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Sonographic Principles and Instrumentation > Chapter 1: Physical Principles > Flashcards

Chapter 1: Physical Principles Flashcards

1
Q

Absorption

A

The conversion of sound energy to heat

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2
Q

Acoustic speckle

A

The interference pattern caused by scatters that produces the granular appearance of tissue on a sonographic image

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3
Q

Acoustic variables

A

Changes that occur within a medium as a result of sound traveling through that medium.
Ex: pressure, density, & particle motion

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4
Q

Amplitude

A

The maximum or minimum deviation of an acoustic variable from the average value of that variable; the strength of the reflector.
Measured in Pascals (Pa)

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5
Q

Attenuation definition

What are the 3 mechanisms of attenuation?

A

A decrease in the amplitude and intensity of the sound beam as sound travels through tissue.
ABSORPTION, Reflection, and Scattering

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6
Q

Attenuation coefficient

A

The rate at which sound is attenuated per unit depth

frequency/2

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7
Q

Axial resolution

A

The ability to accurately identify reflectors that are arranged parallel to the ultrasound beam
longitudinal, axial, radial, range, depth

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8
Q

Backscatter

A

Scattered sound waves that make their way back to the transducer and produce an image on the display

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9
Q

Beam uniformity ratio
SP/SA factor
Beam uniformity coefficient

A

The ratio of the center intensity to the average spatial intensity
BUR = Spatial peak / Spatial average

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10
Q

Capacitive macromachined ultrasound transducers

A

Technology used to create comparable transducer technology to piezoelectric materials

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11
Q

Compression

A

The part of the cycle of movement when molecules are pushed closed together. An area in the sound wave of high pressure and density. Opposite of rarefaction when molecules are spread further apart.

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12
Q

Damping

A

The process of reducing the number of cycles of each pulse in order to improve axial resolution

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13
Q

Decibel

A

A unit that establishes a relationship of comparison between two values of power, intensity, or amplitude

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14
Q

Density

A

Mass per unit volume

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15
Q

Duty factor

A

The percentage of time that sound is actually being produced

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16
Q

Elasticity

Stiffness

A

The ability of an object to resist compression and relates to the hardness of a medium

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17
Q

Frequency

A

The number of cycles per second

Frequency = Propagation speed / Wavelength

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18
Q

Half-intensity depth

Half-value layer depth

A

The depth at which sound has lost half of its intensity

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19
Q

Hydrophone

A

A device used to measure the output intensity of the transducer

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20
Q

Impedance definition

What factors influence impedance

A

The resistance to the propagation of sound through a medium (z). Measured in Rayls
The density and the propagation speed of the medium.

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21
Q

Inertia

A

Newton’s principle that states that an object at rest stays at rest, and an object in motion stays in motion, unless acted on by an outside force.

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22
Q

Intensity

A

The power of the wave divided by the area of which it is spread; the energy per unit area
Watts per square centimeter (W/cm2)

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23
Q

Intensity reflection coefficient (IRC)

A

The percentage of sound reflected at an interface

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24
Q

Intensity transmission coefficient (ITC)

A

The percentage of sound transmitted at an interface

ITC + IRC = 100%

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25
Q

Longitudinal waves

A

Waves in which the molecules of the medium vibrate back and forth in the same direction that the waves are traveling. (Gust of wind blows through grass causing the stalks to bend back and forth.)

26
Q

Nonspecular reflectors

A

Reflectors that are smaller than the wavelength of the incident beam

27
Q

Normal incidence

A

Angle of incidence is 90 degrees to the interface

28
Q

Oblique incidence

A

Angle of incidence is less than or more than 90 degrees to the interface

29
Q

Path length

A

Distance to the reflector

30
Q

Period

A

The time it takes for one cycle to occur

31
Q

Piezoelectric materials
Element
Crystal

A

A material that generates electricity when pressure is applied to it, and one that changes shape when electricity is applied to it

32
Q

Power

A

The rate at which work is performed or energy is transmitted.
Watts (W) or milliwatts (mW)

33
Q

Pressure

A

Force per unit area

The concentration of force

34
Q

Propagation speed

A

The speed at which the sound wave travels through a medium. All sound travels at the same speed through a medium despite its frequency. Affected by medium elasticity and density.

