Medical physics in the electromagnetic spectrum

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

Flashing lights

Infrared: Thermography

Visible: Endoscopy

Parasitic Worm! The stomach wall has relapsed back into the oesophagus. This is a hernia. This is the endoscope coming out of the oesophagus

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: 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. 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) X-rays: Radiotherapy

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 energyHigh 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.