p.4
Introduction to Ultrasound in Diagnostic Imaging
What factors influence the choice of frequency in ultrasound imaging?
A trade-off between spatial resolution and penetration depth.
p.44
Biological Effects of Ultrasound
What is generally assumed about ultrasound in medical imaging?
It is the safest medical imaging modality.
p.20
Ultrasonic Properties of Biological Tissue
What is the mechanism similar to scattering in ultrasonic properties?
Specular (mirror-like) reflection.
p.24
Ultrasonic Transduction and Piezoelectric Devices
What is the microscopic mechanism of piezoelectricity?
It can be understood as a collection of randomly oriented electric dipoles.
p.7
Ultrasonic Plane Waves
What are the two main components of an acoustic wave?
Compressions and rarefactions (expansions).
p.32
Ultrasonic Transduction and Piezoelectric Devices
What is the formula for lateral resolution in ultrasonic transduction?
Lateral resolution is obtained by setting the sinc function = 0 in L F LR λ = ( ) ( F Lx x U λ sinc).
p.2
Introduction to Ultrasound in Diagnostic Imaging
What is the focus of Chapter 12 in the Diagnostic Radiology Physics handbook?
Ultrasound and its various aspects.
p.30
Ultrasonic Transduction and Piezoelectric Devices
How is the lateral beam pattern computed in ultrasound imaging?
By ignoring the η and y terms.
p.31
Ultrasonic Transduction and Piezoelectric Devices
What is pulse-echo imaging typically performed with?
The same focused aperture for transmission and reception.
p.24
Ultrasonic Transduction and Piezoelectric Devices
What happens when an applied force deforms a piezoelectric crystal?
It results in a rearrangement of the dipoles that induces a net charge across the crystal.
p.39
Doppler Physics and Its Applications
What happens to the signal received from the range gate when scatterers are moving in Pulsed-Wave Doppler?
The signal changes with each subsequent pulse, creating a staircase signal.
p.37
Doppler Physics and Its Applications
What additional output do Doppler systems provide besides audio?
The time-frequency spectrum of the demodulated signal.
p.14
Ultrasonic Plane Waves
What is the transmission coefficient for plane waves in fluid media at normal incidence?
It is given by the formula involving the acoustic impedances and amplitudes of the waves.
p.39
Doppler Physics and Its Applications
What operation is used to construct the staircase signal in Pulsed-Wave Doppler?
Sample-and-hold operation.
p.32
Ultrasonic Transduction and Piezoelectric Devices
What does the Rayleigh resolution criterion define?
It defines the resolution as the distance from the peak of the beam to the first zero of the beam.
p.26
Ultrasonic Transduction and Piezoelectric Devices
What improves the bandwidth and sensitivity of an ultrasonic transducer?
Sandwiching the piezoelectric crystal between a backing layer and a matching layer.
p.42
Doppler Physics and Its Applications
What is the relationship between PRF and the depth of the range gate?
Maximum PRF is given by c / (2z), where z is the depth.
p.28
Ultrasonic Transduction and Piezoelectric Devices
What theory is applied to analyze the beam pattern in ultrasonic transduction?
Scalar diffraction theory.
p.24
Ultrasonic Transduction and Piezoelectric Devices
What occurs when a voltage difference is applied across a piezoelectric crystal?
It changes the arrangement of the dipoles, producing a bulk deformation of the crystal.
p.7
Ultrasonic Plane Waves
How does an acoustic wave propagate?
Via transfer of momentum among incremental volumes of the medium.
p.25
Ultrasonic Transduction and Piezoelectric Devices
What is the conventional material used for fabricating transducers in diagnostic imaging?
Ferroelectric ceramic lead zirconate titanate (PZT).
p.13
Ultrasonic Plane Waves
What is the relationship between the amplitudes of incident and reflected waves in ultrasound?
They are related by the reflection coefficient, R.
p.14
Ultrasonic Plane Waves
What happens to the angles of incidence and transmission at normal incidence?
The angles are equal, θ_i = θ_t = 0.
p.2
Ultrasonic Plane Waves
What are Ultrasonic Plane Waves?
A type of wave used in ultrasound imaging.
p.6
Technological Advances in Ultrasound Applications
What are some medical applications of ultrasound?
Cardiac and vascular imaging, imaging of abdominal organs, and in utero imaging of the developing fetus.
p.28
Ultrasonic Transduction and Piezoelectric Devices
What principle is used to analyze the beam pattern produced by an ultrasound transducer?
Huygens-Fresnel principle.
p.49
Biological Effects of Ultrasound
What does the mechanical index (MI) measure?
