Ultrasound

Ultrasound

1. What is it?

   • Ultrasound is sound with a higher frequency that we can hear
     • Electrical systems can be made which produce electrical oscillations of any frequency. These can easily be converted into MECHANICAL VIBRATIONS to produce sound waves of a HIGHER FREQUENCY THAN THE UPPER LIMIT OF HUMAN HEARING. This is called ULTRASOUND
       • What is the range of human hearing?
         • 20 to 20,000 Hz

2. How do ultrasound waves work?

   • Ultrasound waves get partially reflected at a boundary between media
     • 1. When a wave passes from one medium into another, some of the wave is reflected off the boundary between the 2 media, and some is transmitted (and refracted), This is PARTIAL REFLECTION
       • 2. What this means is that you can point a pulse of ultrasound at an object, and wherever there are boundaries between one substance and another, some of the ultrasound gets REFLECTED BACK
         • 3. The TIME IT TAKES FOR THE REFLECTIONS TO REACH A DETECTOR can be used to measure HOW FAR AWAY the boundary is
           • 4. This is how ULTRASOUND IMAGING works

3. In medicine

   • Used in investigating blood flow, diagnosing heart problems, checking on fetal development
     • Breaking down kidney stones
       • 1. Kidney stones are hard masses that can block the urinary tract
         • 2. An ultrasound beam concentrates high-energy waves at the kidney stone and turns it into sand-like particles
           • 3. These particles then pass out of the body in the urine
             • 4. Good method- no need for surgery, relatively painless
     • Pre-natal scanning of a fetus
       • 1. Ultrasound waves can pass through the body, but WHENEVER THEY REACH A BOUNDARY BETWEEN 2 DIFFERENT MEDIA, such as fluid in the womb and the skin of the foetus, some of the wave is REFLECTED BACK AND DETECTED
         • 2. The exact TIMING AND DISTRIBUTION of these echoes are PROCESSED BY A COMPUTER to produce a VIDEO IMAGE OF THE FETUS