Ultrasound Flashcards
What are ultraound waves
sound waves with a frequency of greater than 20kHz
at which frequency are the sound waves in medical ultrasound
2.5-15MHz
What is the Piezoelectric effect
The phenomenon by which mechanical stress may be induced in certain crystalline substances when a potential difference is applied across them
What are the clinical applications of ultrasound
imaging - used for regional anaesthetic techniques, line insertion, POCUS etc
doppler - to evaluate blood flow
used in obstetrics to monitor fetus
elastography
How do you improve image quality with ultrasound
Can use Low frequency prove can be used to look at deeper structures and higher frequency for more peripheral structures.
Gain can be adjusted to get the best contrast to differentiate tissues e.g. muscle and nerve
How does ultrasound work
the ultrasound probe generates a pulsed sound eave of required frequency via the piezoelectric effect
Sound wave passes through the body to a depth determined by the frequency
A proportion of the sound wave is reflected back to the probe every time it reaches a boundary between differing media
sound reaching the transducer imparts mechanical energy which is converted to electrical energy via the piezoelectric effect
the time delay is used to calculate the distance
What is the type of crystal used in USS
special ceramic crystals called piezoelectric crystals
What are the differences between the ultrasound probes
differ in shape, frequency and therefore intended use
lower frequency probes are used to look at deeper tissues
linear probe produces a straight sound wave
convex produces a wilder field of view
What are the risks of ultrasound
tissue heating - can damage the eye
ineffective at looking at bone or parts of the body that have air in them e.g. lungs
cavitation effect - phenomenon that gas bubbles occur in body fluids or empty spaces (only occured in experiment)
what is the range of sound to the human ear
20-20,000hz
