When performing an MRI scan, a patient is placed inside a cylinder containing a strong magnet. Radio waves are introduced, causing the body's atoms to resonate and emit signals. A computer translates these signals into a two-dimensional image. MRI uses magnets to align the spin of hydrogen nuclei in the body. Radio pulses cause the spins to resonate, and the emitted signals are detected to form an image. MRI magnets can be permanent, resistive, or superconductive depending on the required field strength.

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MRI ROOM REQUIRMENT

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When performing an MRI scan, a patient is placed inside a cylinder
that contains a strong magnet. Radio waves are then introduced
into the cylinder, which cause the atoms of the body to resonate.
Each type of body tissue emits characteristic signals from the nuclei
of its atoms, and a computer translates these signals into a two-
dimensional picture.

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The Atom
Everything in nature is made up of tiny bits of matter called atoms.
An atom is the smallest unique part of a chemical element.
Atoms consist of three components:
 · protons, which are positively charged;
 · neutrons, which have no charge;
 · electrons, which are negative charged.
The protons and neutrons form the core or nucleus to the atom,
while the electrons orbit the nucleus like the planets orbit the
sun.

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Spin of the Nucleus
 One important property of the proton is that of spin or intrinsic
angular momentum. The proton rotates about its own axis much
like a top or a gyroscope. Since the proton is a positively
charged particle and spins, it has a magnetic field associated
with it. The hydrogen protons in the body, or spins,behave like
tiny magnets called magnetic dipole vectors (two poles -
northand south), having both orientation and magnitude

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Nuclei are built up of protons and neutrons. The number of protons in a
nucleus determines the chemical element. Nucleus with the same number of
protons but with an different number of neutrons are called isotopes.

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Hydrogen atom
 The simplest atom is Hydrogen. It consists of just one proton
and no neutrons.
 The advantages of hydrogen for MR are:
 1. It is the most common element found in the human body;
primarily in
 water and fat molecules.
 2. It has the highest sensitivity to magnetic resonance of any
element in nature
MR-imaging (MRI) is almost exclusively limited to the study of
hydrogen nuclei

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In a homogeneous magnetic field the
spin vectors of the hydrogen nuclei
(protons) align parallel or anti
parallel to the magnetic field.

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The sample to be scanned is placed into the center of the magnet. The
RF transmitter is turned on for a short duration. The RF energy from the
transmitter is absorbed by the hydrogen nuclei (protons) in the sample.
Once the RF transmitter is turned off, the hydrogen protons in the sample
give up the energy they received from the transmitter in a process called
relaxation. During the relaxation process, the hyrdogen protons emit a
signal that is detected by the antenna system and the RF receiver. The
data acquisition system (DAS), digitizes the signal so that the host
computer can process the data into an image.

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MAGNET TYPES
PERMANENT MAGNET
RESISTIVE
SUPERCONDUCTIVE
LOW FIELD MAGNETS FOR MAGNETIC FIELDS UP TO APPROX. 0.3 T
PERMANENT MAGNETS RESP. RESISTIVE ELECTRO MAGNETS ARE
USED.
HIGH FIELD MAGNETS MRI SYSTEMS USING FIELD STRENGTH FROM
0.5 T UP TO 2.0 T OR EVEN HIGHER, REQUIRE SUPERCONDUCTIVE
ELECTRO MAGNETS.
RF Room
Control Room
Equipment Room

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