT ANSWERS: Runs side to side The vertical axis, or y-axis CORRECT ANSWERS: Runs up and down Unrelated CORRECT ANSWERS: Two items that are not associated Related or Proportional CORRECT ANSWERS: Two items that are associated or affiliated However, the relationship between the items does not have to be specified Directly related or Directly proportional CORRECT ANSWERS: Two items that are associated such that when one item increases, the other increases Inversely related or inversely proportional CORRECT ANSWERS: Two items are associated such that when one item increases, the other decreases Reciprocal Relationship CORRECT ANSWERS: When 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 CORRECT ANSWERS: Unit "Increase by a factor" means CORRECT ANSWERS: To multiply by that number "Decrease by a factor" means CORRECT ANSWERS: To divide by that number Scientific or engineering notation is a shorthand manner to represent what types of numbers? CORRECT ANSWERS: Very large or very small numbers A number in scientific notation form with a positive exponent has a value CORRECT ANSWERS: Greater than 10 A number in scientific notation form with an exponent of zero has a value CORRECT ANSWERS: Between 1 and 10 A number in scientific notation form with a negative exponent has a value CORRECT ANSWERS: Less than 1 2 10⌃9 CORRECT ANSWERS: Prefix: giga Symbol: G Meaning: billion 10⌃6 CORRECT ANSWERS: Prefix: mega Symbol: M Meaning: million 10⌃3 CORRECT ANSWERS: Prefix: kilo Symbol: k Meaning: thousand 10⌃2 CORRECT ANSWERS: Prefix: hecto Symbol: h Meaning: hundred 10⌃1 CORRECT ANSWERS: Prefix: deca Symbol: da Meaning: ten 10⌃-1 CORRECT ANSWERS: Prefix: deci Symbol: d Meaning: tenth 10⌃-2 CORRECT ANSWERS: Prefix: centi Symbol: c Meaning: hundredth 10⌃-3 CORRECT ANSWERS: Prefix: milli Symbol: m Meaning: thousandth 10^-6 CORRECT ANSWERS: Prefix: micro Symbol: μ Meaning: millionth 10^-9 CORRECT ANSWERS: Prefix: nano Symbol: n Meaning: billionth List all these metric terms in increasing order: A. mega B. micro C. milli D. hecto 5 Some parameters are determined by the tissue through which the sound is traveling, also called a __________. CORRECT ANSWERS: Medium What is period? And what is it determined by? CORRECT ANSWERS: The 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? CORRECT ANSWERS: The number of cycles that occurs in one second Determined by the sound source only 1 cycle/second = CORRECT ANSWERS: 1 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 ____________. CORRECT ANSWERS: 20 Hz, infrasonic Audible sound waves that humans can hear are frequencies between _______________________. CORRECT ANSWERS: 20 Hz and 20,000 Hz What is ultrasound's frequency? CORRECT ANSWERS: Greater than 20,000 Hz or 20 kHz Why is frequency important in diagnostic sonography? CORRECT ANSWERS: It affects penetration and image quality Period and frequency are __________ related to each other. CORRECT ANSWERS: Inversely When two reciprocal parameters are multiplied together, the result is: CORRECT ANSWERS: 1 What three parameters describe the size, or magnitude, or strength of a sound wave? CORRECT ANSWERS: Amplitude, power, intensity What is Amplitude? CORRECT ANSWERS: The "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? CORRECT ANSWERS: Initially, 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? CORRECT ANSWERS: Amplitude 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 6 What is power? CORRECT ANSWERS: The 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? CORRECT ANSWERS: Determined by the sound source only It CAN be changed How are amplitude and power related? CORRECT ANSWERS: Both describe the size, or magnitude of a wave. When power increases, so does amplitude Power is proportional to... CORRECT ANSWERS: amplitude^2 What is intensity? CORRECT ANSWERS: The concentration of energy in a sound beam Intensity = Power/area What is intensity determined by? And is it adjustable? CORRECT ANSWERS: Sound Source Yes, it is adjustable How is intensity related to power and amplitude? CORRECT ANSWERS: Intensity is proportional to power Intensity is proportional to amplitude^2 What is the distance or length of one complete cycle called? CORRECT ANSWERS: Wavelength What is wavelength determined by? And is it adjustable? CORRECT ANSWERS: Both the medium and source No, it is not adjustable What is the relationship between wavelength and frequency? CORRECT ANSWERS: As 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? CORRECT ANSWERS: 