MRI, or Magnetic Resonance Imaging, using the magnetic properties of superconductive coils in accordance with other permanent/temporary magnets, produce an image of the human body which is used to help diagnose various conditions and diseases. The superconductive magnet which consists of numerous coils of wire that carries current, is constantly bathed in liquid helium to keep its temperature below the critical point, -269.1 degrees Celsius. This magnet is isolated in a vacuum to eliminate heat loss. The system itself produces a magnetic field of 0.5 - 2.0 Tesla and the magnetic properties of the superconductive coils make it possible to produce such a field and keep MRI cost efficient.
The MRI machine uses three other types of magnets: resistive magnets, permanent magnets, and gradient magnets. Resistive magnets are similar to superconductive magnets except that they do not require the constant bathing in liquid helium to utilize their magnetic properties. Instead, they carry an unusually large amount of current to achieve this. Permanent magnets are also used, but to a much lesser extent than the superconductive magnets for their inability to provide a strong, stable magnetic field over a large enough area. Gradient magnets have a lesser magnetic field than superconductive ones, 0.018 Tesla to 0.027 Tesla, and are used to hone the machine in on key parts of the human body.
These various magnets produce an image of the insides of a human body by utilizing the atomic spins of numerous hydrogen atoms extant in the body, due to the strong magnetic moments of the hydrogen atoms. The strong magnetic field induced by the superconductive coils align the hydrogen atoms either pointing towards the head or pointing towards the feet. There should be a large number of hydrogen atom pairs that negate the spin of each other (one pointing towards the feet cancels the effect of one pointing towards the head). Very miniscule amounts of hydrogen atoms do not cancel each other out, but these exceptions are what allows the MRI machine to map out a picture of the body.
The un-negated hydrogen atoms are then exposed to a radio frequency pulse specific to the element hydrogen which causes the atoms to spin at a distinct frequency and direction. This frequency is called the Larmour frequency and is calculated using the type of tissue being examined and the strength of the magnetic field that is being used. Next, the three gradient magnets are turned on and off to change the magnetic field in a manner that helps "visualize" a specific part of the body that is being scanned. The information is sent to a computer that interprets the proton spins using a mathematical formula called the Fourier transform. In doing so, the computer successfully materializes the mathematical data into "images" that are used to diagnose patients.
The MRI machine uses three other types of magnets: resistive magnets, permanent magnets, and gradient magnets. Resistive magnets are similar to superconductive magnets except that they do not require the constant bathing in liquid helium to utilize their magnetic properties. Instead, they carry an unusually large amount of current to achieve this. Permanent magnets are also used, but to a much lesser extent than the superconductive magnets for their inability to provide a strong, stable magnetic field over a large enough area. Gradient magnets have a lesser magnetic field than superconductive ones, 0.018 Tesla to 0.027 Tesla, and are used to hone the machine in on key parts of the human body.
These various magnets produce an image of the insides of a human body by utilizing the atomic spins of numerous hydrogen atoms extant in the body, due to the strong magnetic moments of the hydrogen atoms. The strong magnetic field induced by the superconductive coils align the hydrogen atoms either pointing towards the head or pointing towards the feet. There should be a large number of hydrogen atom pairs that negate the spin of each other (one pointing towards the feet cancels the effect of one pointing towards the head). Very miniscule amounts of hydrogen atoms do not cancel each other out, but these exceptions are what allows the MRI machine to map out a picture of the body.
The un-negated hydrogen atoms are then exposed to a radio frequency pulse specific to the element hydrogen which causes the atoms to spin at a distinct frequency and direction. This frequency is called the Larmour frequency and is calculated using the type of tissue being examined and the strength of the magnetic field that is being used. Next, the three gradient magnets are turned on and off to change the magnetic field in a manner that helps "visualize" a specific part of the body that is being scanned. The information is sent to a computer that interprets the proton spins using a mathematical formula called the Fourier transform. In doing so, the computer successfully materializes the mathematical data into "images" that are used to diagnose patients.
RSS Feed