Tomography, CT, MRI,
Sialography, and
Ultrasongraphy
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It is radiographic technique designed to image
more clearly objects lying within a plane of
interest.
This is accomplished by blurring the images of
structures lying superficial and deep to the
plane of interest through the process of motion
“unsharpness”.
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As the x-ray tube
move from Lt to Rt
the film moves in
the opposite
direction.
The focal plane is
the most clear area.
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1-the physical location of the
fulcrum within the object to be
imaged.
2- Tomographic movement.
3-Tomographic angle or arc.
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Linear
Circular
Elliptical
Hypocycloidal
Spiral
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A ) mandibular
tomogram
B) maxillary
tomograms in
premolar region
(dome shaped
opacity in the floor
of maxillary sinus)
A
B
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Disadvantages of linear
tomography
 Parasite lines.
 Inconsistent
magnification
 Dimensional
instability
 Non uniform
density.
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Tomographic layer is the thickness of tissue in
the focal plane.
It is determined by the position of the fulcrum
and its width by tomographic angle or arc.
Wide angle tomography. The tomographic
angle is more than 10 degree
Produce images of reduced contrast.
Tissues of greater physical density as bone is
imaged
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Complex
movements result
in maximal blurring
of the images of
objects lying
superficial and
deep to the focal
plane of focus the
streaking parasite
lines are therefore
absent
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Uses an angle of less than 10 degree, it is called
zonography.
Thickness of tissue up to 25mm is sharply
imaged
It is useful when subject contrast is low
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The thick plane of focus allowed the supernumerary
tooth and adjacent permanent teeth to be imaged
clearly in one depth of the field.
The diagnostic value of these images is increased by
their having been steroscopically, allowing for
localization of supernumerary tooth relative to
clinically erupted teeth
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The tomographic angle is more than 10 degree
 Allow visualization of fine structures which that
normal obscured by superimpositions in conventional
radiography.
Disadvantages
 Produce images of reduced contrast.
 Subject contrast results partly from the different
thickness of adjacent structures.
 Wide angle tomography reduce these difference by the
thinness of its cut.
Application of wide angle tomography
 Tissues of greater physical density as bone is imaged.
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As evaluation of maxilla and mandible before implant
placing.
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It is a technique that uses a narrowly
collimated, fan shaped beam of irradiation to
scan an area of interest.
It demonstrate higher contrast with perception
of greater details.
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This view demonstrates higher contrast and
greater detail.
The diagnostic value of such images is
increased by their having been
steroscopically, which allows for the
perception of depth.
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Dr. maha Eshaq Amer
16
Limitation of
conventional
radiography
1- Super imposition.
2- Qualitative rather than
quantitative.

Limitation of
conventional
Tomography
1- Image blurring
2- Degradation of image
contrast
3- Magnification of
screen film
combination
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1-CT minimize the
problem of
superimposition.
2-Improving the
contrast of the image.
3-Finding a way to
record very small
difference in tissue
contrast by:
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A beam of x-rays is
transmitted through a
specific cross section
of the Pt.
The beam of x-ray is
highly collimated
into a thin beam that
only passes through
the cross section
The x ray beam
strikes special
detectors that they
are quantitative.
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Data acquisition
Collection of data by either slice by slice or volume data acquisition.
Relative transmission =log Io/I
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Data processing
Raw data undergo some form of preprocessing
Conversion of transmission measurement into CT images
Each pixel is assigned CT number related to linear attenuated
coefficient
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Image display
Relation between CT number and brightness is referred to as
windowing
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Storage and documentations
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A finally collimated fan x-ray
beam is directed to the series
of scintillation or ionization
chamber.
Both the radiographic tube
and detectors rotate
synchronously around the Pt
The CT image is
reconstructed by the
computers which
mathematically maniputes
the transmission data
obtained from multiple
projections
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The x-ray tube and detectors are in perfect alignment.
the x-ray tube and detectors move around the Pt to
collect a large number of transmission measurement.
As the beam leave the tube it is shaped by a filter.
The beam is collimated to pass through only a slice of
interest.
