X-Rays

X-Rays

1. What are X-Rays?

   • X-Rays are high frequency, short wavelength electromagnetic waves
     • They are transmitted by HEALHY TISSUE, but are ABSORBED by BONES AND METAL
       • They affect photographic films the same way as light, meaning that they can be used to take photographs

2. How are they used?

   • X-Ray photographs can be used to diagnose many medical conditions such as bone fractures or dental problems
     • X-Ray images can be formed electronically using CHARGE-COUPLED DEVICES (CCDs). CCDs are silicon chips divided into a gird of millions of identical pixels
       • CCDs detect X-Rays and produce electronic signals which are used to form high resolution images- same technology used in a digital camera
   • In medicine
     • X-Rays are used to treat cancer
       • X--Rays cause ionisation- high doses of X-Rays KILL LIVING CELLS
         • Treat cancers- have to be carefully focused and at just the right dosage to kill the cancer cells without damaging too many normal cells
           • 1. X-Rays are focused on the tumour using a wide beam
             • 2. The beam is ROTATED around the patient with the tumour at the centre
               • 3. This MINIMISES THE EXPOSURE OF NORMAL CELLS to radiation, and so REDUCES the chances of damaging the rest of the body
     • Radiographers
       • 1. Radiographers who work with X-Ray machines or CT scanners need to take precautions to minimise their X-Ray dose
         • 2. They wear lead aprons, stand behind a lead screen or leave the room while scans are being done
           • 3. Lead is used to shield areas of the patient's body that aren't being scanned, and the exposure time of X-Rays is kept to an absolute minimum

3. CT Scans

   • Computerised axial tomography (CT scans) use X-Rays to produce high-resolution images of soft and hard tissue
     • How does it work?
       • The patient is put inside a cylindrical scanner, and an X-Ray beam is fired through the body from an X-Ray tube and picked up by detectors on the opposite side
         • The X-Ray tube and detectors are rotated during the scan
           • A computer interprets the signals from the detectors to form an image of a 2D slice through the body. Multiple 2D CT scans can be put together to make a 3D scan of the inside of the body