1.54 mm What is the wavelength of other frequency sound waves in soft tissue? CORRECT ANSWERS: Sound 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? CORRECT ANSWERS: wavelength = (1.54mm/μsec)/(frequency) Why is wavelength important in diagnostic ultrasound? CORRECT ANSWERS: Wavelength plays an important role in image quality 7 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? CORRECT ANSWERS: Propagation Speed What does the speed of sound range from? CORRECT ANSWERS: 500m/s to 4000m/s What is Propagation Speed determined by? And is it adjustable? CORRECT ANSWERS: The Medium No, it is not adjustable What is the speed of sound in soft tissue? CORRECT ANSWERS: 1,540 m/s 1.54 mm/μsec 1.54 km/s 1 mile per second What has the slowest propagation speed? And the longest? CORRECT ANSWERS: Slowest: Lung (Air, Gas) Longest: Bone What is the speed of sound in Blood? CORRECT ANSWERS: 1,560 m/s What is the order for speed of sound from lowest to highest in Water, Metals, and Air? CORRECT ANSWERS: Air, Water, Metals What determines the speed of sound in that medium? CORRECT ANSWERS: Stiffness, density What describes the ability of an object to resist compression? CORRECT ANSWERS: Stiffness; 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? CORRECT ANSWERS: Stiffness and Speed are directly related As materials become stiffer, the speed of sound in the material increased Non-stiff media are described as... CORRECT ANSWERS: Elastic or compressible What describes the relative weight of a material? CORRECT ANSWERS: Density How does density affect speed? CORRECT ANSWERS: Density and speed are inversely related. As materials become more dense (heavier), the speed of sound in the material decreases When Stiffness increases, Speed ______ CORRECT ANSWERS: Increases When Density Increases, Speed ________ CORRECT ANSWERS: Increases 10 Frequency, density, particle motion, temperature, period, and pressure CORRECT ANSWERS: Density, particle motion, and pressure Which of the following are considered acoustic parameters? frequency, density, distance, pressure, and period CORRECT ANSWERS: Frequency and period The effects of tissue on sound waves are called _________ _________ ____________. CORRECT ANSWERS: Acoustic Propagation Properties The effects of a medium on an ultrasound wave are called _________ ____________ _________. CORRECT ANSWERS: Acoustic Propagation Properties How are frequency and period related? CORRECT ANSWERS: Inversely How are amplitude and power related? CORRECT ANSWERS: Directly How are amplitude and intensity related? CORRECT ANSWERS: Directly How are power and intensity related? CORRECT ANSWERS: Directly How are wavelength and intensity related? CORRECT ANSWERS: Unrelated How are wavelength and frequency related? CORRECT ANSWERS: Inversely How are acoustic velocity and density related? CORRECT ANSWERS: Inversely How are elasticity and speed of sound related? CORRECT ANSWERS: Inversely How are acoustic velocity and compressibility related? CORRECT ANSWERS: Inversely How are stiffness and sound speed related? CORRECT ANSWERS: Directly How are frequency and sound speed related? CORRECT ANSWERS: Unrelated How are frequency and intensity related? CORRECT ANSWERS: Unrelated How are power and frequency related? CORRECT ANSWERS: Unrelated What are the five parameters to describe pulsed sound? CORRECT ANSWERS: Pulse duration, pulse repetition period, pulse repetition frequency, duty factor, and spatial pulse length What is pulsed ultrasound? CORRECT ANSWERS: A pulse of an ultrasound is a collection of cycles that travel together. The entire pulse moves as a single item 11 What are the two components of pulsed ultrasound? CORRECT ANSWERS: Transmit, 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? CORRECT ANSWERS: Pulse duration (a single "on" time) What is pulse duration determined by? And can it be adjusted? CORRECT ANSWERS: Sound source, NO Pulse duration (μsec) = CORRECT ANSWERS: # cycles x period (μsec) or #cycles/frequency (MHz) Pulse duration is directly proportional to ___________. CORRECT ANSWERS: # cycles in a pulse and to period Pulse duration is ____________ proportional to frequency. CORRECT ANSWERS: Inversely What creates pulses of long duration? CORRECT ANSWERS: Many cycles in the pulse, and individual cycles with long periods What creates pulses of short duration? CORRECT ANSWERS: Few cycles in the pulse, and individual cycles with short periods Which type of pulse duration is more desirable in diagnostic