this is the basics of mri

1. BASICS OF MRI
Presented by:-
Pranali. N. Kulkarni
Ganesh M. Nair
Aaditee S. Kulkarni
Omkar Haldonkar

2. MAGNETIC RESONANCE IMAGING
 Magnetic resonance imaging
(MRI) is a medical imaging
technique used in radiology to
visualize internal structures of
the body in detail.

3. WHAT IS A SPIN????
 Atomic nuclei with an odd number of
protons behave like spinning particles
which in turn create a small nuclear
spin angular momentum.
 This angular momentum of an
µ : magnetic moment
Bo : magnetic flux density
electrically charged particle such as
the nucleus of a proton leads to a
magnetic dipole moment.
 These magnetic moments are
referred to as SPINS.

4. PRECESSION AND LARMOR FREQUENCY
 Acc. To electromagnetic theory
, nucleus of H2 proton posses
magnetic moments to align itself
with the magnetic field in which it
is field.
 This results in precession or
wobbling of magnetic moment
about the magnetic field with an
angular frequency called Larmor
frequency.

5. N N
Z Z
X,Y X,Y
S S

6.  MRI can be explained as interaction of spins with three magnetic
fields

7. BASIC STEPS OF MRI
1) 2)
3)

8. Z
STEP 1
Mz
STEP 2
M(t)
STEP 3
Y
Mxy
X
STEPS OF MRI

9. STEP 1
H
Z Mo
Mo= Equilibrium magnetization.
Mz = Magnetization along z. Anytime the
magnetization vector is displaced along z, it will be
called M.
Mxy= Component of M that is in XY plane

10. STEP 2
M can be displaced by applying a magnetic field H1
(rotating at Larmor freq of hydrogen nuclei)
 RF pulse causes:
At the end of 90 pulse, M=Mxy and Mz=0

11. STEP 3
RF pulse is turned off
Mxy diminishes towards zero
and Mz increases from zero.
After the 90 RF pulse,the
RF coil is switched to receiver
mode.

12. VOLTA FREE INDUCTION DECAY
GE
TIME

13. FREE INDUCTION DECAY
 At room temp. more protons are in a low
energy state.
 The excited proton tends to return to low
energy state with a spontaneous decay.
 This decay is exponential in nature