MRI - Strange physics ahead . Step by step approach of basics of MRI physics with applications in dentistry.

1. MAGNETIC RESONANCE IMAGING
By:
Ujjwala Rastogi
MDS

2. CONTENTS
1. Introduction
2. Basic principle of MRI
3. T1 and T2 relaxation and image weighting
4. K-space and scanning parameter
5. MRI instrumentation
6. MRI Artifacts
7. MRI contrast media
8. Principles of interpretation
9. Conclusion
10. References

3. Introduction
Definition
History
Indications and
Contraindications
Advantages and
Disadvantages

4. Definition
Magnetic Resonance Imaging
Magnet
Radio Frequency = Resonance
Imaging
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. French mathematician & engineer.
Developed Mathematical transformation:
analysis of heat transfer b/w solid bodies.
Rapidly process the frequency signals
of NMR data & utilize this for image
Reconstruction.
Invented tesla coil in 1891
Started studying the magnetic
Properties in1930
He succeeded in detecting and
Measuring single states of rotation
of atoms and molecules, and in
determining the magnetic moments
of the nuclei.
Had the idea of applying magnetic
gradient in 3 spatial dimension
& used computer to create 2D NMR
Images c/d “ZEUGMATOGRAPHY”
Raymond Damadian 1977
Produced the MR image of
The body.

6. Indications
• Diagnosing: strokes; infections of the
brain/spine/CNS; tendonitis
• Visualising: Injuries; torn ligaments – especially in
areas difficult to see like the wrist, ankle or knee
• Evaluating: Masses in soft tissue; cysts; bone
tumours or disc problems.

7. Contraindications
• The strength of the magnet is 5000 times stronger
than the earth so all metals must be removed.
• People with pacemakers or metal fragments in the
eye cannot have a scan
• There has not been enough research done on babies
and magnetism, so pregnant women shouldn’t have
one done before the 4th month of pregnancy – unless
it is highly necessary.

8. Advantages
The MRI does not use ionizing
radiation, which is a comfort to
patients
• Also the contrast dye has a very
low chance of side effects
• ‘Slice’ images can be taken on
many planes

9. Disadvantages
1. Claustrophobia-Patients are in a very enclosed
space.
2. Weight and size - There are limitations to how big
a patient can be.
3. Noise - The scanner is very noisy.
4. Keeping still - Patients have to keep very still for
extended periods of time.
5. Cost - A scanner is very, very expensive, therefore
scanning is also costly.
6. Medical Contraindications - Pacemakers, metal
objects in body etc.

10. Basic principle of MRI
4 steps
Longitudinal
and
transverse
magnetization
MR signal
and
localization
of signal

11. • Placing the patient in the magnet
• Sending radiofrequency (RF) pulse by coil
• Receiving signals from the patient by coil
• Transformation of signals into image by
complex processing in the computer.
Four basics steps are involved in
getting an MR image :

12. • Body has many such atoms that can act as good MR
nuclei
(1H, 13C, 19F, 23Na)
• Hydrogen nuclei is not only positively charged, but
also has magnetic spin
• MRI utilizes this magnetic spin property of protons
of hydrogen to elicit images

13. A Single Proton
There is electric charge
on the surface of the
proton, thus creating a
small current loop and
generating magnetic
moment m.
The proton also
has mass which
generates an
angular
momentum
J when it is
spinning.
Thus proton “magnet” differs from a magnetic bar in that it
also possesses angular momentum caused by spinning.
+
+
+
J
m

14. Why Hydrogen ions are used in
MRI?
an unpaired proton which is positively charged
Every hydrogen nucleus is a tiny magnet which
produces small but noticeable magnetic field.
Hydrogen atom is the only major species in the
body that is MR sensitive
Abundant in the body in the form of water and fat
MRI is hydrogen (proton) imaging
The protons - being little magnets - align
themselves in the external magnetic field like a
compass needle in the magnetic field of the earth.
May align parallel or anti-parallel

15. • Larmor equation
𝜔0is the precession frequency
(in Hz or MHz),
B0 is the strength of the
external magnetic field, which
is given in Tesla (T)
and
𝛾is the so-called gyromagnetic
ratio.
the value for protons is 42.5 MHz/T
The equation states that the precession frequency
becomes higher when the magnetic field strength
increases.

