MRI uses strong magnetic fields and radio waves to produce detailed images of the inside of the body. It is based on nuclear magnetic resonance, which detects the signals from hydrogen atoms in tissue when excited by radio waves in a strong magnetic field. The first MRI scan took 5 hours to produce one image, but modern scanners can produce high-quality, multi-slice images in just minutes. MRI is very useful for imaging soft tissues and does not use ionizing radiation.

1. MAGNETIC RESONANCE
IMAGING
BY,
ARAVINDKUMAR B

2. MRI
 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
 In1997 the first MRI exam was performed on a human
being.
 It took 5 hours to produce one image.

3. 1920 1930 1960 1970 1980
1924 - Pauli
suggests that
may have
angular
momentum
(spin).
1937 – Rabi
nuclear particles measures magnetic
moment of nucleus.
Coins “magnetic
resonance”.
1940 1950
1946 – Purcell
shows that matter
absorbs energy at a
resonant frequency.
1946 – Bloch
demonstrates that
nuclear precession can
be measured in detector
coils.
1959 – Singer
measures blood
flow using NMR
(in mice).
HISTORY
1972 –
Damadian
patents idea for
large NMR
scanner to detect
malignant tissue.
1973 – Lauterbur
publishes method
for generating
1973 –
Mansfield
independently
publishes
gradient
approach t1o9M75R–.Ernst
develops 2D-
Fourier
transform for
MR.
images using
NMR gradients. NMR renamed
MRI
MRI scanners
become clinically
prevalent.
1990 2000
1990 – Ogawa and
colleagues create
functional images
using endogenous,
blood-oxygenation
contrast.
1985 – Insurance
reimbursements
for MRI exams
begin.

4. FATHER OF MRI
• Magnetic resonance imaging inventor

5. • 1944: Rabi
Physics (Measured magnetic moment of nucleus)
• 1952: Felix Bloch and Edward Mills Purcell
Physics (Basic science of NMR phenomenon)
• 1991: Richard Ernst
Chemistry (High-resolution pulsed FT-NMR)
• 2002: Kurt Wuthrich
Chemistry (3D molecular structure in solution by NMR)
• 2003: Paul Lauterbur & Peter Mansfield
Physiology or Medicine (MRI technology)
NOBAL PRIZES FOR MRI

6. WHAT CAN BE DIAGNOSED BY AN MRI
SCAN?
•
•
•
•
•
•
•
•
•
•
Most ailments of the brain, including tumours
Sport injuries
Musculoskeletal problems
Most spinal conditions/injuries
Vascular abnormalities
Female pelvic problems
Prostate problems
Some gastrointestinal tract conditions
Certain ear, nose and throat (ENT) conditions
Soft tissue and bone pathology/conditions

7. •
•
•
•
•
•
A cardiac pacemaker
Certain clips in your head from brain operations
A cochlear implant
A metallic foreign body in your eye
Had surgery in the last 8 weeks
If you are pregnant
WHO CAN’T HAVE AN MRI SCAN?

8. PRINCIPLE
• MRI makes use of the magnetic properties of certain
atomic nuclei.
• 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.
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9. CONTI..
•
•
•
•
The nuclei can be rotated using radio waves, and they
subsequently oscillate in the magnetic field while returning
to equilibrium.
Simultaneously they emit a radio signal.
This is detected using antennas (coils)
Very detailed images can be made of soft tissues.
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10. Randomly arranged
hydrogen atom
After the strong magnetic
field applied

11. MAIN COMPONENTS OF MRI
•
•
•
Scanner
Computers
Recording hardware

12. SCANNER
•
•
An MRI scanner is a large tube that contains powerful
magnets.
Main components of scanner
– Static magnetic field coils
– Gradient coils
– RF (radiofrequency) coils
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15. STATIC MAGNETIC FIELD
COILS
• Three methods to generate magnetic field
1. Fixed magnet
2. Resistive magnet
3. Super conducting magnet
•
•
•
•
Fixed magnets and resistive magnets are generally
restricted to field strengths below 0.4t
High-resolution imaging systems use super conducting
magnets.
The super-conducting magnets are large and complex
They need the coils to be soaked in liquid helium to reduce
their temperature to a value close to absolute zero.
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16. GRADIENT COILS
•
•
•
•
Gradient coils are used to produce deliberate variations in
the main magnetic field
There are usually three sets of gradient coils, one for each
direction.
The variation in the magnetic field permits localization of
image slices as well as phase encoding and frequency
encoding.
The set of gradient coils for the z axis are helmholtz pairs,
and for the x and y axis paired saddle coils.
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18. RADIOFREQUENCY COIL
•
•
•
•
•
•
•
RF coils act as transmitter and receiver
RF coils are the "antenna" of the MRI system
That transmit the RF signal and receives the return signal.
They are simply a loop of wire either circular or
rectangular
Helmholtz pair coils consist of two circular coils parallel
to each other.
They are used as the z gradient coils in MRI scanners
Paired saddle coils are also used for the x and y gradient
coils.
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19. ADVANTAGES OF MRI
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•
•
•
No ionizing radiation
Variable thickness in any plane
Better contrast resolution
Many details without iv contrast
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20. DISADVANTAGES OF MRI
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•
•
•
•
Very expensive
Dangerous for patients with metallic devices placed within
the body
Difficult to be performed on claustrophobic patients
Movement during scanning may cause blurry images
RF transmitters can cause severe burns if mishandled
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