The relative risk of inducing cavitation.
p.43
Doppler Physics and Its Applications
What is the purpose of high-velocity Doppler mode in pulsed-wave Doppler?
To use a higher PRF than the range-gate depth would ordinarily allow, increasing |v max|.
p.4
Ultrasonic Properties of Biological Tissue
What physical processes influence the information in an ultrasonic image?
Propagation, reflection, and attenuation of ultrasound waves in tissue.
p.20
Ultrasonic Properties of Biological Tissue
When does scattering occur in ultrasonic waves?
When the wave encounters a variation in the acoustic impedance of the medium.
p.28
Ultrasonic Transduction and Piezoelectric Devices
How can an aperture be described in the context of ultrasound transduction?
As a collection of point sources.
p.33
Doppler Physics and Its Applications
What is Doppler ultrasound used for?
To image moving blood and estimate blood velocity.
p.35
Doppler Physics and Its Applications
What type of wave does the transmitter emit in Continuous-Wave Doppler?
A continuous sinusoidal wave in the form cos(ω₀t).
p.47
Acoustic Output Metrics in Ultrasound
What does I SPTA stand for in ultrasound exposure measurement?
Spatial Peak Temporal Average Intensity.
p.26
Ultrasonic Transduction and Piezoelectric Devices
What is the purpose of the backing layer in a transducer?
To absorb ultrasound radiated from the back face of the crystal and dampen reverberations within the crystal.
p.12
Ultrasonic Plane Waves
What occurs when c1 < c2 in terms of wave transmission?
The wave is bent away from the normal.
p.7
Ultrasonic Plane Waves
What is an acoustic wave?
A traveling pressure disturbance that produces alternating compressions and rarefactions of the propagation medium.
p.46
Biological Effects of Ultrasound
What is cavitation in the context of ultrasound?
Oscillation in the volume of a gas bubble in response to pressure fluctuations produced by an incident ultrasound wave.
p.52
Patient Safety Considerations in Ultrasound Imaging
What increases the risk of inertial cavitation during ultrasound imaging?
The presence of excess gas, particularly significant volumes of gas bubbles.
p.38
Doppler Physics and Its Applications
How does Pulsed-Wave Doppler address the limitations of CW Doppler?
By transmitting a sequence of short pulses instead of a continuous sine tone.
p.28
Ultrasonic Transduction and Piezoelectric Devices
What is produced by the superposition of spherical wavelets in ultrasound transduction?
The field produced by the aperture.
p.5
Technological Advances in Ultrasound Applications
What capability allows ultrasound to visualize dynamic processes?
The ability to produce real-time images of blood flow and moving structures.
p.14
Ultrasonic Plane Waves
What is the relationship between the amplitudes of incident and transmitted waves in ultrasonic plane waves?
They are related by the transmission coefficient, T.
p.6
Technological Advances in Ultrasound Applications
What are some additional applications of ultrasound mentioned?
Cancer imaging, musculoskeletal imaging, and ophthalmology.
p.44
Biological Effects of Ultrasound
What happens when a high-intensity ultrasound pulse is transmitted through tissue?
A substantial amount of energy can be transferred to the tissue, increasing the risk of adverse effects.
p.49
Acoustic Output Metrics in Ultrasound
What is the formula for calculating the mechanical index (MI)?
MI = p_max / p_max(−) after correction for attenuation.
p.12
Ultrasonic Plane Waves
What does Snell's law describe in the context of ultrasonic plane waves?
The relationship between the angles of incidence and transmission when a wave crosses an interface between two media.
p.37
Doppler Physics and Its Applications
What does the pixel gray scale in a Doppler spectrum represent?
The magnitude of the short-time Fourier transform of the Doppler signal.
p.8
Ultrasonic Plane Waves
What does the pressure plane wave p(x, t) propagate through?
A homogeneous, non-attenuating fluid medium.
p.15
Ultrasonic Properties of Biological Tissue
What are the main causes of attenuation of ultrasonic waves in a medium?
Specular reflections, divergence, scattering from inhomogeneities, and thermal absorption.
p.1
Bibliography and References in Diagnostic Radiology Physics
Who prepared the slide set for the IAEA publication?
E. Okuno from the Institute of Physics of S. Paulo University.
p.29
Ultrasonic Transduction and Piezoelectric Devices
What integral describes the resulting beam in the far field of an unfocused aperture?
The Fraunhofer diffraction integral.
p.46
Biological Effects of Ultrasound
What type of cavitation does low-intensity ultrasound typically produce?
Harmless stable cavitation.
p.22
Ultrasonic Properties of Biological Tissue
What effect does nonlinearity have on an initially sinusoidal wave?
It distorts it into a sawtooth pattern.
p.25
Ultrasonic Transduction and Piezoelectric Devices
What is a key advantage of using PZT in transducers?
