Ultrasound Flashcards
1
Q
What are the parameters for ultrasound
A
Frequency 20 kHz - 20 MHz
Wavelength mm
Frequency MHz
2
Q
Recall the time equation for ultrasound
A
t = 2d/C
3
Q
What are the clinical implications of reflection in US imaging
A
Must image heart avoiding ribs
Acoustic coupling gel must be used
4
Q
Define a decibel
A
A relative measure of intensities
5
Q
How does a transducer work
A
- Voltage applied to piezoelectric crystal which changes thickness causing an oscillating voltage
- When crystal deforms voltage difference is produced between electrodes (pressure wave applied)
6
Q
explain time gain compensation
A
Echoes cannot be viewed simultaneously due to attenuation
Differential amplifications applied to echoes (larger for longer delay)
Output from ramp wave fed into a variable gain amplifier
7
Q
Explain the problems with TGC
A
Attenuation isn’t constant leading to over (less attenuation) or under sampling (brighter/summer echoes)
8
Q
What contrast medium is used in US
A
Micro bubbles
