book study questions Test3 Flashcards
You are given 5 substances:
backing material, PZT, matching layer, gel, skin
five impedances of:
0.8 Mrayls, 1.9 Mrayls, 1.6 Mrayls, 2.0 Mrayls, 1.0 Mrayls
If the impedance of the backing material is 1.9 Mrayls, what are the impedances of the other four?
The impedance of the active layer is similar to the backing material, so:
backing material-1.9Mrayls
PZT-2.0Mrayls
matching layer-1.6Mrayls
gel-1.0Mrayls
skin-0.8Mrayls
in order of the course of the energy from the PZT through the skin
Is pulse length directly or inversely related to pulse duration?
directly
Is Q-factor directly or inversely related to bandwidth?
inversely
Is pulse duration directly or inversely related to bandwidth?
inversely
The sensitivity of transducers that create short duration pulses is likely to be (greater than, less then, or equal to) that of transducers that create long pulses.
less than
Describe an imaging transducer:
low sensitivity
low Q
wide bandwidth
damped
Shorter duration events (such as dampened pulses) are more likely to be wide bandwidth.
True
What occurs when a PZT crystal’s temp is elevated above the Curie point?
the PZT is depolarized
the crystal’s piezoelectric properties are lost and the transducer is ruined
The acoustic impedance of the matching layer is approx the same as the acoustic impedance of skin
False
impedance of matching layer is greater than that of the skin
Imaging transducers are usually of high rather than low bandwidth
True
A very high Q factor transducer is used more often in diagnostic imaging transducers than a low Q factor
False
Imaging transducers are low-Q
A pulse with a long pulse duration is likely to have a narrow bandwith
True
The damping material in a transducer increases the sensitivity
False
damping reduces sensitivity
The damping material in a transducer increases the pulse length
False
damping shortens pulse length
The damping material in a transducer decreases the pulse duration
True
The damping material in a transducer improves the system’s lateral resolution
False
damping does not affect lateral resolution
The damping material in a transducer improves the system’s longitudinal resolution
True
The damping material in a transducer decreases the bandwidth
False
damping increases bandwidth
The damping material in a transducer decreases the quality factor
True
If the frequency of the electrical excitation voltage of a pulsed wave transducer is 6MHz, then the operating frequency of the transducer is 6MHz
False
pulsed wave transducers-frequency of sound is not determined by the elcetrical signal
If the pulse repetition frequency of a transducer is increased, then the frequency of sound produced by the transducer remains the same
True