Transducers ( Us ) Physics

Front 1

What are the 6 different transducer types?

Back 1

1) mechanical

2) linear sequential array

3) convex linear array

4) linear phased array

5) vector array

6) annular array

Front 2

A transducer with a single disc shaped crystal and moving parts is called:

Back 2

Mechanical transducer

Front 3

How are mechanical transducers focused?

Back 3

1) Fixed focusing (mechanical; cannot be changed)

2) internally is a curved element, externally is acoustic lens

Front 4

What is the image shape of mechanical transducers?

Back 4

Fan or sector shaped

Front 5

A transducer with a multiple element array of 5-10 concentric elements (bulls eye) is called:

Back 5

Annular array

Front 6

What is the image shape of an annular array?

Back 6

Fan or sector shaped

Front 7

How are annular arrays focused?

Back 7

They have multiple transmit focal zones (electronic)

Front 8

What are the disadvantages of mechanical transducers?

Back 8

1) parts wear out

2) parts break

3) motion artifacts

4) limited temporal resolution

5) excessive grating lobes

6) more expensive than necessary

Front 9

A group of elements (200+) that can be turned on or off through switches is called:

Back 9

Linear switched array

Front 10

An array (120-250 strips) with a large acoustic footprint that creates a rectangular image is called:

Back 10

Linear sequential array

Front 11

What is sequencing?

Back 11

Refers to exciting groups of elements in a specific pattern to linearly scan a region (common with large or curved linear arrays)

Front 12

How is frame rate determined?

Back 12

The rate at which the sequence of firing all crystals is repeated

Front 13

How are sequential arrays focused?

Back 13

Have a fixed transmit and receive focus without any steering (electronical)

Front 14

An array with 129-250 rectangular shaped strips of PZT arranged side by side in an arc is called:

Back 14

Convex array

Front 15

How are convex arrays focused and steered?

Back 15

1) focusing is electronic

2) steering is in many directions (electronic)

Front 16

An array with 64-128 tightly packed elements in a small area (not side by side) is called:

Back 16

Phased array

Front 17

What are the 2 advantages to linear phased arrays?

Back 17

1) no mechanical parts (electronic beam steering)

2) electronic focusing (effective focal distance and beam width control)

Front 18

What is the image shape of linear phased arrays?

Back 18

1) rectangle, Pie shaped (cardiac)

2) all the elements in the scan head are involved in producing the sound beam

Front 19

How are linear phased arrays steered?

Back 19

Electronically steered (achieved by nano-second time delays)

Front 20

What is transmit steering?

Back 20

Tiny time shifted pulses are applied to each element of the aperture electronically (spherical wave)

Front 21

What is dynamic receive focusing?

Back 21

Time delays to electric signals to achieve more accurate images (this changes continuously with no change to frame rate)

Front 22

What is electronic transmit focusing?

Back 22

Electronically varied array by changing the delay sequence ( nano-second time delay)

Front 23

How do multiple transmit focal zones effect frame rate?

Back 23

Lowers frame rate because of multiple sound pulses at different depths along beam

Front 24

What are the advantages and disadvantages of multiple focus zones?

Back 24

Advantage: better lateral resolution

Disadvantage: diminishes temporal resolution

Front 25

An array similar to sequential except with simultaneous element excitement is called:

Back 25

Linear phased array

Front 26

How are linear phased arrays focused?

Back 26

Electronically

Front 27

How are linear phased arrays steered?

Back 27

Electronically

Front 28

An array (120-150 )with a sloped electrical time delay pattern, a trapezoidal image, with steering and focusing electronical is called:

Back 28

Vector array

Front 29

Characteristics of Ped-off/non-imaging probe are:

Back 29

1) single element

2) symmetrical and lateral beam

3) broad depth of view

4) very narrow

5) no image

6) manually steered with a fixed focus

Front 30

What is the problem with arrays?

Back 30

formation of secondary lobes which produce arifacts

Front 31

A type of secondary lobe that is possible with any type of transducer and that is usually low intensity compared to the main beam is called:

Back 31

Side lobes ( higher frequency transducers reduce the number and intensity of side lobes)

Front 32

A type of secondary lobe, found only with array transducers, occurring because the transducer is diced into small elements, shooting energy off at a large angle, is called:

Back 32

Grating lobes

Front 33

How are grated lobes reduced?

Back 33

The array is no bigger than 1/2 wavelength

Front 34

What is subdicing?

Back 34

Using very thin, closely spaced elements to eliminate grating lobes

Front 35

What is apodizing?

Back 35

Varying the strength of the voltage spikes applied to the crystal in order to eliminate side lobes

Front 36

What is dynamic aperture focusing?

Back 36

Changing the depth of the focal zone to improve lateral resolution resolution at a wide range of depths

Front 37

What is a beam former?

Back 37

Creates the electronic patterns, providing the pulse delay sequences to achieve transmit focusing

Front 38

Advantages to the beam former are?

Back 38

1) stability

2) programmability

3) acceptance of a wide range of frequencies

4) broadband (versatility)

Front 39

What is the switch?

Back 39

A transmit-receive switch that protects the receiver components from the powerful signals created during pulse transmission