Physics final exam review

An acoustic wave is traveling through soft tissue. Its intensity undergoes 6dB of attenuation.  How does the final intensity of the wave relate to the intensity of the wave when it started its journey?

• A) It is now 4x larger

• B) It is now 6x larger

• C) it is now 1/4 as large

• D) it is now 1/10 as large

Answer explanation

•Requires 2 intensities

•Units: dBUnits: dB

•Atennuation means a decrease in intensity

•Relative changesR

• A wave's intensity is 2 mW/cm^2.  There is a change of +9dB.  What is the final intensity?

• A) 6 mW/cm^3

• B) 2 mW/cm^3

• C) 16 mW/cm^3

• D) 16 nsW/cm^3

Which two controls determine a system’s temporal resolution?

• A)Frame rate and sector size

• B)Focal zones and sector depth

• C)Prop speed and frame rate

• D)Depth of view and pulses per image

How many dB represents a 100-fold increase in the intensity of an acoustic pulse

• A) 10

• B) 20

• C) 100

• D) 6

True or false: Side lobes degrade axial resolution.

• True

• False

Answer explanation

The degrade lateral resolution

Two imaging systems produce acoustic pulses; one pulse is 0.4 µsec long and the other is 0.2 µsec long.  Which is most likely to provide the best temporal resolution?

• A) 0.4 µsec system

• B) 0.2 µsec system

• C) They are the same

• D) Cannot be determined

You are producing a diagnostic ultrasound system.  System X has an axial resolution of 0.7 mm whereas System Y is 0.4 mm.  Based on this information, which system will produce the better quality image?

• A) System X

• B) System Y

• C) They have the same quality

• D) Cannot be determined

Two systems produce acoustic pulses.  A pulse from system 1 has a wavelength of 0.5 mm, 4 cycles per pulse, and a PRP of 1.2 msec.  The pulses from system 2 have a wavelength of 1.0 mm, 2 cycles per pulse, and a PRP of 1.8 msec.  Which system will have a lower numerical value of axial resolution?

• A) System 1

• B) System 2

• C) Both are the same

• D) Cannot be determined

The lateral resolution of an ultrasound system is 4mm.  Two structures are separated by 3mm and lie side by side in relation to the sound beam’s main axis.  What will most likely appear on the system’s display?

• A) Two weak echoes, 4 mm apart

• B) Two weak echoes, 3 mm apart

• C) One echo

• D) Two bright echoes, 7 mm apart

Which of the following increases the frame rate by a factor of 3?

• A) Setting imaging depth to 3

• B) Changing imaging depth from 10 cm to 3 cm

• C) Changing sector angle from 90 to 45 degrees

• D) Changing imaging depth from 21 cm to 7 cm