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1.2.2 Electromagnets There are two categories can be used in MR scanner: Resistive and Superconducting Magnets 1.2.2.1.Therefore, they produce a lot of heat, which requires significant cooling of the magnet coils.These magnets are very large that utilizes the principles of electromagnetism to generate the magnetic field, like the ones used in scrap yards to pick up cars.Resistive magnets are typically limited to maximum field strengths can be up to 0.6 Tesla.These superconductors, such as niobium-tin and niobium-titanium are used to make the coil windings for superconducting magnets.Resistive Magnets Resistive magnets are made from loops of wire wrapped around a cylinder through which a large electric current is passed.Once

1.2.2 Electromagnets
There are two categories can be used in MR scanner: Resistive and Superconducting
Magnets
1.2.2.1. Resistive Magnets
Resistive magnets are made from loops of wire wrapped around a cylinder through
which a large electric current is passed. These magnets are very large that utilizes
the principles of electromagnetism to generate the magnetic field, like the ones used
in scrap yards to pick up cars. They are lower in cost, but need a lot of power to run
that means, large current values which runs through loops of wire because of the
natural resistance of the wire. Therefore, they produce a lot of heat, which requires
significant cooling of the magnet coils. Resistive magnets come in two general
categories: iron-core and air-core. Resistive magnets are typically limited to
maximum field strengths can be up to 0.6 Tesla. They usually have an open design,
which reduces claustrophobia. Figure 2 shows Hitachi's Airis 0.3 Tesla (air-core)
system.
1.2.2.2 Superconducting Magnets
Superconducting magnets are Today's most commonly used in MRIs. These
superconductors, such as niobium-tin and niobium-titanium are used to make the
coil windings for superconducting magnets. The magnetic field is generated by a
passing electrical current through coils of wire. The wire is surrounded with a
coolant, such as liquid helium, to reduce the electric resistance of the wire. At 4
Kelvin (-269 Co
) electric wire loses its resistance (Figure 3). Once