imaging? CORRECT ANSWERS: Shorter duration pulses are desirable for imaging because they create images of greater accuracy What is Spatial Pulse Length? CORRECT ANSWERS: The 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? CORRECT ANSWERS: Both the source and the medium. No it is not adjustable. Spatial Pulse Length (mm) = CORRECT ANSWERS: # cycles x wavelength (mm) Spatial Pulse Length is _________ proportional to frequency. CORRECT ANSWERS: Inversely What is the difference between pulse duration and pulse length? CORRECT ANSWERS: Pulse duration is the TIME that a pulse in "on" pulse length is the DISTANCE of the pulse end to end Two characteristics that create long pulses are: CORRECT ANSWERS: Many cycles in the pulse Cycles with longer wavelengths 12 Two characteristics that create short pulses are: CORRECT ANSWERS: Fewer cycles in the pulse Cycles with shorter wavelengths Which types of pulse length is more desirable in diagnostic imaging? CORRECT ANSWERS: Shorter pulses are desirable because they create more accurate images What is the time from start of one pulse to the start of the next pulse called? CORRECT ANSWERS: Pulse Repetition Period Pulse Repetition Period is determined by the ___________ _________ that the sonographer selects. CORRECT ANSWERS: Imaging depth What is PRP determined by? And is it adjustable? CORRECT ANSWERS: Sound Source Yes, it is adjustable When the system is imaging at shallow depths, the time from one pulse to the next is __________. CORRECT ANSWERS: Short What is depth of view? CORRECT ANSWERS: The maximum distance into the body that an ultrasound system is imaging How are PRP and depth of view related? CORRECT ANSWERS: Directly related What are the two components of pulse repetition period? CORRECT ANSWERS: Transmit time (pulse duration) and the receive time Which component of PRP can the sonographer change? CORRECT ANSWERS: Receive time or "listening time" (alter the depth of the image) What is pulse repetition frequency? CORRECT ANSWERS: The number of pulses that an ultrasound system transmits into the body each second What is the PRF determined by? And is it adjustable? CORRECT ANSWERS: Sound Source, Yes When the system is imaging shallow, the pulse repetition frequency is _______. CORRECT ANSWERS: Higher PRF is not related to frequency. It is related only to _____ __ ____. CORRECT ANSWERS: Depth of view How are PRF and depth of view related? CORRECT ANSWERS: Inversely related (as depth of view increases, PRF decreases) 15 What does spatial refer to? CORRECT ANSWERS: Location or space. What is the beam's intensity at the location where it is maximum called? CORRECT ANSWERS: Spatial peak intensity The average intensity across the beam's entire cross-sectional area is called ____________. CORRECT ANSWERS: Spatial average intensity Spatial peak intensity is always _______ than the spatial average. CORRECT ANSWERS: Higher The term temporal refers to ______. CORRECT ANSWERS: Time Measuring the intensity of the beam at the instant in time of its maximal value is called the _________________. CORRECT ANSWERS: Temporal peak intensity What is SPTP? CORRECT ANSWERS: Measured at the location where intensity is maximum (highest value intensity) What is SPPA? CORRECT ANSWERS: Measured at the location where intensity is maximum, averaged over the transmit time (pulse duration) What is SPTA? CORRECT ANSWERS: Measured 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? CORRECT ANSWERS: Measured over the entire cross-sectional area of the sound beam, and over all time (lowest value intensity) All intensities have units of __________. CORRECT ANSWERS: W/cm^2 What is the number that describes the spread of a beam in space called? CORRECT ANSWERS: The Beam Uniformity Coefficient (SP/SA factor) Unitless with a value of 1 or greater What describes the relationship of beam intensities with time? CORRECT ANSWERS: Duty factor For continuous wave ultrasound, the beam is always "on" and the pulse average and temporal average intensities are ____________. CORRECT ANSWERS: The 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. CORRECT ANSWERS: Continuous 16 When pulsed and continuous wave sound beams have the same SATP intensities, the __________ wave beam has the higher SATA intensity. CORRECT ANSWERS: Continuous ________ average intensity is averaged only during the pulse duration ("on" time). CORRECT ANSWERS: Pulse ________ average intensity is averaged during the PRP (both the "on" and "off" times) CORRECT ANSWERS: Temporal The rank of intensities from largest to smallest is: CORRECT ANSWERS: SPTP -> SPPA -> SPTA -> SATA As sound travels in the body, it weakens, or __________. CORRECT ANSWERS: Attenuates After a sound wave is received by the transducer, converted into electricity and returned to the ultrasound system, it is strengthened or __________. CORRECT ANSWERS: Amplifide When a waves intensity doubles, the relative change is... CORRECT ANSWERS: +3 dB When the intensity increases 10-fold, the relative change is... CORRECT ANSWERS: +10 dB. When the intensity is reduced to 1/2 its original value, the relative change is... CORRECT ANSWERS: -3 dB. When the intensity is reduced to 1/10 its original value, the relative change is... CORRECT ANSWERS: -10 dB. A reduction in the intensity of a sound beam to one-half of its original value is _____ dB. CORRECT ANSWERS: -3 dB A reduction in the intensity of a sound beam to one-quarter of its original value is _____ dB. CORRECT ANSWERS: -6 dB -10 dB means that the intensity is reduced to ______ of its original value. CORRECT ANSWERS: One-tenth dB is a mathematical representation with a _________ and _____________ scale. CORRECT ANSWERS: Logarithmic and relative True or False. We need one intensity to calculate decibels. CORRECT ANSWERS: False A waves intensity is 2 mW/cm^2. There is a change of +9 dB. What is the final intensity? CORRECT ANSWERS: 16 Mw/cm^2 Every dB change means that the intensity will ______. CORRECT ANSWERS: Double 17 Every 10 dB change means that the intensity will _______. CORRECT ANSWERS: Increase ten times If the final intensity of a sound beam is more than the initial intensity, then the gain in dB is ________ . CORRECT ANSWERS: Positive If the initial intensity of a sound beam is less than the final intensity, then the gain in dB is _______. CORRECT ANSWERS: Positive What is attenuation determined by? CORRECT ANSWERS: Path length, and frequency of sound Distance and Attenuation are ___________ related. CORRECT ANSWERS: Directly Frequency and Attenuation are _________ related. CORRECT ANSWERS: Directly As sound strikes a boundary, a portion of the wave's energy may be redirected, or _________, back to the sound source. CORRECT ANSWERS: Reflected Reflection is likely to occur when... CORRECT ANSWERS: The boundary is large What is specular reflection? CORRECT ANSWERS: When the boundary is smooth, the sound is reflected in only one direction in an organized manner What is diffuse reflection? CORRECT ANSWERS: When 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? CORRECT ANSWERS: Advantage: 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? CORRECT ANSWERS: The random redirection of sound in many directions Why does scattering happen? CORRECT ANSWERS: When 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. CORRECT ANSWERS: More What is a special form of scattering that occurs when the structure's dimensions are much smaller than the beam's wavelength? CORRECT ANSWERS: Rayleigh scattering Rayleigh scattering = CORRECT ANSWERS: Frequency^4 20 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? CORRECT ANSWERS: Medium A Impedance is important in _______ at boundaries. CORRECT ANSWERS: Reflections Which is better to use while examining a carotid artery., a 7.5 or 3.0 MHz transducer? CORRECT ANSWERS: 7.5 MHz transducer (superficial) What are the three types of angles? CORRECT ANSWERS: Acute - <90 degrees Right - exactly 90 degrees Obtuse - >90 degrees All angles that do not equal 90 degrees are called _________ angles. CORRECT ANSWERS: Oblique What does normal incidence mean? CORRECT ANSWERS: The incident sound beam strikes the boundary at exactly 90 degrees. (also called: perpendicular, orthogonal, right angle) What is an oblique incidence? CORRECT ANSWERS: When the incident sound beam strikes the boundary at any angle other than 90 degrees What is the sound wave's intensity immediately before it strikes a boundary called? CORRECT ANSWERS: Incident intensity What is reflected intensity? CORRECT ANSWERS: The intensity of the portion of the incident sound beam that, after striking a boundary, continues forward in the same general direction it was traveling incident (starting) intensity = CORRECT ANSWERS: Reflected intensity + transmitted intensity What is the intensity reflection coefficient (IRC)? CORRECT ANSWERS: The percentage of the intensity that bounces back when a sound beam strikes the boundary between two media What is the intensity