Chapter 8 Q & A Flashcards
given 5 subtances: Backing material, matching layer, PZT, gel and skin, whose impedences have been emasured. The lables have fallen off. Lables are 0.8Mrayls, 1.9Mrayls, 1.6Mrayls, 2.0Mrayls and 1.0Mrayls.
If the impedence of the backing is 1.9Mryals what are the others?
Why
PZT 2.0 Mryals
matching layer 1.6 Mrayls
gel 1.0 Mrayls
skin 0.8 Mrayls
because the impdedences along the path decrease the closer you get to the skin
PZT>matching>backing>gel>skin
Pulse length is (directly/incersely) related to pulse duration
directly
Q-factor is (directly/inverserly) related to bandwidth
inversely
pulse duration is (directly/inversely) related to bandwidth
inversely
the sensitivity of transducers that create short duration pulses it likely to be (greather/less/equal to)that of transducers that create long pulses
less than
all correctly describe an imaging transducer except
A: high sensitivity
B low Q
C wide bandwidth
D damped
A does not describe imaging transducers
shorter duration events (such as damped pulses) are more likely to be wide bandwidth
True/False
true
short duratoin events are likely to be wide bandwidth
what occurs when a PZT crystal’s temp is raised above the Curie point
PZt is depolarized and the piezoelectric properties are lost
transducer is ruined
the accoustic impedence of the matching layer is approx the same as the accoustic impedance of skin
True/False
False
imaging transducers are usually of high rather than low bandwidth
True
A very high Q factor transducers is used more often in diagnostic imaging than a low Q factor
true/false
false
imaging transducers are low Q
the damping material in a transducer increases the sensitivy
true/false
false
damping material in a transducer increases the pulse length
true/false
false
damping shortens the pulst length
damping material in a transducer decreases the pulse duratoin
true./false
true
damping reduces pulse duration
damping material in a transducer improves the systems lateral resolutoin
true/false
false
damping does not affect lat res
damping material in a transducer improves the systems longitudinal resolution
true/false
true
damping improves longitudinal res
damping material in a transducer decreases bandwidth
true/false
false
damping increases bandwidth
damping material in a transducer decreases the quality factor
true/false
true
damping decreases the Q factor
if the freq of the electrical excitation voltage of a pulsed wave transducer is 6 MHz, then the operating freq of the transducer is 6 MHz
true/false
false
pulsed freq is NOT determined by excitation freq
if the pulse repitition freq of a transducer is increased, then the freq of sound produced by the transducer remains the same
true/false
true
Freq and pulse rep are not related
the diameter of the active element of a transducer helps to determine the freq of the sound that the transducer creates
true/false
false
freq of the electrical excitation voltage of a continuous wave transducer is 6 MHz then the operating freq is 6 MHz
True/false
true
Only CW transducers
two piezoelectric crystals are made from the same material. The thicker crystal will make a continuous wave transducer with a lower freq
true/false
false
with CW element thickness does not determine sound freq
the normal propagatoin speed in piezoelectric material is about 3 to 5 times greater than that is soft tissue
true/false
true
the impedance of a transducer active element is 1.9 Mrayls and the impedance of the skin is 1.4 Mrayls
what is an acceptable impedance for the matching layer?
A 1.2 Mrayls
B 1.4 Mrayls
C 1.726 Mrayls
D 1.95 M rayls
C
the impedance of the matching layer is between that of the active element and the skin
which of the following crystals will produce sound with the lowest freq?
A thin with low speed
B thin with a high speed
C thick with a low speed
D thick with a high speed
C
lowest freq is produced by thick and slow active element
WHich tyupe of transducer has a great Q-factor, therapeutic or imaging
therapeutic
which type of transducer has a greater bandwidth, continuous wave or imaging
imaging
which type of transducer has more backing material, therapeutic or imaging
imaging
in an imaging transducer, what is the purpose of attaching the backing material to the PZT?
A increase bandwidth
B decrease the Q-factor
C improve image quality
D decrease the transducers sensitivity
C
improve image quality
a pulsed wave transducer has a resonant freq of 5 MHz. The lowest freq in the pulse is 2 MHz and the highest is 8 MHz. What is the bandwidth?
A 5 MHz
B 8 Mhz
C 3 MHz
D 6 MHz
E 2 MHz
D
bandwidth is the range of freq found in a pulse
8 MHZ-2 MHz=6 MHz
for the transducer described in # 25, what is the main freq?
(resonant 5 MHz, low 2 MHz, high 8 MHz)
A 5 MHz
B 8 Mhz
C 3 MHz
D 6 MHz
E 2 MHz
A
the resonant , main or center freq is 5 MHz
for the transducer described in # 25, what is the Q-factor
(resonant 5 MHz, low 2 MHz, high 8 MHz)
A 0.8
B 3 MHz
C 5 MHz
D 1.5
E 2 MHz
A
Q-factor is a resonant freq divided by the bandwidth
5 MHz/6 MHz=.8
Band width has no units.
