Modern Medicine

Why is an MRI better than an X-ray or CT scan?
Answered by Discovery Fit & Health
  • Discovery Fit & Health

    Discovery Fit & Health

  1. Although an MRI (magnetic resonance imaging) scan is an expensive proposition, it has advantages over both X-rays and other types of scans. An MRI scanner builds up a model of a part of the body from all different angles, giving a 3-D image, whereas CT (computer tomography) scans operate on just one plane. An X-ray, though good for taking photographs of bones, is not used for soft tissue. The MRI can also produce an image in various shades of color, indicating the differing conditions of the tissue under investigation. During an MRI scan, under the influence of the strong magnetic field, hydrogen atoms in our body become ordered. The protons in the atoms either point up or down. Most cancel each other out - the same number point up as down. There are some odd protons left over, enough to work with. These are bombarded with a radio frequency pulse that causes them to spin. When the radio frequency is switched off, the protons release energy, emitting a signal picked up by wire coils and sent to the MRI machine’s computer system, where the data is converted to an image. Undergoing an MRI isn’t painful, but it’s also not a particularly pleasant experience. Before you start, you need to remove all metal objects such as watches and rings. The nurse will ask you if have any metal inside your body. You have to lie inside a narrow tube, where you must keep completely still during the operation of the machine. While the machine is working, there will be some extremely loud noises; the nurse will give you earplugs. There are smaller scanners that are less enclosed, but they may not be quite as accurate.

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