It provides a relatively high electrical-to-mechanical coupling efficiency at low cost.
p.3
Introduction to Ultrasound in Diagnostic Imaging
What is the frequency range of ultrasound?
Greater than 20 kHz, which is the maximum frequency audible to humans.
p.6
Technological Advances in Ultrasound Applications
How is ultrasound technology evolving?
Ongoing technological improvements continue to expand its use for various applications.
p.31
Ultrasonic Transduction and Piezoelectric Devices
What does the lateral point-spread function (PSF) depend on?
The square of the sinc function.
p.38
Doppler Physics and Its Applications
What is the primary shortcoming of Continuous Wave (CW) Doppler?
The lack of spatial resolution due to the large area of overlap between the transmitter and receiver beams.
p.42
Doppler Physics and Its Applications
What limits the pulse-repetition frequency (PRF) in Pulsed-Wave Doppler?
The depth of the range gate.
p.44
Biological Effects of Ultrasound
How can biological effects of ultrasound be utilized beneficially?
By therapeutic ultrasound devices.
p.20
Ultrasonic Properties of Biological Tissue
What size features cause scattering in ultrasonic waves?
Features with dimensions similar to or smaller than the wavelength.
p.43
Doppler Physics and Its Applications
What happens in high-velocity mode regarding pulse transmission?
The second (and perhaps third) pulse is transmitted before echoes from the first pulse are received.
p.41
Doppler Physics and Its Applications
What does the sample-and-hold step limit in Doppler measurements?
The maximum Doppler frequency that can be measured without aliasing.
p.49
Biological Effects of Ultrasound
Why is the term p_max(−) used in the MI formula?
It reflects that inertial cavitation is triggered by the overexpansion of a gas bubble.
p.20
Ultrasonic Properties of Biological Tissue
How do scattered echoes compare to specular reflections?
Scattered echoes are omnidirectional and significantly weaker than specular reflections.
p.32
Ultrasonic Transduction and Piezoelectric Devices
What is the typical range of the f-number for ultrasound imaging systems?
Typically between 2 and at most 6.
p.41
Doppler Physics and Its Applications
What is the effective sampling frequency in Doppler measurements?
The pulse-repetition frequency (PRF) of the transmitted pulses.
p.14
Ultrasonic Plane Waves
How are the acoustic impedances Z related to the transmission and reflection coefficients?
They are used in the formulas to calculate the coefficients for incident and transmitted waves.
p.9
Ultrasonic Plane Waves
What does the equation of continuity represent?
A mass balance for an incremental volume of the medium.
p.30
Ultrasonic Transduction and Piezoelectric Devices
What does the sinc function represent in the context of ultrasound imaging?
The Fourier transform of the rect function.
p.45
Biological Effects of Ultrasound
What can occur in pulsed Doppler techniques due to multiple pulses being transmitted?
Local heating can occur at the focus.
p.4
Ultrasonic Properties of Biological Tissue
How do higher frequency waves affect ultrasound imaging?
They can be focused more tightly but are attenuated more rapidly by tissue.
p.35
Doppler Physics and Its Applications
What does the measured Doppler spectrum include?
Contributions from all moving scatterers within the area of intersection of the two beams.
p.29
Ultrasonic Transduction and Piezoelectric Devices
What does U(ξ, η) represent?
The field in the aperture plane.
p.46
Biological Effects of Ultrasound
What do most tissues contain that can lead to cavitation?
Small volumes of gas that can coalesce to form cavitation nuclei.
p.7
Ultrasonic Plane Waves
What happens to each incremental volume of the medium in an acoustic wave?
It undergoes small oscillations about its original position but does not travel with the pressure disturbance.
p.30
Ultrasonic Transduction and Piezoelectric Devices
What type of aperture do ultrasound imaging systems typically employ?
A focused rectangular aperture.
p.37
Doppler Physics and Its Applications
What does a pixel in a Doppler spectrum indicate?
The proportion of red blood cells moving at a particular velocity at a specific time.
p.33
Doppler Physics and Its Applications
Who studied the Doppler effect and in what year?
Christian Doppler in 1842.
p.35
Doppler Physics and Its Applications
What form do the received echoes take if the reflectors are moving?
The form cos([ω₀ + ω_D]t), where ω_D = 2πf_D.
p.43
Doppler Physics and Its Applications
What does the Doppler signal consist of in high-velocity mode?
A superposition of echoes from within the range gate due to the first pulse and echoes from shallower depths due to subsequent pulses.
p.37
Doppler Physics and Its Applications
What is the purpose of the spectral display in Doppler systems?
