Medical physics in the electromagnetic spectrum Further information: M C J Barker (1996) Medical imaging Phys. Educ. 31 (March 1996) 70-75 D Hart (1996) Patient radiation doses from diagnostic radiology Phys. Educ. 31 (March 1996) 75-79 D Sumner (1995) X-rays-risks versus benefits Phys. Educ. 30 (November 1995) 338-342 Greg Michael (2001) X-ray computed tomography Phys. Educ. 36 (November 2001) 442-451 Edwin Aird (1996) Radiotherapy: technical aspects and modern trends Phys. Educ. 31 (March 1996) 101-107 Mark Oldham (2001) Radiation physics and applications in therapeutic medicine Phys. Educ. 36 (November 2001) 460-467 History: http://webserver.lemoyne.edu/faculty/giunta/roentgen.html R F Mould (1995) The early history of X-ray diagnosis with emphasis on the contributions of physics 1895-1915 Phys. Med. Biol. 40 (November 1995) 1741-1787 S Foulger (1995) The discovery of X-rays Phys. Educ. 30 (November 1995) 330-334 A Hessenbruch (1995) X-rays for medical use Phys. Educ. 30 (November 1995) 347-355 A Schedel (1995) An unprecedented sensation-public reaction to the discovery of X-rays Phys. Educ. 30 (November 1995) 342-347
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? Pictures from Gerard van Leeuwen Needs explanation
Radio Waves: Mobile Phones 0.2C temperature rise Pictures from Gerard van Leeuwen
Infrared: Near Infrared Spectroscopy
Infrared: Pulse oximetry Heart rate:81 bpm Blood oxygenation: 99%
Infrared: Near Infrared Spectroscopy Picture from Clare Elwell Needs explanation Near infrared spectroscopy (NIRS) www.medphys.ucl.ac.uk/research/borl/research/NIR_topics/nirs.htm Child observes flashing chequerboard which stimulates visual cortex, increasing blood flow. Under the black cap is a NIRS probe which emits and detects NIR light which has diffused into head. Haemoglobin absorbs NIR light strongly. Hence, an increase in blood volume decreases the intensity of the measured signal. Moreover, the absorption spectra of oxy- and deoxy- haemoglobin differ, so measuring at two wavelengths gives a measure of oxygen saturation.
Infrared: Near Infrared Spectroscopy Picture from Clare Elwell Needs explanation
Infrared: Near Infrared Spectroscopy Flashing lights Picture from Clare Elwell Needs explanation
Infrared: Thermography
Infrared: Thermography Picture from Jeff Jones Thermography – shows surface map of temperature by measuring emitted infrared light. On left – normal hands – fingers and blood vessels appear warm On right – Raynaud’s syndrome – reduces blood flow to fingers means they appear cold. Next picture – similar illustration of child’s face
Infrared: Thermography Picture from Jeff Jones
Infrared: Thermography Picture from Jeff Jones Thermography image of healthy back overlaid onto normal photograph.
Visible: Endoscopy
Visible: Endoscopy Picture from Sandy Mosse
Visible: Endoscopy Pictures from Sandy Mosse An endoscope An x-ray image showing an endoscope passing down the oesophagus, into the stomach (far right), then into the intestines.
Visible: Endoscopy Parasitic Worm! This is the endoscope coming out of the oesophagus The stomach wall has relapsed back into the oesophagus. This is a hernia. Parasitic Worm! Pictures from Sandy Mosse Worm is in the stomach
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. Pictures from Sandy Mosse
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. Pictures from Alf Linney
Visible: Scanning laser ophthalmoscope
Visible: Scanning laser ophthalmoscope Picture from Dr. A(Mani). Manivannan, Aberdeen Could mention use in security and biometrics With thanks to Dr. A Manivannan
Visible: Scanning laser ophthalmoscope Picture from Dr. A(Mani). Manivannan, Aberdeen With thanks to Dr. A Manivannan
Visible: Photodynamic therapy
Visible: Photodynamic therapy Picture from David Taylor Dermatological PDT for Bowen’s disease (a kind of skin cancer). A drug called Metvix is rubbed onto the skin as a cream and it is preferentially absorbed by cancer cells. The drug therefore collects in the tumour. When the skin is then illuminated with visible light, the drug breaks down and destroys cells. The process is therefore doubly selective – first the drug collects in the tumour and second, only the tumour is illuminated. http://www.photocure.com/professionals/display.asp?xmlID=163 http://www.photocure.com/professionals/display.asp?xmlID=164
Blue: Treatment of jaundice
Blue: Blue light treatment of jaundice in babies Picture from Topun Austin Premature babies sometimes have jaundice. This makes them look yellow and is due to excess bilirubin, the yellow pigment in bruises. It is usually harmless but can be treated using blue light. The blue light breaks down the bilirubin so that it can be excreted as urine.
X-rays: X-radiography
X-rays: x-radiography Picture from Nature First clinical x-ray taken by Wilhelm Roentgen on 22 Dec 1895, of his wife’s hand, showing wedding ring and bones of fingers. This was taken with a 15 minute exposure; a modern x-ray image has an expose of ~10-ms (CHECK)
X-rays: Computed tomography image (CT scan) Second metatarsal bone (the bone that David Beckham and Wayne Rooney broke!) Picture from www.gehealthcare.com/uken/ This is a CT image which has been processed by computer so that only the bones and the muscles are shown. The second metatarsal bone (the bone that Beckham broke) is shown.
X-rays: Computed tomography image (CT scan) Picture from www.gehealthcare.com/uken/ Similarly, this CT image of the pelvis which has been processed so that only the bones show.
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 Image: Elekta
Which part has received the higher dose?
X-ray CT scan of chest shows lungs, heart and tumour (red) X-rays: Radiotherapy X-ray CT scan of chest shows lungs, heart and tumour (red) Picture from Jeff Jones
X-rays: Radiotherapy A medical physicist decides which angles to shine x-rays from to destroy tumour and minimise damage to other tissue Image: Elekta
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) Picture from www.gehealthcare.com/uken/
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.