16. Main Magnet Field Bo
• Purpose is to align H protons in H2O (little magnets)
[Main magnet and some of its lines of force]
[Little magnets lining up with external lines of force]

17. Net magnetization
• Half of the protons align along
the magnetic field and rest are
aligned opposite
• At room temperature, the
population ratio of anti-
parallel versus parallel protons
is roughly 100,000 to 100,006
per Tesla of B0
• These extra protons produce
net magnetization vector (M)
• Net magnetization depends on
B0 and temperature

18. Longitudinal magnetization
External
magnetic field is
directed along the
z axis. Z axis is
the long axis of
the patient as
well as bore of
the magnet.

19. Transverse magnetization
When radiofrequency pulse
is send, the precessing
protons pick up some
energy from RF pulse.
Some of these protons go to
higher energy level and
start precessing antiparallel
(along negative side of z
axis). The imbalance results
in magnetization into the
transverse (X-Y) plane 
transverse magnetization

20. MR signal
MR Signal
• NMV rotates around transverse plane.
It passes across Receiver Coil inducing voltage in it.
• RF Removed  Signal decreased  Amplitude of
MR Signal decreased
• Free Induction Decay "FID":
– Free (No RF Pulse)
– ID (because of Decay of Induced signal in
Receiver Coil)

21. • Measuring the MR Signal:
– the moving proton vector
induces a signal in the RF
antenna
– The signal is picked up by a
coil and sent to the computer
system.
– The computer receives
mathematical data, which is
converted through the use of
a Fourier transform into an
image.

22. T1 and T2 relaxation and
image weighting
Longitudina
l and
transverse
relaxation
T1 and T2
relaxation
TR and TE
Proton
density
image

23. T1 and T2 relaxation
• When RF pulse is stopped higher energy gained by
proton is retransmitted and hydrogen nuclei relax by
two mechanisms
• T1 or spin lattice relaxation- by which original
magnetization begins to recover.
• T2 relaxation or spin spin relaxation - by which
magnetization in X-Y plane decays towards zero in
an exponential fashion. It is due to incoherence of H
nuclei.

24. T1 relaxation
After protons are
Excited with RF pulse
They move out of
Alignment with B0
But once the RF Pulse
is stopped they Realign
after some Time And
this is called T1 relaxation
T1 is defined as the time it takes for the hydrogen
nucleus to recover 63% of its longitudinal
magnetization

25. T2 relaxation time is the time for 63% of the protons to become dephased
owing to interactions among nearby protons.

26. Repetition Time "TR"
Time from application of one RF pulse
To the application of the next
Or
the time between two excitations is called repetition
time
(it affects the length of relaxation period after
application of one RF excitation pulse to the
beginning of the next).

27. Time to Echo "TE"
Time between RF excitation pulse and
collection of signal
Or
time interval in which signals are measured after RF
excitation
(it affects the length of relaxation period after removal
of RF excitation pulse and the peak of signal
received in receiver coil)

28. TE/2 TE/2
TR (repetition time) = time between RF excitation pulses
FID
TE = time from 90o pulse to center of spin echo
90
o
90o 180o
Spin Echo
Spin Echo (SE) sequence

29. T1 in WaterT1 in Fat
inefficient at receiving
energy
T1 is longer
i.e. nuclei take a lot
longer to dispose
energy to surrounding
water tissue
absorb energy quickly
T1 is very short
i.e. nuclei dispose
their energy to
surrounding fat tissue
and return to B0 in
very short time
FAT WATER

31. T2 Decay
Fat much better at energy exchange than Water
Because T2 depends on:
1-How closely molecular motion of atoms matches Larmor
Frequency
2-Proximity of other spins
So;
Fat's T2 time is very short compared to water
FAT WATER

33. T1 time & T2 Decay are an intrinsic contrast
parameter that are inherent to tissue being
imaged.

34. • By varying the TR and TE one can obtain T1WI
and T2WI
• In general a short TR (<1000ms) and short TE (<45
ms) scan is T1WI
• Long TR (>2000ms) and long TE (>45ms) scan is
T2WI
• Long TR (>2000ms) and short TE (<45ms) scan is
proton density image

