Magnetic resonance imaging (MRI) uses powerful magnets and radio waves to generate detailed images of the inside of the body. It was first developed in the 1970s and allows doctors to diagnose issues without exposing patients to radiation. An MRI scan works by aligning hydrogen atoms in the body using magnetism and radio waves. This causes the atoms to emit signals that are picked up by antennas and used by a computer to construct cross-sectional images of tissues and organs. MRI is useful for dental applications as it can image soft tissues like tooth pulp and the temporomandibular joint with high resolution, aiding in diagnosis and treatment planning.

1. MAGNETIC RESONANCE
IMAGING IN DENTISTRY
Fiona Daley
Dental hygiene Bs.science
Dental Auxiliary School

2. CONTENT
History
Definition
Diagnostic Image
How does MRI work

3. HISTORY
 The first patent of MRI technology was filed by
Raymond Damadian in 1972. The doctor and
researcher discovered that images created using MRI
technology could be helpful during the process of
diagnosing a patient. Damadian was the first person
to use MRI to make a medical diagnosis.


4. Definition
Magnetic Resonance
It is a non-invasive method for mapping internal structure within the body which uses non-
ionizing electromagnetic radiation and employes radio frequency radiation in the presence
of carefully controlled magentic fields to produce high quality cross-sectional images of the
body in any plane.

5. Magnetic Resonance Imaging
Components
 Magnet
 Radio Frequency (Resonance)
 Imagine

6. Magnetic Resonance Imaging Components
help to make Diagnost image.
 How does it creates diganostic image.
First mapping internal structure within the body
Uses non-ionizing electromagnetic radiation(RF),
employes radiofrequency radiation in the presence of carefully controlled
magnetic fields to produce high-quality
cross-sectional images of the body in any plane
The magnetic component create a strong magnetic to change the spin of the
atoms in the bodies and radio signals detect these tiny changes.
Finally the computer process this information and construct images of soft
tissue inside the body,from brain to blood vessels.

7. MRI Diagnostic Image in Dentistry

9. High Resolution of MRI VS X-ray

10. MRI(SWIFT), comparison another
diagnostic image application.

11. 3D MRI of the tooth pulp.

12. Imaging of soft and solid components
without ionizing radiation.

13. Tmj joint disorder diagnose with MRI

14. MRI Scanning of TMJ

15. Other Imagine of MRI done dentistry.

16. Application
Efficacy Of Magnetic Resonance Imaging in dentistry.
 Non-ionzing radiation Diagnostics Imaging
 Soft tissue such as paranasal sinus tooth pulp
 Successful restorative treatment mapping the shape of dental cavities.
 Obtain high contrast between cavities and tooth(SWIFT).
 High-resolution anatomical detail
 Diagnosis TMJ joint disorders

17. Draws Back in MRI in Dentistry.
 Image artifacts can be seen this may due to metal materials and patient
movements also,examinations can be expensive. Some medical and
dental centers have limited access.

18. The Principle of (MRI )
works by obtaining a resonance signal from the hydrogen
nucleus, and therefore, is essentially an imaging of water
in the tissue. Moreover the spin echo and inversion
recovery are the two most commonly used imaging
sequences.
Spinning Atoms (hydrogen) face outside magnetic field
Energy Absorption by RF Coils .

19. Resonance of Hydrogen atoms Measured by RF antenna
which the received signal is sinusoidal in shape.
Imaging by the computer which receives mathematical
data, which is converted through the use of a Fourier
transform into an image.

20. How does MRI work
MRI exploits the presence of vast amount of hydrogen in a
human body as the water content in human body is said to
be about 80%.
At the centre of each hydrogen atom is an even smaller
particle , called proton. Protons are like tiny magnets and
are very sensitive to magnetic fields and has magnetic spin.
MRI utilizes this magnetic spin properties of protons of
hydrogen to elicit images.

21. How does the MRI work
 •The protons i.e. hydrogen ions in a body are spinning in a haphazard
fashion and cancel all the magnetism. That is our natural state.
 •When there is large magnetic field acts on our body, protons in our body
line up in •same direction. •In same way that magnet can pull the needle
of a compass

22. Human body is largely made of water molecules, which
consists of smaller particles i.e hydrogen and oxygen atoms.
 Protons lies at the Centre of each atom, which is sensitive to
any magnetic fields and hence this proton serves as a
magnet. Normally water molecules in our body are
 randomly arranged, but upon entering on the MRI scanner
first magnet causes body’s water molecules to align in one
direction and second magnet was then turned on and off in
a series of quick pulses, causing each hydrogen atom to
alter their alignment and quickly , switches back to their
original relaxed state, when switched off.

23. HOW MRI WORKS

24. MRI Magnetic Coils
Inside the main magnet is a set of gradient coils for
changing the field along the X, Y and Z directions
required for imaging. Inside the gradient coils are the RF
coils producing the field B1 for rotating the spin by an
angle dictated by the pulse sequence. These coils also
detect the signal emitted by the spins inside the body. At
the centre is a patient table which is computer
controlled.
The magnet, the RF body coil and the gradient coil
assembly represent the three major subsystems that
comprise the resonance module of the MR scanner.

25. Magnetic Field Around the Body

26. COMPONETS OF MRI
1) Main magnet (superconducting magnet)
2) Gradientcoils
3) RF coils(radiofrequency)
Schematicdiagram of MRI scanner

27. COMPONETS OF MRI
27

29. COMPONETS OF MRI
 1.Superconducting magnet
A superconducting magnet is the heart
and most expensive part of an MRI
scanner.
In its superconducting state, the wire has
no electrical resistance and therefore can
conduct much larger electric currents than
ordinary wire, creating intense magnetic
fields. ...

30.  .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.

31. COMPONETS OF MRI
Gradient coils
 X coil – create a varying magnetic field from left
to right.
 Y coil- create a varying magnetic field from top to
bottom.
 Z coil- create a varying Magnetic field from head to toe

32. MRI magnet design

33. Radiofrequency RF Coils
 3. RF Coils
Same as Radio waves – high wavelength, low energy
electromagnetic waves.
RF coils are the "antenna" of the MRI system
That transmits the RF signal and receives the return signal.
They are simply a loop of wire either circular or
rectangular.
inside the gradient, coils are the RF coils producing the field B for
rotating the spin by an angle dictated by the pulse sequence. These
coils also detect the signal emitted by the spins inside the body.At
the centre is a patient table which is computer controlled.

35.  COMPONENTS OF MRI 3.RF CoilsStart RF pulses (Excitation- Protons jump to
higher energy state by absorbing radiation).

36. 3.
RF coils Stop RF pulses (Relaxation- Protons
return to their original state emitting
radiation)

37. The MRI might affect Restoration
Material(amalgam)

38. Computer System
 Receives RF signal and performs analog to digital conversion.Digital
signal representing image of body part is stored in temporary image space
or case space. It store digital signal during data acquisition, digital signal
then sent to an image processor were a mathematical formula called
Fourier transformation is applied to image of MRI scan is displayed on a
monitor.