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Physics 3a
Medical Applications of Physics…read more

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· X-rays are high frequency, short wavelength electromagnetic waves
(0.1-10nm), their wavelength being approximately the same size as
the diameter of an atom and they cause ionisation
· Properties of x-rays include:
-they are transmitted by soft tissue
-they are absorbed by dense materials such as bones and metal
-they affect photographic film in the same way as light
· X-rays produce a negative image which shows the bones
· They can diagnose medical conditions such as bone fractures or
dental problems…read more

Slide 3

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· Electrons are stripped from atoms and chemical bonds are broken,
releasing highly reactive ions
· These ions can damage biological molecules like DNA
· Damaged DNA can cause mutations, cancer and death…read more

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Using x-rays to detect soft tissue
· A soft tissue organ can be filled with a contrast medium, such as a
barium meal, to absorb x-rays
· Lead absorber plates protect parts of the body that don't need
investigation and may be damaged by x-rays…read more

Slide 5

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Charged Coupled Devices (CCDs)
· X-ray images can be formed electronically using CCDs
· They are small silicon chips divided up into a grid of millions of
identical pixels
· They detect x-rays and produce electronic signals which are used to
form high resolution images
· The same technology is used in digital cameras…read more

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Precautions when using x-rays:
· X-rays can cause ionisation- low doses may cause illnesses such as
cancer. However a high dose of carefully focused x-rays, using a
wide beam which rotates, can be used to treat cancer
· Radiographers need to take precautions:
-wearing lead aprons
-stand behind a lead screen
-leave the room while scans are being done
· Lead is used to shield the areas of a patient's body that aren't being
scanned and the exposure time is kept to an absolute minimum…read more

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