Ultrasound

Question 1

what is the audible range of sound waves?
1-20Hz
20-2000 Hz
20-20,000 Hz

Answer 1

20-20,000Hz. Hz= cycles per second. ultrasound is anything above 20,000Hz

Question 2

What is the frequency range for medical ultrasound?
20-20,000Hz
1-2MHz
2-18MHz
10-18MHz

Answer 2

2-18MHz = 2-18 million cycles per second

Question 3

what things effect the speed of sound through an object?

Answer 3

the stiffness of the tissue (bulk modulus) and the density

Question 4

how can you calculate the speed of sound (c) in relation to the stiffness (B) and density (p)?

Answer 4

see picture

Question 5

how are the speed of sound, frequency and wavelength related in an equation?

Answer 5

c = f λ (f = frequency; λ = wavelength)

Question 6

what is the speed of sound through soft tissue?

Answer 6

1540 m/s

Question 7

define the frequency of a sound wave?

Answer 7

how many times per second the compression phase passes any single point in the medium, measured in megahertz (MHz).

Question 8

what is a period?

Answer 8

The period (T) of a wave is the time between successive compressions (or rarefactions) at a single position in the medium. The time taken for 1 complete cycle. Inversely related to frequency.
T=1/f

Question 9

what is the definition of a wavelength?

Answer 9

The wavelength (λ) of a wave is the distance between successive compressions (or rarefactions) at a single point in time.

Question 10

what is the speed of sound in air?

Answer 10

330m/s

Question 11

what is the speed of sound in bone?

Answer 11

4080m/s

Question 12

a decrease in 10 decibels is equal to what change in intensity?

Answer 12

10 fold decrease in intensity

Question 13

a decrease in 3 decibels is equal to what change in intensity?

Answer 13

halves the intensity

Question 14

Intensity (dB ratio) =

Answer 14

10 log10 (I1 / I2) (I1 = intensity 1; I2 = intensity 2)

Question 15

what is acoustic impedence?

Answer 15

Acoustic impedance (Z) describes the resistance experienced by an ultrasound beam in the medium. It depends on density (ρ) and elasticity and is, for practical purposes, independent of frequency. Acoustic impedance is measured in Rayls (kg/m2s).

Question 16

What is the calculation for acoustic impedence?

Answer 16

Acoustic impedence (Z, kg m-2 s-1) = density (p) x speed of sound in that material (c)

Question 17

how do you calculate the reflection coefficient?

Answer 17

Reflection coefficient (R) = (Z2 – Z1)2 / Z2 + Z1)2

Question 18

how can you calculate the Nyquist limit if you have the pulse repetition frequency?

Answer 18

Nyquist limit = PRF / 2

Question 19

what is snells law?

Answer 19

The angle of refraction is determined by the change in the speed of sound and is related to the angle of incidence. The angle can be smaller or larger depending on which material the sound is slower through. If the sound speeds up the transmittance angle increases, right image below.

Question 20

what is axial resolution and the axial resolution limit?

Answer 20

Axial (or depth) resolution is the ability to separate two interfaces along the same scan line at varying depths. If the interfaces are too close together, the echo pulses will overlap and be recorded as a single interface- this is the axial resolution limit. It is determined by the spatial pulse length. Axial resolution is about (just above) half the spatial pulse length. If they are closer than this they won’t be differentiated.
SPL= #cycles x λ

Question 21

what calculation is used by an ultrasound machine to plot the depth of an object?

Answer 21

the range equation: T= time, c= speed (1540). divided by 2 as there and back again

Question 22

define the pulse duration?

Answer 22

Pulse duration (PD): the time taken for an entire pulse to be emitted from the ultrasound machine. (#cycles x time)

Question 23

define the spatial pulse length

Answer 23

SPL (spatial pulse length): the length of the pulse as it moves through space. Cycles x wavelength. Distance measurement.

Question 24

define the pulse repetition period

Answer 24

Pulse repetitions period: the amount of time between the start of one pulse and the start of the next pulse (PD + receive time). Inversely proportional to the pulse repetition frequency.
PRP=1/PRF

Question 25

define the pulse repetition frequency

Answer 25

Pulse repetition frequency: determines the number of pulses you can fit in one second. As PRP increased we can image a greater depth, this reduces the PRF. The opposite is also true. Pulse repetition frequency (PRF) = frame rate x lines per frame

Question 26

what is the doppler equation to calculate the speed of blood at an angle?

Answer 26

F(d)= detected frequency, F(t)= transmitted frequency

Question 27

what determines the fundamental frequency a transducer has?

Answer 27

thickness of the PZT. Frequency (f)= c/2x thickness of the PZT. the thickness of the PZT is half a wavelength.

