Transducers and Beams

Question 1

Aperture

Answer 1

A technique of receive focusing that uses fewer crystals to identify echoes from superficial depths and many more crystals to monitor echoes from greater depths. Dynamic aperture is also known as variable aperture.

Question 2

Apodization

Answer 2

describes the excitation of a number of PZT elements with different voltages. This acts to decrease the strength of off-axis sound beams and reduce lobe artifact.

Question 3

Array

Answer 3

an impressive display or range of a particular type of thing.

Question 4

Axial

Answer 4

of, forming, or relating to an axis.

Question 5

Axial Resolution

Answer 5

The ability of a system to display two structures that are close together

Question 6

Beam

Answer 6

a ray or shaft of light.

Question 7

Composite

Answer 7

a thing made up of several parts or elements.

Question 8

Convex array

Answer 8

provide superior superficial imaging but can be more difficult to keep in complete contact with the skin

Question 9

Crystal

Answer 9

highly transparent glass with a high refractive index.

Question 10

Curie point

Answer 10

is the temperature where a material’s permanent magnetism changes to induced magnetism. The force of magnetism is determined by magnetic moments.

Question 11

Damping

Answer 11

a decrease in the amplitude of an oscillation as a result of energy being drained from the system to overcome frictional or other resistive forces.

Question 12

Detail resolution

Answer 12

axial and lateral resolution

Question 13

Dynamic focusing

Answer 13

The process of varying the focusing electrode voltage for a color picture tube automatically so the electron-beam spots remain in focus as they sweep over the flat surface of the screen.

Question 14

Element

Answer 14

a substance that cannot be decomposed into simpler substances by chemical means

Question 15

Elevational resolution

Answer 15

Angle or distance by which two targets must be separated in azimuth to be distinguished by a radar set, when the targets are at the same range.

Question 16

Far zone

Answer 16

Fraunhofer region

Question 17

Focal length

Answer 17

The height and width of the scene captured by a camera lens, which is known as the “field of view.”

Question 18

Focal region

Answer 18

in ultrasonography, the distance along the beam axis of a focused transducer assembly, from the point where the beam area first becomes equal to four times the focal area to the point beyond the focal surface where the beam area again becomes equal to four times the focal area.

Question 19

Focal zone

Answer 19

Throughout the scan the sonographer should constantly check the position of the focal zone(s) and ensure they are at the depth of interest. Multiple focal zones can be used to maximise lateral resolution over depth if motion is not encountered, but it is important to minimise the focal zones used when assessing moving structures i.e. a fetal heart.

Question 20

Focus

Answer 20

Is the center of interest or activity.

Question 21

Grating lobes

Answer 21

two closely related phenomena caused by sound energy that spreads out from the transducer at angles other than the primary path.

Question 22

Lateral

Answer 22

of, at, toward, or from the side or sides.

Question 23

Lateral resolution

Answer 23

as the ability of the system to distinguish two points in the direction perpendicular to the direction of the ultrasound beam. Lateral resolution is affected by the width of the beam and the depth of imaging.

Question 24

Lead zirconate titanate

Answer 24

Lead zirconium titanate is an intermetallic inorganic compound with the chemical formula

Question 25

Lens

Answer 25

an object or device that focuses or otherwise modifies the direction of movement of light, sound, electrons, etc.

Question 26

Linear

Answer 26

arranged in or extending along a straight or nearly straight line.

Question 27

Linear array

Answer 27

Another name for one-dimensional array,

Question 28

Linear phased array

Answer 28

array of antennas in which the relative phases of the respective signals feeding the antennas are varied in such a way that the effective radiation pattern of the array is reinforced in a desired direction and suppressed in undesired directions.[1]

Question 29

Linear sequenced array

Answer 29

can have up to 512 elements spaced over 75-120 mm. The beam produced by such a narrow element will diverge very rapidly after the wave travels only a few millimeters (the smaller the face of the transducer, the more divergent). This would result in poor lateral resolution due to beam divergence and low sensitivity due to the small element size.

Question 30

Matching layer

Answer 30

a layer of material placed in front of an ultrasound transducer to improve the efficiency of energy transfer into and out of a patient

Question 31

Natural focus

Answer 31

he ecology that is best suited to a biological system, e.g. an individual insect-borne disease; the area in which the disease naturally flourishes best; an ecological niche.

Question 32

Near zone

Answer 32

Fresnal zone

Question 33

Operating frequency

Answer 33

defines the basic clock rate at which the CPU core runs. Modern high-end processors run at several billion cycles per second. Operating frequency is a function of the low-level transistor characteristics in the chip, the length and physical characteristics of the internal chip wiring, the voltage that is applied to the chip, and the degree of pipelining used in the microarchitecture of the machine. The last 15 years have seen dramatic increases in the operating frequency of CPU cores.[1]

Question 34

Phased array

Answer 34

a radar antenna consisting of an array of dipoles that are excited in or out of phase with each other to control beam direction and radiation pattern without moving the antenna. Compare dipole (def 3).

Question 35

Phased linear array

Answer 35

a radar antenna consisting of an array of dipoles that are excited in or out of phase with each other to control beam direction and radiation pattern without moving the antenna. Compare dipole (def 3).

Question 36

Piezoelectricity

Answer 36

the ability of certain materials to generate an electric charge in response to applied mechanical stress. The word Piezoelectric is derived from the Greek piezein, which means to squeeze or press, and piezo, which is Greek for “push”.

Question 37

Probe

Answer 37

transducer

Question 38

Resolution

Answer 38

The clarity or fineness of detail that can be distinguished in an image, often measured as the number or the density of the discrete units, such as pixels or dots, that compose it.

Question 39

Resonance frequency

Answer 39

is the tendency of a system to oscillate with greater amplitude at some frequencies than at others.

Question 40

Sector

Answer 40

Produces a fan like image that is narrow near the transducer and increase in width with deeper penetration. It is useful when scanning between the ribs as it fits in the intercostal space. The disadvantge is poor near field resolution.

Question 41

Side lobes

Answer 41

are generated from the edges of the transducer element and project in a different direction from the main beam. These echoes are much weaker than those of the main beam but if a very strong reflector is encountered they may be strong enough on returning to the transducer to be displayed prominently on the image.

Question 42

Transducer

Answer 42

a device that converts variations in a physical quantity, such as pressure or brightness, into an electrical signal, or vice versa.

Question 43

Vector array

Answer 43

Vector array transducers have phasing applied to linear sequenced arrays to steer pulses in various directions.