Exam 1 Flashcards
1
Q
Importance of Physics
A
- Learn DMS
- Understand Artifacts
- Prep for instrument performance measurements
- Become aware of safety and risk factors
2
Q
Doppler Effect
A
Christian Doppler
1840
3
Q
Piezoelectric Effect
A
Piere and Marie Curie
1880
4
Q
Distance Formula
A
Distance = Rate of speed X time of trace
5
Q
Rate of speed in soft tissue?
A
1540 m/s
Or
1.54 mm/us
6
Q
13 microsecond rule
A
Time for sound to travel 1cm and back in soft tissue
7
Q
Linear Scan
A
- Rectangular Display
- Pulses travel in the same direction
8
Q
Sector Scan
A
- each pulse shares origin
- subsequent pulses go out in different directions
9
Q
Doppler Effect -> in ultrasound
A
If an echo generating structure is moving, the echo will have a different frequency than pulse enjoyed by the transducer
10
Q
Metric Measurements
Mega(M)
A
Million (10^9)
11
Q
Metric Measurements
Kilo(k)
A
Thousand(10^3)
12
Q
Metric Measurements
Hecto(h)
A
Hundred (10^2)
13
Q
Metric Measurements
Centi(c)
A
Hundredth(10^-2)
14
Q
Metric Measurements
Mili(m)
A
Thousandth(10^-3)
15
Q
Metric Measurements
Micro(u)
A
Millionth(10^-6)
16
Q
Metric Measurements M k h c m m(u)
A
Mortal kombat has crazy many murders(u)
17
Q
Sound
A
The sensation produced by vibrations through a medium; gas, liquid, etc
18
Q
Wave
A
A disturbance that travels through a medium and moves its energy from one location to another
19
Q
Compression
A
An area of increased particle density
Top of wave
20
Q
Refraction
A
An area of decreased particle density
Bottom of wave
21
Q
Acoustic Variables
A
Pressure
Density
Particle Motion (Disturbance)
Temp
22
Q
Acoustic Variables
Pressure
A
Concentration of force
Units: Pascals (Pa), lbs/sq in, atmospheres
23
Q
Acoustic Variables
Density
A
Concentration of mass or weight
Units: kilo per cubic cm
24
Q
Acoustic Variables
Particle Motion
A
Distance
Units: meter, cm, feet
25
Acoustic Variables
| Temp
Measurement of heat
| Units: Degrees
26
Ultrasound Pulse Principles
- Pulse Repetition Frequency
- Pulse Repetition Period
- Pulse Duration
- Duty Factor
- Spatial Pulse Length
27
Range Equation
Distance = Rate x Time
28
What is a Pulse?
- a short burst of sound energy
- a collection of a number of cycles
- all these cycles travel together
- each Pulse has a beginning, middle, & end
29
PRF
Pulse Repetition Frequency
- number of pulses the ultrasound transducer emits in 1 second of time
- units: Hz or kHz
- typical range of PRF is 1-10 kHz
30
PRP
Pulse Repetition Period
- the time from the beginning of one pulse to the start of the next Pulse
- PRP includes the time the machine is producing the pulse and the time it is listening for the pulse to return
31
What is the relationship between PRP & PRF?
They are reciprocals
Ex)
-PRF=(1/PRP)
-PRP=(1/PRF)
32
Can PRP be changed?
Yes, because PRF is the reciprocal of PRR and PRP can be adjusted on the US machine
33
PD
Pulse Duration
- the time (duration) of an ultrasound pulse
- units: time (microseconds)
- typical PD for US is 0.5-0.3 microseconds
34
PD equation
Pulse Duration = # of cycles in a pulse x period
35
PD increases if?
- Period increases
- #of cycles in pulse increases
- frequency decreases
36
DF
Duty factor
- the fraction of time that the ultrasound machine is sending out a pulse of sound
- DF is expressed as a decimal point or fraction
37
DF equation
Duty factor = Pulse Duration / Pulse Repetition period
38
Acoustic Variables
Pressure
Density
Particle vibrations/movements
Temperature
39
Bigness Parameters
Amplitude
Power
Intensity
Attenuation
40
Amplitude
The maximum variation in an acoustic variable
41
Decibels
- not an exact number
- used to express a ratio or difference between a reflected signal and source signal
- based info logarithmic scale of numbers
42
Positive decibels
```
+3dB = doubling intensity (2x the original)]
+6dB = quadrupling intensity (4x the original)
+9dB = 8x the original
+10dB= 10x the original
+20dB = 100x the original
```
43
Negative decibels
- 3dB = halfing intensity (½ the original)
- 6dB = quartering intensity (¼ the original)
- 9dB = ⅛ the original
- 10dB = 1/10 the original
- 20dB = 1/100 the original
44
Logarithm (log)
-a mathematical numerical rating system
-the number of 10s that are multiplied together to equal a number
Ex) Log of 100 = 2
45
How can a sonography change the amplitude?
Adjusting the Power Control
46
Power
-rate of energy transference
47
The number of pulses emitted in 1 second is termed what?
