How does an MRI work?
We’ve come a long way since Pavlov and Freud, but scoping out the human brain is still a tricky business. Luckily, technology is on our side, and in recent years researchers have found some clever techniques for taking a peek inside humanity’s great “black box” without jostling the goods. Among these, Magnetic Resonance Imaging (MRI) is one of the most popular. The non-invasive machine works on the principle that your body (brain included) consists largely of water, which in turn is made up of oxygen and hydrogen molecules. The hydrogen molecules have a magnetic spin that can be aligned by a strong burst of radio-frequency waves from an MRI machine. Once this is done, a second pulse knocks the hydrogen molecules out of spin alignment. A computer then records how long the atoms of different tissues take to realign themselves. Different tissues have different molecular alignments, and by exploiting this fact a computer can construct a topographical map of the soft tissue in your brain.
Before the MRI exam, your Cape Radiology Group technologist will discuss your medical history with you and answer any questions you might have. You’ll be asked to change into a gown and go to the bathroom to ensure your comfort during the exam. When using MRI, certain items will need to be removed due to the magnetic field, including jewelry, glasses, hearing aids, clothing with zippers, nonpermanent dentures, credit cards, some cosmetics and metal objects, such as hairpins or barrettes. The technologist will position you on the scanning table and make you as comfortable as possible. We also offer earphones and music for your relaxation. While on the scanning table, a large magnet creates a magnetic field that causes protons inside the atoms in your body to line up together and spin in the same direction. As the radio frequency is beamed into the magnetic field, it forces the protons to move out of alignment. When the signal stops, the protons move back into place and release energy. A
Well, I’m too late for you to answer this question. The MRI has a magnet that is always on. The strength of this magnetic field will probably be in the range of 1.5 – 3 Tesla ( 15000-30000 gauss). This is a few hundred times higher than a typical fridge magnet. For this reason you should avoid bringing any metal or cards into the scanner room. An ankle scan will likely mean that you go into the tunnel foot first. This is a good thing if you are claustrophobic and means your head will be outside of the scanner. Scanners make a lot of noise when they are in use. This is caused by changing magnetic fields and resulting forces in the coils of the machine. Don’t let this bother or worry you. You will be given a head telephone or ear plugs to lessen the noise.
