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Lisa!
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What is the source of noises we hear during MRI imaging?
Thanks!
Thanks!
To the other respondents: if you have no clue, please don't offer your incorrect guesses. Lok, your response is ludicrous. f95toli, systems with cryocoolers do often have background noise when you walk into imaging suite, but it is generally inaudible inside the bore and in any case is unrelated to the intense noise that every MRI patient is familiar with. To answer your question, Lisa, you need a little background on how the instrument works:Lisa! said:What is the source of noises we hear during MRI imaging?
Thanks!
To emphasize what marcusl said, this works exactly the same way as a speaker does. In a speaker you have a strong permanent speaker magnet and an electromagnet that is switched on and off rapidly to move the speaker cone. In the same way the gradient coils marcusl mentioned are switched rapidly and the 1.5T main magnetic field he mentioned serve the role of the permanent magnet.marcusl said:Ok, now to the noise. The gradients are produced by big electrical coils that also sit in the main bore. When current (typically around 150A) flows, the wires feel a large sideways Lorentz force because they are in a strong static field. Consequently, these coils are wound on strong formers and are potted to minimize wire movement. Because the current is turned on and off very rapidly, however, the wires exert a strong impulsive force that is heard as a bang even though gross wire motion is controlled. The repetitive banging you hear is the three coils being pulsed over and over with various strengths, timings and sequences to build up the image.
http://www.toshiba-medical.eu/en/Our-Product-Range/MRI/Technologies/Pianissimo/marcusl said:Also, the gradient coils are not encased in a vacuum.
Well I'll be! I hadn't heard of the vacuum-encasement technology before. Thanks!DaleSpam said:
marcusl said:Here is a two-page summary of MRI. The second page shows a sketch of the main magnet and the gradient coils.
http://people.ee.duke.edu/~jshorey/MRIHomepage/work.html"
Despite numerous safety warnings issued by the manufacturers, professional societies, and the government, I have heard numerous stories of ferromagnetic objects being pulled into imaging magnets. The most common one is similar to this story. A metal pail on wheels was filled with water and had a mop wringer in it. The pail was located approximately 10 feet from the bore of a 1.5 T magnet. The magnet pulled it across the floor and lifted it up off the ground three feet into the magnet. The wringer caused serious damage to the magnet in that the cryogen boil off rate increased and the magnetic field homogeneity decreased. The head coil located in the bore of the magnet was destroyed.
The most tragic story was the death of a six year old boy in an MRI magnet. This story should serve as an example and reminder of the responsibility that MRI personnel and administrators have to maintain a safe facility. In July 2001 a boy was injured in an MRI and later died when a ferromagnetic oxygen tank was brought into the magnet room and pulled into the magnet where the boy was being imaged.
Another frightening story was of a law enforcement officer being allowed to go near a magnet with a loaded firearm. The handgun was pulled out of its holster, and into the magnet. The force of the impact with the magnet caused the gun to discharge. Luckily, no one was injured in this incident. In addition to the damage to the MRI and the bullet lodged in the scan room wall, the gun was magnetized. Mechanical objects, in general, do not function properly when magnetized. Please, respect the physical laws of nature that cause ferromagnetic objects to be attracted by magnets!
The main sources of noises from MRI imaging are mechanical vibrations, electromagnetic interference, and acoustic noise from the gradient coils.
Noises from MRI imaging are not harmful to patients. However, they can be uncomfortable and cause anxiety or hearing damage if the sound levels are too high.
Yes, there are several methods that can be used to reduce the noises during MRI scans. These include using sound-absorbing materials, optimizing the MRI sequences, and using special headphones or earplugs for patients.
The loud noises from MRI machines are caused by the rapid switching of the gradient coils, which creates changes in the magnetic field. This generates vibrations that produce the loud banging and buzzing sounds.
Although noises from MRI imaging are not harmful, there are some safety concerns that need to be addressed. These include the potential for acoustic trauma, interference with medical devices, and psychological distress for patients. It is important to follow proper safety protocols and guidelines to minimize these risks.