35. Types of MRI imagings
T1WI
T2WI
FLAIR
STIR
DWI
ADC
GRE
MRA
MRV
MRS
MT
Post-Gd images

36. Short TI inversion-recovery (STIR)
sequence
• In STIR sequences, an inversion-recovery pulse is used to null the
signal from fat (180° RF Pulse).
• When NMVof fat passes its null point , 90° RF pulse is applied. As
little or no longitudinal magnetization is present and the transverse
magnetization is insignificant.
• It is transverse magnetization that induces an electric current in the
receiver coil so no signal is generated from fat.
• STIR sequences provide excellent depiction of bone marrow edema
which may be the only indication of an occult fracture.
• Unlike conventional fat-saturation sequences STIR sequences are not
affected by magnetic field inhomogeneities, so they are more efficient
for nulling the signal from fat.

37. Fluid-attenuated inversion recovery
(FLAIR)
• First described in 1992 and has become one of the corner stones
of brain MR imaging protocols
• An IR sequence with a long TR and TE and an inversion time (TI)
that is tailored to null the signal from CSF
• In contrast to real image reconstruction, negative signals are
recorded as positive signals of the same strength so that the nulled
tissue remains dark and all other tissues have higher signal
intensities.

38. • Most pathologic processes show increased SI on T2-WI, and
the conspicuity of lesions that are located close to interfaces
b/w brain parenchyma and CSF may be poor in conventional
SE or FSE T2-WI sequences.
• FLAIR images are heavily T2-weighted with CSF signal
suppression, highlights hyperintense lesions and improves
their conspicuity and detection, especially when located
adjacent to CSF containing spaces

39. • In addition to T2- weightening, FLAIR possesses considerable
T1-weighting, because it largely depends on longitudinal
magnetization
• As small differences in T1 characteristics are accentuated,
mild T1-shortening becomes conspicuous.
• This effect is prominent in the CSF-containing spaces, where
increased protein content results in high SI (eg, associated with
sub-arachnoid space disease)
• High SI of hyperacute SAH is caused by T2 prolongation in
addition to T1 shortening

40. K-space and scanning
parameter
K-space
Parameters
for scanning

41. K- space
• Simply put, k-space is a matrix usually 512x512 OR 256 x
256 that is used to store data acquired from magnetic
resonance of protons.
• The math is complex but there is an analogy to this.

42. • The k-space is filled up in iterations by using the
resonance data obtained from magnetic field gradients.
• First, we select a slice (in millimeters) by applying a
field gradient in the horizontal plane.
• Within this slice we try to map out objects in both x
and y planes by collecting raw data in these planes.
• The y-plane is called phase encoding direction. To
obtain this one has to apply field gradient in the vertical
(or y-plane) direction.
• The x-plane is called frequency encoding direction.
To obtain this one has to apply field gradient in the
horizontal (or x-plane) direction.

43. This is an example of how the matrix is filled with data
during each slice.

44. THE SECRET IS IN THE K-SPACE
One can see below that the center of k-space is where the
contrast information is stored. The periphery is where the
fine details of the images are stored. This is nicely depicted
in the images below.

45. MRI instrumentation
Magnetism
and magnetic
field strength
Magnets used in
MRI
Gradients
Radiofrequency
coil

48. Magnetism and magnetic field
strength

49. Magnets used in MRI
• It produce magnetic field.
• By it body protons get align.
• It will be around 0.5 to 3.5 Tesla.
• Types:
» Permanent magnet.
» Superconducting magnet.
» Resistive magnet.
» Gradient magnet.

50. Coils
• A coil consists of one or more loops of conductive
wire, looped around the core of the coil.
• Used to create a magnetic field or to detect a
changing magnetic field by voltage induced in the
wire.
• A coil is usually a physically small antenna.
• The perfect coil produces a uniform magnetic field
without significant radiation.

