Electromagnetic Spectrum

Medical physics in the
electromagnetic spectrum
Radio Waves: Mobile Phones
Radio Waves: Mobile Phones
Mobile phones use microwave energy. We know
that microwaves can cook food – can a mobile
phone cause heating?
Radio Waves: Mobile Phones
0.2°C
temperature rise
Infrared: Near Infrared Spectroscopy
Infrared: Pulse oximetry
Heart rate:81 bpm
Blood oxygenation: 99%
Infrared: Near Infrared Spectroscopy
Infrared: Near Infrared Spectroscopy
Infrared: Near Infrared Spectroscopy
8
Flashing lights
H bO 2
H bvol
Hb
Δ concentration (μmolar.cm)
6
4
2
0
-2
-4
-10
0
10
20
T im e (seconds)
30
40
50
Infrared: Thermography
Infrared: Thermography
Infrared: Thermography
Infrared: Thermography
Visible: Endoscopy
Visible: Endoscopy
Visible: Endoscopy
Visible: Endoscopy
This is the
endoscope coming
out of the oesophagus
Parasitic
Worm!
The stomach wall has
relapsed back
into the oesophagus.
This is a hernia.
Visible: Endoscopy with a camera pill
On the right is an x-ray movie showing a pill which has been swallowed
which 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 CT
scan 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
Visible: Scanning laser ophthalmoscope
Visible: Scanning laser ophthalmoscope
Visible: Photodynamic therapy
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 broke!)
X-rays: Computed tomography image (CT scan)
X-rays: Radiotherapy
X-rays: Radiotherapy
X-rays: Radiotherapy
Cancer occurs when cells divide too quickly. The
dividing cells become a tumour which can damage
surrounding tissue or spread to the rest of the
body
X-rays: Radiotherapy
•
•
•
•
•
X-rays or other radiation can damage the DNA in
cells 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 cancer
cells
We must still ensure that healthy tissue is
undamaged
X-rays: Radiotherapy
A linear accelerator generates
x-rays. It rotates around the
body, irradiating the tumour
from all directions
X-rays: Radiotherapy
X-ray CT scan of chest shows lungs, heart and tumour (red)
X-rays: Radiotherapy
A medical physicist decides
which angles to shine x-rays from
to destroy tumour and minimise
damage to other tissue
X-rays: Radiotherapy
The treatment plan lists the directions the x-rays will come from and calculates the
radiation 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 acknowledge
the contributor of every image. If we have inadvertently used
images in error, please contact us.