The Physics of an MRI Machine. Whitney Wright PH106/006 Dr. Probst 06/05/2012 The Physics of an MRI Machine There are many physical concepts used in a Magnetic Resonance Imaging, also known as MRI, machine. There are many physical concepts used when an MRI is taken of the body, such as; radio waves, resonance and pulse sequences, magnetic fields being produced and lastly, magnets. Radio waves much stronger than the magnetic field of the Earth are sent through the body which causes the nuclei in the body to move to a different position.
When the nuclei move back to the place they originated from, they send back radio waves that the scanner on the machine picks up and turns them into a picture. Resonance is very common within multiple branches of physics, without resonance we wouldn’t have television, music or radio. Resonance is also one of the most unexplained phenomenons in physics; it causes glass to break with a high pitched voice, bridges to collapse and also earthquakes causing buildings to collapse.
Within the MRI, nuclear magnetic resonance is used, this is when magnetic fields and radio waves cause the atoms in the body to give off tiny radio waves (Bellis). The explanation of Pulse sequences are defined in a basic way by the article “MRI Physics: pulse sequences” as ‘the pulse sequences define the manner in which the radiofrequency pulses, which generate the detectable signals, and magnetic field gradients, which provide the spatial encoding of the signals’ (Sharma). When the pulse sequences are used a sequence diagram is used to show how the sequences will occur during the MRI.
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There are many different sequences available; each used for creating certain images, the most commonly used is the spin echo sequence. When magnetic fields are produced, it means an electron has moved along a wire creating a magnetic field around that electron. When the wire is in the form of a loop, or multiple loops in this case, a very large magnetic field is produced and it runs perpendicular to the field. The magnets within the MRI are known as the primary magnet and the gradient magnets. The primary magnet or permanent magnet is the coiled wire that creates the magnetic field.
These coils have to be stored at -450( Fahrenheit within a type of liquid helium. These magnetic fields are between 10,000 and 30,000 times stronger than the magnetic field of Earth. The gradient magnets consist of three smaller magnets within the MRI machine. These magnets are about 1/1000 as strong as the primary magnet and allow smaller images of the area to be produced. These magnets help focus on a particular part of the body (Cluett). There are many other physical concepts that I did not discuss used within the MRI machine.
The main concepts are radio waves, resonance, pulse sequences, magnetic fields being produced and magnets. Works Cited Bellis, Mary. "Magnetic Resonance Imaging MRI. " About. com, Investors. New York Times Company, n. d. Web. 5 June 2012. . Cluett, Jonathan. "MRI: What is a MRI?. " About. com, Orthopedics. New York Times Company, 15 Aug. 2011. Web. 5 June 2012. . Sharma, Harish, and Jim Lagopoulos. "MRI physics: pulse sequences. " Acta Neuropsychiatrica 22. 2 (2010): 90. EBSCOhost. Web. 5 June 2012. .
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