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MRI Scans; How does an MRI scanner work?

Posted by Phil Heler, MD on March 27, 2018

MRI has become a vital tool for diagnosing cancer and many musculoskeletal conditions and diseases of the central nervous system.

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MRI Scans; How does an MRI scanner work?



In 2016 there were about 36,000 MRI (magnetic resonance imaging) scanners in the world and about 2,500 are now sold each year. MRI has become a vital tool for diagnosing cancer and many musculoskeletal conditions and diseases of the central nervous system. MRI is a relatively new technology (1980’s) and in fact it was only in 2003 Paul Lauterbur, the director of the Biomedical Imaging Centre at the University of Illinois, and Sir Peter Mansfield, a physicist at the University of Nottingham in Britain, received the Nobel prize in medicine for making discoveries that “led to the development of modern magnetic-resonance imaging”.

An X-Ray is essentially a low cost alternative to MRI. X-Rays utilise small quantities of harmful radiation that travel through the body. This captures a single image of a part of your body to assess injury (fractures or dislocations) or disease (bone degeneration, infections or tumours). The MRI scanner however uses magnetic and radio waves to create pictures of tissues, organs and other structures within the body, which can then be viewed on a computer. There is no exposure to damaging forms of radiation.The images produced by an MRI scan, when compared to other imaging modalities, are much more detailed and therefore are of higher diagnostic quality. So how does an MRI work?

An MRI machine contains two very large magnets that produce a magnetic field. Basically MRI scans produce images because our body contains water molecules. As we all know water is made of hydrogen and oxygen molecules (H2O). These molecules are made of atoms which are in turn comprise of protons and neutrons and electrons. Hydrogen is especially rich in protons. In fact hydrogen, along with oxygen and carbon, make up 99% of the average human body. In an natural state the protons in hydrogen are all randomly arranged but when you turn on a magnetic field these protons align themselves with the direction of the field.

The first magnet which is turned on during your scan aligns all the protons in the water molecules in one direction. A second magnetic field is then quickly turned on and off and this causes the protons to suddenly align and then return to their previous state when the field is turned off. The scanner picks up these signals and a computer turns them into a picture. These pictures are based on the location and strength of the incoming signals.Different protons send out different signals, depending on which tissue the proton can be found in. For example, a proton found in bone will emit a very different  signal when compared to a proton found in blood. Unlike X-Rays however MRIs are very at diagnosing and imaging soft tissue related problems. The brain, spinal cord and nerves, as well as muscles, ligaments, and tendons are seen much more clearly with MRI

We send people for scans on the lower back or neck to help diagnose people who have trapped nerves. From the images we identify exactly what is happening and what is required. For many of these people we can treat them using our IDD Therapy protocol. This is a non-invasive alternative to surgery.