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SPI > Physics > Flashcards

Physics Flashcards

1
Q

What are vertical parallel lines on the display monitor which are made up of many bright dots that represent echoes from various depths?

A

Scan lines

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2
Q

Approximately how many scan lines make up a single frame?

A

96-256

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3
Q

What are the two types of waves?

A

Electromagnetic & mechanical

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4
Q

What is the name of the type of wave which can only propagate through media such as solid liquid or gas?

A

Mechanical wave

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5
Q

What is the name of the type of wave which can propagate through a media or a vacuum?

A

Electromagnetic wave

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6
Q

What is the name of the type of wave that is ultrasound?

A

Mechanical longitudinal wave

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7
Q

What are the four acoustic variables?

A

Pressure
density
temperature
particle motion

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8
Q

What is frequency?

A

Frequency is how many cycles occur in one second

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9
Q

What are the units of frequency?

A

Hz
KHz
MHz

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10
Q

What frequency do you use to scan deep tissue?

A

Low-frequency

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11
Q

What frequencies do we use for shallow tissues?

A

High frequencies

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12
Q

Define period

A

The time it takes to complete one cycle

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13
Q

Define wavelength

A

The length of one cycle

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14
Q

Define propagation speed

A

The speed with which a soundwave moves through a medium

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15
Q

What is the formula for propagation speed

A

C= F (z)

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16
Q

What are the units for propagation speed?

A

Distance over time

Dis/time

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17
Q

How are density and propagation speed related?

A

Increasing density = inversely propagation speed

Decreasing density = increases propagation speed

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18
Q

How are stiffness and propagation speed related?

A

Directly related

Increasing stiffness = increases prop speed

Decreasing stiffness = decreases prop speed

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19
Q

Define density

A

The concentration of molecules in a space

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20
Q

Define stiffness

A

This is the resistance of some material to compression. It is determined by bonds that hold the molecules together.

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21
Q

Define harmonics

A

Higher pressure portion of a soundwave called compression travels faster than the lower pressure portions of a soundwave called refraction. These higher pressure portions of a soundwave when they move faster create the additional frequencies called harmonics. These additional frequencies are even and odd multiples of the TXs frequencies.

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22
Q

Pulse repetition period

A

PRP = PD + Lt

Time, sec, ms

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23
Q

Pulse repetition frequency

A

PRF = 1/ PRP

Units: freq
Hz, KHz, MHz

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24
Q

Define pulse duration

A

The time it takes for one pulse to occur

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25
Define listening time
Time machine shuts down to listen (reception)
26
Define period
The time it takes for one cycle to occur
27
Define duty factor
This is the percent of time the machine is on & the pulse is generated. In ultrasound this is actually less than 1% of the time.
28
Define spatial wave length
This is the length of one pulse
29
Anatomic imaging with ultrasound is achieved with the use of__________ technique. Pulses of ultrasound are generated and are sent into the patient.
Pulse echo
30
Define bandwidth
This is a range of useful frequencies in a short pulse. We create a short pulse with the use of dampening material or backing material. The shorter the pulse the wider the bandwidth.
31
Define attenuation
This is the decrease or loss of amplitude power or intensity of sound as it travels in soft tissue. It limits imaging depth as attenuation increases when we increase the frequency.
32
How do we compensate for the effects of attenuation? There are two ways
2D gain or overall gain | TGC, DGC or SGC
33
What are the three components of attenuation?
Absorption reflection scattering
34
Define absorption
Conversion of sound energy into heat energy. Out of all three this is the dominant factor in losing energy or attenuation
35
Define reflection
Portions of sound that return to the transducer
36
Define scattering
Portions of the sound that scatter and do not return to the transducer
37
Define intensity
Defines the energy or power per-unit area
38
Define amplitude
This is the maximum variation that occurs in an acoustic variable
39
Define power
The rate at which work is done. The rate of energy transfer. Watts
40
What are the six intensity descriptions in order of largest to smallest
``` SPTP SATP SPTA SATA SPPA SAPA ```
41
Define logarithms
This is a technique for rating numbers. The log represents the number of times the number 10 has to be multiplied by itself to get the original number.
42
Define decibels
This is a logarithm scale in our profession.
43
Define attenuation coefficient
It's a constant number for any given frequency
44
Define total attenuation
This is the decrease or loss of amplitude power or intensity of sound as it travels and soft tissue
45
Define acoustic impedance
This is the resistance of medium to sound propagation
46
As density increases impedance ________
Increases
47
As density increases propagation speed________________
Decreases
48
As density decreases impedance_________
Decreases
49
As density decreases propagation speed_______
Increases
50
As stiffness increases impedance ________
Increases
51
As stiffness increases propagation speed ______
Increases
52
As stiffness decreases impedance ________
Decreases
53
As stiffness decreases propagation speed _____
Decreases
54
What are all the names for a normal incidents
``` Perpendicular incident orthogonal incident Right angle Ninety degree Normal incident ```
55
Normal incident is directly dependent on ______
Acoustic impedance
56
What are the only two things that can happen in normal incident?
Reflection and transmission
57
Define resolution
This term is used in ultrasound to define the ability to image accurately. Accuracy is the very essence of diagnostic ultrasound.
58
What are the two aspects of detail resolution
Axial and lateral resolution
59
Define axial resolution
This type of resolution measures the ability of a system to display two structures that are very close together. That is when the structures are parallel to the sound beams main axis.
60
What does L. A. R. R. D stand for?
``` Longitudinal Axial Range Radial Depth ```
61
How do we create a short pulse?
Less ringing | High frequency
62
Why do we want a short pulse?
A shorter pulse length yields better axial resolution
63
Define lateral resolution
This type of resolution measures the ability of a system to display two structures that are very close together. When the structures are perpendicular to the sound beams main access lateral resolution is is the distance that to the structures can have between them side-by-side and still be distinguished from one another
64
What does L. A. T. A. stand for?
Lateral Angular Transverse Azimuthal
65
What is the formula for lateral resolution?
Lr=Db
66
Define spatial pulse length
The length of one pulse
67
Define apodization
A process used to reduce the strength of side and grading lobes. In this process the stronger voltages are used to excite that inner elements and progressively working to the outer elements we use weaker and weaker strength voltages to excite them.
68
Define side lobes
Sound beams that are created by a single element transducer. they are hourglass shaped
69
Define grating lobes
Grating lobes are similar to sidelobes with the exception that they are created by array transducer's instead of mechanical transducers.
70
Define dynamic aperture
We use dynamic aperture to make this sound being narrow over a great range of depths and helps optimize lateral resolution
71
Define mechanical transducer
Mechanical – moving parts. Single circular or disc shaped Crystal. Mechanical steering. The Crystal was converted to an arm which was moved around a path in order to produce the scan plane.
72
Define array transducer
A collection of active elements in a transducer
73
Define element array transducer
A simple slab of PZT cut into a collection of separate pieces called elements
74
Define channel array transducer
The electronics of the transducer. which include the element, wire and microchip

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