MRI

As medical sciences is getting better everyday it is mostly focussing more and more on the specific organ or part of the body having problem rather than doing a trial and error medication. For this it is really important that the doctors have the knowledge of the specific area of problem and body scanners do serves this purpose. They scan the body and develops the image of the inner body organs. There are many scanners out there like

  1. X- rays – This is the most common method used to scan the injured bones, the rays are used as they are blocked by bones and dense tissues of the body.
  2. CT scan – Also called computed tomography this is used to get detailed view of blood vessels and  organs in the body.

Third most important scanning technique is the MRI whose full form is  magnetic resonance imaging, the technique was invented in 1972 by Felix Bloch and Edward Purcell. Although in the early years this scanning technique was not used in human body, perhaps this idea was put by Raymond Damadian as he showed the doctors a way to actually use MRI to detect tumors. After some years of developing the machine so as to use it on human, in 1977 it was the first time that MRI was used on humans.

Physics behind MRI scanning

MRI is claimed to be better than CT scanning as it gives more detailed images of the body parts. Another important difference is MRI do not use radiations as CT or X-rays, as exposure to radiations can be a bit risky and especially X-rays can be harmful for pregnant women.

As we know about 60% percent of our body is  composed of water and chemical composition of water contains 2 hydrogen atoms and one oxygen atom. The hydrogen atom has one proton and one electron, and the nuclei has a characteristic  precession  because of which the magnetic moment  is created. when the body is exposed to a magnetic field of 1.5 to 3 Tesla, these magnetic moment aligns to the direction of magnetic field as the nuclei starts precessing about the magnetic field they are exposed to, this precession is called larmor precession. The frequency of the precession is proportional to the applied magnetic field. Next a radio frequency pulse is applied  which is equal to the frequency of the larmor precession, this causes the energy exchange and as they are in resonance. This causes the direction of magnetic moment to tilt a bit in the direction of the radio frequency pulse applied and when this radio frequency pulse is removed it tends magnetic moment to again come back to its position that is to align in the direction of the magnetic field . As this happens the nuclei emits its own radio frequency pulse, and different tissues in the body gives out different Radio frequency pulse. To detect this pulse  the body is covered by a coil which detects these pulses and these are converted to an image using the computers which uses mathematical methods like fourier transformation. This results in the highly accurate image of the body parts.

Though MRI is simple and has less risks like all these years pregnant women take MRI scans and there has not been any report of  any abnormalities while the child is born, but there are some precautions to be taken as follows

  1. Make sure one does not have any magnetic objects while going into the room
  2. There are many patients who fall sick after MRI, it is really normal because of the sedative given before the scan
  3. One should never move while MRI scan is been taken.
  4.  One should avoid driving after he or she has taken  MRI scan.

 

 

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