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ultrasound physics > exam 2 review > Flashcards

exam 2 review Flashcards

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1
Q

Pulse duration equation

A

PD (time)= Period (time) * # cycles

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2
Q

Spatial pulse length equation

A

SPL (distance)= Wavelength(distance) * # cycles

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3
Q

Frame Time equation

A

Frame Time= PRP (time) * # lines

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4
Q

Frame time equation with color

A

Frame Time= PRP * #lines/packet * #packets/frame

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5
Q

Frame Time on steroids equation

A

Frame Time= 13 ms/cm * ID * #lines/packet * #packets/frame * #foci

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6
Q

Frame rate and Frame time

A

Reciprocal

FR*FT=1

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7
Q

Pulse repetition period and pulse repetition frequency

A

Reciprocal

PRP*PRF=1

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8
Q

Pulse repetition period equation

A

PRP= 13 ms/cm * ID

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9
Q

Duty Factor equation

A

DT (%)= PD/PRP * 100

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10
Q

Bandwidth equation

A 
BW= F(max) - F(min)
BW= 1/PD
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11
Q

Pulsed Wave equation

A

F(o)=Crystal/2*thickness

F(o)= operating frequency

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12
Q

Continuous wave equation

A

F(o)= drive voltage frequency

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13
Q

Beam width equation

A

D/2 @ the focus

D @ 2X the focus

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14
Q

Near zone length equation

A

D(2)*F(o)/6

OR
D(2)/4y

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15
Q

Beam divergence

A

1.85/D*f(o)

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16
Q

Longitudinal resolution

A

SPL/2

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17
Q

Lateral resolution

A

Beam width in the lateral plane

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18
Q

Elevation resolution

A

Beam width in elevation plane

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19
Q

Transducers convert one form of ____ into another.

A

Energy

20
Q

Piezoelectric effect

A

Describes the property of certain materials to create a voltage when they are mechanically deformed or when pressure is applied

21
Q

Transducer construction

A
  1. Backing material
  2. Piezoelectric crystal(s)
  3. Matching layer
22
Q

Importance of matching layer and gel

A

They decrease the reflection at the piezoelectric crystal and skin boundary and increase the percentage of transmitted sound

23
Q

Band width definition

A

range of frequencies in the pulse

24
Q

Beam divergence definition

A

Describes the gradual spread of the ultrasound beam in the far field.

less divergence= larger diameter, higher frequency
more divergence= small diameter, lower frequency

25
Q

Axial Resolution

A

Ability of a system to display two structures that are very close together when the structures are parallel to the sound beams main axis

Determined by the pulse length (shorter pulses have better resolution)

Synonyms= longitudinal, range, radial, or depth resolution

26
Q

Better axial resolution

A
  1. shorter spatial pulse length
  2. shorter pulse duration
  3. higher frequencies
27
Q

Lateral resolution

A

Ability to distinctly identify two structures that are very close together when they are side by side or perpendicular to the sound beams main axis

Determined by the width of the sound beam (narrower beams have better resolution)

Synonyms= angular, transverse, or azimuthal

28
Q

Matching layer function

A
  • Located in front of the Piezoelectric crystals at the face of the transducer
  • Increases efficiency of sound energy transfer between active element and body
  • Protects the active element
  • One quarter wavelength thick
29
Q

Backing material function

A
  • Bonded to the back of the active element
  • Reduces the ringing of the PZT
  • Dampens emitted sound pulse (enhances axial resolution)
30
Q

Continuous wave transducer frequency

A

The frequency is equal to the frequency of the electrical signal

31
Q

Pulsed wave transducer frequency

A

Determined by Speed of sound in the PZT and thickness of the PZT

32
Q

Beam shape characteristics

A
  1. focus
  2. near zone
  3. focal length/near zone length
  4. far zone
  5. focal zone
33
Q

Focus (Focal point)

A

The location where the beam is the narrowest

beam shape=1/2 the width of the beam as it leaves the transducer

34
Q

Near zone (fresnel zone)

A

Region from the transducer to the focus

The beam gradually narrows or converges within the near zone

Beam shape= 1/2 the width of the active element

35
Q

Focal length (focal depth or near zone length)

A

The distance from the transducer to the focus

36
Q

Far zone (far field, Fraunhofer zone)

A

Region that starts at the focus and extends deeper

The beam will diverge/spread out

Beam shape= @ beginning of far zone, beam is 1/2 as wide as the transducer. @ deeper depths, the beam is wider

37
Q

Focal zone

A

Region around the focus where the beam is relatively narrow

38
Q

Shallow focus

A
  • smaller diameter PZT

* lower frequency

39
Q

Deep focus

A
  • larger diameter PZT

* higher frequency

40
Q

What part of the beam gives the best focus?

A

Near zone, right before the natural focus

41
Q

Frame rate

A

Ability to create numerous frames each second

Determined by speed of sound in a medium and imaging depth

42
Q

Pulse duration

A

actual time from start of a pulse to the end of the pulse

Determined by sound source only

Cannot be adjusted by the sonographer

Values= 0.3-2 microseconds

43
Q

Spatial pulse length

A

the distance that a pulse occupies in space from start to finish

determined by the sound source and the medium

Cannot be adjusted by the sonographer

Values (in soft tissue)= 0.1-1 mm

44
Q

Pulse repetition period

A

the time from the start of one pulse to the start of the next pulse

determined by the sound source and the imaging depth

Can be adjusted by the sonographer

Values= 100 microseconds-1 millisecond

45
Q

Pulse repetition frequency

A

number of pulses that a system transmits into the body each second

determined by sound source and imaging depth

Can be adjusted by the sonographer

Values= 1,000-10,000 Hz

46
Q

Duty factor

A

percentage of fraction of time that the system transmits a pulse

determined by sound source only

Can be adjusted by the sonographer

Values= 0.2-0.5%

ultrasound physics (3 decks)

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