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

Ch. 12 Physics Flashcards

(56 cards)

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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

24
Q

Linear phased array wavelets interfere constructively and deconstructively creating a

Study These Flashcards
A

single sound pulse

25
Linear phased array: The overall pattern of the electrical signals determines the sound beams
steering direction and focus
26
Linear phased array: specific electrical patterns create a sound beam which are
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
Time delayed electric spikes create beam steering to the right or left or in other words
the sound beam is steered if the spike line has a slope
28
When all active elements are fired at the same time straight across the transducer, the sound beam is directed
straight down
29
If the right electrical spike excites the right active first, then the next, and then the next, beam will be
steered to the left (and vice versa)
30
Linear phased array: the electrical within the ultrasound system that creates these patterns is called the
beam former
31
Linear phased array: focusing during transmission has a ____ pattern that creates a focused sound beam during _______
curved, transmission
32
Linear phased array: focusing during transmission has a straight line pattern that creates an _____ sound beam
unfocused
33
Linear phased array: focusing during receiving is called
dynamic receive focusing
34
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.
reception, reflection, continuously, multiple
35
Annular phased array has multiple ____ shaped elements arranged like a ________
disc, bull's eye target
36
Annular phased array beam steering
mechanical steering
37
What is not possible with Annular phased arrays
electronic steering
38
Annular phased array beam focusing is called ____ and has multiple _____
multi-focusing, transmit focal zones
39
Annular phased array: remember, ____- diameter crystals create shallow focus beams, and _____ diameter crystals create deeper focus beams
smaller, larger
40
Annular phased array image shape
sector
41
Annular phased array damaged PZT crystal
only a portion of the image is lost, side-to-side band of dropout at a particular depth
42
Linear sequential array active elements arranged in
a line
43
Linear sequential array beam steering
a small group of crystals are fired simultaneously to create each sound beam
44
Linear sequential array can also be steered in a
slop pattern phase delay
45
What does lope pattern phase delay create
parallelogram shaped image
46
Linear sequential array beam focusing types
electronic transmit focusing and receiving focus
47
Linear sequential array electronic transmit focusing is achieved with a
curved excitation pattern of the active elements
48
Linear sequential array receiving focus is achieved by
introducing electrical delays in the signals returning from the transducer
49
Is focusing the beam at many depths possible with Linear sequential array
yes
50
Linear sequential array image shape
rectangular
51
Linear sequential array damaged PZT crystal
only a portion of the image directly below the damaged element is affected (band/linear dropout)
52
Curvilinear array (convex or curved) crystals are arranged
side-by-side in a bowed line
53
Curvilinear array (convex or curved) beam steering, beam is directed
straight out of the crystals, and pulses travel in different directions as they radiate out from the transducer
54
Curvilinear array (convex or curved) beam focusing is
focused electronically
55
Curvilinear array (convex or curved) beam focusing during transmission is acheived by
exciting the active element in a fixed group with a curved spike like pattern
56
Curvilinear array (convex or curved) beam focusing, dynamic receive focusing acheived by
introducing varying phase delays in the signals returning from the transducer

Vascular I & Physics I (19 decks)

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