Transducers Flashcards
What is the piezoelectric effect?
heat is applied which causes crystals to vibrate and send sound wave to medium
What is the most common piezoelectric material?
lead zirconate titanate (PZT)
PZT is also called?
crystal, ceramic, active element
What is polarization?
heating of PZT to Curie temperature to activate piezoelectric properties
What is depolarization?
PZT is heated past Curie temperature and loses piezoelectric properties
What is Curie temperarure?
365 degrees C
Phased transducers can be?
steered electronically
Vector transducers can?
angle the image; rectangle to trapezoid
Which type of transducer contains multiple closely spaced crystals with an individual connection?
Array
Which type of transducer has multiple crystals and electronic steering?
phased array
Phased array transducers are always?
adjustable or multifocus
Mechanical transducers are also called?
Liquid path, motorized, wobble, fixed focus
A mechanical transducer contains how many elements?
1
Image shape of a mechanical transducer
fan or sector shaped
How is a mechanical transducer steered?
Mechanically; motor rotates single crystal
Which type of transducer has a single fixed focus?
mechanical
Mechanical transdcuers have _____ resolution in the far field
decreased
If the element of a mechanical transducers is damaged, what will happen to the image?
completely lost; one crystal
Which artifact is created with a mechanical transducers?
side lobes
What is side lobe artifact?
hyperechoic lines appear to the side of anatomy in the far field
What is used to correct side lobes?
Apodization
How are the elements arranged in a linear array?
straight line
How are the elements arranged in a convex array?
bowed or arched line (curved)
Linear arrays are also called?
Linear switch array
A linear array image has what shape?
rectangle
A linear array has what type of steering?
electronic
How are the elements energized in a linear sequential/switched array?
individually in a sequence
How are the elements energized in a linear segmental array?
in groups
If a crystal is damaged in an array, what will happen to the image?
single vertical dropoff
Image shape of a curved array transducer
fan or sector
Which is the only type of transducer that is both mechanical and electric?
annular phased array
How are the elements of an annular phased array arranged?
concentric circles (onion)
An annular phased array has what kind of steering?
mechanical
If a crystal malfunctions in an annular phased array, what will happen to the image?
horizontal dropout
What artifact is created by linear phased array?
grating lobes
What corrects grating lobes?
apodization and subdicing
What are grating lobes?
hyperechoic lines on the side of anatomy in the near field
Vector arrays contain a combination of _____ steering and _______ focal zones
electronic; multiple
