Download Basic MR Imaging (MRI) and MR spectroscopy (MRS)

Basic Physics
Principles of MRI
MRI
The physics basics
Magnetic Resonance Imaging
MRI Overview
No ionizng radiation 
Superior soft tissue contrast 
High resolution and multiplanar capability

History
1946 MR phenomenon - Bloch & Purcell
1952 Nobel Prize - Bloch & Purcell
1950
1960 NMR developed as analytical tool
1970
1972 Computerized Tomography
1973 Backprojection MRI - Lauterbur
1975 Fourier Imaging - Ernst
1977 Echo-planar imaging - Mansfield
1980 FT MRI demonstrated - Edelstein
Gradient Echo Imaging
1986
NMR Microscope
1987 MR Angiography - Dumoulin
1991 Nobel Prize - Ernst
1992 Functional MRI
1994 Hyperpolarized 129Xe Imaging
2003 Nobel Prize - Lauterbur & Mansfield
General description

When B0 applied to it, the momentum rate
will be:
Substituting I we have:
 This is Larmor equation.
 From Larmor equation the Larmor
frequency is:


mp can be divided to mpz and mpxy (mpz is assumed to be
in B0 direction)

If mpxy=0 ===> dmp/dt=0 means that there is no
change in the direction of dipole moment and no signal

If the sample contain large amount of protons, net
magnetic moment will be M

If M is in Z direction there is no signal.
When M direction changes as a results of an arbitrary B
we have signal and
B could be B0z+B1


Quantum mechanical discription

From the quantum view any nucleus with angular momentum of I
has a magnetic moment of

For any atom magnitude of nuclear angular moment is l (l is nuclear
spin quantum number):

In a magnetic field B0 the z component of mp can have
different
possible orientation with values of

For a single proton magnitude of I=1/2 and hence ml=±1/2
For 1H
l=1/2
==>
ml=±1/2
For 31P
l=1/2
==>
ml=±1/2
For 19F
l=1/2
==>
ml=±1/2
For 23Na
l=3/2
==>
ml=-3/2 , -1/2, ½, 3/2
Nucleus with I=1 have Quadrapole state






Energy state of each proton is:

If a proton move from one state to another
a change of energy is happens which is
equal to
and hence


Statistical distribution of spin states

In a large amounts of proton and the absence of B0 there
is no net magnetization

If a magnetic field of B0 is applied to them;

Changing from one state to another release a photon of:

The life time of each spin is:
Bloch equations

Bloch equations describe the behavior of nuclear
magnetic moment of a sample with large amount of
dipole moment in a magnetic field B;

If an stimulus changes the direction of M from B (assume
B=Bz) then changes to the Mz is given by:

Changes to x and y direction of M are: