This document provides an overview of computed tomography (CT) scanning. It discusses the history and invention of CT, its common uses in medicine, working principles including components like the gantry and detectors, generations of CT technology, and the mathematical principles behind image reconstruction. CT scanning uses X-rays and computers to produce cross-sectional images of the body and has become an important medical imaging tool since its invention in the 1970s.

1. Guided by:
Dr. Deepanshu Garg
Department of Oral Medicine and Radiology
College of Medical sciences, Bharatpur
Submitted by:
Shekhar Kumar Mandal
BDS IV, Roll no:26
Batch 2nd

2. INTRODUCTION
Computed tomography is also known as "CAT
scanning" (Computed Axial Tomography).
Tomography is from the Greek
word "tomos" meaning "slice" or "section"
and "graphia" meaning "describing".
Computed tomography is an examination that
uses X-ray and computer to obtain a cross-
sectional image of the human body

3. History
Invented in 1972 by British engineer Godfrey
Hounsfield of EMI Laboratories, England and by South
Africa-born physicist Allan Cormack of Tufts
University, Massachusetts. Hounsfield and Cormack
were later awarded the Nobel Peace Prize for their
contributions to medicine and science.
The first clinical CT scanners were installed between
1974 and 1976. The original systems were dedicated to
head imaging only, but "whole body" systems with
larger patient openings became available in 1976.
CT became widely available by about 1980.

4. Common uses of CT Scan
• One of the best and fastest tools for examining the chest,
abdomen and pelvis
• Severe injuries from incidents such as a motor vehicle
accident.
• Acute symptoms such as abdominal pain or difficulty
breathing
• Detecting many different cancers and its size, precise
location and the extent of the tumor's involvement with
other nearby tissue.
• Detection, diagnosis and treatment of vascular diseases
• To assess for pulmonary embolism/ abdominal aortic
aneurysms (AAA).
• Valuable in diagnosing and treating spinal and cranial
problems

5. Working Principle
Beams from one or several small X-ray sources are passed
through the body and intercepted by one or more radiation
detectors. These radiation detectors produce electrical
impulses that are proportional to the intensity of the X-ray
beam emerging from the body.
The intensity of the X-ray beam exiting the body is
determined by:
a. The energy of the X-ray source
b. The distance between the source of X-rays and the
detector
c. The attenuation of the beam by materials in the object
being scanned.

6. The efficiency of the scanning system can be
increased multiple folds by using multiple X-ray
beams and equivalent number of detectors.
Each scan produces a penetration or absorption
profile. However, construction of the image
requires profiles obtained at different angles
through the patient under study. The X-ray source
and detector assembly are rotated around the
patient (360⁰) to produce multiple profiles of the
particular site of interest.

7. Components of CT Scan
Gantry
Data Acquisition System/computer
Operating Console

8. Gantry
• The gantry assembly is the largest
of these systems.
• Can be tilted upto 300 degree.
• It is made up of all the equipment
related to the patient, including
-the patient Support,
-the Positioning couch,
-the Scanner housing.
-heart of the CAT scanner,
the X-ray Tube, as well as
-Detectors that generate
and detect x rays

9. The CT X-ray Tube
Tubes operates with three phase or high frequency
generators and rotating anode.
 Anode heat capacity: –3.5MHU upto 8MHU(MILLION HEAT
UNIT)
Operates at 120 kVp and 200-800 mA.
High X-Ray output reduces the exposure time and
improves image quality as well as decrease bone
absorption.
Focal spot size ranges from 0.5 to 2mm
Low slice thickness result in higher spatial resolution
and contrast, less partial volume artifact and higher
patient dose.

10. Collimator
 Thin fan shaped Collimator is used to reduce exposure.
 Postpatient collimator are also used to remove the scattered
photons as well as control slice thickness that ranges from 1
to 3 mm.
 The x-ray beam is collimated at two points ,one close to the
x-ray tube and the other at the detector. The collimator at the
detector is the sole means of controlling scatter radiation.
The collimators also regulate the thickness of the
tomographic section (voxel length)

11. Detectors
Made up of multiple discrete cells or detectors .
Capture energy that has not been attenuated by the patient
Two types of detectors are used
Crystal Scintillation Detectors
Gas Filled Detectors
Scintillation Detectors
Coupled optically to photodiode
Materials Used
I. Sodium Iodide
II. Bismuth Germanium Oxide
III. Cesium Iodide
IV. Cadmium Tungstate

