MRI provides physicians with a tool to assess a patient’s health. To have an MRI exam, the patient lies in a very strong magnetic field that is generated by powerful magnets. The MRI machine then applies radio waves to the patient’s body; radio waves are electromagnetic waves.
MRI uses radio waves as this kind of electromagnetic wave affects hydrogen atoms, which the body has in abundance. They are two hydrogen atoms in every water molecule (H2O), and the human body contains a lot of water (around 65-70% by weight). The strong magnetic field aligns hydrogen atoms as if they were little compass needles, and the radio waves interfere with this alignment. The MRI machine uses computers to analyze the signals given off by the atoms as they change alignment. Because, hydrogen atoms are involved, MRI works best in areas with a lot of water or fat content such as the brain.
Images produced by MRI allow doctors to spot diseased tissue and organs. These images are particularly useful in finding tumours growing in the nervous system, either in the spinal cord or the brain,
This technology is also used in functional magnetic resonance imaging (fMRI). An fMRI allows scientists who study the brain to measure the activity of the brain cells while the person is awake and thinking. Blood flow normally increases to brain cells that particularly active for example when a person starts thinking, the working part of the brain begins to get an increased blood flow. The modern fMRI techniques take advantage of a naturally occurring substance in the blood that can be affected by the magnetic fields of the machine. This substance is deoxyhemoglobin, a molecule found in red blood cells. Since it is already present in the blood, no injections are needed.
By taking images while a person performs various mental tasks or is being subjected to various sensations, scientists can study which part or parts of the brain contribute to behaviour.
Also Read: Radionuclide Imaging Techniques