Question 28

what is the curie temperature?

Answer 28

the temperature above which you remove the dipoles in the PZT material (350 degrees c)

Question 29

which part of the probe stops all the sound waves being reflected by the skin surface?

Answer 29

matching layer

Question 30

what is the purpose of the backing layer

Answer 30

dampening. Therefore dampening shortens the spatial pulse length. It also stops the sound from being transmitted backward into the transducer. It also stops the sound from being a pure frequency, and a few other frequencies are produced- more bandwidth

Question 31

what is the q factor

Answer 31

measures the purity of frequencies from the transducer. Q=f0/f(range). – A high Q-factor transducer indicates a narrow bandwidth and a long SPL. o “High Q” transducers are commonly used in Doppler ultrasound application, where a narrow bandwidth is needed to accurately quantify flow rate. – A low Q-factor transducer indicates a broad bandwidth and a short SPL. Heavy dampening.

Question 32

what is the modified Bernoulli equation?

Answer 32

ΔP=4×v ^2 '4vsquared' where: Δ 𝑃 ΔP is the pressure gradient in mmHg, 𝑣 v is the peak velocity of the regurgitant jet in m/sec.

Question 33

what is the pulse duration for 5 cycles of 5MHz ultrasound?

Answer 33

Time for 1 wavelength (period, T)= 1/f. PD=Number of cycles×T. therefore the answer is 1microsecond OR the number of cycles/ frequency

Question 34

what is azimuthal resolution?

Answer 34

lateral resolution. Azimuthal resolution in ultrasound imaging refers to the ability to distinguish between two points that are side by side (perpendicular to the direction of the ultrasound beam) within the same imaging plane.

Question 35

in ultrasound, as pulse repetition frequency increases, the duty factor...

Answer 35

Duty Factor= Pulse Repetition Period/Pulse Duration. As the pulse repetition frequency (PRF) increases, the duty factor also increases. This is because the time between pulses (PRP) decreases while the pulse duration remains constant, leading to a higher proportion of time during which the transducer is actively emitting ultrasound waves. ​

Question 36

Q factor is determined by: a) bandwidth only b) impedence and bandwidth c) frequency and band width d) pulse duration and bandwidth

Answer 36

C. Q= fundamental frequency/ renge of frequencies (or band width)

Question 37

Low-frequency ultrasound transducers have A Longer wavelengths and less penetration B Shorter wavelengths and greater penetration C Shorter wavelengths and less penetration D Longer wavelengths and greater penetration

Answer 37

D

Question 38

Which Doppler angle yields the greatest Doppler shift? A 60 degrees B 0 degrees C 45 degrees D 90 degrees

Answer 38

B angles more than 60 are not considered accurate 30-60 are the easiest.

Question 39

lateral resolution is primarily determined by... a) frequency b) inherent to the transducer c)beam diameter

Answer 39

C

Question 40

which is true about harmonic ultrasound? a) a returning harmonic signal will be attenuated to a lesser degree than a returning fundamental signal b) harmonic production decreases with depth c) fewer artifacts are detected with fundamental imaging than with tissue harmonic imaging d) the bandwidth of the transducer determines the range of harmonic frequencies that can be detected by the transducer

Answer 40

a,d???

Question 41

if the frequency of a sound wave increases what happens to the spatial pulse length?

Answer 41

decreases

Question 42

does wavelength have a greater effect on axial, lateral, temporal or far zone resolution in ultrasound

Answer 42

axial. Axial resolution is directly related to the pulse duration, which is determined by the wavelength of the ultrasound wave. Specifically, better axial resolution is achieved with shorter wavelengths. This is because shorter wavelengths result in shorter pulse durations, allowing the system to distinguish smaller reflectors that are closer together along the beam axis.

Question 43

arrange the following media in terms of ultrasound speed from highest to lowest? fat, air, bone, muscle

Answer 43

bone, muscle, fat, air

Question 44

the speed of sound depends on which of the following? frequency, wavelength, amplitude, the medium

Answer 44

primarily on the medium. Frequency: The frequency of sound (the number of cycles per second) does not directly affect the speed of sound in a specific medium. Frequency relates to the pitch of the sound (higher frequencies correspond to higher pitches) and is related to the wavelength and speed of sound, but it does not dictate the speed itself. Wavelength: Wavelength is inversely proportional to frequency (λ = v / f, where λ is wavelength, v is velocity, and f is frequency). While wavelength is related to frequency and speed of sound, it does not independently determine the speed of sound in a medium. Amplitude: Amplitude refers to the intensity or loudness of sound, which is related to the energy carried by the sound wave. Amplitude affects the perception of sound (loudness), but it does not affect the speed of sound in a given medium.