12. Gas Filled Detectors
 Materials Used
 Xenon
 Krypton
 Xenon + Krypton
 Have high atomic number, are inert, and display minimal afterglow. The gas is
contained under high pressure in the detector array.
 Since 90% of 50 is 45, the output is same. The overall efficiency of both the
detectors is same
Gas Filled Detectors Scintillation Detectors
Sensitive face: 100%
Detection Efficiency:
45%
Sensitive face: 50%
Detection Efficiency: 90%

13. Data Acquisition System
The DAS consists of the following parts
X-ray photons come on the dectector
The detector detects the intensity in form of current.
The current is converted into voltage.
The analog integrator removes spikes.
The analog signal is converted into digital form.
This signal can now be processed and reconstructed
in the computer.
Detector
Current to
Voltage
Convertor
Pre
Amplifier
Analog
Integrator
Analog to
Digital
Convertor
Computer

14. Image Reconstruction
• After enough transmission measurements (detector)
• Sent to the computer for processing
• A software called Fourier Slice Transform is used.
• More than 250,000 reconstruction algorithms are used
(example: algebraic reconstruction technique) to
compute the image.

15. Operating Console
 It is master control center of the CT scanner.
 It is used to input all of the factors related to taking a scan.
 Typically, this console is made up of a computer, a
keyboard, and multiple monitors.
 Often there are two different control consoles, one used
by the CAT scanner operator, and the other used by the
physician.

16. GENERATIONS OF CT
• FIRST-GENERATION EMI CT SCANNER
• SECOND GENERATION OF CT : Reducing Scan time
• THIRD GENERATION OF CT : Rotate/rotate, wide fan beam
• FOURTH-GENERATION CT SCANNERS
• FIFTH GENERATION ELECTRON-BEAM CT (EBCT)
• SIXTH GENERATION OF CT: Slip ring Scanners/Helical/Spiral CT
• SEVENTH GENERATIONOF CT: Multiple detector array

17. FIRST-GENERATION EMI CT SCANNER
• It was a dedicated head scanner in which the patient's head
was recessed via a rubber membrane into a water-filled box.
• The device was designed such that the water-filled box
rotated (in 1° increments) along with the single-narrow-
beam, single-detector assembly, resulting in a fixed path
length through patient plus water for all rays and
transmission measurements.
• Only 2 x-ray detectors used
• About 4.5 minutes/scan with 1.5 minutes to reconstruct slice
• Pencil beam geometry allowed very efficient scatter
reduction, best of all scanner generations

18. SECOND GENERATION OF CT
The first waterless full-body CT scanner was
developed and installed by Ledley et al. at
Georgetown University in February 1974.
Incorporated linear array of 30 detectors
Fan shaped X-ray beam, translate rotate mode
Scan time: 10-90 sec

19. THIRD GENERATION OF CT
• More than 800 detectors were used
• It is characterized by linked tube–detector arrays undergoing
only rotational motion, is known as third-generation
geometry.
• Scan time range from 17 sec to little more than 1 min
RING ARTIFACT
If one of the detectors is out of calibration on a third-
generation (rotating x-ray tube and detector assembly)
scanner, the detector will give a consistently erroneous
reading at each angular position, resulting in a circular
artifact called as RING ARTIFACT.
Xenon Detector Array:
Ring artifacts were minimized by using an inherently stable
xenon array. Each small chamber acted as an ionization
chamber.

20. Xenon detector array

21. FOURTH-GENERATION SCANNERS
• Developed principally to suppress Ring artifacts.
• Several thousands of ring detectors are used.
• Mechanical motion is rotation of X-ray source around a
fixed detector array.
• As fan beam passes across each detector, and image
projection is acquired
• Scan time is: ½ - 1 second
• During tube rotation, the part of the ring between the
tube and the patient would tilt out of the way of the x-
ray beam (the peculiar wobbling motion of the ring
was called nutation).
• Another disadvantage of fourth-generation designs was
scattering.

