Transducers and Beams Flashcards
Aperture
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.
Apodization
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.
Array
an impressive display or range of a particular type of thing.
Axial
of, forming, or relating to an axis.
Axial Resolution
The ability of a system to display two structures that are close together
Beam
a ray or shaft of light.
Composite
a thing made up of several parts or elements.
Convex array
provide superior superficial imaging but can be more difficult to keep in complete contact with the skin
Crystal
highly transparent glass with a high refractive index.
Curie point
is the temperature where a material’s permanent magnetism changes to induced magnetism. The force of magnetism is determined by magnetic moments.
Damping
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.
Detail resolution
axial and lateral resolution
Dynamic focusing
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.
Element
a substance that cannot be decomposed into simpler substances by chemical means
Elevational resolution
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.
Far zone
Fraunhofer region
Focal length
The height and width of the scene captured by a camera lens, which is known as the “field of view.”
Focal region
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.
Focal zone
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.
Focus
Is the center of interest or activity.
Grating lobes
two closely related phenomena caused by sound energy that spreads out from the transducer at angles other than the primary path.
Lateral
of, at, toward, or from the side or sides.
Lateral resolution
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.
Lead zirconate titanate
Lead zirconium titanate is an intermetallic inorganic compound with the chemical formula
Lens
an object or device that focuses or otherwise modifies the direction of movement of light, sound, electrons, etc.
Linear
arranged in or extending along a straight or nearly straight line.
Linear array
Another name for one-dimensional array,
Linear phased array
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]
Linear sequenced array
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.
Matching layer
a layer of material placed in front of an ultrasound transducer to improve the efficiency of energy transfer into and out of a patient
Natural focus
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.
Near zone
Fresnal zone
Operating frequency
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]
Phased array
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).
Phased linear array
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).
Piezoelectricity
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”.
Probe
transducer
Resolution
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.
Resonance frequency
is the tendency of a system to oscillate with greater amplitude at some frequencies than at others.
Sector
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.
Side lobes
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.
Transducer
a device that converts variations in a physical quantity, such as pressure or brightness, into an electrical signal, or vice versa.
Vector array
Vector array transducers have phasing applied to linear sequenced arrays to steer pulses in various directions.
