X-Rays

X-Rays

1. Properties

   • They have a high frequency and very short wavelength (about the same size as the diameter of an atom)
   • They cause ionisation (adding or removing electrons in atoms and molecules)
   • They affect photographic film in the same way as visible light (turning it black)
   • They are absorbed by metal and bone
   • they are transmitted by (pass through) healthy body tissue
   • X-rays are part of the electromagnetic spectrum

2. CCDs (charge-coupled device)

   • Modern X-ray machines use CCDs instead of photographic film, which convert the x-ray energy to light
   • The images are formed electronically, allowing them to be recorded and stored more easily than the images from photographic film

3. Uses

   • 1. Imaging using X-rays
     • They are transmitted (pass through) the body - except in areas where they are absorbed by dense structures like bone
     • In old X-Ray machines, the white photographic film was placed behind the patient. Where the X-rays were transmitted (through soft tissue), the film would turn black. Where the X-Rays were absorbed (bones) the film would stay white. Fractures would then show up as dark areas.
       • This method can be used for dental treatment, as decayed teeth will absorb X-rays less strongly than healthy teeth. Decayed areas turn up as dark areas.
   • 3. CT scans (Computerised tomography)
     • Multiple images of the body are taken and processed by the computer to produce a three-dimensional (3D) image, allowing doctors to see the body at different points of views and levels
     • Some organs with soft tissue like the small intestine can be filled with contrast medium that absorbs X-Rays so that they can be seen
   • 2. Cancer treatment
     • Cancer is a disease in which cells divide uncontrollably because of changes in their DNA, forming tumours
     • Low doses of X-rays may cause cancer - whereas high doses may kill cancerous cells.
     • You direct high energy X-rays at the tumours. This causes so much damage to the cancerous cells that they die. This treatment is called radiotherapy.

4. Precautions

   • X-ray machines produce relatively low energy X-rays, which reduce the risk of them damaging human tissue
   • Patients are limited to the number of X-rays they are allowed to have so their bodies are not exposed to too much radiation
   • Shielded walls containing lead and warning signs show when the room is in use
   • Only radiographers use the equipment and can wear lead aprons