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SON-111 Physics > Ultrasound Basic Physics Principles > Flashcards

Ultrasound Basic Physics Principles Flashcards

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1
Q

Directly Proportional

A

related so that one becomes larger or smaller when the other becomes larger or smaller

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2
Q

Related

A
  1. Being connected; associated.

2. Having a close harmonic connection.

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3
Q

Proportional

A
  1. Forming a relationship with other parts or quantities; being in proportion.
    1. Properly related in size, degree, or other measurable characteristics; corresponding.
    2. Having the same or a constant ratio.
    3. One of the quantities in a mathematical proportion.
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4
Q

Inversely Proportional

A

related so that as one becomes larger the other becomes smaller

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5
Q

Reciprocal Relationship

A

A number related to another in such a way that when multiplied together their product is 1. For example, the reciprocal of 7 is 1/7 ; the reciprocal of 2/3 is 3/2 .

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6
Q

Acoustic Propagation Properties

A

The medium has an effect on the variables of the wave.

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7
Q

Biologic Effects

A

Effect of the ionizing radiation on living organisms.

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8
Q

Pressure

A

concentration of force

units: lb/sq inch, Pascals Pa

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9
Q

Density

A

concentration of mass or weight

units: kg/cubic cm

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10
Q

Distance

A

measure of particle motion

units: cm, feet, miles

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11
Q

Transverse Wave

A

The molecules vibrate at 90 degrees to the direction of energy travel

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12
Q

Longitudinal Wave

A

The molecules vibrate in the same direction as the energy travels

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13
Q

In-phase wave

A

Two waves with the same frequency are “in phase” if they have the same phase and therefore line up everywhere

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14
Q

Out-of-phase wave

A

Two waves are out of phase if the peaks of one wave align with the troughs of the other

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15
Q

Constructive Interference

A

Peaks encounter peaks, troughs encounter troughs

= stronger wave results

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16
Q

Destructive Interference

A

Peaks encounter Troughs, troughs encounter Peaks

= smaller wave results

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17
Q

Source

A
  1. Physics- The point or part of a system where energy or mass is added to the system.
  2. A person or thing from which something comes into being or is derived or obtained.
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18
Q

Medium

A

substance that the sound travels through

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19
Q

Period

A

The time of a cycle

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20
Q

Frequency

A

How many cycles per second

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21
Q

Amplitude

A

Strength of the beam

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22
Q

Power

A

Rate that work is performed; rate of energy transfer

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23
Q

Intensity

A

Concentration of energy in certain areas of the sound beam (used for bioeffects)

24
Q

Wavelength

A

The distance that one complete cycle occupies; the cycle length

25
Q

Propagation speed

A

The speed at which sound wave moves through the medium

26
Q

Density

A

The concentration of matter (mass per unit volume)

27
Q

Stiffness

A

the resistance of material to compression

28
Q

Pulsed Sound

A
  • A pulse is a collection of cycles that travel together

- In continuous wave US cycles repeat continuously

29
Q

Pulse Duration

A

Time from the start of one pulse to the end of the pulse

30
Q

Spatial Pulse Length

A
  • The distance a pulse occupies in space
  • DISTANCE from the start of the pulse to the end of the pulse
  • Units: meter, mm, any unit of distance
31
Q

Pulse Repetition Frequency

A
  • Number of pulses that occur in a single second
  • Similar to frequency (number of events occurring per second)
  • Units: Hz or per second
32
Q

Pulse Repetition Period

A
  • Time from the start of one pulse to the start of the next
  • Includes both the time that the pulse is on and the time that it is off (dead time)
  • Determined by: sound source
  • Units: Seconds, microseconds
33
Q

Duty Factor

A
  • Percentage of time that the system is transmitting a pulse (or ‘on’ / not listening)
  • Units – No units (unitless)
34
Q

Spatial

A
  • Related to space / areas of the beam

- Spatial intensity is greatest at the center of the beam and at the focus of the beam

35
Q

Peak

A

the highest intensity area or time of the sound beam (maximum value)

36
Q

Average

A

take peak, low, and medium intensities and average them together to get average intensity (mean value)

37
Q

Temporal

A
  • Temporal non-uniformity

- Occurs with time

38
Q

Pulsed

A
  • In continuous wave US cycles repeat continuously
  • Continuous wave US cannot form images
  • Must have listening time to form images
  • A pulse is a collection of cycles that travel together
39
Q

Decibel

A
  • Decibel is 1/10th of a Bel
  • Relative, not absolute units
  • Two intensities or amplitudes are required for computation of decibels
  • Decibels involve the use of mathematical logarithms
40
Q

Attenuation

A

a reduction in intensity as wave travels through a medium

41
Q

Reflection

A
  • Occurs when sound energy strikes a boundary and some gets sent back to transducer. For reflection to occur, we MUST HAVE…..
    1. An acoustic interface between two media……and…
    2. The media must have different impedances for reflection to occur
42
Q

Specular Reflection

A
  • very smooth surfaced, mirror-like reflector
  • Reflector is very large compared to sound beam’s wavelength
  • Reflection is well-defined and regular
43
Q

Backscatter

A
  • Backscatter – scatter returning in the same general direction as the transducer
  • But sound is disorganized and random
  • Occurs when boundary has irregularities about the same size as the sound’s wavelength
44
Q

Diffuse / Scattering / Non-Specular Reflection

A
  • the random redirection of sound waves in multiple directions
  • Produced when sound beam strikes a rough surface
  • Where surface irregularities are same size or smaller than the wavelength
45
Q

Scattering

A
  • Attenuation process in which the beam interacts with interfaces smaller than the wavelength of the beam
  • Causes the US energy to be dispersed in multiple directions
46
Q

Rayleigh Scattering

A
  • sound scatters symmetrically in all directions
  • Not related to incidence angle
  • Directly proportional to the frequency4
  • If frequency is doubled, Rayleigh scattering is 16 times greater
47
Q

Absorption

A
  • Conversion of sound to heat
  • Transfer of energy from the sound beam to the tissue
  • Directly proportional to frequency
  • Higher frequency; higher absorption, more attenuation
48
Q

Attenuation Coefficient

A

are numerical values that express how different materials will attenuate the sound beam per unit path length

49
Q

Half Value Layer Thickness

A

is the thickness of the material at which the intensity of radiation entering it is reduced by one half

50
Q

Impedance

A

a material’s resistance to sound traveling through it (unit is Rayl)

51
Q

Normal Incidence

A

Incoming sound strikes the boundary at 90 degrees

52
Q

Oblique Incidence

A

sound beam strikes at any angle other than 90 degrees

53
Q

Refraction

A

A bending from the straight line path or a change in direction of a sound wave traveling from one medium to another (goes in same general direction)

54
Q

Snell’s Law

A

For two given media, the sine of the angle of incidence bears a constant relation to the sine of the angle of refraction

55
Q

Range Equation

A

a relationship between the distance to a reflector and the time it takes for a pulse of ultrasound to propagate to the reflector and return to the transducer.

56
Q

13 Microsecond Rule

A

In soft tissue, every 13 microsec of go-return time means the reflector is 1 cm deeper in the body

SON-111 Physics (5 decks)

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