transmission coefficient (ITC)? CORRECT ANSWERS: The percentage of ultrasound intensity that passes in the forward direction when the beam strikes an interface between two media IRC (%) + ITC (%) = CORRECT ANSWERS: 100% A sound wave with intensity of 50 W/cm^2 strikes a boundary and is totally reflected. What is the intensity reflection coefficient? CORRECT ANSWERS: 100% 21 A sound wave with intensity of 50 W/cm^2 strikes a boundary and is totally reflected. What is the reflected intensity? CORRECT ANSWERS: 50 W/cm^2 IRC (%) = CORRECT ANSWERS: (Z2-Z1/Z2+Z1)^2 x 100 If the two media have identical impedances, there will be... CORRECT ANSWERS: No reflection If two media have slightly different impedances, there will be... CORRECT ANSWERS: A small reflection If two media have substantially different impedances, there will be... CORRECT ANSWERS: A large reflection A pulse of ultrasound is propagating in soft tissue, such as liver. The pulse strikes a boundary with a different soft tissue at normal incidence. What portion of the intensity is reflected back toward the transducer? Why? CORRECT ANSWERS: A very small percentage of sound, typically less than 1%, is reflected at a boundary between two soft tissues Very little reflection occurs when the impedances have similar, but not identical, values Sound is traveling in a medium and strikes a boundary with normal incidence. If 63% of the wave's intensity is reflected back toward the transducer what percentage is transmitted? CORRECT ANSWERS: 37% ITC (%) = CORRECT ANSWERS: (transmitted intensity/ incident intensity) x 100 or 1 - intensity reflection coefficient Sound is traveling from bone to soft tissue. The impedances of the media differ significantly, and 90% of the beam's intensity is reflected. What percentage of the intensity is transmitted? CORRECT ANSWERS: 100% of the energy must be accounted for If 90 % is reflected 10% must be transmitted In ___________ incidence, it is complicated to tell whether the sound ill reflect or transmit after striking a boundary. CORRECT ANSWERS: Oblique What two principles always apply to reflection with oblique incidence? CORRECT ANSWERS: Conservation or energy reflection angle = incident angle incident intensity (W/cm^2) = CORRECT ANSWERS: reflected intensity + transmitted intensity angle of incidence = CORRECT ANSWERS: angle of reflection 22 If the sound beam bends or changes direction after is strikes an interface at an oblique angle, this is called... CORRECT ANSWERS: refraction What is refraction? CORRECT ANSWERS: a change in direction of wave propagation when traveling from one medium to another. Refraction only occurs if two conditions are satisfied: CORRECT ANSWERS: oblique incidence (not normal) and propagation speeds of the two media are different What is snell's law? CORRECT ANSWERS: sin(transmission angle)/sin (incident angle) = speed of Medium 2/speed of Medium 1 Under what conditions will the transmission angle equal the incident angle? CORRECT ANSWERS: if the two media are the same Under what conditions will the transmission angle be greater than the incident angle? CORRECT ANSWERS: when medium 2 is greater than medium 1 Under what conditions will the transmission angle be less than the incident angle? CORRECT ANSWERS: when 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? CORRECT ANSWERS: The 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? CORRECT ANSWERS: 0%, refraction cannot occur with normal incidence What property has units of rayls? How is it determined? CORRECT ANSWERS: Impedance Impedance = density x speed What is the elapsed time from pulse creation to pulse reception called? CORRECT ANSWERS: go-return time or time-of-flight The time-of-flight is ________ related to the depth that a sound pulse travels. CORRECT ANSWERS: directly depth (mm) = CORRECT ANSWERS: 1.54 mm/μsec x go-return time (μsec)/2 For every _____ μsec of go-return time, the object creating the reflection is 1 centimeter deeper in soft tissue. CORRECT ANSWERS: 13 25 resolution? Which transducer probably has a lower numerical measure of axial resolution? CORRECT ANSWERS: The 5 MHz transducer. The higher frequency transducer creates a shorter pulse and thus has a lower numerical measure of axial resolution. Lower numbers mean improved image quality. Wha happens during transmission? CORRECT ANSWERS: electrical energy from the system is converted into sound What happens during reception? CORRECT ANSWERS: the reflected sound pulse is converted