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Vascular I & Physics I > Ch. 12 Physics > Flashcards

Ch. 12 Physics Flashcards

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1
Q

The two characteristics of sound to make 2D images are

A

sound travels in a straight line and sound beams must be narrow to optimize LATERAL resolution

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2
Q

Mechanical transducers have what kind of active element

A

single circular/disc shaped

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3
Q

Mechanical transducer sector shape

A

fan

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4
Q

Mechanical transducer type of steering

A

mechanical

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5
Q

Mechanical transducer beam focusing type

A

fixed focus (conventional or mechanical)

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6
Q

Mechanical transducer beam INTERNAL focusing uses

A

curved active element

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7
Q

Mechanical transducer beam EXTERNAL focusing uses

A

acoustic lens

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8
Q

Mechanical transducer damage to PZT crystals causes

A

entire image to be lost

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9
Q

What we use today

A

Transducer arrays

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10
Q

Transducer arrays contain

A

multiple active elements

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11
Q

Array transducers comprise of a slab of PZT cut into a collection of separare pieces called

A

elements

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12
Q

Array transducers each ACTIVE element is

A

connected by a wire to its own electronic circuitry

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13
Q

Array transducers: a combination of the active element, the wire and the systems electronics

A

a channel

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14
Q

Array transducers: generally all have ______ active elements (except annular phased arrays)

A

100-300

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15
Q

Array transducer types

A

linear phased, annular phased, linear sequential, curvilinear, vector

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16
Q

The time difference between electrical spikes when steering is about

A

10 nanoseconds

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17
Q

Linear phased array footprint

A

small

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18
Q

Linear phased array image shape

A

sector

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19
Q

Linear phased array beam steering

A

electronic steering or phasing

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20
Q

Linear phased array beam focusing

A

focused electronically

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21
Q

Linear phased array damage to PZT crystal results in

A

inconsistent or erratic beam steering and focusing

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22
Q

Linear phased array all the active elements in the probe are fixed to create

A

each sound pulse

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23
Q

Linear phased array each sound pulse creates

A

wavelets

24
Q

Linear phased array wavelets interfere constructively and deconstructively creating a

A

single sound pulse

25
Q

Linear phased array: The overall pattern of the electrical signals determines the sound beams

A

steering direction and focus

26
Q

Linear phased array: specific electrical patterns create a sound beam which are

A

all active elements fired at the same time straight across the transducer, time delayed electric spikes (phased delays) create beam steering to the right or left

27
Q

Time delayed electric spikes create beam steering to the right or left or in other words

A

the sound beam is steered if the spike line has a slope

28
Q

When all active elements are fired at the same time straight across the transducer, the sound beam is directed

A

straight down

29
Q

If the right electrical spike excites the right active first, then the next, and then the next, beam will be

A

steered to the left (and vice versa)

30
Q

Linear phased array: the electrical within the ultrasound system that creates these patterns is called the

A

beam former

31
Q

Linear phased array: focusing during transmission has a ____ pattern that creates a focused sound beam during _______

A

curved, transmission

32
Q

Linear phased array: focusing during transmission has a straight line pattern that creates an _____ sound beam

A

unfocused

33
Q

Linear phased array: focusing during receiving is called

A

dynamic receive focusing

34
Q

Linear phased array: dynamic receive focusing, a more accurate image can be created when the US receiver introduces variable time delays to some of the electrical signals during _______. The time delays used during receive focusing depends upon the depth of the ______ created. Therefore, the delayed patterns during receive-focusing change ______. Allows for focusing at _____ depths.

A

reception, reflection, continuously, multiple

35
Q

Annular phased array has multiple ____ shaped elements arranged like a ________

A

disc, bull’s eye target

36
Q

Annular phased array beam steering

A

mechanical steering

37
Q

What is not possible with Annular phased arrays

A

electronic steering

38
Q

Annular phased array beam focusing is called ____ and has multiple _____

A

multi-focusing, transmit focal zones

39
Q

Annular phased array: remember, ____- diameter crystals create shallow focus beams, and _____ diameter crystals create deeper focus beams

A

smaller, larger

40
Q

Annular phased array image shape

A

sector

41
Q

Annular phased array damaged PZT crystal

A

only a portion of the image is lost, side-to-side band of dropout at a particular depth

42
Q

Linear sequential array active elements arranged in

A

a line

43
Q

Linear sequential array beam steering

A

a small group of crystals are fired simultaneously to create each sound beam

44
Q

Linear sequential array can also be steered in a

A

slop pattern phase delay

45
Q

What does lope pattern phase delay create

A

parallelogram shaped image

46
Q

Linear sequential array beam focusing types

A

electronic transmit focusing and receiving focus

47
Q

Linear sequential array electronic transmit focusing is achieved with a

A

curved excitation pattern of the active elements

48
Q

Linear sequential array receiving focus is achieved by

A

introducing electrical delays in the signals returning from the transducer

49
Q

Is focusing the beam at many depths possible with Linear sequential array

A

yes

50
Q

Linear sequential array image shape

A

rectangular

51
Q

Linear sequential array damaged PZT crystal

A

only a portion of the image directly below the damaged element is affected (band/linear dropout)

52
Q

Curvilinear array (convex or curved) crystals are arranged

A

side-by-side in a bowed line

53
Q

Curvilinear array (convex or curved) beam steering, beam is directed

A

straight out of the crystals, and pulses travel in different directions as they radiate out from the transducer

54
Q

Curvilinear array (convex or curved) beam focusing is

A

focused electronically

55
Q

Curvilinear array (convex or curved) beam focusing during transmission is acheived by

A

exciting the active element in a fixed group with a curved spike like pattern

56
Q

Curvilinear array (convex or curved) beam focusing, dynamic receive focusing acheived by

A

introducing varying phase delays in the signals returning from the transducer

Vascular I & Physics I (19 decks)

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