X-rays for Medical Diagnosis
X-rays are part of the electromagnetic waves with
- high frequency
- short wavelength ( same diameter as an atom)
- affect photograph film the same way as light
- are used to diagnose medical conditions (bone fractures)
- are transmitted by healthy tissues
- are absorbed by denser materials
Can be formed electronically using Charge-coupled devices, CCDs are:
- silicon chips (sixe of post stamps)
- divided into millions of identical pixels
- detect X-rays and produce electronic signals which are used to from high resolution images.
- the same technology used to take photos with digital cameras.
Computerised axial tomography use X-rays to produce high resolution images of soft and hard tissue.
- Patient is put inside the cyclindrical scanner
- X-ray beam is fired through the body from an X-ray tube and picked up by detectors on the opposite side.
- X-ray tube and detectors are rotated during the scan
- Computer interprets the signals to form an image of a two dimensional slice through the body.
Multiple two-dimensional CT scans can be put together to make a three-dimensional image of the inside of the body.
X-rays to Treat Cancer
X-rays cause ionisation so high doses will kill living cells. They can therfore be used to treat cancers just like gamma radiation.
X-rays have to be carefully focused at the right dosage to kill cancer cells without damaging too many normal cells
To treat Cancer:
1) X-rays are focused on the tumour using a wide beam
2) This beam is rotated round 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.
Prelonged exposure to ionising radiaton can be dangerous so Radiographers take precautions to minimise their X-ray dose.
They, stand behind a lead screen, leave the room, wear lead aprons and special badges so their radiaiton dose can be monitored and regulated.
Lead is used to shield areas of the patient's body that aren't being scanned and the exposure time is kept to a minimum