DMS 104 Final Exam Review Questions With Complete
Solutions
Advantage of CW Correct Answers CW ultrasound can
measure very high velocities.
Aliasing Correct Answers Pulsed Doppler's significant
disadvantage is aliasing, the inability to correctly measure high
velocities. High velocities appear negative. Aliasing is the most
commonly observed artifact in pulsed Doppler imaging.
B - SCAN: B-mode Correct Answers provides data along a
straight line as an US beam propagates. If the location and
angulation of the transducer are known by the ultrasound
system, it is possible to create a two-dimensional image from
multiple B-mode pulses.
Bi-directional Doppler Correct Answers Bi-directional Doppler
- a more sophisticated ultrasound system that distinguishes
between positive and negative Doppler shifts. The positive and
negative Doppler signals are processed independently. Flow
toward and away from the transducer is identified.
Continuous wave (CW): Correct Answers Doppler units use
two crystals in the transducer: one to transmit the sound waves
of constant frequency continuously and one to receive the
reflected echoes continuously
While the transmitter is constantly sending out US energy (duty
factor --- 1.0) the receiver is continuously listening.
, Sound cannot be used for imaging.
Continuous waves major disadvantage: Correct Answers Range
ambiguity.
Echoes can come from anywhere along the length of the beam.
The spectrum produced by a continuous wave system displays
Doppler shifts created by any blood cells intersecting the path of
the sound beam.
Coupling gel is applied between the transducer and patient's skin
during scanning to Correct Answers Eliminate the crystal air
interface
CURIE TEMPERATURE - If we heat piezoelectric material
above this temperature, the material is ________________and
loses its piezoelectricity forever. Correct Answers Depolarized
Currie Temperature Correct Answers If we heat piezoelectric
material above this temperature, the material is depolarized and
loses its piezoelectricity forever! We cannot heat sterilize or
autoclave transducers. (300-400C) (365 C for PZT)
Damping material Correct Answers 1. shortens the spatial pulse
length and pulse duration.
2. improves picture quality.
3. increases bandwidth (the range of frequencies within the
pulse).
4. decreases the "Q" factor. A low Q transducer.
5. decreases the transducer's sensitivity to reflected echoes
6. decreases output intensity
Solutions
Advantage of CW Correct Answers CW ultrasound can
measure very high velocities.
Aliasing Correct Answers Pulsed Doppler's significant
disadvantage is aliasing, the inability to correctly measure high
velocities. High velocities appear negative. Aliasing is the most
commonly observed artifact in pulsed Doppler imaging.
B - SCAN: B-mode Correct Answers provides data along a
straight line as an US beam propagates. If the location and
angulation of the transducer are known by the ultrasound
system, it is possible to create a two-dimensional image from
multiple B-mode pulses.
Bi-directional Doppler Correct Answers Bi-directional Doppler
- a more sophisticated ultrasound system that distinguishes
between positive and negative Doppler shifts. The positive and
negative Doppler signals are processed independently. Flow
toward and away from the transducer is identified.
Continuous wave (CW): Correct Answers Doppler units use
two crystals in the transducer: one to transmit the sound waves
of constant frequency continuously and one to receive the
reflected echoes continuously
While the transmitter is constantly sending out US energy (duty
factor --- 1.0) the receiver is continuously listening.
, Sound cannot be used for imaging.
Continuous waves major disadvantage: Correct Answers Range
ambiguity.
Echoes can come from anywhere along the length of the beam.
The spectrum produced by a continuous wave system displays
Doppler shifts created by any blood cells intersecting the path of
the sound beam.
Coupling gel is applied between the transducer and patient's skin
during scanning to Correct Answers Eliminate the crystal air
interface
CURIE TEMPERATURE - If we heat piezoelectric material
above this temperature, the material is ________________and
loses its piezoelectricity forever. Correct Answers Depolarized
Currie Temperature Correct Answers If we heat piezoelectric
material above this temperature, the material is depolarized and
loses its piezoelectricity forever! We cannot heat sterilize or
autoclave transducers. (300-400C) (365 C for PZT)
Damping material Correct Answers 1. shortens the spatial pulse
length and pulse duration.
2. improves picture quality.
3. increases bandwidth (the range of frequencies within the
pulse).
4. decreases the "Q" factor. A low Q transducer.
5. decreases the transducer's sensitivity to reflected echoes
6. decreases output intensity
