Ultrasound: Transducers

Front 1

ultrasound transucers convert electrical signals into _________ , and mechanical acoustic energy into _________

Back 1

mechanical acoustic enrgey
electiral signals

Front 2

examples of pizoelectric materials

Back 2

ceramics, quartz, lithium, lead zinconate titanate (PZT), tourmaline

Front 3

Curie point

Back 3

heat at which negative charges align and remain when cooled, used in process to make transducers

Front 4

For transducers, the thinner the crystal, and the higher the higher the pizoelectric material's propogation speed, the _______ the resonant frequency

Back 4

higher

Front 5

Resonant frequency:

Back 5

f (MHz) = c (mm/sec) / 2 x thickness;

Front 6

Most effective thickness of the crystal

Back 6

half the wavelength

Front 7

bandwith =

Back 7

range of operating frequencies within a transducer

Front 8

Q factor, transducer Q

Back 8

tranducer's center (or resonant) frequency dvided by bandwith

For example, a a transudcer with center fire frequency of 3.375 and a 4 MHz bandwidth (2-6), would have a Q factor of 0.9735

Front 9

low Q factor used for ______

high Q factor used for _______

Back 9

pulse echo ultrasound

therapeutic US and Doppler - high Q rings longer, has long pulse length, narrow range of frequencies and resultant narrow bandwidth

Front 10

lighter dampening leads to _____ pulse and _____ bandwith

heavy damping leades to _______ pulse and _______ bandwith

Back 10

longer, narrower
(long pulse -> less listening -> poor resolution)

shorter, wider
(short pulses -> longer receiving times -> better resolution)

Front 11

goal of dampening

Back 11

reduce the number of cycles of pulse, reduce ringing, shorter pulse, better receiving

Front 12

2 damping criteria

Back 12

acoustic impedance - reduces reflections at crystal-damping interface

absorb energy - to dampen vibrations of piezoelectric element

Front 13

reduction in pulse length leads to __________ resolution, but causes __________ sensitivity

Back 13

increased, decreased

Front 14

Multi-Hertz frequencies pros

Back 14

ability to switch between frequency depending on image need (high frequency for better resolution, low frequency for better penetration; adult vs ped; switch between body sites, )

Less transducers needed

Front 15

conventional pulse:
harmonic pulse:

Back 15

transmitted and recieved pulse at a certain range