x-rays

x-rays

1. form part of the electromagnetic spectrum

2. very short wave length ( same order of magnitude as the diameter of atoms

3. can cause ionisation - knock of electrons from atoms

4. (CT) affect photographic film in the same way light does

5. x-rays transmitted by healthy tissue absorbed by metal and bone to produce shadows

6. everything hit by x-ray turns black everythin absorbed x-rays stays white.....teeth and bone

7. Ultrasound

   • sound=vibrations........vibrations per second = frequency(Hz)
     • ultrasound are waves of frequencies greater than 20 000 Hz ie beyond hearing limit of hearing range for humans
   • transducer- produce and detect ultrasound waves
   • ultrasound waves are partially reflected when they meet different media
     • time taken for reflections to reach detector measured
       • each boundary distance measured
         • image formed
     • S(distance meters) = v (speed m/s) x t(time seconds)
     • as ultrasonic waves pass from one medium or substance into another , they are partially reflected at the boundary. the time taken for these reflections is a measure of how far away the boundary is
   • pre-natal scanning (regular intervals during pregnancy)
   • imaging of kidneys and destruction of kidney stone - ultrasound can break down kidney stone and then can be passed out the body
   • non-ionising and produce accurate images ( of soft tissue)
   • electronic systems produce electronic oscillations, which are used to generate ultrasonic waves
   • imaging of damaged ligaments and muscles

8. CT ( computerised tomography) scans- x-ray tube emits x-rays towards the person in all directions (360 degree turn)

   • connect to a CCD ( charge coupled device that turns x-rays into light so image can be displayed on a screen electronically)
     • produce a much more detailed image......produce 2 and 3 dimmensional images .....higher dose of x ray radiation.........distinguish between different soft tissues.....more expensive
       • safety to limit and moniture exposure- lead shielding - absorbs x -rays and film badges to see how much x -rays a person has been exposed to ( adequate proective clothing,screening

9. x ray machine - cheaper .... 2 d image only and a lower does of x-ray radiation

10. used in hospitals to diagnose and treat some emdical problems like bone fractures....dental problems....