To effectively present the pulsatile characteristics of intra-cardiac and vascular flow.
p.42
Doppler Physics and Its Applications
In the context of Pulsed-Wave Doppler, what does the variable 'z' represent?
The depth at which the range gate is positioned.
p.40
Doppler Physics and Its Applications
What does the vertical dotted line represent in the Doppler signal illustration?
The sample time for obtaining the Doppler signal.
p.29
Ultrasonic Transduction and Piezoelectric Devices
What does the equation involving η, ξ, and λ represent?
It involves a two-dimensional spatial Fourier transformation with effective spatial frequencies.
p.34
Doppler Physics and Its Applications
What is the Doppler equation used to calculate Doppler frequency?
fD = (c / |v|) * fo * cos(θD)
p.30
Ultrasonic Transduction and Piezoelectric Devices
What dimensions are typically treated as separable in medical ultrasound imaging?
Lateral (x) dimension within the image plane and elevation (y) dimension perpendicular to the image plane.
p.46
Biological Effects of Ultrasound
When is cavitation most likely to occur in vivo?
When microbubble contrast agents are employed or if the lungs are exposed to ultrasound.
p.36
Doppler Physics and Its Applications
What does the Doppler equation indicate about MHz transmit frequencies used for diagnostic ultrasound?
They will produce Doppler frequencies of at most a few kHz, which is within the range of audible frequencies.
p.43
Doppler Physics and Its Applications
What formula is used to calculate maximum velocity in high-velocity Doppler mode?
v max = (D o / PRF) * (c / 4 * cos θ).
p.49
Acoustic Output Metrics in Ultrasound
What does p_max represent in the MI formula?
The peak rarefactional pressure.
p.39
Doppler Physics and Its Applications
What is done to the output of the sample-and-hold operation in Pulsed-Wave Doppler?
It is low-pass filtered to obtain a smoothly varying Doppler signal.
p.32
Ultrasonic Transduction and Piezoelectric Devices
What is the f-number of a transducer?
F / L is called the f-number of the transducer.
p.45
Biological Effects of Ultrasound
What is the effect of a single pulse at diagnostic imaging intensities on tissue temperature?
The local temperature rise is small.
p.52
Patient Safety Considerations in Ultrasound Imaging
When should caution be exercised when using contrast agents?
In echocardiography of patients with pulmonary hypertension or other unstable cardiopulmonary conditions.
p.39
Doppler Physics and Its Applications
What is the relationship between the smoothed signal frequency and the Doppler frequency?
The frequency of the smoothed signal is equal to the Doppler frequency.
p.47
Acoustic Output Metrics in Ultrasound
How is ultrasound exposure traditionally quantified?
By measuring the spatial peak temporal average intensity (I SPTA).
p.38
Doppler Physics and Its Applications
What happens as the echo from each successive transmission is received in Pulsed-Wave Doppler?
A single sample at the expected arrival time of echoes from the range gate is acquired and held until the next pulse echo is received.
p.2
Ultrasonic Transduction and Piezoelectric Devices
What is Ultrasonic Transduction?
The process of converting electrical energy into ultrasound waves and vice versa.
p.25
Ultrasonic Transduction and Piezoelectric Devices
What are many modern transducers made of?
Composites of PZT and a non-piezoelectric polymer.
p.15
Ultrasonic Plane Waves
What is the formula for the amplitude of a wave in the presence of attenuation?
P(x, t) = P₀ e^(-αx) cos(ωt - kx), where α is the attenuation coefficient.
p.16
Ultrasonic Properties of Biological Tissue
How is the attenuation coefficient α related to frequency in soft tissues?
α is proportional to f^m, where 1 < m < 2.
p.29
Ultrasonic Transduction and Piezoelectric Devices
What is the relationship between U(y, x, z) and the spatial frequencies kx and ky?
They are related through the two-dimensional spatial Fourier transformation.
p.35
Doppler Physics and Its Applications
What does a CW Doppler transducer consist of?
Two adjacent piezoelectric elements angled slightly toward one another.
p.47
Biological Effects of Ultrasound
Why does repeated insonation increase the risk of thermal bioeffects?
Because heat may accumulate more quickly than it can be dissipated by blood flow.
p.11
Ultrasonic Plane Waves
What are the angles involved at a planar interface in ultrasound?
Angle of incidence (θᵢ), angle of reflection (θᵣ), and angle of transmission (θᵗ).
p.53
Bibliography and References in Diagnostic Radiology Physics
Which book discusses Doppler ultrasound physics and instrumentation?
'Doppler Ultrasound: Physics, Instrumentation and Signal Processing' by D.H. Evans and W.N. McDicken.
p.11
Ultrasonic Properties of Biological Tissue
How is acoustic impedance (Z) defined for a plane wave?
