Transducers and Beams Flashcards
size of the source
Aperture
A method for reducing side lobes (lateral array elements) in some arrays. It gradually decreases the vibration of the transducer surface with distance from its center by improving the directivity.
Apodization
A collection of active elements within a transducer housing
Array
Perpendicular to scan plane
Axial
The minimum distance 2 structures are separated from front to back or anterior to posterior, and still be distinguished as separate by the ultrasound machine
Axial Resolution
width of the pulse as it travels away from the transducer
Beam
Man Made-improves bandwidth, sensitivity, resolution elements
Composite
Crystals arranged in an arc; sector shape format
Convex array
Natural materials: Quartz, Rochelle salts, tourmaline
Man-made: Lead zirconate titanate or PZT barium titanate, lead metaniobate, lead titanate
Crystal
Transducer crystals lose their piezoelectric properties if they are heated above a critical temperature
Curie point
Material bonded to the back of the active element; limits “ringing” of the crystal; shortens pulse duration and spatial pulse length, therefore improving image quality
Damping
the machine’s ability to see and differentiate small structures and represent them (anatomically) correctly on the ultrasound image
Detail resolution
continually changing focus
Dynamic focusing
piezoelectric element, active element, or crystal
Element
Slice thickness resolution
Elevational resolution
Place where the beam begins to diverge (Fraunhofer zone)
Far zone
the distance from the transducer face to the focus
Focal length
Focus Near Zone Focal Length (focal depth, near zone length) Far Zone Focal zone
Focal region
the area of highest, most uniform beam intensity
Focal zone
improve resolution at given depth
Focus
unwanted parts of the ultrasound beam emitted off axis that produce image artifacts due to error in positioning the returning echo.
Grating lobes
Scan plane width or beam diameter
Lateral
The minimum distance that two side by side structures can be separated and still show 2 separate echoes on the screen.
Lateral resolution
one of the world’s most widely used piezoelectric ceramic materials (man made)
Lead zirconate titanate
external focusing
Lens
Arranged in or extending along a straight or nearly straight line
Linear
parallel scan line, width & length of image are approximately equal for superficial structures
Linear array
Beam steering and focusing is electronic
Phased array or electronic sector
Linear phased array
no fixed focus , with rectangle image, sequencing beams large acoustic footprint
Linear sequenced array
Reduces reflections at transducer - tissue interface
Also called impedance matching layer
Matching layer
transition point between the near field and the far field of a non focused transducer
Natural focus
Region between the transducer and the focus
Also called the Fresnel zone
Near zone
Resonant Frequency or natural frequency depends on thickness of the crystal, and Speed of sound in the crystal
Operating frequency
adjustable, multi-focus
Phased array
phased focus control is applied to a linear sequenced array.
Phased linear array
electricity or electric polarity due to pressure especially in a crystalline substance
Piezoelectricity
to search into or examine thoroughly
Probe
the machine’s ability to image structures with accuracy
Resolution
The operating frequency of a transducer
Resonance frequency
pie shaped image
Sector
some of the energy from transducer radiates at various angles to the transducer face
Side lobes
any device that converts one form of energy into another
Transducer
Combination of phased array electronics and linear sequential array probes to provide electronic steering and multiple focal zones
Vector array
