Radiation

Radiation

1. Medical Physics

   • Medicine
     • Both ionising and non-ionising radiation are used by doctors and medical physicists. Compromises have to be made as ionising radiation can give a very clear image from inside the body but can risk damage to the patient's cells.
   • X-Rays
     • X-rays are high energy EM waves that get absorbed by dense materials like bone and metal. Radiographers use their properties to take x-ray photographs that can be used to diagnose things like bone fractures. They are a type of ionising radiation.
   • CAT Scans
     • Computerised Axial Tomogrophy (CAT) scans use x-rays to produce an image of a 2D slice through a body. They use intense beams of x-rays that are strongly ionsing but they can be used on soft tissue as well as bone unlike x-rays.
   • Endoscopes
     • Visible light is one type of non-ionising radiation used in modern medicine. They reflect light along optical fibers and can be used to see inside patients to investigate without the need for invasive surgery. They can even be used for keyhole surgery.
   • Ultrasound
     • Sound waves with frequencies above 20kHz (beyond the range of human hearing) are called ultrasound which is a non-ionising method of medical imaging making it safer.
     • Kidney stones are hard masses that can block the urinary tract and can be extremely painful. The ultrasound concentrates high energy waves at the stones and turns it into sand like particles which then pass out the body in urine. It is a good method as requires no surgery and is relatively painless.
     • It can be used to diagnose soft tissue problems and to perform pre-natal scans of a foetus in the womb. The waves get reflected off the different tissue boundaries and the times and distributions of the echoes are processed by a computer to form an image on a screen.
     • As it works in real time it can show things changing and moving. This makes it useful for investigating problems with blood flow (particularly in the heart and liver). Special ultrasound machines can measure the speed of blood flow and identify any blockages in the veins and arteries.

2. Intensity of Radiation

   • Definition: Radiation is energy emitted from a source. It can be in the form of a wave (e.g. gamma) or a particle (e.g. alpha).
   • The intensity of radiation decreases as the distance from the source increases (e.g. a flame emitting infrared radiation, it gets less hot as you move further away from it).
   • It also depends on the medium that is is passing through. Unless it is passing through a vacuum, atleast some of it will always be absorbed along the way by the medium it passing thorough. Generally, the more dense a medium, the more it gets absorbed, decreasing the intensity of radiation (e.g. sunglasses, the dark glass absorbs some of the light reducing it's intensity).
   • The more intense the radiation, the more energy it carries per second or the higher the power. The higher the power the more energy that gets transferred per second when it hits an object. Obviously, the surface area of the object affects the amount of radiation that smacks into it. A big object is going to catch more radiation than a small one so the intensity of radiation equals the power of radiation divided by the area it falls on.