Anyone got a P3 Edexcel Exam Tomorrow? I need help...

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two topics

medical physics - :'(

particles in action - :|

Posted Wed 23rd May, 2012 @ 20:51 by ax5za

5 Answers

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Tracers/PET scanning
Radioactive substance (emits gamma- you need it to leave the body) with a SHORT half life (only need it for the time of tracing)
Will be swallowed/injected with a nutrient that goes to the target organ; eg glucose will go to the brain. The gamma is the thing you want to detect.

For PET scanning - the tracer will be a B+ (positron) and it will annihilate with the electrons in the cells of the target organ (where all equivalent mass will be converted to energy (Gamma) - which will then be detected. This is compared to the metabolic rate of the cells - the ones doing more work will have more gamma - or simply the more cells (ie - a tumor) = the more annihilation.

For treatment; (radiotherapy) you'd want a source with a longer half life, less energising power, and something that emits beta/alpha (more ionising to the malignant cells).

It works in kind of the same way, but the source is absorbed by the cancerous cells and it ionises and destroys them.

There's also Endoscopy; where you will also need to know about the critical angle; this will be given to you in the exam, but it is found out using the refractive index of a substance. 
Angle of incidence should ALWAYS be equal to the angle of reflection (against the normal) To get total internal reflection (like you need for endoscopy) you need to shine the light at an angle LARGER than the critical angle. 
The light is shone down the flexible tube (making use of glass fibres/fibre optics) reflected off of the organs and shone back through a different tube where an image is displayed on a monitor. 
it means we don't have to have large operations because we can use keyhole surgery (laporoscopy) - only a small incision (if any) needs to be made to insert the tube.

There's lots of things that branch of the medical science topic, but look on line at what the exam board are looking for specifically (past papers/mark schemes) to give you a good idea at what they will be asking you. 

I have uploaded some notes on the whole of P3 as well as parts of it explained. Might be a bit too late however; it is the night before the exam!

Best wishes and good luck with your exam!
-Sophie

Answered Wed 23rd May, 2012 @ 21:49 by Sophie :o)
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I doo! What's up?

Answered Wed 23rd May, 2012 @ 21:05 by Sophie :o)
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i really need help with medical physics... :(

Answered Wed 23rd May, 2012 @ 21:22 by ax5za
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thank you SO much. good luck x

Answered Thu 24th May, 2012 @ 00:03 by ax5za
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I SO FAILED IT!

Answered Thu 24th May, 2012 @ 15:06 by LucySPG