12/9/2014 Medical Physiology CC:Echocardiology Harold Smulyan Flashcards
Frequency
Pitch – in the audible range
Audible Sound
Humans – 15,000 to 20,000 Hz
Dogs – 40,000 Hz
Ultrasound
Over 20,000 Hz
*Travels in straight lines
Velocity
- Independent of Frequency
* Dependent on the MEDIUM
Why are the lungs your deadly enemies when you are doing echocardiography?
Because they absorb the ultrasound and you can’t see the heart
Ultrasound (propagated wave) ___ and ___ by an interface between two media of different acoustic impedance
reflected; refracted
T or F: Most of the sound in medical ultrasound gets refracted rather than reflected
True, that’s why ultrasound images are not great
In ultrasound we are interested in:
distance and the time it takes to get back
d=(velocity)x(time)
Piezoelectric effect
Electricity resulting from pressure
Transducer probe
Probe that sends and receives the sound waves
How is the piezoelectric effect used in medical ultrasound?
- Probe w/ one or more piezoelectric crystals
- electric current applied to crystals
- rapid shape changes or vibration of crystals produce sound waves that travel outward
- when sound or pressure waves hit the crystals –> emission of electrical currents
* same crystals can be used to send and receive sound waves
Describe the Doppler effect in the context of its applicability in medical ultrasound
Target –> blood cells
- target stationary
freq transmitted = freq received - target moving towards transducer
freq transmitted < freq received
*red - target moving away from transducer
freq transmitted > freq received
*blue
What are the different views of an ultrasound in 2D?
Parasternal Long Axis
Parasternal Short Axis
- aortic, tricuspid & pulmonic valve level
- mitral valve level
- mid-ventricular level
- apical level
Apical
- 4 or 2 chambers