Z = ρ₀ * c, where ρ₀ is the undisturbed mass density of the medium and c is the speed of sound.
p.12
Ultrasonic Plane Waves
What happens to a wave transmitted into a second medium when c1 > c2?
The wave is bent toward the normal.
p.21
Ultrasonic Properties of Biological Tissue
What happens near the focus of beams used for diagnostic imaging?
Density variations produced by the wave become significant.
p.10
Ultrasonic Plane Waves
How is the intensity of an ultrasound wave defined?
As the average power per unit cross-sectional area.
p.42
Doppler Physics and Its Applications
What does 'c' represent in the formula for maximum PRF?
The speed of sound in the medium.
p.44
Biological Effects of Ultrasound
Why are biological effects of ultrasound undesirable during diagnostic imaging?
Because they can pose risks to the patient.
p.33
Doppler Physics and Its Applications
What happens to the frequency of waves in the direction of motion according to the Doppler effect?
The frequency is compressed.
p.35
Doppler Physics and Its Applications
How is a Doppler signal recovered from the received signal?
Via frequency demodulation of the received signal.
p.32
Ultrasonic Transduction and Piezoelectric Devices
What is the general range for lateral resolution in ultrasound?
Generally in the 1-2 mm range.
p.52
Patient Safety Considerations in Ultrasound Imaging
Why might low-MI scanning not always be feasible?
Some contrast-enhanced imaging protocols require disrupting microbubbles at MI > 1 to obtain diagnostic information.
p.54
Bibliography and References in Diagnostic Radiology Physics
Which book focuses on diagnostic ultrasound principles and instruments?
Diagnostic Ultrasound: Principles and Instruments, 7th edn. by Kremkau.
p.45
Biological Effects of Ultrasound
How is thermal absorption used in therapeutic ultrasound?
For hyperthermia treatment of cancerous tumors by transmitting high-intensity pulses.
p.53
Bibliography and References in Diagnostic Radiology Physics
What is the focus of 'Foundations of Biomedical Ultrasound'?
Biomedical ultrasound principles.
p.9
Ultrasonic Plane Waves
What does the wave number (k) represent?
k = 2π/λ, where λ is the wavelength.
p.11
Ultrasonic Properties of Biological Tissue
What does ρ₀ represent in the context of acoustic impedance?
The undisturbed mass density of the medium.
p.11
Ultrasonic Properties of Biological Tissue
What is κ in the context of ultrasound?
The compressibility of the medium.
p.40
Doppler Physics and Its Applications
What operation is described in the context of Pulsed-Wave Doppler?
Sample-and-hold operation.
p.44
Biological Effects of Ultrasound
What are the two most important mechanisms for biological effects of ultrasound?
Thermal absorption and cavitation.
p.8
Ultrasonic Plane Waves
Which equations are used to formulate a pressure plane wave?
Euler’s equation and the equation of continuity.
p.9
Ultrasonic Plane Waves
What is Euler's equation derived from?
Newton’s second law of motion.
p.16
Ultrasonic Plane Waves
What is the equation for a monochromatic plane wave?
P(t, x) = p₀ cos(kx - ωt), where k is the wave number and ω is the angular frequency.
p.10
Ultrasonic Plane Waves
What is the formula for intensity in terms of pressure amplitude and medium density?
I = P^2 / (2 * ρ * c), where P is pressure amplitude, ρ is undisturbed mass density, and c is the speed of sound.
p.22
Ultrasonic Properties of Biological Tissue
What happens to the compressive segments of a wave in nonlinear propagation?
They catch up to the rarefactional segments ahead of them.
p.21
Ultrasonic Properties of Biological Tissue
What causes nonlinearity in acoustic propagation?
The pressure wave alters the density of the medium.
p.35
Doppler Physics and Its Applications
What are the simplest Doppler systems typically used?
Continuous-wave (CW) Doppler systems, usually small hand-held devices.
p.13
Ultrasonic Plane Waves
What does a negative value of the reflection coefficient (R) imply?
That the reflected wave is inverted with respect to the incident wave.
p.15
Ultrasonic Plane Waves
What does the variable ω represent in the wave equation?
The radian frequency, calculated as ω = 2πf.
p.27
Ultrasonic Transduction and Piezoelectric Devices
What determines the length of the transmitted pulse in ultrasonic transduction?
The bandwidth of the transducer.
p.13
Ultrasonic Properties of Biological Tissue
What is the formula for acoustic impedance (Z) in plane waves?
