Physics Mod 4

Question 1

5 basic subsystems that comprise the ultrasound system

Answer 1

1) transducer
2) pulser (transmitter)
3) front end (receiver)
4) back end (scan converter)
5) storage and display

Question 2

5 basic functions of the front end receiver

Answer 2

1) Amplification (gain)
2) compensation (TGCs; time gain compensation)
3) compression
4) demodulation
5) rejection

3-5 are not user controllable

Question 3

Goal of compression

Answer 3

Reduce dynamic range of the signal

Question 4

Noise floor define

Answer 4

Amplitude level below which no signals are visible because of the presence of noise

Question 5

Signal to noise ratio

Answer 5

Amplitude of the signal divided by the amplitude of the noise

Question 6

Signal coherance to improve SNR

Answer 6

Signals double with perfect constructive interference

Noise has partial constructive interference so only 1.4 as large (square root of 2)

Question 7

Transmit vs receiving frequency

Answer 7

Transmit = fundamental frequency
Receive = 2xtransmit = second harmonic

Question 8

Broadband transducer define

Answer 8

Fits both transmit bandwidth and receive bandwidth

Question 9

Harmonic generation vs depth

Answer 9

Nearfield = weak harmonic generated
Farfield = harmonic frequency attenuated faster than produced

Question 10

Harmonic energy and grating lobes

Answer 10

Lower energy grating lobes = weaker harmonic signal = reduce energy in grating lobes = improved lateral resolution

Question 11

Clutter reduction

Answer 11

Clutter zone is the nearfield zone
Harmonic signal significant weaker than fundamental signal in the clutter zone
Harmonic imaging reduces clutter