Ch. 3 Vocab Flashcards
Axial Resolution
the minimum reflector separation along the sound path that is required to produce separate echoes (to distinguish between reflectors.) AR (mm)=SPL (mm) / 2
Lateral Resolution
the minimum reflector separation perpendicular to the sound path that is required to produce separate echoes. LR(mm)= Beam width (mm)
Piezoelectricity
conversion of pressure to electric voltage.
Curie Point
the temperature at which an element material loses its piezoelectric properties.
Damping Material
a mixture of a plastic or epoxy resin attached to the rear face of the transducer element.
Matching Layer
a material attached to the front face of a transducer element to reduce the reflections at the transducer surface.
Coupling Medium
a gel used to provide a good sound path between a transducer and the skin by eliminating the air in between the two.
Sound Beam
the region of a medium that contains virtually all of the sound produced by a transducer.
Side Lobes
weaker beams of sound traveling out of a single element in directions different from those of the primary beam.
Aperture
size of a transducer element (for a single-element transducer) or a group of elements (for an array).
Near Zone Length (NZL, Fresnel Zone)
the region of a sound in which the beam diameter decreases as the distance from the transducer increases.
Far Zone Length (Fraunhover Zone)
the region of a sound in which the beam diameter increases as the distance from the transducer increases.
Natural Focus
the narrowing of a sound beam that occurs with an unfocused flat transducer element.
Array
a transducer assembly containing several piezoelectric elements.
Lens
a curved material that focuses a sound or light beam.
Focus
the concentration of the sound beam into a smaller beam area than would exist otherwise.
Focal Region
the region of minimum beam diameter and area.
Focal Length
the distance from a focused transducer to the center of a focal region or to the location of the spatial peak intensity. D/2
Focal Zone
the length of the focal region.
Elements
the piezoelectric component of a transducer assembly.
Scanning
the sweeping of a sound beam through the anatomy to produce an image.
Frame
a single image produced by one complete scan of the sound beam.
Real-time sonography
presenting images in a rapid sequential format like a movie.
Linear array
array made of rectangular elements arranged in a line.
Convex array
curved linear array.
Phased array
an array that steers and focuses the beam electronically with small time delays.
Line sequenced array
linear array operated by applying voltage pulses to groups of elements sequentially. It produces rectangular images composed of many parallel, vertical scan lines.
Linear phased array
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.
Convex (curved) sequence array
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.
Slice thickness
the thickness of the scanned tissue volume perpendicular to the scan plane.
Elevation resolution
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.
Partial-volume artifact
the section thickness artifact that occurs when the slice thickness is wider than the scanned structure.
Grating Lobes
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.
Vector Array
a linear sequenced array that emits pulses from different starting points and (by phasing) in different directions.
Apodization
nonuniform (involving different voltage amplitudes) driving elements in an array to reduce grating lobes.
Dynamic focusing
continuously variable reception focusing that follows the increasing depth of the transmitted pulse as it travels.
Dynamic aperture
the aperture that increases with increasing focal length (to maintain constant focal width.)
