Exam 1 Study Questions Flashcards by Destinee McCoy

What is time per cycle?

Period

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What is it called when there is a large, smooth interface?

Specular reflection

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What is the maximum variation per cycle?

Amplitude

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Less than 20 Hz

Infrasound

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What is length per cycle?

Wavelength

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What is cycles per second?

Frequency

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What is the speed of a wave through a medium?

Propagation speed

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When the structure’s dimensions are much smaller than the beams wavelength (red blood cells)

Rayleigh scattering

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When the incident sound beam strikes the boundary at exactly 90 degrees

Normal incidence

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Backscatter

Diffuse reflection

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Define axial resolution

The ability to clearly define two separate reflectors that are very close together and parallel to the sound beam

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List 3 of the acoustic parameters and their applicable units

Period
Frequency
Amplitude
Power
Intensity
Wavelength
Propagation speed

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Define constructive interference

A pair of in-phase waves results in the formation of a single wave of greater amplitude

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Define destructive interference

A pair of out-of-phase waves results in the formation of a single wave of lesser amplitude

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Define specular reflection

A sound wave is reflected off of a smooth, flat surface and in one direction

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Define diffuse reflection

A sound wave is reflected off a rough, uneven surface in multiple directions (backscatter)

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Define half-value layer/half-value thickness

The distance sound travels in a tissue that reduces the intensity of sound to one-half its original value.

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If system A has a wavelength of 5mm for a two-cycle pulse and system B has a wavelength of 2mm for a two-cycle pulse, which one is going to provide the best axial resolution?

System B

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Define impedance

Acoustic resistance to sound traveling in a medium

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What is the formula for impedance?

Impedance = density x propagation speed
z=c(p)

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If the intensity at the start of the path is 10 mW/cm2 and the attenuation over the path is 6dB, the intensity at the end of the path is _____ mW/cm2

-6 = ¼ (10 x ¼) = 2.5 mW/cm2

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If the intensity at point A is 20 mW/cm and at point B it is 10 mW/cm, the attenuation from A to B is _____ dB.

-3 dB

-3 = ½ 20 x ½ = 10

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If the incident angle is 40 degrees and the transmission angle is 30 degrees, what is the change is speed from Medium 1 to Medium 2 ____

Decreases

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Propagation speed increases if stiffness ____

Increases

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If power is doubled and area remains the same, intensity ____

Increases

Destructive interference results in a wave where the amplitude ____

Decrease

As a wave travels through a medium, the intensity of the wave ____

Increases

29. Frequency decreases as period ____

Increases

If the frequency is increased, the attenuation ____

Increases

If the wavelength increases, frequency ____

Decreases

The depth is changed from 6 cm to 12 cm, the pulse repetition frequency ____

Decreases

33. How many mm are in 8 km

8,000,000

Which is adjustable by the sonographer?

Amplitude

Refraction occurs when ____

An interface is encountered at oblique incidence with different propagation speeds

Which of the sequences of metric abbreviations are in increasing order?

u, m, c, d, M

Spatial pulse length is determined by:

Both the sound source and medium

If the frequency is doubled, the wavelength is:

Halved

What is a unit for intensity?

mW/cm^2

How are pulse repetition period and depth related?

Directly

A wave is non-perpendicular at an interface. The propagation speed of medium 1 is higher than medium 2. The transmitted wave will have an angle that _______ the incident angle

Is less than

What determines attenuation?

Path length and frequency

How are cholesterol level and life span related?

Inversely

What is the fraction of time that ultrasound is emitted?

Duty factor

Which one of the following contributes the most to attenuation?

Absorption

_____ is measured in Rayls

Impedance

The horizontal axis on a graph is the _______ axis.

x-axis

Convert 12 inches to centimeters (2.54 cm = 1 inch)

30.48 cm

What is 1,300,000 in scientific notation?

1.3x10^6

What is 0.000000351 in scientific notation?