51. Different Types of MRI Coils
in MR Systems
• Gradient coils
• RF coil
1. Transmit Receive Coil
2. Receive Only Coil
3. Transmit Only Coil
4. Multiply Tuned Coil

52. Gradient Coils
• Coils that produce magnetic field gradients along x-
,y-,and z-directions to encode spatial information
• Selective excitation: (during RF) excite those spins
within a thin “slice” of the subject
• Frequency encoding: (during readout) make the
signal’s frequency depend on position
• Phase encoding: (between excitation and readout)
make the signal’s phase depend on position

53. Radio Frequency Coil
• RF coils are components of every scanner .
• Used for two essential purposes – transmitting and
receiving signals at the resonant frequency of the
protons within the patient.
• A typical coil is a tuned LC circuit and may be
considered a near-field antenna

54. Comprehensive Receiving coils
 standard configuration：
QD head coil QD Neck Coil QD Body Coil
QD Extremity Coil Flat Spine Coil Breast Coil

55. Making Images of the NMR
Signal
• Uniform magnetic field to set the stage (Main Magnet)
• Gradient coils for positional information
• RF transceiver (excite and receive)
• Digitizer (convert received analog to digital)
• Pulse sequencer (controls timing of gradients, RF, and
digitizer)
• Computer (FFT to form images, store pulse sequences,
display results, archive, etc.)

56. MRI Artifacts
Motion
related
artifacts
Para-
magnetic
artifacts
Phase Wrap
artifacts
Frequency
artifacts
Susceptibility
artifacts
Clipping
artifact
Chemical
Shift Artifact Spike artifact
“Zebra”
artifact

57. Motion Artifacts  Motion artifacts are caused by
phase mis-mapping of the protons.
Para-Magnetic Artifacts  Para-magnetic artifacts
are caused by metal (~ iron
Phase Wrap Artifacts  Phase wrap artifacts are
caused by mis-mapping of phase.

58. Frequency Artifacts  Frequency artifacts are
caused by „dirty‟ frequencies. Faulty electronics,
external transmitters, RF-cage leak, non-shielded
equipment in the scanner room, metal in the patient,
Susceptibility Artifacts  Susceptibility is the ability
of substances to be magnetized, for example iron in
blood.
Clipping Artifact  Signal clipping or „over flow‟
occurs when the receiver gain is set to high during the
pre-scan.

59. Chemical Shift Artifact  Chemical shift artifacts are
caused by different resonance frequencies of hydrogen
in lipids and hydrogen in water
Spike Artifact  A spike artifact is caused by one
„bad‟ data point in k-space
“Zebra” Artifact  The “Zebra” artifact may occur
when the patient touches the coil, or as a result of
phase wrap.

60. MRI contrast media
Definition
Classification of
MR contrast
media
Mechanism of MR
contrast enhancement
Gadolinium
Other MR
contrast
Agents

61. Contrast  In MRI: relative difference of
the signal intensity between two
adjoining tissues.
Contrast agent  Substance
administered during MRI to:
• Enhance natural contrast
• Obtain dynamic information
Definition

62. Classification of MR contrast
media
Contrast agent
PARENTERAL
Relaxivity
Positive
relaxation agent
(T1 agent)
Negative
relaxation agent
(T2 agent)
Susceptibility
Paramagnetic
agent. Eg
gadolinium
Superamagnetic
agent. Eg iron
oxide
ORAL
Positive contrast. Eg
Manganese chloride, Gd-
DTPA, oil emulsions
Negative
contrast.
T1 agent : Affects T1 relaxation of the tissue.
T1 of the tissue in which contrast media is accumulated is reduced.
Reduction in T1 results into increase in the signal intensity on T1-W images ,
hence called positive relaxation agent. Eg. Gadolinium, Mn-DPDPT2 agent : Affects T2 relaxation and reduce T2 of the tissue where they
accumulate.
This results in reduction in the signal intensity of the tissue on T2-W images.
Eg. Iron oxide particles, gadolinium (high doses)
Gadolinium : Positive agent, but at higher doses cause T2 shortening
resulting into decreased signal on T2-W images. When initially pass through
vascular bed of brain local T2 shortening and decreased in the signal of
T2-W images  effect used in perfusion studies.
Superparamagnetic agent : Negative contrast, causes proton dephasing 
T2 shortening and signal loss.
Positive contrast : image degradation can occur with peristaltic
movements of bowel. For MR Enterography, sorbitol (3%) with or
without barium or polyethylene glycol solutions can be used as oral
contrast.
Negative contrast : they decrease signal from bowel lumen reducing the
motion related image degradation. Eg. Superparamagnetic iron oxide
particle reduce signal by suseptibility effects. Barium , blue- berry or
pinapple juice (contain manganese) and perfluorochemicals are also used
to reduce signal from bowel.

