Ch. 3 Vocab

Question 1

Axial Resolution

Answer 1

the minimum reflector separation along the sound path that is required to produce separate echoes (to distinguish between reflectors.) AR (mm)=SPL (mm) / 2

Question 2

Lateral Resolution

Answer 2

the minimum reflector separation perpendicular to the sound path that is required to produce separate echoes. LR(mm)= Beam width (mm)

Question 3

Piezoelectricity

Answer 3

conversion of pressure to electric voltage.

Question 4

Curie Point

Answer 4

the temperature at which an element material loses its piezoelectric properties.

Question 5

Damping Material

Answer 5

a mixture of a plastic or epoxy resin attached to the rear face of the transducer element.

Question 6

Matching Layer

Answer 6

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

Question 7

Coupling Medium

Answer 7

a gel used to provide a good sound path between a transducer and the skin by eliminating the air in between the two.

Question 8

Sound Beam

Answer 8

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

Question 9

Side Lobes

Answer 9

weaker beams of sound traveling out of a single element in directions different from those of the primary beam.

Question 10

Aperture

Answer 10

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

Question 11

Near Zone Length (NZL, Fresnel Zone)

Answer 11

the region of a sound in which the beam diameter decreases as the distance from the transducer increases.

Question 12

Far Zone Length (Fraunhover Zone)

Answer 12

the region of a sound in which the beam diameter increases as the distance from the transducer increases.

Question 13

Natural Focus

Answer 13

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

Question 14

Array

Answer 14

a transducer assembly containing several piezoelectric elements.

Question 15

Lens

Answer 15

a curved material that focuses a sound or light beam.

Question 16

Focus

Answer 16

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

Question 17

Focal Region

Answer 17

the region of minimum beam diameter and area.

Question 18

Focal Length

Answer 18

the distance from a focused transducer to the center of a focal region or to the location of the spatial peak intensity. D/2

Question 19

Focal Zone

Answer 19

the length of the focal region.

Question 20

Elements

Answer 20

the piezoelectric component of a transducer assembly.

Question 21

Scanning

Answer 21

the sweeping of a sound beam through the anatomy to produce an image.

Question 22

Frame

Answer 22

a single image produced by one complete scan of the sound beam.

Question 23

Real-time sonography

Answer 23

presenting images in a rapid sequential format like a movie.

Question 24

Linear array

Answer 24

array made of rectangular elements arranged in a line.

Question 25

Convex array

Answer 25

curved linear array.

Question 26

Phased array

Answer 26

an array that steers and focuses the beam electronically with small time delays.

Question 27

Line sequenced array

Answer 27

linear array operated by applying voltage pulses to groups of elements sequentially. It produces rectangular images composed of many parallel, vertical scan lines.

Question 28

Linear phased array

Answer 28

linear array operated by applying voltage pulses to all elements, but with small time differences (phasing) to direct ultrasound pulses out in various directions. The elements are arranged in a straight line. Produces a sector-type image that comes to a point at the top.

Question 29

Convex (curved) sequence array

Answer 29

linear array operated by applying voltage pulses to groups of elements sequentially but sends pulses out in different directions from different points across the curved array surface. The elements are arranged as a curved line. It produces a sector image with a curved top.

Question 30

Slice thickness

Answer 30

the thickness of the scanned tissue volume perpendicular to the scan plane.

Question 31

Elevation resolution

Answer 31

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

Question 32

Partial-volume artifact

Answer 32

the section thickness artifact that occurs when the slice thickness is wider than the scanned structure.

Question 33

Grating Lobes

Answer 33

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

Question 34

Vector Array

Answer 34

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

Question 35

Apodization

Answer 35

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

Question 36

Dynamic focusing

Answer 36

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

Question 37

Dynamic aperture

Answer 37

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