Ultrasound Physics Test 1 Practice

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• For a linear array with aperture D, the near-field distance N increases with D^2; which of the following statements is true?
• Which processes contribute to attenuation?
• Which statement about axial resolution is true?
• How does transducer frequency affect resolution and penetration?
• Which statement best describes the function of time gain compensation in ultrasonography?
• How does attenuation in bone compare to soft tissue for the same frequency?
• What does M-mode show?
• Which statement best describes the constraint on increasing PRF in practice?
• Which statement about intensity ranges is true?
• Which unit is used for intensity?
• Which statement correctly describes the relation between density and propagation speed?
• For a linear array with aperture D and wavelength λ, which expression approximates the near-field distance N?
• What is Fraunhofer zone also known as, and what region does it describe?
• Name a technique to reduce speckle in ultrasound images?
• How does depth affect dynamic range and SNR in ultrasound imaging?
• How does backing (damping) material influence pulse duration and bandwidth?
• Spatial pulse length SPL is defined as n × λ. If the pulse contains 6 cycles and the wavelength is 0.3 mm, what is the SPL?
• What is the definition of intensity in ultrasound physics?
• What does SPPA stand for?
• What is the definition of period in ultrasound wave terminology?
• What is the velocity of sound in human soft tissue at 37°C (approximately)?
• If the transducer frequency doubles from 5 MHz to 10 MHz while other parameters unchanged, what happens to the Doppler frequency shift for the same v and c?
• The typical speed of sound in bone is approximately:
• What is dynamic range in ultrasound imaging, and how does it affect image contrast?
• Which statement distinguishes Color Doppler from Power Doppler?
• SPL is inversely proportional to which variable?
• What is the principle of tissue harmonic imaging and why does it improve resolution and reduce near-field artifacts?
• Tissue harmonic imaging helps reduce near-field clutter and improve angular resolution by which mechanism?
• Why is coupling gel used in ultrasound and what properties should it have?
• What is the wavelength at 0.5 MHz given a speed of sound of 1540 m/s?
• How is the duty factor defined?
• What is spatial-peak temporal-average intensity (SPTA) and why is it important?
• What effect does increasing duty factor have on energy deposition and heating risk?
• What do TI and MI indicate in ultrasound safety?
• Which of the following best describes acoustic impedance?
• What distance does sound cover in one microsecond if its speed is 1.54 mm/µs?
• What is the definition of period in wave terminology?
• Which arrangement correctly classifies 16 kHz and 20 kHz frequencies?
• For a 3.5 MHz transducer in tissue (c ≈ 1540 m/s) with a single-cycle pulse, what is the approximate axial resolution?
• How does transducer bandwidth relate to axial resolution and damping?
• Name two common strategies to mitigate Doppler aliasing in PW Doppler.
• The AR formula AR ≈ (n × c) / (2f) shows AR is directly proportional to which variables?
• SPL is defined as the product of the number of cycles in the pulse and which parameter?
• Which expression correctly gives the reflection coefficient magnitude between two media with impedances Z1 and Z2?
• What is the wavelength for a 1 MHz ultrasound wave?
• If amplitude is doubled, by what factor does power change?
• List two imaging advantages of tissue harmonic imaging compared to fundamental frequency imaging.
• If frequency decreases, the wavelength:
• Attenuation is determined by which factors?
• Define the Q factor and its relation to bandwidth.
• What is refraction in ultrasound and how can it create artifacts?
• What type of waves are ultrasound in tissue?
• What are the common units for attenuation in ultrasound?
• Which imaging mode provides velocity and direction information?
• Pulse duration is defined as what?
• In sector-based imaging, what happens to the number of scan lines when sector width increases?
• In a medium where the speed of sound is 1540 m/s, what is the wavelength at 2 MHz?
• What is the fundamental relationship between speed, frequency, and wavelength in ultrasound?
• At normal incidence, is the reflection strong or weak when the incident medium impedance is 1.5 MRayl and the second medium impedance is 1.6 MRayl?
• What is the commonly cited average speed of sound in soft tissue in millimeters per microsecond?
• What is the duty factor in ultrasound?
• What is the general principle behind 3D ultrasound imaging?
• Lateral resolution is primarily determined by which beam property across the scan plane, and can be improved by focusing and higher frequency?
