Chapter 2: Ultrasound Transducers

Question 1

element that generates electricity when pressure is applied to it and that changes shape when electricity is applied to it

Answer 1

piezoelectric element

Question 2

most commonly made piezoelectric element material

Answer 2

lead zirconate titanate

Question 3

the actual transducer inside the scanhead

Answer 3

crystal or element

Question 4

temperature at which material will obtain piezoelectric properties

Answer 4

Curie Point

Question 5

Transducers are ___-sterilized

Answer 5

cold

Question 6

frequency is related to two factors

Answer 6

thickness of the piezoelectric element
propagation speed of element

Question 7

________ is the primary determinant of resonating frequency of transducer

Answer 7

thickness of the element

Question 8

A thicker element will produce a _____ frequency

Answer 8

lower

Question 9

A thinner element will produce a _____ frequency

Answer 9

higher

Question 10

resonating frequency is typically between __-__ MHz

Answer 10

2
15

Question 11

if the transducer sends out a pulse before it receives the last one, it is unable to recognize where the echo originated, and therefore, cannot display it correctly on the monitor

Answer 11

depth ambiguity

Question 12

waves that, when stacked, have matching peaks and troughs; undergo constructive interference

Answer 12

in phase waves

Question 13

waves that, when overlapped, are opposite of each other; undergo destructive interference

Answer 13

out of phase waves

Question 14

tiny point sources of sound on transducer

Answer 14

wavelet

Question 15

wavelets create a propagating sound wave whose direction of travel is perpendicular to wavefront, which is line tangential to all the wavelets

Answer 15

Huygen’s principle

Question 16

The ultrasound machine produces between __ and ___v in order to drive piezoelectric elements

Answer 16

10
500

Question 17

lies between element and patient’s skin

Answer 17

matching layer

Question 18

steps down the impedance from that of the element to the patient’s skin

Answer 18

matching layer

Question 19

has an impedance value between matching layer and patients skin

Answer 19

coupling gel

Question 20

sits on back of transducer behind the elements; provide damping of piezoelectric element; composed of an epoxy resin loaded with tungsten

Answer 20

backing material/damping material

Question 21

decreases number of cycles in a pulse, effectively decreasing spatial pulse length

Answer 21

backing material/damping material

Question 22

The backing material shortens the pulse to __-__ cycles per pulse.

Answer 22

2
3

Question 23

ability to detect weak returning echoes

Answer 23

sensitivity

Question 24

Damping material ______ sensitivity

Answer 24

decreases

Question 25

The more damping there is, the ______ the pulse and the _____ the bandwidth

Answer 25

shorter wider

Question 26

term used to quantitate the purity of the beam

Answer 26

Quality factor

Question 27

operating frequency divided by the bandwidth

Answer 27

quality factor

Question 28

Pulsed wave transducers have ____ Q-factors

Answer 28

low

Question 29

Continuous wave transducers have ____ Q-factors

Answer 29

high

Question 30

all the scan lines placed next to each other

Answer 30

frame

Question 31

Two methods for sending out scan lines

Answer 31

electronic scanning mechanical scanning

Question 32

performed with transducers that have multiple active elements

Answer 32

electronic transducers

Question 33

system can selectively excite the elements as needed to shape and steer the beam; no motors needed for beam steering, may be either sequenced or phased, can produce various image shapes

Answer 33

electronic transducers

Question 34

often used in vascular or small parts; rectangular image; elements arranged in a line, next to each other, but are fired in small groups in sequence; beam can be electronically steered

Answer 34

linear sequenced array

Question 35

elements fired in groups, curve-shaped image, abdominal and ob/gyn

Answer 35

curved sequenced array

Question 36

other names for linear sequenced array

Answer 36

linear sequential array linear array

Question 37

other names for curved sequenced array

Answer 37

convex curvilinear curved sequential array

Question 38

more commonly known as sector or vector array; small footprint; used for cardiac imaging, neonatal brain imaging, some endocavity transducers; electronic steering needed for every scan line; sector shaped or "pie" shaped;

Answer 38

phased arrays

Question 39

flat topped trapezoidal image shape; all the scan lines originate from a common point of origin; uses phasing to steer and focus the beam

Answer 39

vector array

Question 40

changing the timing of shocking of the elements in order to shape and steer the beam

Answer 40

phasing

Question 41

3 different ways to create a 3D image

Answer 41

freehand technique mechanical technique 2D transducer or matrix array

Question 42

acquire real time volumes using transducers with up to ______ elements

Answer 42

10,000

Question 43

There are ___-____ elements in a standard 1D array

Answer 43

128 512

Question 44

contains two piezoelectric elements

Answer 44

continuous wave

Question 45

Continuous wave has no _____ resolution

Answer 45

range

Question 46

the ability of a system to distinguish between closely spaced objects

Answer 46

spatial resolution

Question 47

Resolution is divided into four different components:

Answer 47

axial lateral elevational contrast

Question 48

minimum distance between two reflectors can be parallel to the beam, and still appear as two dots on the screen

Answer 48

axial resolution

Question 49

LARRD

Answer 49

longitudinal axial radial range depth

Question 50

The shorter the pulse used, the _____ the axial resolution

Answer 50

better

Question 51

Axial resolution is = to

Answer 51

1/2 of SPL

Question 52

relates to the width of the beam and reflectors that lie perpendicular to it

Answer 52

lateral resolution

Question 53

LATA

Answer 53

lateral azimuthal transverse angular

Question 54

diameter of a beam determined by both frequency and diameter of element itself; takes on shape of hourglass appearance

Answer 54

aperture

Question 55

narrowest point of beam

Answer 55

focal point

Question 56

region from transducer face to focal point

Answer 56

near zone or fresnel zone

Question 57

length of near zone

Answer 57

near zone length

Question 58

region distal to focal point

Answer 58

far zone or fraunhofer zone

Question 59

spreading out of beam

Answer 59

divergenice

Question 60

Natural focus zone; lateral resolution varies with depth

Answer 60

unfocused transducers

Question 61

shorter NZL, more divergence in far field

Answer 61

smaller aperture

Question 62

third dimension of beam

Answer 62

elevational resolution

Question 63

resolution in third dimension of beam, thinnest plane optimal, fixed focusing

Answer 63

elevational resolution

Question 64

ability to distinguish between different shades of gray

Answer 64

contrast resolution

Question 65

represents time, ability to display structures in real time; relates to how quickly frames are generated; also known as frame rate

Answer 65

temporal resolution

Question 66

frame rate units

Answer 66

Hz, frames per second

Question 67

PRF is ______ related to frame

Answer 67

directly