2 X-Rays In Medicine To know how x-rays are used in medical physics Thursday, April 06, 2017To know how x-rays are used in medical physics
3 X-RaysWhat are x-rays, what properties do they have and how are they work?X rays are high frequency, short wavelength EM waves (wavelength roughly the same size diameter of an atom)X-rays are transmitted (pass through) healthy tissue and are absorbed by denser materials such as bone and metal
4 Electromagnetic Spectrum The properties of electromagnetic waves (EM waves) change as the frequency (wavelength) changesThey can be split into seven basic types – all of these EM waves form a continuous spectrum (the different regions merge into each other)We can only detect a narrow range of EM waves (visible light)
5 Electromagnetic Radiation Electromagnetic radiation travels as waves and transfers energy from one place to anotherAll electromagnetic waves can travel through a vacuum, and they all travel at the same speed in a vacuumThe types of radiation that occur in different parts of the spectrum have different uses and dangers, which depend on their wavelength and frequency
6 Electromagnetic Spectrum The electromagnetic spectrum is made up of the following: -Radio waves (1m – 104m) – lowest frequency, longest wavelengthMicrowaves (10-2m (3cm))Infra-red (10-5m (0.01mm))Visible light (10-7m)Ultra violet (10-8m)X-rays (10-10m)Gamma rays (10-12m)– highest frequency, shortest wavelength
7 X-Rays X-rays have a lower frequency than gamma radiation X-rays mostly pass through skin and soft tissue, but they do not easily pass through bone or metal so X-rays are used to produce photographs of bones to check for damage such as fracturesThey are also used in industry to check metal components and welds for cracks or other damageLower doses of X-rays can cause cells to become cancerous, so precautions are taken in hospitals to limit the dose received by patients and staff when X- ray photographs are taken
8 ElectronicX-rays can be formed electronically – charge-coupled devices (CCDs) are silicon chips which detect X-raysX-rays can also be passed through the patient many times, creating lots of 2D images – these can then be linked forming a 3D image
9 CT ScannersComputerised axial tomography (CT) scans use X-rays to produce high res. images of soft and hard tissuePatients are placed inside a cylindrical scanner and an X-ray bean is fired through the body from an X-ray tube. These are picked up by detectors on the opposite sideCT scans use a lot of X-rays so can distinguish between tiny variations in tissue density – though this has its risks…
10 Treating CancersX-rays can be carefully focused to ionise cancer cells without damaging too many normal cellsX-rays are focused on the tumour and the beam rotated minimizing healthy cell exposure
11 PrecautionsWhat precautions must be taken with x-rays and CT scanners?X-ray dosage needs to be minimised by workers: -Lead apronsStand behind lead screensLeave the roomPatients have lead shields across areas of the body which are not being scannedExposure time is minimised
12 Practice QuestionsComplete the x-rays practice questions…
13 X-RaysQuestion 1 The teeth are particularly dense parts of our head. The skull is hard tissue, but relatively thin, and the rest is mainly made of soft tissue in the brain, which transmits X-rays rather than absorbing them. Question 2 X-rays are ionising radiation, which means that they could ionise molecules in the cells of our organs. This could lead those cells to malfunction and eventually develop into cancer cells.
14 X-RaysQuestion 3Medical staff operating the X-ray machine should wear lead lined suits and always activate the machine from behind a screen.The screen should be made of thick concrete, or lead, as those materials are good absorbers of X-ray radiation. They should also limit the total amount of time that they spend operating the machines.
15 X-RaysQuestion 4 Surgery requires a longer rehabilitation time and carries a higher risk of infections. Radiotherapy is a non-invasive technique and therefore the patient doesn’t need to be anaesthetised.
16 X-RaysQuestion 5 The X-ray radiation is focused / collimated by special (non-glass) lenses only on the area of the body affected by the tumour. In this way the cancer cells are exposed to a high dose of X-rays, which kills them, whereas the healthy cells in other parts of the body receive a very small amount of radiation with little risk of being damaged.