The beam is attenuated by Pt and the transmitted
photons is measured by detectors.
The detectors convert the photon into electrical pulse
(analog).
The electrical signals converted into digital by ADC
The digital data are sent to the computer for processing
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Data for a single plan
image is acquired from
multiple projection
made during the course
of 360 degree rotation
around the Pt.
The single plane image
is constructed from
absorption
characteristics of the
subject and displayed as
a differences in optical
density ranging from -1000
to +1000
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The CT is recorded and
displayed as a matrix of
individual blocks (voxel
) each square of image
matrix is a pixel.
The size of pixel (0.1
mm) is determined by
computer program used
to construct the image.
The length of the voxel
(1 to 20 mm) is
determined by width of
x ray beam,
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which is controlled by
pre-Pt and post Pt
collimators.
Each pixel is assigned CT
number representing
density.
The number is
proportional to the
degree to which the
material within the voxel
has attenuated the x-ray
beam.
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The absorption measurement range in CT
expressed in HU is referred to as the ww.
It determine the maximum number of shades
of gray that can be displayed on the CT
monitor.
The CT number range from-1000 to +1000
As ww↑ the contrast ↓.
contrast is optimized with medium ww
WL is the middle of ww
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1-Sella tursica,
2-temporal horn of
lateral ventrical,
3- mid brain,
4-fourth ventrical,
5-cerebellum
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1- Lt cerebellum,
2-tentorum cerebelli,
3- insular cortex,
4-fourth ventricle,
5- Lt frontal lobe,
6-falx cerebi
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1-Caudate nucleus,
2-lateral ventricle,
internal capsule
limbs 3-anterior, 4
posterior
5-Lentiform nuclei
6-Third ventricle.
7-fourth ventricle,
8-corpus callosum
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1 Lt max antrum,
2 nasopharynx,
3-spinal cord,
4- odontoid
processC2,
5-mastoid air cells,
6- masseter muscle,
7-MD,
8-zygomatic bone,
9-lateral pterygoid
muscle,
10-trapezius
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1-Lt Ms.
2-Nasopharynx.
3-spinal cord,
4- odontoid process,
5-mastoid air cells,
6-masseter muscle,
7-MD,
8-zygomatic bone,
9-lat Pterygoid
muscle,
10- trapezius
muscle
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1-medulla,
2-clivus ,
3-condyle,
4-zygomatic arch,
5- temporal muscle,
6-sphenoid sinus,
7- external auidatory
meatus.
Foramen magnum
arrow head
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1-Rt eye,
2-sphenoid bone,
3-cerebulum,
4-internal auidatory
meatus.
5-nasal cavity
6- Rt temporal fossa.
7-Rt medial rectus
muscle.
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1-Sphenoid sinus,
2-temporal lobe,
3-clivus,
4-mastoid air cell,
5- cerebellum,
6- fourth
ventrical,
7- internal
occipital
protuberance
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Dr. maha Eshaq Amer
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It is radiographic
demonstration of major
salivary gland by
introducing a
radiopaque contrast
medium into their
ductal system.

Procedure 
I-Pre operative phase:
A-Preliminary preoperative
radiography.
B- Preparation of the
patient.
II-Filling phase:
Exploration of duct
orifice.
Dilatation of the duct by
lacrimal probs.
Canuula is inserted into
the dilated duct and
connected with syringe
which contain the
contrast media.
Injection is performed
slowly until the Pt fill
fullness
The filling phase
radiograph is taken.
.1
.2
.3
.4
.5
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III-Emptying phase
The cannula is removed
and gland is stimulated
to excretion by
massaging while
salivary flow is
Stimulated by sucking
lemon.
After 5 min the
emptying phase
radiographs is taken.
One hour later, other
radiographs are taken.
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They must posses sufficient radiopacity to
provide good delineation of the anatomic
structures.
It must have proper viscosity, not very high as
need more pressure, not very low as it will
escape the gland.
It must be readily excreted from the gland.
It must be non toxic, and non harmful.
It must possess physiologic properties similar
to those of saliva.
