# Key Terms Flashcards

1
Q

Absorption

A

Conversion of sound to heat

2
Q

Acoustic

A

Having to do with sound

3
Q

Acoustic Variables

A

Pressure, density, and particle vibrations

4
Q

Amplitude

A

Maximum variation of an acoustic variable or voltage

5
Q

Attenuation

A

Decrease in amplitude and intensity with distance as a wave travels through a medium

6
Q

Attenuation Coefficient

A

Attenuation per centimeter of wave travel

7
Q

Backscatter

A

Sound scattered back in the direction from which it originally came

8
Q

Bandwidth

A

Range of frequencies contained in an ultrasound pulse

9
Q

Compression

A

Reduction in differences between small and large amplitudes

10
Q

Constructive Interference

A

Combination of positive or negative pressures

11
Q

Continuous Wave

A

A wave in which cycles repeat indefinitely

12
Q

Contrast Agent

A

A suspension of bubbles or particles introduced into circulation to enhance the contrast between anatomic structures, thereby improving their imaging

13
Q

Coupling Medium

A

A gel used to provide a good sound path between a transducer and the skin by eliminating the air between the two

14
Q

Cycle

A

One complete variation of an acoustic variable

15
Q

Decibel

A

Unit of power or intensity ratio

16
Q

Density

A

Mass divided by volume

17
Q

Destructive Interference

A

Combination of positive and negative pressures

18
Q

Duty Factor

A

Fraction of time that pulsed ultrasound is on

19
Q

Echo

A

Reflection

20
Q

Energy

A

Capability of doing work

21
Q

Fractional Bandwidth

A

Bandwidth divided by operating frequency

22
Q

Frequency

A

Number of cycles per second

23
Q

Fundamental Frequency

A

The primary frequency in a collection of frequencies that can include odd and even harmonics and subharmonics

24
Q

Harmonics

A

Frequencies that are even and odd multiples of another

25
Q

Hertz

A

Unit of frequency

26
Q

Impedance

A

Density multiplied by the sound propagation speed

27
Q

Incidence Angle

A

Angle between incident sound direction and a line perpendicular to the boundary of a medium

28
Q

Intensity

A

Power divided by area

29
Q

Intensity Reflection Coefficient

A

Reflected intensity divided by incident intensity

30
Q

Intensity Transmission Coefficient

A

Transmitted intensity divided by incident intensity

31
Q

Interference

A

Combinations of positive and or negative pressures

32
Q

Kilohertz

A

One thousand hertz

33
Q

Longitudinal Wave

A

Wave in which the particle motion is parallel to the direction of wave travel

34
Q

Medium

A

Material through which a wave travels

35
Q

Megahertz

A

One million hertz

36
Q

Nonlinear Propagation

A

Sound propagation in which the propagation speed depends on pressure causing the wave shape to change and harmonics to be generated

37
Q

Oblique Incidence

A

Sound direction that is not perpendicular to media boundaries

38
Q

Penetration

A

Imaging depth

39
Q

Period

A

Time per cycle

40
Q

Perpendicular

A

Geometrically related by 90 degrees

41
Q

Perpendicular Incidence

A

Sound direction that is perpendicular to the boundary between media

42
Q

Power

A

Rate at which work is done

43
Q

Pressure

A

Force divided by the area in a fluid

44
Q

Propagation

A

Progression or travel

45
Q

Propagation Speed

A

Speed at which a wave moves through a medium

46
Q

Pulse

A

A brief excursion of a quantity from its normal value

47
Q

Pulse Duration

A

Interval of time from beginning to end of a pulse

48
Q

Pulse Repetition Frequency

A

Number of pulses per second

49
Q

Pulse Repetition Period

A

Interval of time from the beginning of one pulse to the beginning of the next

50
Q

Pulsed Ultrasound

A

Ultrasound produced in pulsed form by applying electric pulses or voltages of one or a few cycles to the transducer

51
Q

Range Equation

A

Relationship between round trip pulse travel time. propagation speed, and distance to a reflector

52
Q

Rarefaction

A

Region of low density and pressure in a compressional wave

53
Q

Rayl

A

Unit of Impedance

54
Q

Reflection

A

Portion of sound returned from a media boundary

55
Q

Reflection Angle

A

Angle between the reflected sound direction and a line perpendicular to the media boundary

56
Q

Reflector

A

Media boundary that produces a reflection

57
Q

Refraction

A

Change of sound direction on passing from one medium to another

58
Q

Scatterer

A

An object that scatters sound in many directions because of its small size or its surface roughness

59
Q

Scattering

A

Diffusion or redirection of sound in several directions upon encountering a particle suspension or a rough surface

60
Q

Sound

A

Traveling wave of acoustic variables

61
Q

Spatial Pulse Length

A

Length of space over which a pulse occurs

62
Q

Speckle

A

The granular appearance of images and spectral displays that is caused by the interference of echoes from the distribution of scatterers in tissue

63
Q

Specular Reflection

A

Reflection from a large flat, smooth boundary

64
Q

Stiffness

A

Property of a medium

65
Q

Strength

A

Nonspecific term referring to amplitude or intensity

66
Q

Transmission Angle

A

Angle between the transmitted sound direction and a line perpendicular to the media boundary

67
Q

Transverse Wave

A

A sound wave in which the particle motion is perpendicular to the direction of wave travel

68
Q

Ultrasound

A

Sound having a frequency greater than what humans can hear. Greater than 20 Hertz

69
Q

Wave

A

Traveling variation of one or more quantities

70
Q

Wavelength

A

Length of space over which a cycle occurs