into electricity What is the piezoelectric effect? CORRECT ANSWERS: the property of certain materials to create a voltage when they are mechanically deformed What is the reverse piezoelectric effect? CORRECT ANSWERS: when a voltage is applied to piezoelectric materials, they change shape What are the materials that change sound into electricity (and vice versa)? CORRECT ANSWERS: piezoelectric or ferroelectric What materials are commonly used in clinical transducers? CORRECT ANSWERS: lead zirconate titanate (PZT) also known as ceramic, active element, or crystal What are the 7 components of a basic transducer? CORRECT ANSWERS: case, electrical shield, acoustic insulator, PZT or active element, wire, matching layer, and backing material (also called the damping element) What is the case? CORRECT ANSWERS: the cylindrical tube, constructed of metal or plastic, that protects the internal components of the transducer from damage. What is the electrical shield? CORRECT ANSWERS: Thin metallic barrier lining the inside of the case. What is acoustic insulator? CORRECT ANSWERS: A 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? CORRECT ANSWERS: Provides an electrical connection between PZT and the ultrasound system. What is the matching layer? CORRECT ANSWERS: increases 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)? CORRECT ANSWERS: bonded to the back of the active element, it reduces the "ringing" of the pulse. 26 The matching layer and gel _________ the efficiency of sound transfer between the transducer's PZT and the skin. CORRECT ANSWERS: increase How thick are the matching layer and the active element of a basic ultrasound transducer? CORRECT ANSWERS: The 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? CORRECT ANSWERS: high degree of sound absorption, and acoustic impedance similar to PZT. What are additional consequences related to the use of a backing material? CORRECT ANSWERS: decreased sensitivity wide bandwidth low quality factor What does decreased sensitivity mean? CORRECT ANSWERS: the transducers with damping material are less able to convert low-level sound reflections into meaningful electrical signals during reception. What is bandwidth? CORRECT ANSWERS: the 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. CORRECT ANSWERS: narrow, wide quality factor = CORRECT ANSWERS: main frequency/bandwidth A shorter pulse has a _________ Q-factor. CORRECT ANSWERS: lower A longer pulse has a ______ Q-factor. CORRECT ANSWERS: higher How is PZT created? CORRECT ANSWERS: created 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? CORRECT ANSWERS: the temperature that the PZT is polarized is called the Curie temperature or Curie point. 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? CORRECT ANSWERS: Sterilization is the destruction of all microorganisms by exposure to extreme heat, chemical agents, or radiation. 27 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. CORRECT ANSWERS: directly Q-factor is ___________ related to bandwidth. CORRECT ANSWERS: inversely Pulse duration is __________ related to bandwidth. CORRECT ANSWERS: inversely T or F. Shorter duration events (such as dampened pulses) are more likely to be wide bandwidth. CORRECT ANSWERS: True. What occurs when a PZT crystal's temperature is elevated above the Curie point? CORRECT ANSWERS: the PZT is depolarized In a continuous wave transducer, electrical frequency = CORRECT ANSWERS: acoustic frequency The frequency of sound emitted by a continuous wave transducer is determined by what? CORRECT ANSWERS: the 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? CORRECT ANSWERS: speed of sound in the PZT and the thickness of the PZT How does the speed of sound in PZT affect frequency? CORRECT ANSWERS: in 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? CORRECT ANSWERS: For 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. CORRECT ANSWERS: one-half frequency (MHz) = CORRECT ANSWERS: sounds 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. CORRECT ANSWERS: False. True or False. Imaging transducers are usually of high rather than low bandwidth. CORRECT ANSWERS: True. 30 At depths more than two bear zone lengths, the beam is _______ than the active element. CORRECT ANSWERS: wider What is the focal zone? CORRECT ANSWERS: a region around the focus where the beam is relatively narrow and image detail is superior (half located in near and other half located in far) The focus marks the end of the _________. CORRECT ANSWERS: near