Ch 1-4 8 Flashcards Preview

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Flashcards in Ch 1-4 8 Deck (56):
0

When one value increases, and so does the other value, the two values are said to be ___________.

Directly Proportional

1

The molecules vibrate in the same direction as the sound travels. I.e, sound waves.

Longitudinal Wave

2

The molecules vibrate at 90 degrees to the direction of energy travel. i.e. Water ripples

Transverse Wave

3

concentration of force
units: lb/sq inch, Pascals Pa

Pressure

4

concentration of mass or weight
units: kg/cubic cm

Density

5

measure of particle motion
units: cm, feet, miles

Distance

6

The distance of one wave cycle.

Wavelength

7

•The length of time it takes to complete one single cycle of sound or to one complete single wavelength.

Units: seconds, msec, hours – all units of time
=1/frequency

Period

8

The # of wave cycles per second.
1 cycle per second = 1 hertz Hz

Frequency

9

The speed at which wave cycles travel.

Propagation Speed

10

(Sin Angle of Incidence)/(Sin Angle of Refraction)= c1/c2

Where c1 & c2 are the speeds of sound in the two mediums

Snell's Law

11

Z=P/V
Where P = excess pressure and
V=the particle velocity. OR
Z=P x c
Where c=speed of light

Acoustic Impedance

12

The dominant factor in attenuation (80%).
-conversion of sound to heat

Absorption

13

Occurs at a boundary between 2 different media with different impedances.
-the sound bounces back (toward transducer)

Reflection

14

z=P x V , measured in Rayls. (z=Density x Prop Speed)

Impedance

15

Smooth surface that causes sound to bounce back toward the transducer.

Specular Reflector

16

Scatter returning in the same general direction as the transducer.

BackScatter

17

Interface has irregularities one wavelength or smaller.

Non-specular scattering.

18

Sound scatters symmetrically in all directions. Not related to incidence angle. Increase frequency, and increase this.

Rayleigh scattering.

19

%R=Reflected Intesity/Incidence Intensity=((z2-z1)/(z2+z1))^2

Intensity Reflection Coefficient

20

90 degrees. (Porn)

Normal Incidence

21

not 90 degrees

Oblique Incidence

22

a bending from a straight line or path or a change in direction of a wave travelling from one medium to another. Must have two things: an Oblique Incidence, and2 media with different propagation speeds. Related to the change in acoustic velocity. (If medium 2 is faster, then it will increase the transmit angle.

Refraction

23

Sin (angle of transmit)/ sin (angle of incidence)=prop speed 2/prop speed 1

Snell's Law

24

"bulk modulus." The extent to which a material cannot be compressed. To increase this will increase propagation speed.

Stiffness

25

aka Harmonics

Non-linear Propagation

26

Pulse, then listen for echo

Puled Ultrasound

27

Time from the start of one pulse to the end of the same pulse. THis can only be changed by changing the transducer.

Pulse Duration

28

% of the time that the system is transmitting a pulse and not "listening." Determined by the sound source.

Duty Factor

29

# of pulses that occur in a single second(Hz/sec). Determined by the sound source.

Pulse Repetition Frequency (PRF)

30

Time from the start of a pulse to the start of the next pulse (includes "listening time").

Determined by the sound source. CAN be changed by the sonographer by changing the listening time.
= 1/PRF

Pulse Repetition Period (PRP)

31

The distance a pullse occupies in space. # of cycles in a pulse x wavelength. Determined by the sound source and the medium. Cannot be changed by the sonographer.
Increase freq, Increase this

Spatial Pulse Length

32

Weakening of a sound wave as it travels through media. Decrease in amplitude and decrease in intensity. Increase frequency and increase this

Attenuation

33

+3 Db doubles the sound
+10 dB ten times the sound

Decibels

34

# value that expresses how different materials attenuate the sound beam per unit length (dB/cm). The average attenuation coefficient in soft tissue is 1/2 the transducer frequency.

Attenuation Coefficient

35

The distance the sound beam travls when its intensity is reduced to 1/2 its original value.

Half-Value Layer

36

The fraction of the original intensity after attenuation.

Intensity Ratio

37

a peak aligns with a peak; increase in amplitude

Constructive Interference

38

a peak aligns with a trough; decrease in amplitude

Destructive Interference

39

Distance to Boundary = (go-return time x speed)/2
d=ct/2

Range Equation

40

Every 13 microseconds of go-return time means the reflector is 1 cm deeper in the body

13 microsecond rule

41

when wave peaks and troughs continue to line up.

In-Phase Wave

42

When troughs from one wave continually line up with the peaks from another wave.

Out-of-Phase Wave

43

The strength of the sound beam, maximum variation from the baseline (dB)

Amplitude

44

The rate that work is performed, rate of energy transfer in the entire beam. Measured in watts.
P=I x CS
P is proportional to Amplitude squared

Power

45

Concentration of energy in certain areas of the sound beam
I=P/CS (watts/cm^2)

Intensity

46

The highest intensity area or time of the sound beam

Peak

47

(Peak + low + medium)/3

Average Intensity

48

Greatest at the center and in focal zone of the sound beam

Spatial Intensities

49

Occurs with Time

Temporal non-uniformity

50

Is greatest at the center of the beam

Spatial non-uniformity

51

Related or proportional

Related, Proportional, Directly Proportional

52

As one value increases, the other value decreases.

Inversely proportional.

53

The effects that are made on the human body

Biological Effects

54

The thing that is creating the sound wave

Source

55

The material that the sound wave is traveling through

medium