• Which range is audible to humans?
• Which statement best describes the units used in the wavelength formula for ultrasound?
• How long is the round-trip travel time to a reflector 20 cm deep in tissue?
• Lateral resolution is improved by focusing and higher frequency; it is determined by which beam property?
• Which tissue feature typically produces Rayleigh scattering in ultrasound imaging?
• What is a consequence of impedance mismatch between two media?
• Which tissue property leads to posterior enhancement behind a structure?
• Which statement best differentiates A-mode from B-mode imaging and includes a typical clinical application for each?
• What technique enables focusing at multiple depths and across the beam, and how does it affect image quality?
• For transcranial Doppler imaging requiring deep penetration through the skull, which frequency range is typically used and why?
• If the speeds of two media are identical, which statement is true?
• What are the units of Spatial Pulse Length as given?
• Which Doppler modality displays velocity information over a region rather than a single depth?
• What is a consequence of using a lower-frequency transducer for deep tissue imaging?
• Which factor causes near-field length to scale with the square of the transducer diameter, assuming wavelength is constant?
• Density is defined as what?
• Which expression correctly defines acoustic impedance?
• Which method can help reduce aliasing when depth resolution is not required?
• To reduce aliasing in Doppler ultrasound, which strategy increases the pulsed repetition frequency (PRF)?
• Why should the Doppler angle be kept near 0 or 180 degrees for velocity measurements?
• What is speckle and why does it occur?
• When switching from 2D to 3D imaging, how is frame rate typically affected?
• In continuous wave Doppler, the duty factor can reach which maximum value?
• What characterizes out-of-phase waves?
• Name the three acoustic variables.
• Which statement describes the relationship among amplitude, power, and intensity?
• Why do cystic structures show posterior enhancement?
• In ultrasound array transducers, what does pitch refer to?
• Why do calcifications or bones create shadowing?
• Which factors affect frame rate in 2D ultrasound?
• A linear array with element spacing of 0.6 λ is likely to exhibit which artifact, and how can you mitigate it?
• What is energy per unit area of sound called?
• SPL is directly proportional to which factor?
• Which range is infrasonic?
• Using an attenuation coefficient of about 0.5 dB/cm/MHz, what is the total attenuation in decibels for 3 cm depth at 2 MHz?
• Axial resolution example: If SPL is 1.2 mm, what is the axial resolution approximately?
• Tissue harmonic imaging improves angular resolution by what mechanism?
• Which frequency ranges classify ultrasound, audible sound, and infrasound?
• Which technique directly reduces Doppler aliasing by increasing the pulse repetition frequency?
• Spectral Doppler aliasing occurs when which condition is met?
• Which acronym means Spatial Peak Pulse Average?
• Which two characteristics affect the speed of sound in a medium?
• Not an acoustic variable?
• Define pulse repetition period (PRP) and its relationship to pulse repetition frequency (PRF) and Doppler measurement.
• Dynamic focusing provides what benefit to image quality?
• Which property does wavelength influence most directly in axial resolution?
• What causes the speckle pattern seen in ultrasound images?
• State the general Doppler equation used in ultrasound for the Doppler shift fD given transmitter frequency f0, target velocity v, incidence angle θ, and tissue speed c.
• Which medium presents a significant obstacle to ultrasound transmission due to impedance mismatch?
• Doppler shift equation for velocity along the beam?
• Which Doppler modality samples velocity along a line at a specific depth?
• What capability may be available when using 3D ultrasound imaging to display a volume in real time?
• Constructive interference occurs when peaks align with peaks and troughs align with troughs. This results in:
• Contrast B-mode imaging with M-mode, including the type of information each provides.
• For pulsed-wave Doppler with PRF = 12 kHz, f0 = 5 MHz, θ = 60°, find the maximum measurable velocity without aliasing (assume c = 1540 m/s).
• Why are phantoms used in ultrasound quality assurance?
• Out-of-phase waves can produce destructive interference. What happens to the resultant amplitude?
• What is the wavelength in soft tissue for an ultrasound transducer operating at 5 MHz if the speed of sound is approximately 1540 m/s?
• What is the typical frequency range for diagnostic ultrasound?
• Higher frequency has what effect on wavelength?
