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About This QuizAn MRI machine is more than just a big, claustrophobia-inducing tube. How much do you know about what's going on inside -- or what's going on inside your body while you're in there?
The biggest and most important component of an MRI system is the:
As its name suggests, a magnetic resonance imaging (MRI) system has a magnet at is core. This magnet is so powerful it can suck metal objects into the tube (and out of a person's body).
The first MRI examination was performed on a human being in:
The 1977 conduction of the first-ever MRI exam was a breakthrough in medical science. It let doctors examine the interior of the human body in a way that had been impossible.
For the purpose of an MRI, which element within the body is most important?
Hydrogen atoms have one proton and a large magnetic moment. This means they react strongly to magnetic fields and are ideal for examination in an MRI machine.
An MRI system uses an RF pulse to change the:
spin of atoms' nuclei
An MRI's RF pulse changes the spin, or precession, of atoms' nuclei. The hydrogen atoms line up with the direction of the MRI's magnetic field.
shape of the nuclei
amount of metal in a person's cells
The most common type of magnet used in MRI systems is the:
Although all three types of magnets can be used in an MRI machine, the superconducting magnet is the most common. In general, large enough resistive magnets are too expensive, and powerful enough permanent magnets are too big.
In a superconducting magnet, the coils are bathed in liquid helium:
to keep the system from overheating
to reduce the amount of resistance in the wire
At normal temperatures, it would take lots of power to send electricity through all the wire in a superconducting magnet. But at the very cold temperature of liquid helium, there's almost no resistance in the wire, greatly reducing the need for power.
to keep the area around the coils sterile
An MRI system creates an image when:
All the hydrogen atoms in your body line up, creating an outline.
Hydrogen atoms facing opposite directions cancel each other out, creating a reverse outline.
The hydrogen atoms go back to their normal position, releasing energy.
Imagine each hydrogen atom as a tiny magnet. In the MRI machine, they all line up. When the RF pulse disappears, they go back to their normal positions, releasing energy, which the system uses to make an image.
What component of an MRI system allows it to choose exactly where in the body to acquire an image?
Gradient magnets are small magnets that change the field within an MRI system. When turned on and off very rapidly, they essentially change the focus of the overall field.
What does an MRI system use to convert mathematical data into a picture?
RF pulse converter
Fourier transform uses mathematical functions to change the data retrieved by the MRI system into a picture that a doctor can examine to make a diagnosis.
MRI scans tend to be very noisy. The noise comes from:
opposition of the main magnetic field to the current in the gradient magnets' wires
The stronger the main magnetic field in an MRI, the louder the banging will be when it encounters the current in the gradient magnets' wires. For this reason, many MRI centers give patients earphones or earplugs.
movement of the magnet from place to place
stray particles within the system being thrown about by the magnetic field
Monty Rakusen/Cultura/Getty Images