23. FIFTH GENERATION -ELECTRON-BEAM CT (EBCT)
• Fast imaging
• X-ray source is not an X-ray tube rather a focused,
steered, and micro wave- acclerated electron beam
incident on a tungsten target.
• Scan time : <50 ms
• Principally applied to cardiac imaging

24. SIXTH GENERATION OF CT
• Helical CT scanners acquire data while the table is
moving
• Mostly used nowadays

25. SEVENTH GENERATION OF CT
Multidetector /Multislice /Multirow CT
• Most recent advancement,
introduced in 1998.
• This uses usually 64-128
adjacent multiple detector
arrays in conjunction with a
helical CT scanner , the
collimator spacing is wider and
more of the x-rays that are
produced by the tube are used
in producing image data.
• Scanning time: 0.25 second

26. Mathematical principle of CT scan
• Mathematical principles of CT were first developed in 1917 by
Radon
• ”Proved that an image of an unknown object could be
produced if one had an infinite number of projections through
the object.”
• The internal structure of an object can be reconstructed from
multiple projections of the object.
• Plain film imaging reduces the 3D patient anatomy to a 2D
projection image
• Density at a given point on an image represents the x-ray
attenuation properties within the patient along a line
between the x-ray focal spot and the point on the detector
corresponding to the point on the image

27. Tomographic acquisition
Single transmission measurement through the patient made
by a single detector at a given moment in time is called a ray
A series of rays that pass through the patient at the same
orientation is called a projection or view
Two projection geometries have been used in CT imaging:
 Parallel beam geometry with all rays in a projection parallel to one
another
 Fan beam geometry, in which the rays at a given projection angle
diverge
Purpose of CT scanner hardware is to acquire a large number
of transmission measurements through the patient at different
positions
Single CT image may involve approximately 800 rays taken at
1,000 different projection angles
Before the acquisition of the next slice, the table that the
patient lies on is moved slightly in the cranial-caudal direction
(the “z-axis” of the scanner

28. IMAGE RECONSTRUCTION
The photon recorded by the detectors
represent a composite of absorption
characteristics of all elements of the
patient in the path of x-ray beam.
Computer algorithms use these photon
count to construct one or more digital
cross-sectional image.
The X-ray beam attenuation is collected
in a grid like pattern called matrix.
These cross sectional image of the body
is divided into tiny blocks called as
VOXEL (VOlume Element){3D}.
Each square of image matrix is called as
Pixel{2D}.
Image are typically 512 x 512 or 1024 x
1024 pixels.

29.  Composition and thickness of voxel along with quality of beam
determine the degree of attenuation.
 Attenuation is followed by Lambert's law of absorption.
 So for a single block of homogeneous tissue and monochromatic
beam of x–ray
N = N0e-µx
since e is natural log, N0 is initial photon, N is transmitted
photon, x is thickness of slab
 Similarly if N no. of block is there then the equation becomes
N=N0e-(µ1+µ2+µ3…………………µn)x
 To solve this problem we must have transmission reading taken from
at least to different direction .
 Since the more is projection and lines more is equation formed
 As for example orignal EMI scanner 28,800 reading Fan beam scanner
can take 1 lak to2 lak. Readings.
CT THEORY

30. Mathematical methods of image reconstruction
1.Back projection
Also called summation method. It Is the oldest means of image reconstruction.
Its principle demonstrates when a ray from two projection is superimosed, or back projected
They produce a crude reproduction of original object.
Filtered back-projection is one of this method. modification of these methods, called the Feldkamp
reconstruction, is used for MDCT and cone-beam reconstructions to account for the diverging x-ray beam.
2.Iterative methods
It start with assumption that all point in matrix have same value and it was compared with measured
value and make correction until Values come with in acceptable range.
It is used instead of filtered back-projection to reduce noise from images. This technique allows the use of
low-dose protocols yet still produces images with comparable or better image qualit
3.Analytical methods
Most commonly used now.
It start with assumption that all point in matrix have same valueAnd it was compared with measured value
and make correction until Values come with in acceptable range

31. Fig: Image reconstruction.
• A:Assume four volumes with differing linear attenuation coefficients (µ). A beam entering the
object with N0 photons is reduced in intensity by object. The intensity of the remnant beam is
measured by the detector array. The value of each cell in the object can be determined by
solving four (or more) independent simultaneous equations. Such a brute-force approach is
computationally intensive, and in practice much faster algorithms are used to reconstruct
images.
• B:This task is conceptually similar to sudoku problems in that the exposure to the detector is
known, and the filtered back-projection algorithms estimate the exposure intensity at each
voxel.
•

32. CT Tomographic images
• For image display, each pixel is
assigned a CT number representing
tissue density.
• CT numbers, aka Hounsfield
units (HU), in honor of the inventor
Hounsfield, range from −1000 to
+1000, each corresponding to a
different level of beam attenuation.
• Most monitors may display only 256
gray-scales and the human eye can
perceive only 64 shades of gray.

