Transducers and Beams

Question 1

Aperture

Answer 1

The size of a source of ultrasound

Question 2

Apodization

Answer 2

The non-linear excitation of crystal elements

Question 3

Axial Resolution

Answer 3

The ability of the system to accurately display 2 objects very close together that are parallel to the beams main axis

Question 4

Array

Answer 4

Collection of active Elements in a transducer

Question 5

Axial

Answer 5

Along the axis of the beam

Question 6

Beam

Answer 6

description of the width of a pulse as it travels away from the transducer

Question 7

Composite

Answer 7

Acoustic impedance of composite piezoelectric elements is closer to that of soft tissue, so matching is easier and more efficient with these transducers

Question 8

Convex array

Answer 8

Crystals arranged in an arc; sector shape format

Question 9

Crystal

Answer 9

piezoelectric element or active element

Question 10

Curie point

Answer 10

Temperature point at which transducer crystals lose their piezoelectric properties

Question 11

Damping

Answer 11

• Placed behind the active element

- Reduces the “ringing” of the pulse

Question 12

Detail resolution

Answer 12

Determined by the transducer

Question 13

Dynamic focusing

Answer 13

focusing the beam by altering the electric stimulation of various transducer elements either singly or in groups

Question 14

Element

Answer 14

A single piece of PZT has been cut into many small pieces

Question 15

Elevational resolution

Answer 15

“Slice Thickness” Thickness of the sound beam

Question 16

Far zone

Answer 16

“Fraunhofer Zone”

• The part of the beam after the focus
• Sound beam is Diverging

Question 17

Focal length

Answer 17

distance from the transducer to the center of the focal region

Question 18

Focal region

Answer 18

An area with multiple focal zones

Question 19

Focal zone

Answer 19

Area surrounding the Focal point where the best image is achieved

Question 20

Focus

Answer 20

Concentrates the sound energy into a narrower beam. The best image resolution is at the focus

Question 21

Grating lobes

Answer 21

• “an artifact”
• From an Array Transducer (Multiple Elements)
• Weaker then the central beam
• Can produce extra echoes on an image if they hit a strong reflector
• A line of band of echoes in an anechoic structure

Question 22

Lateral

Answer 22

Scan plane width or beam diameter

Question 23

Lateral resolution

Answer 23

The ability of a system to accurately display 2 closely objects perpendicular to the beams main axis, also known as transverse resolution

Question 24

Lead zirconate titanate

Answer 24

PZT (most often used in diagnostic US transducers)

Question 25

Lens

Answer 25

Used to improve image resolution by reducing the beam width of the transducer

Question 26

Linear

Answer 26

Arranged in or extending along a straight or nearly straight line

Question 27

Linear array

Answer 27

"Sequential" or "Switched" array

Question 28

Linear phased array

Answer 28

Linear sequenced with phased focal control

Question 29

Linear sequenced array

Answer 29

Rectangular in shape with a fixed focus and no electrical steering

Question 30

Matching layer

Answer 30

Reduces the Impedance differences between the transducer

Question 31

Natural focus

Answer 31

- Ultrasound beam from a flat aperture will get narrow and then spread out within and angle range - The depth where beam is most narrow is the natural focus of the aperture

Question 32

Near zone

Answer 32

- "Fresnel’s Zone" - The area between the transducer and the focal point - The part where the sound beam is converging

Question 33

Operating frequency

Answer 33

Element thickness: the operating frequency of a transducer is such that thickness is equal to one half the wavelength in the transducer element material

Question 34

Phased array

Answer 34

flat arrangement of elements typically smaller footprint than linear probe, which produces a sector field of view

Question 35

Piezoelectricity

Answer 35

When voltage is applied to these materials, they change shape and vibrate

Question 36

Probe

Answer 36

an instrument that is used especially for examining parts of the body

Question 37

Resolution

Answer 37

Ability to image accurately

Question 38

Resonance frequency

Answer 38

The operating frequency of a transducer, also known as the natural frequency

Question 39

Sector

Answer 39

Curvilinear array transducers; The area between an arc and two radii of a circle

Question 40

Side lobes

Answer 40

A line of band of echoes in an anechoic structure “an artifact”

Question 41

Transducer

Answer 41

converts one form of energy to another

Question 42

Vector array

Answer 42

Combination of phased array electronics and linear sequential array probes to provide electronic steering and multiple focal zones

Question 43

Phased linear array

Answer 43

small surface area that touches skin (compact footprint, square shape about 1cm on each side); no moving parts and electronically steered