• The typical speed of sound in fat is approximately:
• Why do mirror image artifacts occur and when are they common?
• What is the purpose of the matching layer in an ultrasound transducer?
• How does increasing transmitted frequency f0 affect the Doppler shift magnitude for fixed velocity and angle?
• How does increasing line density affect frame rate in 2D ultrasound?
• Which imaging mode yields a two-dimensional grayscale image representing reflectivity versus depth?
• What causes grating lobes in array transducers and how can they be minimized?
• Which description defines grating lobes and a typical method to reduce them?
• If Z1=1.6 MRayl and Z2=5 MRayl, approximately what percent of the incident energy is reflected at normal incidence?
• Which expression correctly represents the axial resolution AR in terms of the pulse count n, the speed of sound c, and the transmit frequency f?
• Which statement best describes the difference between specular and Rayleigh scattering in tissue, and what is a typical ultrasound example of each?
• If the center frequency is 5 MHz and bandwidth is 2 MHz, the quality factor Q is approximately what value?
• What is the primary difference between color Doppler imaging and spectral Doppler?
• State Snell's law for ultrasound refraction and define the variables.
• In ultrasound safety indices, what is the difference between SPTA and SPPA?
• Which statement correctly describes in-phase waves?
• What is the approximate speed of sound in soft tissue, and what does this value influence in ultrasound imaging?
• In sector-based ultrasound imaging, how does increasing sector width affect frame rate?
• What happens to attenuation as frequency increases?
• Hertz is defined as what?
• Under which conditions does refraction occur?
• What is the wavelength (in millimeters) of a 5 MHz ultrasound wave?
• The fraction of incident ultrasound intensity reflected at an interface with Z1 = 1.60 MRayls and Z2 = 1.70 MRayls is?
• How is amplitude measured?
• Destructive interference occurs when the resultant wave is:
• Which tissue feature typically produces specular scattering in ultrasound imaging?
• With f0 = 5 MHz, c = 1540 m/s, θ = 60°, and target velocity v = 0.5 m/s, what is the Doppler frequency shift fD?
• An echo returns after 130 μs in tissue; what is the depth of the reflector?
• To avoid grating lobe artifacts in a linear array, what is the typical maximum element spacing relative to wavelength?
• Define mechanical index (MI) and describe how it scales with peak negative pressure and frequency.
• What determines lateral resolution in ultrasound imaging, and what is the typical focal-zone value if the beam width is 0.6 mm?
• Which property has the greatest influence on the speed of sound in a medium?
• SPTA stands for?
• How does dynamic focusing affect lateral resolution?
• If two media have identical impedances, what happens to reflections?
• In a medium where velocity is constant, how are wavelength and frequency related?
• Pulse repetition period (PRP) is defined as what?
• In Doppler imaging, which modality provides high sensitivity to low-velocity flow but does not show directional information?
• What is the speed of sound in soft tissue?
• What happens to bandwidth when damping is increased?
• If the speed of sound in tissue is 1540 m/s and the frequency doubles, what happens to the wavelength?
• When two waves are in-phase at a point, what is typically observed in the resultant wave?
• In spectral Doppler, flow toward the transducer is indicated by which velocity sign relative to the baseline?
• What is the effect of using a smaller pitch in an array?
• What is the formula for pulse duration?
• What is one trade-off of using a higher transmitted frequency?
• What is the purpose of damping in a transducer?
• Axial resolution is approximately SPL/2. Which factor primarily determines axial resolution?
• Under what condition can total internal reflection occur in ultrasound, and what would be observed at the interface?
• How does the incidence angle θ affect the Doppler shift in the Doppler equation?
• If frequency doubles, the wavelength will:
• Duty factor is defined as the ratio of what?
• To improve penetration, which choice would you make regarding transmitted frequency?
• Which statement about power in ultrasound is true?
• Approximately how long is the round-trip travel time for 1 cm depth in soft tissue?
• Temporal intensities order largest to smallest according to the provided ordering?
• Which expression correctly defines the reflection coefficient at normal incidence between two media with impedances Z1 and Z2?
• Period is inversely related to which property?
• What is peak pressure or height of a wave known as?
• What is the effect of constructive interference on the amplitude of the resultant wave?
• Power Doppler compared to Color Doppler: which statement is true?
