Restricted © Siemens AG 2013 All rights reserved.siemens.co.uk/education Topic 15: A peep inside Siemens Education

Restricted © Siemens AG 2013 All rights reserved. A peep inside Course requirements for GCSE Physics Students should: Develop knowledge and understanding of the relationship between the properties of electromagnetic waves and their uses Use scientific theories, models and evidence to develop hypotheses, arguments and explanations Develop and use models to explain systems, processes and abstract ideas

Restricted © Siemens AG 2013 All rights reserved. A peep inside Learning objective We are learning to: Explain how MRI scanners produce images Apply their understanding of waves and particles to this application Describe typical uses of MRI images

Restricted © Siemens AG 2013 All rights reserved. A peep inside How can a doctor make the best possible diagnosis?

Restricted © Siemens AG 2013 All rights reserved. A peep inside The importance of images There are various situations in which medical diagnosis will be assisted by detailed imaging, such as broken bones, tumours, etc and the pros and cons of various imaging technologies, such as ultrasound, CT scans, X-rays and MRI scans, need to be considered X-rays are often used for the imaging of hard material such as bones Ultrasound is quick and easy but gives lower resolution images CT scans are high quality but only work in one plane, whereas MRI scans can work in any plane, producing high quality images of the inside of the body from the desired perspective CT and X-ray imaging uses ionising radiation

Restricted © Siemens AG 2013 All rights reserved. A peep inside CT Scan Ultrasound Scan MRI Scan X-ray image

Restricted © Siemens AG 2013 All rights reserved. A peep inside A carbon atom A hydrogen atom Atomic structure

Restricted © Siemens AG 2013 All rights reserved. A peep inside What does an MRI scanner consist of? There are four key components: 1)A powerful permanent magnet 2)Gradient coils, which produce a variable magnetic field 3)Radio frequency (RF) coils, which produce radio waves 4)Scanner, which detects energy emitted from the body

Restricted © Siemens AG 2013 All rights reserved. A peep inside How does MRI work? (1) Although there are many different elements in the body, hydrogen is very common. It is present in water and in fats. Hydrogen nuclei are the key to the production of MRI scans. Normally, these nuclei spin in random directions around their individual magnetic fields.

Restricted © Siemens AG 2013 All rights reserved. A peep inside How does MRI work? (2) The MRI scanner has a powerful magnet, which produces a magnetic field, many times stronger than that of the Earth. In this magnetic field the nuclei line up either north or south. About half go each way, but there are a few unmatched ones.

Restricted © Siemens AG 2013 All rights reserved. A peep inside How does MRI work? (3) When radio waves are produced by the RF coils, the unmatched nuclei spin the other way. The gradient magnets alter the magnetic field so that images can be produced from any direction.

Restricted © Siemens AG 2013 All rights reserved. A peep inside How does MRI work? (4) When the radio frequency coils are switched off and the pulse of RF waves stops, the extra nuclei return to their normal position, emitting energy.

Restricted © Siemens AG 2013 All rights reserved. A peep inside How does MRI work? (5) The energy released by these nuclei is detected by the scanner, which sends a signal to the computer, which converts it to an image.

Restricted © Siemens AG 2013 All rights reserved. A peep inside What advantages does MRI offer? It can work in any plane: think of the different directions one could slice an apple in. Each slice is a two dimensional view; this is what the images are like. Being able to select the plane offers medical staff real advantages The images have a very high resolution: the detail is good and it can discriminate between matter that is similar There are no known biological hazards with MRI: it doesn’t use ionising radiation

Restricted © Siemens AG 2013 All rights reserved. A peep inside What are the drawbacks? Noise: continuous hammering around Patient has to be still for anything up to 90 minutes: movement causes blurring and requires a repeat scan Expensive: complex equipment which needs skilled operation and takes time to scan Claustrophobic: some patients find it unpleasant Dangerous: magnetic materials can be caused to fly across the room

Restricted © Siemens AG 2013 All rights reserved. A peep inside Typical diagnostic application: slipped disc

Restricted © Siemens AG 2013 All rights reserved. A peep inside Typical diagnostic application: slipped disc Nerves in this area are compromised from the pressure of the prolapsed disc

Restricted © Siemens AG 2013 All rights reserved. A peep inside Typical diagnostic application: sprained wrist (if compressed gives pain, swelling and restriction of movement) (Tendons of the wrist) (Nerve and artery of the ulna bone run through here to the hand) (One of the bones in the wrist)

Restricted © Siemens AG 2013 All rights reserved. A peep inside Sample assessment task This diagram shows a simplified cutaway view of an MRI scanner Explain how it produces images for clinical diagnosis (6)