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Water soluble
contrast media:
Have less
radiographic density.
Dissipate more
quickly and are less
irritating.
E.example urografin
and renografin
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Oil based contrast
medium:
Need higher injection
pressure due to higher
viscosity.
Prolonged retention in
gland with risk of
allergic reaction.
Have higher
radiopacity
Example lipidol, and
pantopaque
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I-Chronic
inflammation of
salivary gland
(sialectasia) this
may be:
A-Obstructive
inflammatory due to
calculi (sialolithiasis);
strictures (constriction
of the ductal wall near
the orifice), or stenosis
(construction of the
ductal wall along the
whole course of the
main duct)
B- Non obstructive
inflammation:
Due to autoimmune disease,
or due to bacterial
infection as acute
suppurative parotitis,
recurrent parotitis, or
due to viral infections as
mumps, or due to
inflammation secondary
to allergic reaction
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II-Neoplasm of salivary
gland.
A-Extrinsic
(normal architecture of the
gland and its secretory
function but deviation
of the ducts due to
external pressure of the
tumor)
B- Intrinsic
which arise from the
gland itself it can be
benign or malignant as
pleomorphic adenoma,
Warthins tumors,
mucoepidermoid
carcinoma and
III-Developmental
disturbance of SG
As Tracher collin
syndrome, and
Goldenhar syndrome.
IV-Trauma of salivary
gland
Hemorrhage lead to
hematoma lead to
fibrosis lead to sialocele
V- Metabolic diseases
As diabetus mellitus
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Allergy to compounds contained in contrast
media.
Period of acute inflammations.
When preoperative radiograph shows calculus
close to duct orifice.
Pt performing thyroid function test using
iodine-containing material
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This lateral view
demonstrates
parenchymal
blushing.
Normal fine
branching is
visible.
Lack of
parenchymal
blushing at the
anteroinferior
margin is caused by
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A
B,
A, Lateral projection of the parotid demonstrating
opacification all the way to the terminal ducts and
acini.
B, Anterior-posterior projection of the same gland
demonstrating "parenchymal blushing" from acinar
opacification.
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Slightly oblique lateral 
view
demonstrating
parenchymal
opacification of the
submandibular gland.
Arrowhead points to an 
obstruction (radiolucent
sialolith) within the
main duct.
Opacification of the 
parenchyma is patchy
resulting from fibrosis
secondary to chronic
obstruction.
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Lateral view of 
submandibular
glands
demonstrating a
radiolucent sialolith
in the main duct.
This is to be 
differentiated from
inclusion air
bubbles,
in which the interface
with the contrast
media is convex.
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Lateral view of the 
submandibular
gland shows
prominent
intermittent stricture
and dilation of the
main and secondary
ducts, which is
typical of advanced
sialodochitis.
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A
B
A) Lateral projection demonstrates punctate sialectases
distributed throughout the gland, which is suggestive
of autoimmune sialadenitis. The "sausage-link"
appearance of the main duct indicates that
sialodochitis is present.
B) A-P projection of the same gland. 51
A
B
Punctate (small
spherical), globular
(larger spherical),
and cavitary (larger,
irregular) sialectases
with some dilation
of the main duct are
suggestive of
advanced
autoimmune disease
with parenchymal
destruction with
retrograde infection
in lateral (A) and AP
(B) projections.
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Sialogram of left 
parotid gland (AP
view).
A mass within the
gland is inferred by
the appearance of
the ducts displaced
around the lesion.
This is referred to as
the "ball-in-hand"
appearance, which is
suggestive of a space
occupying mass.
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MRI
Dr. maha Eshaq Amer
54
A
B
A hydrogen nuclei in an external magnetic field. most
nuclei are in lower energy state and are aligned parallel
with magnetic field.
B the axis of spinning protons ossilate with slight tilt
from being absolutely parallel with the flux of the
external magnet.
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1
2
1-Precession. The
tilting of the
spinning hydrogen
nuclei around the
direction of the
external magnetic
field.
The rate of
precession is
resonant or Larmor
frequency.
