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Magnetic Resonance Imaging


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Basics of MRI scanning for A level Applied Science

Published in: Health & Medicine, Technology

Magnetic Resonance Imaging

  1. 1. Magnetic Resonance Imaging The MRI Scanner
  2. 2. How does it work? The Basics <ul><li>Patient is bathed in a magnetic field 5000 times stronger than the earths </li></ul><ul><li>This field causes some of the body’s nuclei to behave like tiny compasses and line up </li></ul><ul><li>Then the nuclei are hit by pulsing radio waves </li></ul><ul><li>Once the pulses stop the nuclei go back to their state induced by the magnet </li></ul><ul><li>The energy now released by the nuclei acts like miniature radio stations giving out a signal </li></ul><ul><li>These radio waves are picked up by a computer where they are translated into an image. </li></ul>
  3. 3. What is so good about MRI? <ul><li>They have given doctors the chance to detect cancers earlier than ever before </li></ul><ul><li>They allow a view into the body without surgery </li></ul><ul><li>They are a non invasive way of diagnosing diseases and conditions </li></ul><ul><li>Gives a clearer set of images than CAT scans do. </li></ul>
  4. 4. Contraindications <ul><li>The strength of the magnet is 5000 times stronger than the earth </li></ul><ul><li>So all metals must be removed! </li></ul><ul><li>People with pacemakers cannot have a scan </li></ul><ul><li>If you have any metal fragments in the eye you cannot have a scan – it would rip the eye open. </li></ul><ul><li>These magnets are so powerful they could pull a car in! </li></ul><ul><li>There has not been enough research done on babies and magnetism, so pregnant women shouldn’t have one done before the 4 th month of pregnancy – unless it is highly necessary. </li></ul>
  5. 5. How it works – in depth <ul><li>The body is made of billions of atoms </li></ul><ul><li>The nuclei spins on an axis, a bit like a spinning top </li></ul><ul><li>The atom that the MRI uses is the hydrogen atom </li></ul><ul><li>It has a single proton and is the most strongly affected by the Magnetic field – it is more likely to line up than other atoms </li></ul><ul><li>Inside the magnetic field the protons are lined up and ready to go.. </li></ul>
  6. 6. <ul><li>The MRI scanner now releases a Radio Frequency that is only picked up by hydrogen </li></ul><ul><li>This RF makes the protons spin at a particular frequency, in a particular direction – This is the Resonance bit </li></ul><ul><li>When the RF is turned off, the nuclei start to lose the energy and return to where they were in the magnetic field </li></ul><ul><li>The coil now picks up that excess energy and sends the signals to the computer – which is the Imaging part of the scan </li></ul>
  7. 7. How the image is made <ul><li>Often, patients are injected with a contrast dye during the scan </li></ul><ul><li>The dye will reach different tissues at different rates </li></ul><ul><li>The image being sent back to the computer will have different strengths depending on the level of contrast dye in the tissues </li></ul>
  8. 8. The Uses of the MRI <ul><li>Diagnosing: MS; strokes; infections of the brain/spine/CNS; tendonitis </li></ul><ul><li>Visualising: Injuries; torn ligaments – especially in areas difficult to see like the wrist, ankle or knee </li></ul><ul><li>Evaluating: Masses in soft tissue; cysts; bone tumours or disc problems. </li></ul>
  9. 9. The Future of MRI <ul><li>MRI research is ever changing. </li></ul><ul><li>Smaller, lighter machines are always been developed. </li></ul><ul><li>Work is on going to develop area specific machines to scan small areas like feet, arms, hands. </li></ul><ul><li>Ventilation dynamic research is being tested with Helium to examine lung function </li></ul><ul><li>Brain mapping is having and will continue to grow and give us a better image of how the brain works than ever before </li></ul>
  10. 10. A real advantage in choice <ul><li>The MRI does not use ionizing radiation, which is a comfort to patients </li></ul><ul><li>Also the contrast dye has a very low chance of side effects </li></ul><ul><li>‘ Slice’ images can be taken on many planes </li></ul>
  11. 11. And the disadvantages? <ul><li>Claustrophobia. Patients are in a very enclosed space. </li></ul><ul><li>Weight and size. There are limitations to how big a patient can be. </li></ul><ul><li>Noise. The scanner is very noisy. </li></ul><ul><li>Keeping still. Patients have to keep very still for extended periods of time. </li></ul><ul><li>Cost. A scanner is very, very expensive, therefore scanning is also costly. </li></ul><ul><li>Medical Contraindications. Pacemakers, metal objects in body etc. </li></ul>