35
Q

Pulse duration

A

The time during which the sound is actually being transmitted
The “on” time

36
Q

Pulse repetition frequency

A

The NUMBER of pulses of sound produced in 1 second. (kilohertz)
Inversely related to repetition period.

37
Q

Pulse repetition period

A

The TIME taken for 1 pulse to occur. (Start of 1 to start of next)
Inversely related to pulse repetition frequency. Includes ‘on’ and ‘off’ time.

38
Q

Rarefaction

A

Part of a cycle of movement consisting of the area in the sound wave of low pressure and density. Opposite of compression. Molecules will show differences in density as rarefaction and compression occur.

39
Q

Rayleigh scatterers

A

Small scattering reflectors

40
Q

Reflection

A

The echo; the portion of sound that returns from an interface

41
Q

Refraction

A

The change in the direction of the transmitted sound beam that occurs with oblique incidence angles and dissimilar propagation speeds

42
Q

Scattering

A

The phenomenon that occurs when sound waves are dispersed into different directions because of the small reflector size compared with the incident wavelength.

43
Q

Snell’s law

A

Law used to describe the angle of transmission at an interface based on the angle of incidence and the propagation speeds of the two media.

44
Q

Spatial pulse length

A

The length of a pulse as calculated by the number of cycles multiplied by the wavelength.

45
Q

Specular reflections

A

Reflections that occur when the sound impinges upon a large, smooth, reflector at a 90 degree angle.

46
Q

Total attenuation

A

The total amount of sound (in dB) that has been attenuated at a given depth

47
Q

Transverse waves

A

Type of wave in which the molecules in a medium vibrate at 90 degrees to the direction of travel. (Doing the wave in a stadium.)

48
Q

Wavelength

A

The length of a single cycle of sound. (lambda)

49
Q 
Giga
Mega
Kilo
Hecto
Deca
A 
Billion            1,000,000,000
Million           1,000,000
Thousand     1,000
Hundred       100
Ten                10
50
Q 
Nano
Micro
Milli
Centi
Deci
A 
Billionth             0.000,000,001
Millionth            0.000,001
Thousandth      0.001
Hundredth        0.01
Tenth                 0.1
51
Q

What are the different parameters of sound?

A

Amplitude, power, intensity, propagation speed, and wavelength

52
Q

What 2 properties influence the propagation of sound in a medium?

A

Stiffness (elasticity) and Density (inertia)

53
Q 
Stiffness is (directly/inversely) related to propagation speed.
Density is (directly/inversely) related to propagation speed.
A

Directly

Inversely

54
Q

Higher frequencies travel (faster/slower) through a medium.

A

Trick question. All sound, regardless of its frequency, travels at the same speed through any particular medium.

55
Q

Power and intensity are proportional to amplitude squared.

A

If amplitude doubles, power quadruples.
If amplitude triples, power increases 9x.
If amplitude is halved, power decreases by 1/4

56
Q

What are the 5 specific parameters of pulsed wave sound?

A 
Pulse repetition frequency (PRF)
Pulse repetition period (PRP)
Pulse duration (PD)
Duty factor (DF)
Spatial pulse length (SPL)
57
Q

Pulse repetition frequency is (directly/inversely) related to imaging depth.

A

Inversely. As imaging depth increases, the longer for echos to return, the fewer pulses per second.

58
Q 
Frequency is (directly/inversely) proportional to attenuation.
Path length is (directly/inversely) proportional to attenuation.
A

Directly

Directly

59
Q

What is the typical range of frequency for diagnostic ultrasound imaging?

A

1 to 20 MHz

60
Q

What is the typical wavelength used in clinical imaging?

A

0.1 - 0.8 mm

61
Q

What is the speed of sound in soft tissue?

A

1540 m/s

62
Q

At what frequency do sound waves become ultrasonic?

What range is used for diagnostic ultrasound?

A

> 20,000 Hz (20 KHz)

2 - 15 MHz

Sonographic Principles and Instrumentation (6 decks)

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