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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
Q

Define listening time

A

Time machine shuts down to listen (reception)

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26
Q

Define period

A

The time it takes for one cycle to occur

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27
Q

Define duty factor

A

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.

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28
Q

Define spatial wave length

A

This is the length of one pulse

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29
Q

Anatomic imaging with ultrasound is achieved with the use of__________ technique. Pulses of ultrasound are generated and are sent into the patient.

A

Pulse echo

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30
Q

Define bandwidth

A

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
Q

Define attenuation

A

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
Q

How do we compensate for the effects of attenuation? There are two ways

A

2D gain or overall gain

TGC, DGC or SGC

33
Q

What are the three components of attenuation?

A

Absorption
reflection
scattering

34
Q

Define absorption

A

Conversion of sound energy into heat energy. Out of all three this is the dominant factor in losing energy or attenuation

35
Q

Define reflection

A

Portions of sound that return to the transducer

36
Q

Define scattering

A

Portions of the sound that scatter and do not return to the transducer

37
Q

Define intensity

A

Defines the energy or power per-unit area

38
Q

Define amplitude

A

This is the maximum variation that occurs in an acoustic variable

39
Q

Define power

A

The rate at which work is done. The rate of energy transfer.

Watts

40
Q

What are the six intensity descriptions in order of largest to smallest

A 
SPTP
SATP
SPTA
SATA
SPPA
SAPA
41
Q

Define logarithms

A

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
Q

Define decibels

A

This is a logarithm scale in our profession.

43
Q

Define attenuation coefficient

A

It’s a constant number for any given frequency

44
Q

Define total attenuation

A

This is the decrease or loss of amplitude power or intensity of sound as it travels and soft tissue

45
Q

Define acoustic impedance

A

This is the resistance of medium to sound propagation

46
Q

As density increases impedance ________

A

Increases

47
Q

As density increases propagation speed________________

A

Decreases

48
Q

As density decreases impedance_________

A

Decreases

49
Q

As density decreases propagation speed_______

A

Increases

50
Q

As stiffness increases impedance ________

A

Increases

51
Q

As stiffness increases propagation speed ______

A

Increases

52
Q

As stiffness decreases impedance ________

A

Decreases

53
Q

As stiffness decreases propagation speed _____

A

Decreases

54
Q

What are all the names for a normal incidents

A 
Perpendicular incident 
orthogonal incident
Right angle
Ninety degree
Normal incident
55
Q

Normal incident is directly dependent on ______

A

Acoustic impedance

56
Q

What are the only two things that can happen in normal incident?

A

Reflection and transmission

57
Q

Define resolution

A

This term is used in ultrasound to define the ability to image accurately. Accuracy is the very essence of diagnostic ultrasound.

58
Q

What are the two aspects of detail resolution

A

Axial and lateral resolution

59
Q

Define axial resolution

A

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
Q

What does L. A. R. R. D stand for?

A 
Longitudinal 
Axial
Range
Radial
Depth
61
Q

How do we create a short pulse?

A

Less ringing

High frequency

62
Q

Why do we want a short pulse?

A

A shorter pulse length yields better axial resolution

63
Q

Define lateral resolution

A

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
Q

What does L. A. T. A. stand for?

A

Lateral
Angular
Transverse
Azimuthal

65
Q

What is the formula for lateral resolution?

A

Lr=Db

66
Q

Define spatial pulse length

A

The length of one pulse

67
Q

Define apodization

A

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
Q

Define side lobes

A

Sound beams that are created by a single element transducer. they are hourglass shaped

69
Q

Define grating lobes

A

Grating lobes are similar to sidelobes with the exception that they are created by array transducer’s instead of mechanical transducers.

70
Q

Define dynamic aperture

A

We use dynamic aperture to make this sound being narrow over a great range of depths and helps optimize lateral resolution

71
Q

Define mechanical transducer

A

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
Q

Define array transducer

A

A collection of active elements in a transducer

73
Q

Define element array transducer

A

A simple slab of PZT cut into a collection of separate pieces called elements

74
Q

Define channel array transducer

A

The electronics of the transducer. which include the element, wire and microchip

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