Ultrasound Flashcards
What is Ultrasound
accoustic energy due to alternating compressing and rarefying potential
> 20Mhz, inaudible to human ears
How is it generated: Generator
electric
Oscillator circuit produces high frequency
How is it generated: Crystal
synthetic
uniform beam
Transducer
Transducer
electric to accoustic energy
reverse pizoelectric effect
creates vibration @ frequency of oscillator circuit of generator
vibrating crystals causes sound head to vibrate
How is it generated: sound head
transfers accoustic tissue
ceramic, alum, stainless steel, must match crystal (not interchangeable)
Applicator
houses crystal and sound head
held by PT
hard insulated plastic
Electromagnetic vs. Mechanical
electromagnetic- protons move along wave
mechanical- molecules bump into neighbor, propagating energy
Mechanical longitudinal wave
microstreaming
along the direction the wave travels, liquid/gases
Mechanical transverse wave
perpendicular to the direction traveled
solid
Spatial
size of transducer
Spatial Average Intensity
power/ERA= W/cm2
Spatial Peak Intensity
generally over center
Spatial Average Temporal Peak
when SAI is on
Spatial Average Temporal Average
STAPx duty cycle, measures what is delivered to tissue
Beam Nonuniformity Ratio
spatial peak intensity: spatial average intensity