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 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

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?

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

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

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