• What is the commonly used average speed of sound in soft tissue for diagnostic ultrasound?
• Why does deeper ultrasound require higher transmit power or longer acquisition?
• Distinguish side lobes from speckle and explain their impact on image quality.
• In color Doppler displays, which color convention is commonly used to represent flow toward the transducer, and how is direction encoded in spectral Doppler?
• Spatial Pulse Length is determined by which factors?
• How does frame rate relate to depth and number of scan lines per frame? If PRF = 15 kHz and 120 scan lines are used per frame, what is the frame rate?
• Compare pulsed-wave (PW) and continuous-wave (CW) Doppler in terms of depth specificity and velocity measurement capability.
• In the impedance reflection calculation, what unit is used for acoustic impedance?
• How does increasing the number of cycles in a pulse affect SPL and axial resolution?
• In ultrasound imaging, which parameter primarily determines depth calibration and time-of-flight calculations in soft tissue?
• Intensity is determined by what?
• To improve axial resolution, which statement is most accurate?
• In ultrasound imaging, which mode is best for tracking motion along a single line, such as cardiac walls?
• Which statement accurately contrasts color Doppler and power Doppler in terms of velocity sensitivity and directional information?
• What is the Fresnel (near) zone in ultrasound?
• Using α ≈ 0.5 dB/(cm·MHz), what is the approximate attenuation in dB for 6 cm depth at 3 MHz?
• What is the typical power range for ultrasound beams?
• Which of the following pairs correctly match the acoustic variable with its unit?
• What does B-mode imaging generate?
• What is the difference in range resolution between pulsed wave and continuous wave Doppler?
• Which expression correctly defines the wavelength λ given the speed of sound c and frequency f?
• A Doppler sample volume defines the depth interval from which signals are sampled. How does increasing the sample volume length affect velocity measurement accuracy?
• If the number of cycles is fixed and the ultrasound frequency increases, pulse duration
• Pulse duration PD equals n × T, with T = 1/f. If a transducer emits 4 cycles at a center frequency of 3 MHz, what is the pulse duration?
• What type of wave is sound?
• Speed and wavelength are related how in a given medium?
• Why are curved array transducers commonly used for abdominal imaging?
• Describe the trade-off between transducer frequency, penetration depth, and axial resolution.
• Give typical speeds of sound for fat and bone and explain how these differences affect propagation.
• Which ultrasound display is a one-dimensional amplitude versus depth plot commonly used in ophthalmology?
• If a 5.0 MHz transducer operates in soft tissue (c ≈ 1540 m/s), what is the wavelength of the ultrasound wave in tissue?
• If an echo is received after 51.9 μs in tissue with c ≈ 1540 m/s, what is the reflector depth?
• How does adjusting the focal depth influence the lateral resolution across the image?
• What is ultrasound speckle, and why can it sometimes be used advantageously in tissue characterization?
• With a pulse duration of 6 μs and PRF of 1 kHz, what is the duty cycle?
• What is the main trade-off when moving from 2D to 3D/4D imaging regarding sampling and frame rate?
• Frame persistence (temporal averaging) affects speckle and motion perception how?
• When depth resolution is not required, which Doppler modality can be used to avoid aliasing entirely?
• Which statement about the axial resolution formula AR ≈ (n × c) / (2f) is true?
• Which equation relates speed, frequency, and wavelength?
• Which combination represents Spatial Peak, Temporal Peak?
• If two waves of equal amplitude are perfectly out of phase, the resultant amplitude is:
• Which ultrasound display shows amplitude as a function of depth in one dimension (often used in ophthalmology)?
• Define thermal index (TI) and its clinical purpose.
• If peak negative pressure remains constant but frequency is increased, how does the mechanical index change?
• What is a phased-array transducer and how does it steer the beam?
• What type of wave is sound?
• If power increases, what happens to amplitude and intensity?
• Near field length formula for a circular-aperture transducer with diameter D and wavelength λ?
• Using the soft tissue rule (1.54 mm divided by frequency in MHz), what is the wavelength at 2 MHz?
• Which statement describes a characteristic of A-mode imaging?
• Wavelength is true about what statement?
• In tissue harmonic imaging, which signal is detected and at what frequency relative to the transmitted frequency?