Pulse Repetition Frequency
48
The beginning of one pulse to the beginning of the following pulse is termed pulse is termed what?
Pulse Repetition Period
49
What is the relationship between PRF and PRP?
They are reciprocals
50
When we increase depth what happens to the Pulse Repetition Period
PRP increases
51
When we increase depth what happens to Pulse Repetition Frequency?
PRF Decreases
52
What term measures the duration of the US pulse?
Pulse Duration
53
What formula for Pulse Duration? What are the units?
PD= (# of cycles in pulse) x (period)
54
What term do we use for the fraction of time the US machine is sending out a pulse?
Duty Factor
55
What is the equation for the above term? What are the units?
```
DF = PD / PRP
DF% = PD / PRP x 100
```
56
What term do we use for the length of an US pulse?
Spatial Pulse Length
57
What is the equation for SPL?
SPL = (# of cycles in pulse) x wavelength(mm)
58
What are the units for PRP?
Seconds
59
What are the units for PRF?
Hz of kHz
60
What is the term when the US machine has just sent out a pulse and is waiting for it to come back?
Receiving time
61
If Period decreases, what happens to the Pulse Duration?
PD decreases
62
What happens to SPL if Frequency increaseS?
SPL Decreases
63
Three components of attenuation?
Reflection
Absorption
Scatter
64
As path length increases, the attenuation of ultrasound in soft tissue?
Path length increases = path length increases
65
Units of attenuation?
dB/cm
66
T/F
| In a given medium, the attenuation is unrelated to the speed of sound
True
67
What are the units of half layer thickness?
Cm & mm
68
As Frequency decreases, what happens to the depth of penetration?
It increases
69
T/F Amplitude, power and intensity can be changed by the sonographer?
True
70
Which intensity is related to tissue heating?
SPTA
71
What is the importance of describing sound beam intensities in a variety of ways with regard to space and time?
Intensity is important in bio effects
72
What are the units of the transmitted intensity of a sound wave?
Watts/cm^2
73
As the sound travels in the body, what happens to the intensity of the wave?
Intensity decreases
74
What determines the initial amplitude if a wave?
The transducers capability determines the initial amplitude
75
Requirements for refraction
- oblique incidence
| - different propagation speeds between the media
76
Refraction
Bending of a beam of sound, or change in direction of a beam of sound as it passes from one medium to another
77
Oblique incidence
Anything besides 90 degree incidence
- reflection uncertain
- transmission uncertain
78
Relation of incidence angle and reflection angle “Law of Reflection”
Incidence angle = reflection angle
| 40 degree = 40 degree
79
Average impedance for soft tissue
1,630,000 Rayls
Or
1.63 x 10^6
80
2 factors for reflection to occur
1) angle @ which sound strikes the boundary must be 90 degrees
2) the 2 tissues or mediums must have different acoustic impedances
81
IRC & ITC relationship
- IRC & ITC must = 100% of original intensity
- all sound must be accounted for
Ex: if IRC is 3% then ITC should be 97%
82
Reflected sound
The sound that is reflected @ the boundary or interface & returns to the transducer
83
Transmitted sound
| Transmission
The sound that continues to propagate I. The direction it was going, after hitting a boundary of interface
84
Incident sound
The sound that is coming from the sound source & going to the medium
85
How is Rayleigh scattering affected by Frequency?
Frequency increases, scattering increases
86
Scattering
- occurs when sound encounters irregular, boundaries or tissue
- redirected into many directions
87
2 types of scattering
Backscatter (diffused reflection): sound returns toward the transducer
Rayleigh scattering : sound is redirected in all directions
88
dB in relation to increasing or decreasing power or gain
+dB = increases in value (turn up power or gain)
-dB = decrease in value (turn down power or gain
89
Relationship between Period & Frequency (PRP & PRF)
Reciprocals (inversely related)
| -PRF = 1/PRP or PRP = 1/PRF
90
Sound speed in different tissues
Solids are faster than liquids, liquids are faster than gases
91
Density of medium
Density increase = speed of sound decrease
Density decrease = speed of sound increase
92
Hardness of medium
- Dominant role
- the stiffer or less elastic a medium is the faster the sound travels in it
- stiffness increase then the speed increases
- stiffness decreases then the speed of sound decreases
93
2 properties of medium affecting speed of sound
1) hardness of medium (stiffness)
| 2) density of medium ( related to weight)
94
What affects propagation speed
- only the medium affects propagation speed
| - if the medium does not change, the speed of sound will not change
95
What affects wavelength?
- transducer Frequency
| - the medium sound travels in
96
Wavelength
- Reciprocal of frequency
- length of space that one wave occupies
- units: mm, meters, inches, etc
- US units = mm
- US wavelength = 0.1-0.8
97
Ultrasound Frequencies
Usually between 2.0-12.0mHz
Choice of frequency affects:
1) penetration
2)image resolution - increased frequency
Frequency is determined by the transducer
98
Categories of sound
Infrasound: <20Hz
Audible sound: within range of hearing 20Hz - 20,000Hz
Ultrasound: >20,000Hz
99
Image depth equation
(Rate x Time) / 2
