test review Chapter 8 & 9 Flashcards
thinner PZT crystal
PZT with higher speeds
high freq pulsed trandsucers
thicker PZT crystals
PZT with lower speeds
lower freq pulsed transducers
pulses with short duratoin and length
use backing material
reduced sensitivity
wide bandwidth (broadband)
lower Q-factor
improved axial resolution
imaging tranducer characteristics
depolarizes
loses the piezoelectric properties
PZt at the curie point
piezoelectric effect
when PZT changes shape
lead zirconate titanate
ceramic
active element
crystal
names for PZT
backing or damping material
reduces ringing in the transducer
main frequency/bandwidth=
Q Factor
speed of
4-6 mm/µs
propagation speed of PZT material
speed is 4 times greater than in soft tissue
prop speed of PZT
thinner PZT crystal
higher freq output
thicker PZT crystal
lower freq output
optimizes pulses created by imaging transducers
backing material improvements
greater than the matching layer
20 x that of the skin
impedence of the active element
thin barrieir of cork isolates or uncouples the internal components of the transducer from the case
accoustic insulator
increases the efficiency of sound energy transfer between the active element and the body
matching layer
larger diameter transducer
higher freq
deeper focus
smaller diameter transducer
lower freq
shallow focus
lower freq transducer
shorter near zone
higher freq transducer
longer near zone
diameter^2 x freq/6 =
focal depth
larger diameter
higher freq
less divergence
smaller diameter
lower freq
more divergence
how is freq of sound determined?
thickness of pzt
how is focal depth determined
transducer diameter
freq of sound
how is divergence determined
transducer diameter
freq of sound
improved lateral resolution
larger diameter transducer
higher freq
depth where sound beam is half the diameter of the beam at the transducer
focal depth
frequency does not change, diamter of the transducer increase, what happens to the wavelength?
no change in wavelength
frequency does not change, diamter of the transducer increase, what happens to the near zone length?
near zone length increases
what determines the spread of the beam in the far field?
transducer diamter
freq of sound
less divergence
larger diamter
higher Freq
more divergence
smaller diameter
lower freq
spherical waves
defracction patterns
Huygens wavelets
created by small pieces of PZT
V shaped
Fresnal zone
near zone
Fraunhofer zone
far zone
sound beam
1
near zone
Fresnal zone
sound beam
2
far zone
Fraunhofer zone
sound beam
3
focal zone
sound beam
4
focus
