Magnetic Resonance Imaging: How It Works and What You Should Know

Magnetic Resonance Imaging: How It Works and What You Should Know


Magnetic Resonance Imaging, better known as an MRI is a machine used to produce detailed images of the human body. This is done using strong magnetic fields along with radio waves that penetrate the body and generate images of body parts which were otherwise impossible to see despite the existence of X- rays, CT scans, and Ultrasounds.

The MRI was a game changer as it allows doctors to look inside parts such as joints, cartilage, ligaments, tendons; allowing treatments to be more accurate and effective. The ability to see the insides of body structures gives doctors the capability to treat an array of disorders such as heart strokes, tumors, aneurysms, injuries on the spinal cord, multiple sclerosis as well as eye and ear-related problems. It is evident that the MRI is integral to healthcare in today’s world, despite the complexity in the creation of the machine it’s important to understand its functioning the concept behind it.

How the MRI Works

As we know, the human body is mostly composed of water. The hydrogen nuclei in the water molecules align to magnetic fields. The MRI machine is capable of producing extremely high magnetic fields between 0.2 to 3 Tesla (easily over a thousand times stronger than a fridge magnet). This strong magnetic field causes the nuclei to spin in alignment. The MRI scanner also produces radio frequency currents. These currents create varying magnetic fields. Depending upon the amount of energy radiating from the magnetic fields and the energy absorbed by the protons, the molecules flip, and spin.

When switched off, the protons gradually go back to their normal position. This process of returning to normal state is called precession. The precession process produces a radio signal that is measured and analyzed by the built-in receivers in the machine and then ultimately converted into an image.

Due to the fact that protons in different parts of the body go through the precession process at different rates, the scanner is capable of identifying different types of body tissues. The scanner can also be set in order to adjust to produce different contrasts for different tissues. The magnetic fields in the MRI scanner can also produce 3-dimensional figures that enable the viewing of internal organs at multiple different angles.

MRI Safety and Concerns

There are no known hazards to human from being exposed to magnetic fields such as those used in MRIs. In fact, this method of imaging does not use ionizing radiation which is employed by other imaging devices, the MRI contrast materials are known to have an extremely low chance of side effects.

The MRI is safe if conducted by a trained professional as strict precautions must be observed so that all goes well. There are many factors that need looking into before the scan takes place in order to ensure the safety of the patient. Metal objects have the potential to play with magnetic fields and therefore can be pulled out of pocket or one body and will fly towards the source of the magnetic field at a high velocity. Therefore, it is extremely dangerous to enter a scan having paperclips, pens, keys, scissors, jewelry and other such items as they could become harmful projectiles in the MRI.

To ensure safety patients and medical staff should be checked for metal objects prior to entering the scanning theatre, as long as the patient does not have implants inside their body, then an MRI is not advisable without proper consultation.

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