63. • spin density
• Relaxivity (T1, T2)
• Magnetic suseptibility
• Diffusion
• Perfusion of contrast agent.
In MR imaging, contrast
mechanism is
multifactorial and
includes
Mechanism of MR contrast
enhancement

64. Relaxivity  determines
the strength of an MR
contrast medium.
Paramagnetic ions
increase relaxation of
water protons by a dipole-
dipole relaxation. This
phenomenon in which
excited protons are
affected by nearby excited
protons or electrons is
called dipole-dipole
interaction.
The dipole-dipole
interaction affects the
rotational and translational
diffusion of water
molecules leading to their
relaxation.
The more and closer the
water molecules approach
the paramagnetic ions,
greater will be the
relaxation.

65. Rare earth metal of lanthanide group Atomic no 64
Free Gd ions tend to accumulate in the body and do not get excreated.
Free Gd ions are toxic.
Therefore, Gd ions are combined with chelates such as DTPA,
DOTA, BOPTA that causes their rapid and total renal secretion.
Gd causes both T1 and T2 relaxation of the tissues in which it is
accumulated.
Increased T1 relaxation  bright signal on T1-W images.
Usual dose – 0.1 mmol/Kg Median lethal dose(LD 50) : 6-30 mmol/kg
Overall adverse reaction rate : 3-5 %
Gadolinium

66. • Iron oxide
• Mn-DPDP (mangafodipir trisodium)
• Dysprosium Chelates
Other MR contrast Agents

67. • Purpose: Our goal was to evaluate the efficacy of dynamic contrast-
enhanced fat-suppressed MRI of the temporomandibular joint (TMJ)
in detecting early joint involvement in patients with rheumatoid
arthritis (RA).
• Method: Conventional T1-and T2-weighted, gadolinium-enhanced
T1-weighted, and dynamic gadolinium-enhanced fat-suppressed SE
imaging sequences were performed in 22 patients with RA.
• Results: The dynamic gadolinium-enhanced fat-suppressed T1-
weighted SE sequence was more sensitive than the other techniques in
detecting early changes in inflamed synovium of periarticular tissue
and in detecting condylar bone marrow involvement. In patients with
RA, 17 joints with joint pain showed synovial proliferation in 10
(59%) cases and joint effusion in 4 (24%). Of 14 joints with joint
sound, 4 (29%) showed synovial proliferation and 7 (50%) showed
joint effusion. A lower positional change of the disk was observed in
joints with RA than in those with TMJ disorders (82 patients).
• Conclusion: Gadolinium-enhanced fat-suppressed MRI was extremely
effective in diagnosing early changes of the inflamed TMJ.
Severity of Synovium and Bone Marrow Abnormalities of the Temporomandibular Joint
in Early Rheumatoid Arthritis: Role of Gadolinium-Enhanced Fat-Suppressed T1-
Weighted Spin Echo MRI, Suenaga, Shigeaki; Ogura, Tadashi; Matsuda, Takemasa;
Noikura, Takenori. Journal of Computer Assisted Tomography:
May/June 2000 - Volume 24 - Issue 3 - pp 461-465
Neuroimaging

68. MRI in Dentistry
Applications
with
interpretation
Signal
intensity
Indications in
oral and
maxillofacial
region
Normal
anatomy
Maxillofacial
disorders

69. Applications with
interpretation
• MR images are commonly acquired using Spin echo
pulse sequence.
• T1 and T2 Weighted images are obtained for
examinations of oral and maxillofacial regions.
• T1-Weighted images  anatomical evaluation
• T2- weighted images  detection of pathological
processes.
• Both T1 and T2 - Weighted images are studied for
disease detection, extent and character.

70. • Images in the Coronal and Axial planes are routinely
obtained for three-dimensional evaluation of disease
in MR examinations.
• Images in the Sagittal plane are sometimes added.
• To understand normal MRI Anatomy of Oral and
Maxillofacial regions, it is necessary to be familiar
with some terms that express MR signal intensities.