3.51x10^-7

All sound waves carry __________ from one location to another.

Energy

What type of wave is a sound wave?

Longitudinal

What is the definition of density?

Concentration of mass in a volume

Acoustic parameters include:

Period, frequency, amplitude, power, intensity, wavelength, and propagation speed

A _________ is a collection of cycles that travel together.

Pulse

________ are desirable for imaging because they create images with better axial resolution.

Shorter pulses

What determines axial resolution?

Spatial resolution

A cycle includes ________.

One positive half wave and one negative half wave

Used to help focus the beam

Lens

Converts electrical to mechanical energy

Piezoelectric materials

Lowers the acoustic impedance mismatch between the transducer and the patient

matching layer

Delivers the drive voltage to the crystal and echo voltage to the recievers

Wires

Dampening component

Backing material

The ability to distinguish between two structures

Resolution

The operating or main frequency

Resonant frequency

Where the beam reaches its minimal diameter

Focus

Fresnal

Near field zone

Fraunhofer

Far field zone

True or false: damping lengthens the pulse

False

True or false: PZT stands for lead zirconate titanate

True

In the near zone beam width ____ as distance from the transducer increases.

Decreases

Doubling the aperture ____ the near zone length.

Increases

A higher-frequency transducer produces more or less divergence in the far field?

Less

True or false: in pulse-echo system, the desired Q factor is an large as possible

False

True or false: the beam diameter is constant in the near zone

False

Divergence of a sound beam of an unfocused transducer occurs in the ____ zone

Fraunhofer

In a sound wave, regions where the pressure is higher than normal are called regions of ____.

Compression

Bandwidth can be increased by increasing ____.

Damping

What is the depth of the object if the go-return time is 7 us?

1.54 x 7 / 2 = 5.39 mm

At what part of the beam is the intensity the greatest?

At the focus

What is the name given to describe electronic focusing of multi-element transducers?

Phasing

According to the range equation, which of the following are necessary to calculate the distance to the reflector?

Propagation speed and go-return time.

When a sonographer increases the maximum imaging depth during an exam, what happens to the PRF?

It decreses

The reverse piezoelectric effect describes the ____ of a sound wave.

Transmission

The thickness of the element is equal to ____ the wavelength of the resonate frequency.

1/2

Reflection of the sound beam from a large interface with a rough surface is called ____.

Diffuse reflection

The optimal impedance of the matching layer would be about ____ rayls if the element is 25 rayls and tissue is 3.5 rayls.

15 rayls

The optimal thickness of the matching layer is ____ of the wavelength of resonant frequency.

25%

For modern day ultrasound scanners, the most favorable resolution factor is ____.

Axial

The size of the focus of a 2 MHz, 8mm diameter single element unfocused transducer is ____

4 mm

The most commonly used material in modern transducer elements is ____.

Lead zirconate titanate

What determines the PRF of a sound wave?

Imaging depth

Backing material improves____ axial resolution.

Improves

Heating a transducer above the ____ ____ will cause depolarization.

Curie point

Two ultrasound systems have near zone lengths of 8cm. At the focus System G has a lateral resolution of 3.0mm, whereas System p has a lateral resolution of 5.0mm. Which system is more likely to produce higher quality pictures at the focus?

System G

Slice thickness can be improved by ____.

Curving the element or using a lens

Which of the following transducers would give the shallowest focus?

Diameter = 1mm; Frequency = 2 MHz (smaller diameter and lower frequency)

What is the most common form of fixed focusing?

Internal

The range equation relates ____, ____, and ____.

Distance, velocity, and time.

Two crystals of the same thickness are used for transducers A and B. The propagation velocity on transducer A's crystal is twice that of transducer B. Which means transducer ____ operates at ____ the operating frequency.

A; twice

Which quantity is unitless?

Q-factor

The Q value of a transducer is determined by ____.

Bandwidth

What can be used to focus an ultrasound beam?

Curved crystal, acoustic lens, and phasing.