zone At the depth of the focus, the sound beam starts to __________ or widen, which marks the beginning of the ____________ zone. CORRECT ANSWERS: diverge, far (Fraunhofer) At depths more than twice the focal length, the beam's width __________ that of the transducer. CORRECT ANSWERS: exceeds Adjustable focus systems are called ______________. CORRECT ANSWERS: Phased array What characteristics of a fixed-focus transducer determine the focal depth? CORRECT ANSWERS: transducer diameter and frequency of the sound How does transducer diameter affect the focal depth? CORRECT ANSWERS: increasing diameter results in a deeper focus; therefore, transducer diameter and focal depth are directly related. (beams from larger diameter active elements will have deeper focus) How does frequency affect focal depth? CORRECT ANSWERS: Higher frequency sound results in a deeper focus; therefore, frequency and focal depth are directly related Even with high frequency sound, an extremely small diameter locates the focus ___________. CORRECT ANSWERS: shallower focal depth (cm) = CORRECT ANSWERS: diameter (mm)^2 x frequency (MHz)/61.6 or diameter (mm)^2/40 x wavelength (mm) A pair of 6 MHz probes are identical except for active element diameter. The active element diameters are 6mm and 10mm, respectively. The sound beam of which probe will have a shallower focus? CORRECT ANSWERS: 6mm active element. Smaller diameter crystals produce beams with shallower foci. A pair of 9 mm diameter probes are identical except for frequency, which is 3 MHz and 6 MHz, respectively. Which beam will have a shallower focus? CORRECT ANSWERS: 3 MHz beam. (focal depth increases with increasing frequency) True or False. Transducer frequency and near zone length are inversely related. CORRECT ANSWERS: False. (directly related) 31 True or False. Wavelength and near zone length are inversely related. CORRECT ANSWERS: True True or False. Active element diameter and near zone length are directly related. CORRECT ANSWERS: True Beam divergence describes... CORRECT ANSWERS: the gradual spread of the ultrasound beam in the far field. How does transducer diameter affect beam divergence in the far field? CORRECT ANSWERS: Smaller diameter crystals produce beams that spread out, or diverge, more in the far zone. (crystal diameter and beam divergence are inversely related) Larger diameter crystals produce beams that diverge less in the far field Larger diameter crystals and higher frequency sound improve ______________ in the far field. CORRECT ANSWERS: lateral resolution How does frequency alter beam divergence in the far field? CORRECT ANSWERS: Lower frequency sound beams spread out or diverge more in the deep far zone. (frequency and beam divergence are inversely related) A pair of 6 MHz probes are identical except for active element diameter, which is 6 mm and 10 mm, respectively. Which beam will be more compact in the far field? CORRECT ANSWERS: 10mm active element has a less divergent beam. (larger diameter crystals produce beams that diverge less in the far field) A pair of 9 mm diameter probes are identical except for frequency, which are 3 MHz and 6 MHz. Which sound beam will spread out more in the far field? CORRECT ANSWERS: 3 MHz beam is more divergent. (beams are more compact as frequency increases) True or False. Transducer frequency and beam divergence are inversely related. CORRECT ANSWERS: True. True or False. Active element diameter and beam divergence are inversely related. CORRECT ANSWERS: True. What are sound waves are produced by? What shape do they diverge in? CORRECT ANSWERS: tiny pieces of PZT, V-shape When is the V-shaped wave created? And what are they called? CORRECT ANSWERS: when the source is about the size of the sound's wavelength. Called spherical waves, diffraction patterns, or HUYGEN'S wavelets Huygen's principle states... CORRECT ANSWERS: that a large active element may be thought of as millions of tiny, distinct sound sources. 