You are given 5 substances: backing material, PZT, matching layer, gel, and skin, whos impedances have been measured. Unfortunately the labels identifying the impedances of each substance have fallen off these materials. There are 5 labels, indicating impedances of 0.8 Mrayls, 1.9 Mrayls, 1.6 Mrayls, 2.0 Mrayls, and 1.0 Mrayls. If the impedance of the backing material is 1.9 Mrayls, what are the impedances of soft tissue, matching layer, gel and PZT? Why?
soft tissue: 0.8 Mrayls
gel: 1.0 Mrayls
matching layer: 1.6 Mrayls
PZT: 2.0 Mrayls
Impedance decreases as it moves from the PZT to the skin
Pulse length is __________ related to pulse duration. (directly, inversely)
directly
Q-factor is __________ related to bandwidth (directly, inversely)
inversely
Pulse duration is __________ related to bandwidth. (directly, inversely)
inversely
The sensitivity of transducers that create short duration pulses is likely to be __________ that of transducers that create long pulses. (greater than, less than, equal to)
less than
All of the following correctly describe an imaging transducer except:
A. high sensitivity
Transducers have low sensitivity
True or False.
Shorter duration events (such as dampened pulses) are more likely to be wide bandwidth.
True
What occurs when a PZT crystal's temperature is elevated above the Curie point?
the PZT is depolarized
True or False.
The acoustic impedance of the matching layer is approximately the same as the acoustic impedance of skin.
False.
matching layer is greater than skin impedance
True or False.
Imaging transducers are usually of high rather than low bandwidth
True.
aka wide bandwidth
True or False.
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
True or False.
A pulse with a long pulse duration is likely to have a narrow bandwidth.
True.
True or False.
The damping material in a transducer increases the sensitivity.
False.
damping reduces sensitivity
True or False.
The damping material in a transducer increases the pulse length.
False.
damping shortens pulse length
True or False.
The damping material in a transducer decreases the pulse duration.
True.
True or False.
The damping material in a transducer improves the system's lateral resolution.
False.
damping does not affect lateral resolution
True or False.
The damping material in a transducer imporves the systems lateral resolution.
True.
True or False.
The damping material in a transducer decreases the bandwidth.
False.
damping increses bandwidth
True or False.
The damping material in a transducer decreases quality factor.
True
True or False.
If the frequency of the electrical excitation voltage of a pulsed wave transducer is 6 MHz, then the operating frequency of the transducer is 6 MHz.
False.
With pulsed wave transducers, the frequency of sound is not determined by the electrical signal.
True or False.
If the pulse repetition frequency of a transducer is increased, then the frequency of sound produced in the transducer remains the same.
True.
Frequency and PRF are not related.
True or False.
The diameter of the active element of a transducer helps to determine the frequency of the sound produced by the transducer.
False.
The thickness does
True or False.
If the frequency of the electrical excitation voltage of a continuous wave transducer is 6 MHz, then the operating frequency of the transducer is 6 MHz.
true
True or False.
Two piezoelectric crystals are made from the same material. The thicker crystal will make a pulsed transducer with a higher frequency.
False.
Thicker crystal = lower frequency
True or False.
Two piezoelectric crystals are made of the same material. The thicker crystal will make a continuous wave transducer with a lower frequency.
False.
with continuous wave, the active element thickness does not determine frequency
True or False.
The normal propagation speed in piezoelectric material is about 3 to 5 times greater than is soft tissue.
True.
The impedance of a transducer active element is 1,900,000 rayls, and the impedance of the skin is 1,400,000 rayls. What is an acceptable impedance for the matching layer?
C. 1,726,00 rayls because it is between the two impedances
Which of the following crystals will produce sound with the lowest frequency?
C. thick and low speed
Which type of transducer has a greater Q-factor: therapeutic or imaging?
therapeutic
Which type of transducer has greater bandwidth: continuous wave or imaging?
imaging
Which type of transducer has more backing material: therapeudic or imaging?
imaging
In an imaging transducer, what is the purpose of attaching the backing material to the PZT?
to improve the image quality
A pulsed wave transducer has a resonant frequency of 5 MHz. The lowest frequency in the pulse is 2 MHz and the highest is 8 MHz. What is the bandwidth?
6 MHz
8 MHz - 2 MHz
A pulsed wave transducer has a resonant frequency of 5 MHz. The lowest frequency in the pulse is 2 MHz and the highest is 8 MHz. What is the main frequency?
5 MHz
A pulsed wave transducer has a resonant frequency of 5 MHz. The lowest frequency in the pulse is 2 MHz and the highest is 8 MHz. What is the Q-factor?