Z = ρo * c, where ρo is the density and c is the speed of sound.
p.9
Ultrasonic Plane Waves
What is the formula for the speed of sound in a medium?
c = √(κ/ρ₀), where κ is the bulk modulus and ρ₀ is the density.
p.47
Acoustic Output Metrics in Ultrasound
What is the significance of the focal point in ultrasound exposure?
It is where the transmitted signal is measured at the greatest intensity.
p.48
Acoustic Output Metrics in Ultrasound
What is the significance of the Mechanical Index (MI)?
It reflects the potential for mechanical bioeffects from ultrasound exposure.
p.48
Acoustic Output Metrics in Ultrasound
What additional factor is considered in the tissue thermal model for TI?
The pulse repetition frequency.
p.25
Ultrasonic Transduction and Piezoelectric Devices
What does the acronym PZT stand for?
Lead (Pb), zirconium (Zr), and titanium (Ti).
p.13
Ultrasonic Plane Waves
What does the reflection coefficient (R) indicate in ultrasound?
It indicates the relationship between the incident and reflected wave amplitudes.
p.14
Ultrasonic Plane Waves
What does the reflection coefficient R represent in ultrasonic wave transmission?
It represents the ratio of the amplitude of the reflected wave to the amplitude of the incident wave.
p.2
Ultrasonic Properties of Biological Tissue
What do Ultrasonic Properties of Biological Tissue refer to?
The characteristics of biological tissues that affect ultrasound propagation.
p.46
Biological Effects of Ultrasound
What happens during inertial cavitation?
The rarefractional phase of the pressure wave expands the bubble beyond its maximum stable volume, resulting in a sudden collapse.
p.54
Bibliography and References in Diagnostic Radiology Physics
What is the title of the book by Kinsler et al. on acoustics?
Fundamentals of Acoustics, 4th edn.
p.13
Ultrasonic Plane Waves
How can an ultrasound image be interpreted?
As a map of the relative variations in acoustic impedance in the tissues.
p.33
Doppler Physics and Its Applications
What happens to the frequency of waves in the opposite direction of motion according to the Doppler effect?
The frequency is expanded.
p.12
Ultrasonic Plane Waves
What can refraction lead to in clinical imaging applications?
It can be an important source of artifacts.
p.21
Ultrasonic Properties of Biological Tissue
How does sound speed depend on density in acoustic propagation?
Sound speed depends on density according to the relationship ρκ^1 = c.
p.34
Doppler Physics and Its Applications
What does 'c' represent in the Doppler equation?
The speed of sound in the medium.
p.27
Ultrasonic Transduction and Piezoelectric Devices
What is the formula for axial resolution in ultrasonic transduction?
AR = (2 * λ) / (N * c), where N is the number of cycles and λ is the wavelength.
p.34
Doppler Physics and Its Applications
When is a Doppler system most sensitive to motion?
When the motion is directly toward or away from the transducer (θD = 0 or θD = π).
p.27
Ultrasonic Transduction and Piezoelectric Devices
What type of waveform is typically used in diagnostic ultrasound?
Radio-frequency pulse waveform.
p.17
Ultrasonic Properties of Biological Tissue
How does the sound speed in soft tissues compare to that in water?
It is similar at body temperature.
p.38
Doppler Physics and Its Applications
What is the purpose of the range-gate cursor in Pulsed-Wave Doppler?
To determine the location from which Doppler data will be acquired within a B-mode image.
p.36
Doppler Physics and Its Applications
How do the simplest Continuous-Wave (CW) Doppler devices work?
They direct the demodulated Doppler signal to a speaker for the physician to interpret audibly.
p.40
Doppler Physics and Its Applications
What is illustrated by the ten consecutive echo signals in the Pulsed-Wave Doppler section?
Echo signals received from a scatterer moving toward the transducer.
p.29
Ultrasonic Transduction and Piezoelectric Devices
What is the significance of the Fraunhofer diffraction integral in ultrasonic transduction?
It describes the beam behavior at and beyond the focus of a focused aperture.
p.8
Ultrasonic Properties of Biological Tissue
What does ρ₀ represent in the context of ultrasonic waves?
The undisturbed mass density of the medium.
p.15
Ultrasonic Plane Waves
What does the monochromatic plane wave equation represent?
It describes the behavior of ultrasonic waves in a medium.
p.16
Ultrasonic Properties of Biological Tissue
What does the symbol α represent in the context of ultrasonic plane waves?
The frequency-dependent amplitude attenuation coefficient (in Np/m).
p.11
Ultrasonic Plane Waves
What does an ultrasound image display?
The magnitude (absolute value of amplitude) of ultrasound echoes.
p.38
Doppler Physics and Its Applications
What type of signals are received in Pulsed-Wave Doppler when a scatterer is moving toward the transducer?
