Medical Applications of Physics
- Created by: Lottie.Beth
- Created on: 26-02-17 20:18
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- Medical Applications of Physics
- X-rays
- Properties
- Transmitted (pass through) healthy tissue but absorbed (stopped) by denser materials e.g. bones/metal
- Cause ionisation (adding/remoi-ng atoms/ molecules)
- High frequency & short wavelength (=atom's diameter) electromagne-tic waves
- Imaging
- X-rays affect photographic film the same way as visible light- turning it black
- This means it can be used to diagnose medical conditions like bone fractures/ dental probs
- Older imaging machines- white photographic film behind patient & as x-rays pass through part of body needing to be imaged, the film turns black where the x-rays hit
- Fractures show up as dark areas in the image of the bones on the film & stays white where the bones are
- Calcium atoms that make up bones=larger so absorb x-ray protons better but soft tissue in the body=smaller atoms that don't absorb as well
- Can be used for dental treatment as well because decayed teeth will absorb x-rays less strongly than healthy teeth
- Fractures show up as dark areas in the image of the bones on the film & stays white where the bones are
- Or, can be formed electronically using charge-coupled devices (CCDs)
- Silicon chip divided into grid of millions of pixels & used instead of photographic film
- Detect x-rays and produce electronic signals to form high-resolution images
- Electronically formed images=more easily recorded & stored
- X-rays affect photographic film the same way as visible light- turning it black
- Cancer treatment
- Cancer=disea-se where cells divide uncontrollably due to changes in their DNA and form tumors
- Radiotherapy= one method killing cancer
- Direct high energy x-rays at tumours to cause so much damage to the cancerous cells, they die
- Ionisation kills living cells. Focusing x-rays @ right dosage kills cancer cells without damaging too many normal cells
- To reduce damage to normal cells x-rays focused on tumour using wide beam which rotates around the patient with the tumour at the centre
- This minimises exposure of normal cells to radiation and reduces chance of damaging the rest of the body.
- Safety risks & precautions
- Ionising properties of x-rays can damage DNA in the cells- effects= increasingly damaging to dividing cells & low doses may cause cancer
- Patients only have ltd. no. x-rays to reduce risk of being exposed to too much radiation
- X-ray machines produce relatively low energy x-rays which reduce risk of them damaging human tissue
- Shielding walls containing lead built into all x-ray rooms to protect people outside
- Warning signs stop people entering when in use
- Only trained, specialist radiographers allowed to use machines
- Leave room/ stand behind lead screen when in use or wear lead aprons as a protective layer of clothing when can't stand behind screen
- Lead used to shield areas of patients body not being scanned
- Exposure time to x-rays kept to minimum
- Properties
- CT scans
- CT/CAT= Computerised Axial Tomography
- How it works
- Patient put in cylindrical scanner & x-rays fired through body by x-ray tube & picked up by detectors opposite side
- Large number of images combined by a computer=det-ailed 3D image of organs under investigation
- Helps in study of tumours in cancer patients where high quality= essential
- Some CT scans (e.g. on brain/abdome-n) may be given a contrast medium(liquid containing dye e.g, barium) so shows up clearly on images
- Contrast medium helps distinguish blood vessels from other structures in body
- Safety Issues
- Just like other forms of high energy radiation, can cause damage to cells in body & increase cancer risk
- Not recommended for pregnant women as small chance x-rays may cause damage to unborn child
- Children are at increased risk than adults so only have them if justified by a serious condition
- Require much longer exposure to radiation than normal x-ray so potentially more harmful
- X-rays
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