medical physics in em spectrum

8/13/2019 medical physics in EM spectrum

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Medical physics in the

electromagnetic spectrum



Radio Waves : Mobile Phones




Mobile phones use microwave energy. We knowthat microwaves can cook food – can a mobile

phone cause heating?




0.2C temperature

rise



Infrared : Near Infrared Spectroscopy



Infrared : Pulse oximetry

Heart rate:81 bpm

Blood oxygenation: 99%



Time (seconds)

-10 0 10 20 30 40 50

concentration(

molar.cm)

-4

-2

0

2

4

6

8

HbO2

Hbvol

Hb


Flashing lights



Infrared : Thermography



Visible : Endoscopy



Visible : Endoscopy

ParasiticWorm!

The stomach wall has

relapsed backinto the oesophagus.This is a hernia.

This is theendoscope comingout of the oesophagus



Visible : Endoscopy with a camera pill

On the right is an x-ray movie showing a pill which has been swallowedwhich contains a camera. It passes through the gut, taking a movie which is

sent to a receiver outside the body, shown on the left.



Visible : New approaches to Endoscopy

Another new method is virtual endoscopy. Here, we take a high resolution CTscan of the body using x-rays and then, using a computer, identify the gut wall

and show it as if it is viewed through an endoscope.

This prevents the discomfort which

patients may feel during endoscopy

This movie shows a polyp in the wall

of the gut.



Visible : Scanning laser ophthalmoscope




With thanks to

Dr. A Manivannan



Visible : Photodynamic therapy



Blue : Treatment of jaundice



Blue : Blue light treatment of jaundice in babies



X-rays : X-radiography



X-rays : x-radiography



X-rays : Computed tomography image (CT scan)

Second

metatarsal bone

(the bone that

David Beckham and

Wayne Rooney broke!)



X-rays : Computed tomography image (CT scan)



X-rays : Radiotherapy



Cancer occurs when cells divide too quickly. Thedividing cells become a tumour which can damage

surrounding tissue or spread to the rest of the

body




• X-rays or other radiation can damage the DNA incells and kill them

• This is why radiation can be dangerous

• But cells which are dividing rapidly are more likely

to be killed

• So we use x-rays to kill the rapidly-dividing cancercells

• We must still ensure that healthy tissue is

undamaged




A linear accelerator generates

x-rays. It rotates around the

body, irradiating the tumour

from all directions




X-ray CT scan of chest shows lungs, heart and tumour (red)




A medical physicist decides which

angles to shine x-rays from

to destroy tumour and minimise

damage to other tissue




The treatment plan lists the directions the x-rays will come from and calculates theradiation dose to the tumour (in purple) and rest of body (grey)




Summary :

• Medical physicists use all parts of the electromagnetic

spectrum to diagnose and treat illnesses

• Different parts of the spectrum interact in different ways with

the body because they have different energies

Low energy High energy



Medical physics in the

electromagnetic spectrum



Acknowledgements :

• Thanks to Dr Gerard van Leeuwen, Dr Clare Elwell, Dr

Kevin Howells, Dr Sandy Mosse, Dr Paul Campbell, Dr

Topun Austin, Dr Alf Linney, GE Healthcare, Paul Burke and

Jeff Jones, and Elekta for providing images.

• This lesson was developed by Adam Gibson, Jeff Jones,

David Sang, Angela Newing, Nicola Hannam and Emily

Cook

•

We have attempted to obtain permission and acknowledgethe contributor of every image. If we have inadvertently used

images in error, please contact us.

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