33. Multiplanar Reformatted Imaging
• Data from a single CT imaging procedure, consisting of either multiple
contiguous or one helical scan, can be viewed as images in the axial,
coronal, or sagittal planes or in any arbitrary plane depending on the
diagnostic task; this is referred to as multiplanar reformatted
imaging
• Have the capability of viewing normal anatomy or pathologic
processes simultaneously in three orthogonal planes often facilitates
radiographic interpretation
• These are two-dimensional and require a certain degree of mental
integration by the viewer for interpretation.
• This limitation is overcomed by computer programs that reformat
data acquired from axial CT scans into three-dimensional images.
• Three-dimensional reformatting requires that each original voxel,
shaped as a rectangular solid, be dimensionally altered into multiple
cuboidal voxels. This process, called interpolation, creates sets of
evenly spaced cuboidal voxels (cuberilles) that occupy the same
volume as the original voxel.

34. Fig: Three-dimensional rendering. Three-dimensional images can be reconstructed from the cuberilles, thresholded for
bone (left) or soft tissue (right), oriented in any arbitrary direction, and made to appear to have depth by highlighting
structures near the front and shadowing structures near the back. This patient has hemifacial microsomia and
demonstrates incomplete development of the left frontal, sphenoid, temporal maxillary, zygomatic, and mandibular
bones. Note also the reduced size of the left orbit, depression of the tip of the nose, missing and incompletely erupted
left maxillary teeth, deviation of the right mandible to the left, sunken left midface, and malformation of the left ear.

35. CT Scan Methodology
• X-ray tube and detectors rotate around the patient, with the axis of
rotation running from the patient’s head to toe.
• Detectors measure the average linear attenuation coefficient, µ,
between the tube and detectors. Attenuation coefficient reflects
the degree to which the X-ray intensity is reduced by the material it
passes through
• 2D measurement are taken in a helical manner all around the
patient
• Attenuation data is summed up from thousands of angles used in a
process called reconstruction
• Contrast dye is sometimes used to make the internal organs more
visible in the image
• Bone appears white; gases and liquids are black; tissues are gray
• Measurements taken in Hounsfield units (Hu
• The same study data can show bone structure or soft tissue detail,
simply by altering the window and leveling (ie, which Hu range will
the 0-255 greyscale values will correspond to)

36. Scanning methods
1. Digital projection
1. AP, PA, Lat or Oblique projection
2. Surview, Scanogram
2. Conventional CT
1. Axial -Start/stop
3. Volumetric CT
1. Helical or spiral CT - Continuous acquisition

37. Digital Projection
X-ray tube and detector remain stationary .Patient
table moves continuously with X-rays “on” Produces an
image covering a range of anatomy similar to a
conventional X-ray image, e.g. flat plate of the
abdomen .Image used to determine scan location.
Volume CT
X-ray tube and detector rotate 360°. Patient table
moves continuously with X-ray’s “on” Produces a helix
of image information. This is reconstructed into 30 to
1000 images .

38. Principles of CT Interpretation
CT interpretation is based on an organized and
comprehensive approach.
 CT images are viewed in sequential anatomic order,
examining each slice with reference to slices above and
below.
This image analysis is made dramatically easier by viewing CT
images on a PACS workstation.
The interpreting physician can scroll up and down the stacked
image display.
The radiologist must seek to develop a three-dimensional
concept of the anatomy and pathology displayed. This
analysis is fostered by the availability of image
reconstructions in coronal and sagittal as well as axial planes.
Must be interpreted with reference to the scan parameters,
slice thickness and spacing, administration of contrast, timing
of scanning relative to contrast enhancement, and presence
of artifacts.

39. In these images, bone is white or light grey, soft
tissue is medium gray, and air is dark grey to black.
Axial images are oriented so that the observer is
looking at the patient from below.
 The patient’s right side is oriented on the left side of
the image.
PACS workstation viewing of digital images allows the
interpreter to actively manipulate the image, magnify,
change image brightness and contrast, measure
attenuation, and create oblique and three-
dimensional image reconstructions to optimize
interpretation.