71. • The intensity of signal from each tissue on MR images is
termed the “Signal Intensity”.
1) Low signal intensity: If the signal intensity from a tissue
is lower than that of muscle on T1 or T2 –Weighted
images.
2) High signal intensity: If the signal intensity from a tissue
is same or higher than that from fat tissue on T1 or T2 –
Weighted images.
3) Intermediate signal intensity: If the signal intensity from
a tissue is somewhere between muscle and fat tissue signals
on T1 or T2 –Weighted images.
Signal intensity

72. Signal intensity for each
tissue
Fat tissues: appears high signal intensity on T1-Weighted images and
low signal intensity on T2-Weighted images with fat suppression.

73. Signal intensity for each
tissue
Muscle tissue: appears as low signal intensity on both T1 and T2-
weighted images with fat suppression except Lingual muscles 
intermediate signal intensity on T1-weighted images due to their
relatively high fat component compared to other muscles.

74. Muscle tissue: appears as low signal intensity on both T1 and T2-
weighted images with fat suppression except Lingual muscles 
intermediate signal intensity on T1-weighted images due to their
relatively high fat component compared to other muscles.

75. Cortical bone tissue: signal intensity void on T1 and T2-weighted
images.
Cancellous bone tissue : high intensity on T1-weight images and
low intensity on T2-weighted images with fat suppression.

76. Lymph nodes and tonsils: low intensity on T1-
Weighted images and intermediate –high signal
intensity on T2-Weighted images with fat
suppression.
Teeth : signal void on T1 and T2-weighted images;
except pulp tissue which has intermediate signal
intensity on T1 –Weighted images and high signal
intensity on T2 weighted images with fat
suppression.

77. Signal intensities differ among the tissues of the salivary glands.
Parotid gland: high signal intensity on T1-weighted images and low
signal intensity on T2-weighted images with fat suppression

78. Submandibular gland: intermediate signal intensity on T1 –
weighted images and low signal intensity on T2-weighted images
with fat suppression.

79. Sublingual gland: intermediate signal intensity on T1–weighted
images and high signal intensity on T2-weighted images with fat
suppression
Temporo-Mandibular Joint (TMJ):
• The discs of the TMJ have low signal intensity on T1 and T2-
weighted images.
• TMJ effusion appears as low signal intensity on T1-weighted
images and high signal intensity on T2-weighted images.

80. Blood vessels:
• usually have void signal intensity due to blood flow termed
“signal void”, on both T1 and T2 –weighted images,
• some vessels with lower flow rate appear with high signal
intensity on T2-weighted images with fat suppression and low
intensity on T1-weighted images, like the signal from water

81. T1 W Images: T2 W Images: FLAIR Images:
• Subacute
Hemorrhage
• Fat-containing
structures
• Anatomical
Details
• Edema
• Demyelination
• Infarction
• Chronic
Hemorrhage
• Edema,
• Demyelination
• Infarction esp.
in
Periventricular
location
Which scan best defines the abnormality

85. Indications of MRI in the oral
and maxillofacial region
1. Diagnosis and evaluation of benign and malignant
tumors of jaws.
2. Tumor staging evaluation of the site, size and extent
of all soft tissue tumors and tumor like lesions,
involving all areas including.
The salivary glands
The pharynx
The Sinuses
The orbits.

86. 3. To evaluate structural integrity of trigeminal nerve
in trigeminal neuralgia.
4. In surgery of parotid gland MRI can detect the
cause of facial nerve within the glandular tissue and
help lessen the post-operative facial nerve palsy.
5. For the assessment of intracranial lesions involving
particular posterior cranial fossa, the pituitary and
the spinal cord.

87. 6. For non-invasive evaluation of the integrity and
position of articular disk within the TMJ.
7. Investigation of the TMJ to show both the bony and
soft tissue components of joint including disc
position:
a). When diagnosis of internal derangement is in
doubt,
b). As a preoperative assessment before disc surgery,
c). Implant assessment.

