MRI uses strong magnetic fields and radio waves to produce detailed images of the inside of the body without using ionizing radiation. It works by aligning hydrogen atoms in the body that are then stimulated by radio waves to produce signals detected by antennas. A computer analyzes these signals to create clear images of tissues, organs, bones, and other internal structures.

1. Awesh
202266
Civil Engineering

2. MAGNETIC RESONANCE IMAGING
MRI

4. INTRODUCTION
 MRI is a radiology technique.
 That uses magnetism, radio waves,
and a computer to produce images
of body structures.
 MRI is based on the principles of NMR.

5.  It is a medical imaging modal which uses non-ionizing
radiation rather than ionizing radiation to produce image
of body structures inside the body.

6. • MRI makes use of the magnetic properties of certain
atomic nuclei (out of regular position).
• Hydrogen nucleus (single proton) present in water
molecules, and therefore in all body tissues.
• The hydrogen nuclei partially aligned by a strong
magnetic field in the scanner, instead of moving randomly.
Principal of Working

7. • The nuclei can be rotated using radio waves,
and they subsequently oscillate in the magnetic
field while returning to equilibrium (while turned off).
• Simultaneously they emit a radio signal.
• This is detected using antennas (coils).
• A computer then analyze these signals and
converges them into images.

8. (a) (b)
Randomly Arranged
Hydrogen Atom
After the strong magnetic
field applied

10. 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 electrically charged
particle such as the nucleus of a proton leads to a
magnetic dipole moment.
These magnetic moments are referred to as SPINS.

11.  In the presence of an external magnetic field protons
show a certain type of movement called precession.
 The number of times proton precess per second is
called precession frequency.
 The precession frequency is calculated using
Larmour Equation.
Proton Precession
ω=ɣ B0

12. o Simplest element with atomic number of 1
and atomic weight of 1.
o When in ionic state (H+), it is nothing but a proton.
o Proton is not only positively charged,
but also has magnetic spin (wobble)!
o MRI utilizes this magnetic spin property of protons
of hydrogen to elicit images!!
Why Hydrogen?🤔🤔

13.  No ionizing radiation.
 Variable thickness in any plane.
 Better contrast resolution.
 Many details without iv contrast.
Advantages

14.  Very expensive .
 Dangerous for patients with metallic
devices placed within the body.
 Movement during scanning may cause
blurry images.
 RF transmitters can cause severe burns
if mishandled.
Disadvantages