Ten consecutive echo signals.
p.9
Ultrasonic Plane Waves
What is the acoustic wave equation obtained from?
Combining Euler's equation and the equation of continuity.
p.41
Doppler Physics and Its Applications
What is the formula for the maximum velocity that can be measured by a pulsed-wave Doppler system?
v max = (c * f D * cos(θ)) / (2 * PRF).
p.33
Doppler Physics and Its Applications
What does the Doppler effect apply to?
Echoes from moving reflectors such as red blood cells and waves radiated from moving sources.
p.22
Ultrasonic Properties of Biological Tissue
What is the physical basis of the tissue harmonic imaging mode?
The transformation from a sinusoidal to a sawtooth wave.
p.41
Doppler Physics and Its Applications
What does the variable 'c' represent in the Doppler equation?
The speed of sound in the medium.
p.54
Bibliography and References in Diagnostic Radiology Physics
Which book provides insights into diagnostic ultrasound imaging?
Diagnostic Ultrasound Imaging: Inside Out by Szabo.
p.9
Ultrasonic Plane Waves
How is the radian frequency (ω) calculated?
ω = 2πf, where f is the frequency.
p.54
Bibliography and References in Diagnostic Radiology Physics
What type of resource is 'Diagnostic Radiology Physics: a Handbook for Teachers and Students'?
A handbook that includes various chapters on diagnostic radiology physics.
p.21
Ultrasonic Properties of Biological Tissue
How does the compressive phase of the wave propagate compared to the rarefactional phase?
The compressive phase propagates at a higher velocity than the rarefactional phase.
p.45
Biological Effects of Ultrasound
How does blood flow affect heat dissipation in B-mode imaging?
Blood flow typically dissipates the heat before the same volume of tissue is insonified again.
p.49
Biological Effects of Ultrasound
How does frequency relate to the likelihood of inertial cavitation?
Inertial cavitation is more likely at lower frequencies, as indicated by the f^(-1/2) term in the MI formula.
p.20
Ultrasonic Properties of Biological Tissue
What causes the speckle texture in ultrasound images?
Constructive and destructive interference of echoes scattered backward from cellular-scale tissue features.
p.47
Acoustic Output Metrics in Ultrasound
Where is the transmitted signal measured for I SPTA?
At the point with greatest intensity within the radiated field, usually the focus of the transducer.
p.26
Ultrasonic Transduction and Piezoelectric Devices
Where is the matching layer bonded in an ultrasonic transducer?
To the front face of the piezoelectric crystal.
p.53
Bibliography and References in Diagnostic Radiology Physics
What is the title of the consensus report by the Bioeffects Committee of the AIUM?
Consensus Report on Potential Bioeffects of Diagnostic Ultrasound: Executive Summary.
p.30
Ultrasonic Transduction and Piezoelectric Devices
What is the significance of the length of the aperture (L) in ultrasound imaging?
It determines the characteristics of the lateral beam pattern.
p.9
Ultrasonic Plane Waves
What does κ represent in the context of the speed of sound?
The bulk modulus of the medium.
p.48
Acoustic Output Metrics in Ultrasound
What does the Thermal Index (TI) represent?
The ratio of the acoustic power output by the scanner to the estimated acoustic power needed to raise the temperature of the tissue by 1 °C.
p.45
Biological Effects of Ultrasound
What is the difference in heating between diagnostic imaging and therapeutic ultrasound?
Therapeutic ultrasound uses high-intensity pulses that produce more rapid heating than those used for diagnostic imaging.
p.16
Ultrasonic Properties of Biological Tissue
What is the primary consequence of frequency-dependent attenuation in ultrasound?
Higher frequency waves are attenuated more rapidly than lower frequency waves, resulting in shallower penetration depths.
p.33
Doppler Physics and Its Applications
What is represented in the schematic of the Doppler effect?
The relative separation of the maxima of consecutive cycles of the radiated wave as a function of the Doppler angle, θ D.
p.41
Doppler Physics and Its Applications
What does the variable 'θ' represent in the Doppler equation?
The angle between the direction of the sound wave and the direction of the moving object.
p.34
Doppler Physics and Its Applications
What is the significance of the Doppler angle (θD) in the Doppler effect?
It is the angle between the direction of motion and a ray pointed from the reflector to the receiver.
p.48
Acoustic Output Metrics in Ultrasound
How do different tissue types affect the calculation of the Thermal Index (TI)?
Different thermal models are used for soft tissue, skeletal bone, and cranial bone.
p.5
Ultrasonic Properties of Biological Tissue
How does ultrasound achieve contrast among soft tissue structures?
