Outline the generation of an ultrasound image.
Voltage applied to a crystal leads to the production of vibrations. This produced the ultrasound beam which hits the tissue and is reflected back to the probe.
Brightness of an image depends upon the…
Strength of vibrations which return to the probe
Location of areas of an image depend upon…
Time for the wave to return to the probe (depth of penetration)
Frequency of the beam is proportional to what values?
Directly to resolution. Inversely to penetration
Outline/ define the ultrasound opacities.
White (lots of energy back) = Hard. Black (little energy back) = SOFT
Reverberation artefacts
Second reflections due to reverb off a round (hollow) structure - useful for finding the widest part of a follicle
Refraction artefacts
Doesn’t reflect a structures true position
Acoustic enhancement
The deeper (and more reflected back) a beam goes the less is reflected back (cumulative)
How can you identify on an ultrasound that a foetus is dead?
No heart beat, foetal membranes become flaccid
What is a twin line?
Allantochorionic membrane join between twin foetuses
How can foetuses be aged by ultrasound?
Crown-rump length, biparietal distance, trunk diameter
How can foetuses be sexed?
Teats and scrotum from 70-120 days, genetal tubercle migration (male - just behind umbilicus, female - between hindlegs and tail)
