Ch. 8, 9, & 10 Flashcards
T/F
The acoustic impedence of the matching layer is approximately the same as the acoustic impedance.
False. The impedance of the matching layer is greater than the impedance of the skin
T/F
Imaging transducers are usually of high rather than low bandwidth.
True
T/F
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
T/F
A pulse with a long pulse duration is likely to have a narrow bandwidth
True. Longer events tend to have a narrow bandwidth. Shorter have a wider bandwidth
T/F
The damping material in a transducer increases the sensitivity
False
Damping reduces sensitivity
T/F
The damping material in transducer increases the pulse length
False
Shortens pulse length
T/F
The damping material in a transducer decreases pulse duration
True
T/F
The damping material in a transducer improves the system’s lateral resolution.
False
Damping does not affect lateral resolution
T/F
The damping material in a transducer improves the system’s longitudinal resolution
True
T/F
The damping material in a transducer decreases bandwidth
False
Damping increases bandwidth
T/F
The damping material in a transducer decreases the quality factor
True
T/F
If the frequency of the electrical excitation voltage of a pulsed wave transducer is 6MHz, then the operating frequency of the transducer is 6 MHz.
False.
Pulse wave transducers, the frequency of sound Is not determine by electrical signal
T/F
If the pulse repetition frequency of a transducer is increased, then the frequency of sound produced by the transducer remains the same
True
Frequency and PRF are not related
T/F
The diameter of the active element of a transducer helps deter the frequency of a sound that the transducer creates.
False
Diameter of the active element does not determine the frequency of sound created by transducer
T/F
If the frequency of the electrical excitation voltage of a continuous wave transducer is 6MHz, then the operating frequency of the transducer is 6MHz.
True
Frequency of voltage and frequency are identical with continuous ave transducers
T/F
Two piezoelectric crystals are made from the same material the thicker the crystal will make a pulsed transducer with a higher frequency.
False
Thicker active elements create sound with lower frequency not higher
T/F
Two piezoelectric crystals are made from the same material. The thicker will make a continuous wave transducer with a lower frequency.
False
With continuous wave transducer, active element thickness does not determine the sound beam’s frequency.
T/F
The normal propagation speed in piezoelectric material is about 3 to 5 times greater than that in soft tissue.
True
Sound travels faster in PZT than soft tissue
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?
1,200,000
1,400,000
1,726,000
1,950,000
1,726,000
The impedance of the matching layer is btw that of the active element and the skin
What crystals will produce sound with the lowest frequency?
Thick and with a low speed
Which type of transducer has a greater Q factor: therapeutic or imaging?
Therapeutic have a higher Q factor than imaging transducers
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?
Improve 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 8MHz. What is the bandwidth?
8-6= 6MHz
A pulsed wave transducer has a resonant frequency of 5 MHz. The lowest frequency in the pulse is 2 MHz and the highest is 8MHz. What is the main frequency?
Main frequency is 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 8MHz. What is the Q factor?
.8
5MHz/6MHz
Unitless value less than 1. Bandwidth has no units.
What is the ability to accurately distinguish two structures lying close together called?
Resolution
The ability to distinguish two structures lying close together front to back or parallel to the sound beam is called
Longitudinal, axial, range, radial, depth resolution
Axial resolution and lateral resolution are measured with units of ___.
Distance such as mm
When the number of cycles in a pulse increases while the frequency remains the same, the numerical value of the range resolution ___.
Increases
Decreases
Same
Increases
With more cycles, the longer the pulse so the numerical value of range resolution increases
When the number of cycles in a pulse increases (more ringing) while the frequency remains the same, the image quality
Improves
Degrades
Remains the same
Degrades
____ frequency transducers have the best range resolution.
High
4 synonyms for axial range resolution
Longitudinal Axial Range Radial Depth
Synonyms for lateral resolution
Lateral
Angular
Transverse
Azimuthal
The length of a pulse is 8 mm. What is the minimum stance btw two reflectors, positioned one in front of the other, that still produces two echoes on our image?
4 mm
-this value is 1/2 the pulse length