40. Artifacts
Artifacts refer to components of the image that do not faithfully
reproduce actual anatomic structures because of distortion,
addition, or deletion of information.
Partial volume artifacts/volume averaging:
when a voxel contains tissues of different densities the resulting CT
number for that voxel is an intermediate value that does not
represent either tissue. The resulting image may be a blurring of
the junction of the tissue or a loss of part of a thin cortical layer of
bone
Beam hardening artifact
Results from greater attenuation(absorption) of low-energy x-ray
photons as they pass through tissue. Mean energy of the x-ray
beam is increased (the beam is “hardened”), resulting in less
attenuation at the end of the beam than at its beginning. Beam-
hardening errors are seen as areas or streaks of low density as
darkening in middle of an axial slice.

41. Motion artifact
Results when structures move to different positions during
image acquisition. Motion is demonstrated in the image as
prominent streaks from high- to low-density interfaces or as
blurred or duplicated images
Metal Streak artifacts:
Occurs due to near complete absorption of x-ray photons
by metallic restorations. Appears as opaque streak in
occlusal plane.

42. Ring artifacts
Ring artifacts are seen as high- or low-density circular
rings in the image.
Quantum mottle artifacts
Produce noise in the image seen as salt-and-pepper
pattern of random dark and light specks throughout
the image. The image noise results from insufficient x-
ray transmission data caused by inappropriate
radiation settings for the size of the patient.

43. Contrast agents
CT contrast is used to make specific organs, blood
vessels and/or tissue types "stand out" with more
image contrast to better show the presence of disease
or injury.
Route of contrast agent used in CT
1. Intravenous injection
2. Orally
3. Rectally
4. Intra articular
- Arthrography or inhaled

44. COMPOUNDS USED:
Iodide compound contrast
a) Diatrizole ( urograffin hypaque )
1500 moSml/kg
b) Metrizoate ( Isopaque ) 1500
c) Iothalamate ( Conray ) 1500
Ionic -- LOCM
a) Loxaglate ( hexabrix ) 490
None Ionic – LOCM
I. Iopamidole ( Niopam , Isovue )
470
II. Iohexol ( Ominpaque )
“
III. Iomeprol ( Iomeron )
“
IV. Ioversol ( Optiray )
“
V. Iopromide ( Ultravist )
“
None Ionic – ISO
1. Iotrolan ( Isovist ) 300
2. Iodixanol
( visipaque )
Barium compound contrast
1. Baritop 100 ( 100% all part of GIT )
2. EPI -C ( 150% large bowel )
3. E-Z HD ( 250 % esophagus ,
stomach and duodenum )
4. E-Z paque ( 100% small bowel
5. Polibar ( 115% large bowel )
6. Polibar rapid ( 100% large bowel )
7. Water -soluble 20 ml {Urograffin 150 ,
gastromiro }
8. Barium suspension – low density ( 2%
w/v

45. • Once the iodine/barium contrast has been injected into the
blood stream, it circulates through the heart and passes
into the arteries, through the body's capillaries and then
into the veins and back to the heart.
• As CT images are being acquired, the CT's x-ray beam is
attenuated (weakened) as they pass through the blood
vessels and organs flush with the contrast. This causes the
blood vessels and organs filled with the contrast to
"enhance" and show up as white areas on the x-ray or CT
images. The kidneys and liver eliminate the contrast from
the blood.
• Toxicity may occur rarely that include flushing , nausea ,
metal taste in moth , peripheral burning , rigors urticaria ,
warm , pain , abdominal pain bronchospasm , none cardiac
pulmonary edema, arrhythmias, hypotension,
nephrotoxicity , CIN , hematological crisis in sickle cell
patient , neurotoxicity , thyroid diseases.

47.  Painless, noninvasive and accurate.
 Ability to image bone, soft tissue and
blood vessels all at the same time.
 Provides very detailed images of many
types of tissue
 Fast and simple; in emergency cases, they
can reveal internal injuries and bleeding
quickly enough to help save lives.
 Cost-effective imaging tool for a wide
range of clinical problems.
 Less sensitive to patient movement than
MRI and CT can be performed if you have
an implanted medical device of any kind,
unlike MRI.
 Provides real-time imaging, making it a
good tool for guiding minimally invasive
procedures such as needle biopsies and
needle
 Diagnosis may eliminate the need for
exploratory surgery and surgical biopsy.
 No radiation remains in a patient's body
after a CT examination.
 Usually have no immediate side effects.
Slight increase in cancer from larger
amounts of radiation, such as from
radiation therapy.
Not recommended for pregnant
women unless medically necessary
because of potential risk to the baby.
Manufacturers of intravenous
contrast indicate mothers should not
breastfeed their babies for 24-48
hours after contrast medium is given.
Rare risk of serious allergic reaction
to contrast materials exist, so
radiology department should be well-
equipped to deal with them.

