DAVIES LATEST
ULTRASOUND
PHYSICS REVIEW
Ultrasound propagation velocity depends on: - ANSWERS-Density and
compressibility
You notice that the image in the far field is less bright compared to the
near field. This is due to: - ANSWERS-Sound attenuation
As sound propagates thru tissue, the beam strength is weakened thru
absorption, reflection and other interactions w the medium. This
weakening of beam strength is termed attenuation and accounts for
decreased brightness of the image in the far field compared to the near
field
Acoustic impedance: - ANSWERS-Equals density times the propagation
speed
Z=pc
What determines the speed of sound? - ANSWERS-Medium thru which
sound waves passes
END OF
PAGE
1
, DAVIES LATEST
ULTRASOUND
PHYSICS REVIEW
You will NOT see refraction in the sonographic image if: - ANSWERS-
The sound beam is perpendicular to the interface
Refraction is a bending of the sound beam and occurs whenever the
beam strikes an interface where the propagation speed is different
between the two media and the angle of incidence is not perpendicular
(oblique incidence)
The rate of sound attenuation in lowest in: - ANSWERS-Water
When you perform a doppler exam, the freq of the transmitted signal is
determined by: - ANSWERS-The freq of the electric signal applied to
the txd
Broad bandwidth txd can be driven at different freq. In doppler sono,
longer duration pulses generally are used. The freq is determined by the
pulse transmitter (s). The sonographer can change the ultrasound freq for
doppler studies, similar to the way she/he can change the freq in B mode
imaging.
END OF
PAGE
2
, DAVIES LATEST
ULTRASOUND
PHYSICS REVIEW
Power divided by the beam area is equal to the: - ANSWERS-Intensity
The unit for intensity is watts/m2, which is "power per unit area"
Axial resolution is determined chiefly by: - ANSWERS-Pulse duration
The shorter the pulse duration, the better the axial resolution
Choose two benefits of tissue harmonic imaging - ANSWERS-Grating
lobe artifacts are reduced and lateral resolution is improved
Grating lobe beams are not strong enough to generate harmonics and are
therefore greatly reduced in harmonic imaging. Lateral resolution is
improved bc the harmonic beam width is narrower since harmonics are
generated only from the portion of the beam w the highest intensity
signal
***Acoustic impedance increases w which of the following: -
ANSWERS-Increased tissue density
END OF
PAGE
3
, DAVIES LATEST
ULTRASOUND
PHYSICS REVIEW
Increased propagation speed
***When you adjust the pulse repetition freq, you are changing: freq,
you are changing: - ANSWERS-The number of pulses per second
***Which of the following would increase the spatial pulse length? -
ANSWERS-Increased number of cycles per pulse
Doppler pulses used for diagnostic purposes are
typically______________cycles long: - ANSWERS-5-30
The time it takes for one pulse to occur is known as the: - ANSWERS-
Pulse duration
The length of space over which one cycle occurs is known as the: -
ANSWERS-Wavelength
Bandwidth refers to: - ANSWERS-Range of freq in a pulse
END OF
PAGE
4
ULTRASOUND
PHYSICS REVIEW
Ultrasound propagation velocity depends on: - ANSWERS-Density and
compressibility
You notice that the image in the far field is less bright compared to the
near field. This is due to: - ANSWERS-Sound attenuation
As sound propagates thru tissue, the beam strength is weakened thru
absorption, reflection and other interactions w the medium. This
weakening of beam strength is termed attenuation and accounts for
decreased brightness of the image in the far field compared to the near
field
Acoustic impedance: - ANSWERS-Equals density times the propagation
speed
Z=pc
What determines the speed of sound? - ANSWERS-Medium thru which
sound waves passes
END OF
PAGE
1
, DAVIES LATEST
ULTRASOUND
PHYSICS REVIEW
You will NOT see refraction in the sonographic image if: - ANSWERS-
The sound beam is perpendicular to the interface
Refraction is a bending of the sound beam and occurs whenever the
beam strikes an interface where the propagation speed is different
between the two media and the angle of incidence is not perpendicular
(oblique incidence)
The rate of sound attenuation in lowest in: - ANSWERS-Water
When you perform a doppler exam, the freq of the transmitted signal is
determined by: - ANSWERS-The freq of the electric signal applied to
the txd
Broad bandwidth txd can be driven at different freq. In doppler sono,
longer duration pulses generally are used. The freq is determined by the
pulse transmitter (s). The sonographer can change the ultrasound freq for
doppler studies, similar to the way she/he can change the freq in B mode
imaging.
END OF
PAGE
2
, DAVIES LATEST
ULTRASOUND
PHYSICS REVIEW
Power divided by the beam area is equal to the: - ANSWERS-Intensity
The unit for intensity is watts/m2, which is "power per unit area"
Axial resolution is determined chiefly by: - ANSWERS-Pulse duration
The shorter the pulse duration, the better the axial resolution
Choose two benefits of tissue harmonic imaging - ANSWERS-Grating
lobe artifacts are reduced and lateral resolution is improved
Grating lobe beams are not strong enough to generate harmonics and are
therefore greatly reduced in harmonic imaging. Lateral resolution is
improved bc the harmonic beam width is narrower since harmonics are
generated only from the portion of the beam w the highest intensity
signal
***Acoustic impedance increases w which of the following: -
ANSWERS-Increased tissue density
END OF
PAGE
3
, DAVIES LATEST
ULTRASOUND
PHYSICS REVIEW
Increased propagation speed
***When you adjust the pulse repetition freq, you are changing: freq,
you are changing: - ANSWERS-The number of pulses per second
***Which of the following would increase the spatial pulse length? -
ANSWERS-Increased number of cycles per pulse
Doppler pulses used for diagnostic purposes are
typically______________cycles long: - ANSWERS-5-30
The time it takes for one pulse to occur is known as the: - ANSWERS-
Pulse duration
The length of space over which one cycle occurs is known as the: -
ANSWERS-Wavelength
Bandwidth refers to: - ANSWERS-Range of freq in a pulse
END OF
PAGE
4
