7 Transducers Flashcards
What is a transducer?
Any device that converts one form of energy into another
What is the piezoelectric effect?
Property of certain materials to create a voltage when pressure is applied or when the material is mechanically deformed
What are some piezoelectric materials?
Ferroelectric material
Natural - quartz, Rochelle salts, tourmaline
Synthetic - man-made, barium titanate, lead titanate, lead metaniobate, lead zirconate titanate (PZT)
What is Curie temperature or Curie point?
When PZT is heated above this temp (360C or 680F), it loses its piezoelectric properties - the PZT is depolarized
What size is the active element of a basic imaging transducer?
1/2 wavelength thick
What is the active element of a basic imaging transducer?
Piezoelectric crystal - ceramic, PZT or crystal
What are the components of a basic imaging transducer?
Case Backing material Wire Crystal Matching layer
What is the wire in a basic imaging transducer?
The electrical connection for the voltage from the system that excites the crystal which produces sound during transmission
What is the matching layer of a basic imaging transducer?
1/4 wavelength thick layer with impedance between those of the skin and the active element to increase the percentage of transmitted US between the active element and the skin
What is the damping element or backing material of a basic imaging transducer?
Material bonded to the active element to reduce it’s “ringing”
Short pulses create better images
What are the characteristics of an imaging transducer?
Damping is effective Short pulse length & duration Low sensitivity Wide bandwidth Low Q Decreased output power
What is bandwidth?
Range of frequencies between the highest and the lowest frequency emitted from the transducer
What type of bandwidth is in imaging transducers?
Wide bandwidth or broadband
What is Quality factor?
Unitless number representing the extent of damping
Imaging transducers are low-Q transducers when compared to therapeutic transducers because imaging transducers use backing material
What determines the resonant frequency of a pulsed transducer?
Main or center frequency of sound determined by crystal thickness and propagation speed of the piezoelectric material
