Chapter 3

Question 1

Aperture

Answer 1

size of a transducer element (for a single-element transducer) or group of elements (for an array)

Question 2

Apodization

Answer 2

nonuniform (i.e involving different voltage amplitudes) driving of elements to an array to reduce grating lobes

Question 3

Array

Answer 3

a transducer assembly containing several piezoelectric elements

Question 4

Axial

Answer 4

in the direction of the transducer axis (sound travel direction)

Question 5

Axial Resolution

Answer 5

the minimum reflector separation along the sound path that is required to produce separate echoes (i.e to distinguish between two reflectors)

Question 6

Beam

Answer 6

region containing continuous wave sound; region through which a sound pulse propagates

Question 7

Composite

Answer 7

combination of piezoelectric ceramic and a nonpiezoelectric polymer

Question 8

Convex array

Answer 8

curved linear array

Question 9

Crystal

Answer 9

element

Question 10

Curie Point

Answer 10

temperature at which an element material loses its piezoelectric properties

Question 11

Damping

Answer 11

material attached to the rear face of transducer element to reduce pulse duration; the process of pulse duration reduction

Question 12

Detail resolution

Answer 12

the ability to image fine detail and to distinguish closely spaced reflectors.

Question 13

Disk

Answer 13

a thin, flat, circular object

Question 14

Dynamic aperture

Answer 14

aperture that increases with increasing focal length (to maintain constant focal width)

Question 15

Dynamic focusing

Answer 15

continuously variable reception focusing that follows the increasing depth of the transmitted pulse as it travels

Question 16

Element

Answer 16

the piezoelectric component of transducer assembly

Question 17

Elevational resolution

Answer 17

the detail resolution in the direction perpendicular to the scan plane. it its equal to the section thickness and is the source of section thickness artifact

Question 18

far zone

Answer 18

the region of a sound beam in which the beam diameter increases as the distance from the transducer increases; also called far field

Question 19

focal length

Answer 19

distance from a focused transducer to the center of a focal region or to the location of the spatial peak intensity.

Question 20

focal region

Answer 20

region of minimum beam diameter and area

Question 21

focal zone

Answer 21

length of the focal region

Question 22

focus

Answer 22

the concentration of the sound beam into a smaller beam area that would exist otherwise

Question 23

grating lobes

Answer 23

additional weaker beams of sound traveling out in directions different from the primary beam as a result of the multi-element structure of transducer arrays

Question 24

lateral

Answer 24

perpendicular to the direction of sound travel

Question 25

lateral resolution

Answer 25

minimum reflector separation perpendicular to the sound path that is required to produce separate echoes

Question 26

lead zirconate titanate

Answer 26

a ceramic piezoelectric material. abb PZT.

Question 27

lens

Answer 27

a curved material that focuses a sound or light beam

Question 28

linear

Answer 28

adjectival form of line

Question 29

linear array

Answer 29

array made of rectangular elements arranged in straight line

Question 30

linear phased array

Answer 30

linear array operated by applying voltage pulses to all elements, but with small time differences (phasing) to direct ultrasound pulses out in various directions

Question 31

linear sequenced array

Answer 31

linear array operated by applying voltage pulses to groups of elements sequentially.

Question 32

matching layer

Answer 32

material attached to the front face of a transducer element to reduce the reflections at the transducer surface

Question 33

natural focus

Answer 33

the narrowing of a sound beam that occurs with an unfocused flat transducer element

Question 34

near zone

Answer 34

the region of sound beam in which the beam diameter decreases as the distance form the transducer increases; also called near field

Question 35

operating frequency

Answer 35

preferred (max efficiency) frequency of operation of a transducer

Question 36

phased array

Answer 36

an array that steers and focuses the beam electronically (with short time delays)

Question 37

phased linear array

Answer 37

linear sequenced array with phased focusing added linear sequenced array with phased steering of pulses to produce a parallelogram- shaped display

Question 38

piezoelectricity

Answer 38

conversion of pressure to electric voltage

Question 39

probe

Answer 39

transducer assembly

Question 40

resolution

Answer 40

the ability to distinguish echoes in terms of space, time, or strength (called detail, temporal, and contrast resolutions)

Question 41

resonance frequency

Answer 41

operating frequency

Question 42

scanhead

Answer 42

transducer assembly

Question 43

sector

Answer 43

a geometric figure bounded by two radii and the arc of the circle included between them

Question 44

sensitivity

Answer 44

ability of an imaging system to detect weak echoes

Question 45

side lobes

Answer 45

weaker beams of sound traveling out from a single element in direction different form those of a primary beam

Question 46

sound beam

Answer 46

the region of a medium that contains virtually all of the sound produced by a transducer

Question 47

source

Answer 47

an emitter of ultrasound; transducer

Question 48

transducer

Answer 48

a device that converts energy from one form to another

Question 49

transducer assembly

Answer 49

transducer element with damping and matching material assembled in a case

Question 50

ultrasound transducer

Answer 50

a device that converts electric energy to ultrasound energy; and vice versa

Question 51

vector array

Answer 51

linear sequenced array that emits pulses from different starting points and (by phasing) in different directions.