Why Ultrasound?
    Over half a century old technique! 
    Arguably  the  most  widely  used  imaging  technologies  in 
    medicine. 
    Portable, free of radiation risk, and relatively inexpensive 
    compared to MRI, CT and PET
    Tomographic,  i.e.,  offering  a  “cross-sectional”  view  of 
    anatomical structures. 
    “Real  time,”-  providing  visual  guidance  for  interventional 
    procedures
           Do you expect any 
           similarities?
  Most amazing is that sound can actually help us to see what is 
  hidden, just like the way bats 'see'.
  Bats always have the night shift. They go hunting for things to eat at 
  night where food isn't well lit. 
  Fortunately, bats are gifted with a system of locating things with 
  sound. First they emit sound.
  •
   The human ear cannot hear below 20 Hz.
  •
   Elephants can use infra sound.
  •
   The human ear cannot hear above 20,000 Hz. 
  •
   Bats use ultrasound to locate food. 
  •
   Dolphins use it to communicate. 
  Ultrasound  used  in  medical  imaging  operate  at  frequencies  way 
  above human hearing: about 2 million Hz - 20 million Hz (2-20 MHz).
   Sound travels in waves. Ultrasound physics has to do 
   with the higher frequencies of sound. 
   Human hearing is from about 20 cycles per second or 
   20HZ (a low hum) to about 20,000 cycles per second 
   or 20KHZ. 
   A grasshopper sends out sound 
   waves at 40KHZ. A dog can hear at 
   about 30KHZ and bats send chirps 
   and listens for the echoes at 100KHZ.