32 Where does destructive interference occur? CORRECT ANSWERS: in the areas where the sound beam is absent What does resolution refer to? CORRECT ANSWERS: accuracy in imaging Lateral resolution distinctly identifies two structures that are very close together when they are _________ to the sound beam. CORRECT ANSWERS: perpendicular What is lateral resolution determined by? CORRECT ANSWERS: the width of the sound beam (narrower beams have better resolution) Synonyms to lateral resolution are: CORRECT ANSWERS: angular, transverse, azimuthal resolution (LATA) Where is lateral resolution best? CORRECT ANSWERS: at the focus where the beam is narrowest. lateral resolution (mm) = CORRECT ANSWERS: beam diameter (mm) Which type of resolution is superior in clinical imaging systems: lateral resolution or axial resolution? CORRECT ANSWERS: Axial resolution because ultrasound pulses are shorter than they are wide. Higher frequencies improve both axial and lateral resolutions because... CORRECT ANSWERS: axial: the shorter pulses associated with high frequency sound lateral: in the far field, high frequency pulses diverge less than low frequency ones. (high frequency sound beams are narrower than low frequency beams) How does focusing improve lateral resolution? CORRECT ANSWERS: by concentrating the sound energy into a narrower beam What are the three methods of focusing? CORRECT ANSWERS: external focusing - with a lens internal focusing - with a curved active element phased array focusing - with the electronics of the ultrasound system Internal and External focusing may be used with... CORRECT ANSWERS: single element transducers Both external and internal focusing are considered _____. CORRECT ANSWERS: fixed (conventional or mechanical) focal depth and the extent of focusing cannot be changed What does external focusing use? CORRECT ANSWERS: a lens What does internal focusing use? CORRECT ANSWERS: a curved piezoelectric crystal that concentrates the sound energy into a narrower beam 35 In M-mode, what does the X-axis display? CORRECT ANSWERS: time With B-mode Which axis is related to the strength of the reflection? CORRECT ANSWERS: the z-axis How does an ultrasound system create high quality, two-dimensional images? CORRECT ANSWERS: Two characteristics of sound that make it difficult to create two-dimensional images are: sound travels only in a straight line, and sound beams must be narrow to optimize lateral resolution. The use of multiple pulses to create a two-dimensional image overcomes both of these difficulties. In a mechanical transducer, the PZT crystal is _______________ to create the image. CORRECT ANSWERS: physically moved Mechanical transducer image shape: CORRECT ANSWERS: fan or sector-shaped Mechanical transducers have a _________ focal depth. CORRECT ANSWERS: fixed When there is any damage done to the crystal in a mechanical transducer, CORRECT ANSWERS: the entire image is lost Array transducers are comprised of... CORRECT ANSWERS: a single slab of PZT cut into a collection of separate pieces called elements. Each active element is connected by a wire to its own electronic circuitry int he ultrasound system. The linear phased array has ___ moving parts. And the beam is steered and focused using an electrical techniques called _________. CORRECT ANSWERS: no, phasing What is the image shape created by a phased array? CORRECT ANSWERS: fan or sector- shaped Elements of a phased array are what shape? CORRECT ANSWERS: rectangular and narrow Sound beams are focused ___________ with linear phased array transducers. CORRECT ANSWERS: electronically Advantage of phased array systems is: CORRECT ANSWERS: the availability of electronically controlled, adjustable focusing, which allows the sonographer to match the beam's characteristics to the clinical circumstances. Damage to one of the elements of a phased array transducer results in... CORRECT ANSWERS: inconsistent or erratic beam steering and focusing. 36 How many elements in a phased array probe are excited to create a single sound pulse? CORRECT ANSWERS: All the active elements in a linear phased array probe are fired to create each sound beam. What is the beam former? CORRECT ANSWERS: the electronics within the ultrasound system that create the voltages to the transducer element When the spike line is straight, an ____________ is created. CORRECT ANSWERS: unfocused sound beam How does the pattern of electrical spikes from the beam former focus the sound beam during transmission? CORRECT ANSWERS: When the outer crystals are excited earlier than the inner crystals, the curved pattern creates a focused sound beam. This means the beam will be directed straight ahead. Brightness of the display is affected by? CORRECT ANSWERS: Receiver amplification (gain) Acoustic speckle is an artifact produced by what? CORRECT ANSWERS: interference of tiny acoustic wavelets Side lobe artifact is a result of what condition? CORRECT ANSWERS: Acoustic energy radiating in a direction different than the main axis of the beam