Without the need for an injected contrast agent.
p.26
Ultrasonic Transduction and Piezoelectric Devices
What does the matching layer do in an ultrasonic transducer?
Reduces the reflection coefficient between the transducer and the tissue, increasing sensitivity to weak echoes.
p.37
Doppler Physics and Its Applications
What type of Doppler display is mentioned in the text?
Pulsed Doppler spectral display.
p.8
Ultrasonic Properties of Biological Tissue
What is κ in the context of ultrasonic waves?
The compressibility of the medium, indicating fractional change in volume per unit pressure.
p.2
Doppler Physics and Its Applications
What is the significance of Doppler Physics in ultrasound?
It is used to measure the velocity of moving objects, such as blood flow.
p.47
Acoustic Output Metrics in Ultrasound
What effect does temporal averaging have on I SPTA measurements?
It results in a greater measured exposure for modalities like pulsed Doppler.
p.8
Ultrasonic Plane Waves
What does u(x, t) represent in the equations for ultrasonic waves?
The particle velocity produced by the wave.
p.12
Ultrasonic Plane Waves
What is the limiting case of refraction?
Occurs when c2 > c1 and θi > arcsin(c1 / c2), resulting in θt being imaginary and total reflection.
p.34
Doppler Physics and Its Applications
What does 'fo' represent in the Doppler equation?
The frequency of the incident wave.
p.10
Ultrasonic Plane Waves
How is intensity related to pressure amplitude for acoustic plane waves?
Intensity is proportional to the square of the pressure amplitude.
p.53
Bibliography and References in Diagnostic Radiology Physics
What is the main subject of 'Physical Principles of Medical Ultrasonics'?
The physical principles underlying medical ultrasonics.
p.27
Ultrasonic Transduction and Piezoelectric Devices
What does FWHM stand for?
Full-width at half maximum.
p.17
Ultrasonic Properties of Biological Tissue
Why is the similarity between water and soft tissue important?
It justifies the use of equations for fluid media to analyze wave propagation in biomedical ultrasound.
p.42
Doppler Physics and Its Applications
What is the formula for maximum Doppler frequency (D_max) in relation to PRF?
D_max = (D_o * PRF * c * v * cos(θ)) / 4.
p.25
Ultrasonic Transduction and Piezoelectric Devices
How do composite materials of PZT and non-piezoelectric polymers benefit transducers?
They have a lower acoustic impedance, improving acoustic coupling into tissue and increasing bandwidth.
p.10
Ultrasonic Plane Waves
How is acoustic intensity expressed in decibels?
I dB = 10 * log10(I / I_ref), where I_ref is the reference intensity.
p.10
Ultrasonic Plane Waves
What does the variable 't S E I ∆' represent in the context of acoustic intensity?
It is evaluated over a surface perpendicular to the propagation direction.
p.15
Ultrasonic Plane Waves
What is the wave number (k) in the context of ultrasonic waves?
k = 2π/λ, where λ is the wavelength.
p.54
Bibliography and References in Diagnostic Radiology Physics
What is the focus of Shung's book published in 2006?
Diagnostic Ultrasound: Imaging and Blood Flow Measurements.
p.48
Acoustic Output Metrics in Ultrasound
What are the two key acoustic output metrics mentioned?
Thermal Index (TI) and Mechanical Index (MI).
p.9
Ultrasonic Plane Waves
What is a monochromatic plane wave solution?
P(x,t) = P₀ cos(kx - ωt), where P₀ is the amplitude, ω is the radian frequency, and k is the wave number.
p.27
Ultrasonic Transduction and Piezoelectric Devices
Why is there a division by 2 in the axial resolution formula?
Because the pulse makes a round trip from the transducer to a reflector and back.
p.48
Biological Effects of Ultrasound
What is the purpose of additional exposure parameters in ultrasound?
To more accurately reflect the risks of producing thermal and mechanical bioeffects.
p.11
Ultrasonic Plane Waves
Why is understanding acoustic wave reflection important?
It is valuable for interpreting ultrasound images.
p.2
Biological Effects of Ultrasound
What are the Biological Effects of Ultrasound?
The impact of ultrasound on biological tissues and organisms.
p.11
Ultrasonic Plane Waves
What is the relationship between sound speed in two materials?
c₁ is the sound speed in the first material, and c₂ is the sound speed in the second material with a higher speed.
p.54
Bibliography and References in Diagnostic Radiology Physics
What is the title of the book by Zagzebski on ultrasound physics?
Essentials of Ultrasound Physics.
p.53
Bibliography and References in Diagnostic Radiology Physics
What type of resource is 'Diagnostic Radiology Physics: a Handbook for Teachers and Students'?
A handbook covering various aspects of diagnostic radiology physics.