2-Spin up and spin
down.
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The combined effect of
spinning up and
spinning down energies
state is a weak net
magnetic momentum,
(MV) parallel with
applied external
magnetic field.
When RF is directed to
tissues with H2 nuclei
that are aligned in z axis
by external static
magnet field, the proton
in the tissues that have
Larmor frequency
matching that of RF
absorb enrgy and shift
from the direction
induced by imaging
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Repetition time (TR) is
the time between the
excitation pulses. Echo
time (TE) is the time
between last excitation
and echo.
T1 and T2 are the
relaxation time , it will
determine the relative
densities of different
tissue on the final
image.
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T1-weighted image is
produced with short
TR and TE tissues as
fat appear bright while
tissues with high water
content as CSF, and
cyst appear dark.
T2-weighted image is
produced with long TR
and TE tissues as CSF,
cysts, necrotic LN
appear bright and
muscles appear dark
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Indication
Tumor staging
evaluation of the size,
site, and extent of soft
tissue.
Investigation of TMJ
to show hard and soft
tissue components of
the joint.
Assessment of intracranial lesion.
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Disadvantages
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Advantages
Not using ionized
radiations
High resolution images.
Excellent differentiation
between soft tissue
Metallic restoration do
not produce artifact.
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Cortical bone is not
imaged
Scanning time is long
& very annoying to
pt.
Limited availability&
expensive
Pt with pacemaker
cannot be imaged
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A
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B
A)T1
B) T2
C) proton denisty
C
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A) Closed sagittal view showing the disk
with its posterior band (arrow)
anterior to the condyle.
B) Open view showing the normal
relationship of the disk and condyle
and the posterior band of the disk
(arrow).
C, Coronal view showing the disk (white
arrow) laterally displaced. The joint
capsule (black arrowhead) bulges laterally.
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A well-defined mass in the deep lobe of the right
parotid gland
as imaged with coronal Tl-weighted format (A) and
axial T2-weighted format (B).
The tumor (arrows) is low-signal on the Tl-weighted
image and high-signal on T2-weighted
images. Histopathologic diagnosis was benign mixed
tumor.
63
US
Dr. maha Eshaq Amer
64
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Sound is a result of periodic changes in the
pressure of air against the ear drum.
Audible sound is 15 to 20 KHz while
ultrasound used in diagnosis from 1 - 20
MHz.
Transducer is device used to convert electric
current into ultra sound and vice versa.
As US pass through tissue or interact with
tissues of different acoustic impedance, it is
attenuated by a combination of absorption,
reflection, refraction and diffusion.
Sonic waves that are reflected back (echoed)
to the transducer in turn produce electric
signal that is amplified, processed, and
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Examination of SG
Examinations of swelling of the neck including
LN and thyroid gland.
Examination of maxillary sinus.
It is sometimes used to locate the apex of the
root.
Assessment of blood flow in the carotid artery
thus aiding in the detection any aneurysm,
stenosis, or thrombosis of the carotids as well
as carotid body tumors.
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
Advantages
1-Sound waves are not
ionizing radiation
2-Show good
differentiation
between soft tissues.
3-Shows good
differentiation
between soild and
cystic lesions
4- widely available and
inexpensive
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Disadvantages
1-limited use in head and
neck because sound
waves are absorbed by
bone.
2-technique is operator
dependent.
3-images are difficult to
interpret for
inexperienced
operators.
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Parasagittal image of
TMJ area showing
the articular disk in
its normal position
superior to the
condyle in the
closed mouth
position. Glenoid
fossa (curved row),
articular disk (long
arrow), and condyle
(short arrow)
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well-delineated, solid
mass is suggested
by echo returns
within the lesion.
Ultrasound
appearance is
typical of a benign
salivary tumor.
69
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Echo-free mass with
well-defined
margins presents a
typical cystic
appearance.
70
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The mass in the
submandibular
gland (arrowheads)
demonstrates a
heterogeneous
hypoechoic pattern
compared with the
adjacent tissue. The
histopathologic
diagnosis was
adenoid cystic
carcinoma.
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