88. Normal anatomy
11. CORONOID
PROCESS
6. BUCCAL SPACE
FAT
77. MASSETER Ms
145. TEMPORALIS
MUSCLE
146. TONGUE
55. LINGUAL
SEPTUM
142. SUBMANDIBULAR
SPACE
35. HYOGLOSSUS Ms
151. ZYGOMATIC ARCH
103. MYLOHYOID Ms
27. GENIOGLOSSUS Ms

89. 19. FACIAL VEIN
64. MANDIBULAR RAMUS 77. MASSETER Ms
112. ORBICULARIS
ORIS Ms
118. PAROTID GLAND
119. PG , ACCESSORY
120. PG, DEEP LOBE
121. PG, SUPERFICIAL LOBE
136. STENSEN’S DUCT
148. UVULA

90. 3. Ant. BELLY OF DIGASTRIC Ms
28. GENIOHYOID Ms
35. HYOGLOSSUS Ms
45 INTERNAL CAROTID
ARTERY
46. INTERNAL JUGULAR VEIN
56.LONGUS COLLI Ms
141. SUBMANDIBULAR GLAND
142. SUBMANDIBULAR SPACE
58. MANDIBLE

91. 1.ANTERIOR
BAND OF
ARTICULAR
DISC
2. ARTICULAR
DISC
4. GLENOID
FOSSA
6.INTERMEDIATE
(CENTRAL) THIN
ZONE
9.MANDIBULAR
CONDYLE(HEAD
12. POST. BAND
OFARTICULAR
DISC
13. POST. DISC
ATTACHMENT
9.MANDIBULAR
CONDYLE(HEAD)
5. INFERIOR JOINT
SPACE
7. LATERAL
PTERIGOID
MUSCLE RAPHE
15. UPPER HEAD
OF LATERAL
PTERIGOID Ms.
14. SUPERIOR
JOINT SPACE

92. Maxillofacial Disorders
• Foci of bright signal intensity are intermixed with the more typical
hypointense signal of fibroosseous tissue on both T1 and T2 –
weighted images.
Fibrous Dysplasia

93. • The soft tissue mass exhibits low to intermediate signal intensity on
T1 –weighted images and high signal intensity on T2 –weighted
image.
Osteosarcoma

94. • cystic fluid exhibits low to intermediate signal intensity on T1-wt
images and high signal intensity on T2- wt images , whereas the
partially completed crown appears as an area devoid of signal or of
low signal because of its low mobile proton density.
• The cyst wall is of intermediate intensity on T2-wt images (not as
bright as sinus mucosa)
Dentigerous Cyst

95. Ameloblastoma
• Purely cystic areas have been noted to exhibit low
signal intensity on T1-wt images and high signal
intensity on T2-wt images.

96. Sjogren’s Syndrome
• Enlarged parotid gland with an inhomogeneous speckled or
nodular pattern(salt and pepper appearance) on T2-wt
images

97. Temporomandibular Joint
• Axial plane - to define the
location of the joints and
provide a global view of the
surrounding anatomy.
• Coronal images - are
routinely obtained because
they provide information
about mediolateral
relationships at the TMJ.
• Sagittal images - are
assigned from the axial in an
oblique plane corresponding
to the axis of the condyle
and body of the mandible
Proton Density-Weighted Imaging
( PDWI ) Slice At Closed Mouth
PDWI Slice at Open Mouth

99. MRI is a complex but effective imaging system that has a
variety of clinical indications directly related to the
diagnosis and treatment of oral and maxillofacial
abnormalities.
While not routinely applicable in dentistry, appropriate use
of MRI can enhance the quality of patient care in selected
cases.
Conclusion

100. MRI research is ever changing.
Smaller, lighter machines are always been developed.
Work is on going to develop area specific machines to scan
small areas like feet, arms, hands.
Ventilation dynamic research is being tested with Helium to
examine lung function.
Brain mapping is having and will continue to grow and give
us a better image of how the brain works than ever before.
Further advances in 3D imaging and dynamic scanning will
enhance the use of this imaging technique even further.
MRI in future

101. References
1. Textbook of Dental and Maxillofacial Radiology Freny R
Karjodkar 2nd edition
2. MRI made easy Govind B Chavan 2nd edition 2013
3. Magnetic Resonance Imaging (MRI) – A Review Girish
Katti, 2013
4. D. W. McRobbie, E. A. Moore, M. J. Graves, M. R. Prince.
MRI – From Picture to Proton (2003). Cambridge University
Press.
5. Gandy. S. MRI Physics Lecture Series (2004). Soft Tissue
Contrast in MRI. NinewellsHospital, NHS Tayside
6. Evert J Blink Application Specialist MRI