Question 45

a red blood cell is an example of a: specular reflector, mirror reflector, Rayleigh reflector, strong reflector

Answer 45

A red blood cell is an example of a Rayleigh reflector in the context of ultrasound imaging. Here’s why: Rayleigh scattering occurs when the size of the scatterer (such as a red blood cell) is much smaller than the wavelength of the incident ultrasound wave. In this case, the scattered waves are dispersed equally in all directions. Red blood cells are much smaller than the wavelength of ultrasound waves commonly used in medical imaging (typically in the range of 1-15 MHz), making them effectively scatterers that contribute to Rayleigh scattering.

Question 46

add more moch exam qs

Answer 46

s

Question 47

Which component affects axial resolution the most? a) the width of the beam b) the spatial pulse length c) image depth d) intensity of the beam

Answer 47

B axial resolution is the resolution along the beam path SPL and therefore the frequency or number and cycles in a pulse, are most impoantant

Question 48

Which component affects lateral resolution the most? a) the width of the beam b) the spatial pulse length c) image depth d) intensity of the beam

Answer 48

A To recognize the objects discretely, the ultrasound beam must be narrower than the distance between the objects. The width of an ultrasound beam decreases with increasing frequency. In a focused ultrasound beam, where the width of the beam is restricted, the lateral resolution is best at the focal point of the ultrasound beam because this is the narrowest part of the beam

Question 49

which is not true for broad bandwidth ultrasound probes a) improve near-field resolution by using the higher frequency of the spectrum b) generally have longer spatial pulse lengths c) improve far-field resolution by using the lower frequency of the spectrum

Answer 49

B is false uses a range of frequencies at the same time when scanning. axial resolution is improved because these transducers use shorter SPLs

Question 50

which is the correct definition for spatial compound imaging? a) sending a range of frequencies from a transducer at the same time to improve image quality b) a 3d and 4d imaging technique to help understand organs in relation to space c) removes signals receives by the transducer that are more likely to come from artefacts d) addition of images obtained from different angles

Answer 50

D is correct. Compound images were perceived to have improved contrast resolution, border definition, and/or increased signal-to-noise ratio compared with noncompounded images A is broad bandwidth

Question 51

turning off what setting can help identify renal calculi?

Answer 51

spatial compounding

Question 52

which type of doppler imaging is described here: one crystal is constantly sending echoes, and one is constantly receiving. all Doppler shifts along the path of the sound wave are measured, making differentiation of blood-flow velocity from two blood vessels in the path of the sound wave impossible

Answer 52

continuous wave. used in echocardiography

Question 53

which type of doppler imaging is described here: The same crystal is used for sending and receiving signals. A gate is positioned over the blood vessel of interest, and only frequencies from this gate are sampled. usually used in duplex mode.

Answer 53

Pulsed wave Pulsed-wave Doppler is performed by using the same crystal for sending and receiving sound. Pulsed-wave Doppler is used in combination with B-mode imaging; this is termed duplex Doppler. A blood vessel is selected in the B-mode image for Doppler interrogation, and an electronic region of frequency sampling, called the gate, is positioned in the blood vessel. The electronic gate is the only area from which echoes are accepted for flow quantification.

Question 54

which of these is not a cause of spectral broadening in doppler ultrasound? a) turbulent flow b) slow flow c) the probe is too close to the vessel of interest.

Answer 54

B

Question 55

colour doppler is a type of continuous wave doppler, true or false?

Answer 55

false type of pulsed wave doppler

Question 56

which is false about colour doppler? a) it is not angle dependent b) The maximum velocity it can display is limited c) The said and direction of the blood flow is displayed as a coloured overly on top of a b moe image d) a large sampling window can be used

Answer 56

A

Question 57

which is not prone to aliasing artefact? a) color doppler b) power doppler c) pulsed wave doppler

Answer 57

B

Question 58

which has no directional information generally? a) color doppler b) power doppler c) pulsed wave doppler

Answer 58

B new thrall: Power Doppler is a signal-processing method that analyzes the total strength of the Doppler signal. This could be related to the direction of the blood flow (directional power Doppler) or ignoring direction of blow flood (nondirectional power Doppler). This is determined by the concentration of the moving red blood cells. With power Doppler, a color map of the Doppler shift will be created, where the hue and brightness of the color represent the power of the Doppler signal. Power Doppler information is superimposed on the grayscale B-mode image, and a color-coded reference scale is displayed on the ultrasound machine monitor when the machine is in power Doppler mode.

Question 59

which doppler imaging setting is not angle dependent? a) power doppler b) colour doppler c) PW doppler d) spectral doppler

Answer 59

A Both continuous wave and PW Doppler are types of spectral Doppler, making spectral traces.