48. Limitations of CT Scanning of the
Body
• Soft-tissue details in areas such as the brain, internal
pelvic organs, and joints (such as knees and shoulders)
can often be better evaluated with magnetic resonance
imaging (MRI).
• In pregnant women, while CT can’t be performed
safely, other imaging exams not involving radiation,
such as ultrasound or MRI, is preferred if they are likely
to be as good as CT in diagnosing your condition.
• A person who is very large may not fit into the opening
of a conventional CT scanner or may be over the
weight limit—usually 450 pounds—for the moving
table

49. SIGNIFICANCE OF CT IN MAXILLOFACIAL REGION
❍ Evaluation of the presence and extent of clinically suspected
pathology in the head and neck region including cysts,
tumors and infections.
❍ Detection of the extension of disease process into the
paranasal sinuses, base of skull and orbit.
❍ Determination of the location, extent and displacement of
maxillofacial skeletal fractures, including detection of
subdural and epidural hematomas.
❍ Salivary gland imaging.
❍ Evaluation of potential implant sites using 3D image
reconstruction.
❍ Evaluation of the components of the TMJ.
❍ CT-guided fine needle aspiration biopsies.
❍ Virtual surgeries.

50. Odontogenic infections
• Cellulitis - soft tissue swelling obliterating fat planes.
• Abscess- irregular zone of low density with a peripheral rim of contrast
enhancement.
• Acute osteomyelitis- zone of increased contrast enhancement.
• Chronic osteomyelitis- destructive pattern with peripheral rim of contrast
enhancement.
• Carl W Hardin and RIC Harnsberger (1985)made use of CT in evaluation of
infections and tumors involving the masticator spaces and found that CT is
helpful in differentiating inflammation from frank abscess. Alan A
Schwimmer et al (1988) emphasized the role of CT in the diagnosis and
management of temporal and infra temporal space abscesses.
Mandibular body affected by suppurative
osteomyelitis.

51. Salivary gland disease
Salivary calculi seen as high
density, non- contrast
enhancing mass along the
course of the duct.
Nick Bryan et al performed CT
in 27 patients with salivary
gland neoplasm and
concluded that when CT is
combined with the clinical in
formation and laboratory
findings, the overall specificity
in identifying the tumor
becomes 90%.
CT of the neck demonstrates
a stone (blue arrow) in the
submandibular region of a
dilated Wharton's Duct (red
arrow)

52. ODONTOGENIC CYSTS
Appear as localized,
expansile degenerative
area having a fluid
density throughout the
lesion. Do not show
contrast enhancement in
contrast aided imaging
(except Aneurysmal
Bone Cyst)
Fig: Axial CT images of a
keratocystic odontogenic tumor
in the mandible

53. ODONTOGENIC TUMOURS
• Ameloblastomas-bicortical expansion,
thinning and breach of bony walls,
extension of tumor into adjacent soft tissue
spaces. Focal cystic degenerations
commonly seen in multi-locular lesions.
• Plexiform ameloblastomas have high
contrast enhancement due to high
vascularity.
• Cystic ameloblastomas show a
predominant fluid density.
• Malignant ameloblastomas have a grossly
destructive pattern.
• Focal hyper dense areas suggesting
calcifications maybe noticeable in Pindborg
tumour.

54. MALIGNANCIES
Seen as focal high contrast
enhancement areas. Invasive lesions
show no/minimal expansion.
Demarcation from surrounding soft
tissue is difficult without contrast
aided imaging. Reparative lesions like
central giant cell granulomas also
manifest as destructive, contrast
enhancing lesions showing minimal
or no expansile pattern.
Fig: Osteosarcoma of jaw in
CT

55. Fibro-osseous lesions
CT pattern depends on the
maturative stage of lesion.
Cemental lesions are
distinguished based on the
continuity of the lesions with
the roots of the tooth and
the periodontal ligament
space, separating the lesion
from the bony alveolus.
Fig: Fibrous dysplasia of the mandible

56. MAXILLARY LESIONS
Maxillary lesions share
similar pictures in
contrast to mandibular
lesions which make this
difficult to distinguish
them.
Significantly greater
tumor extent is
demonstrated by CT than
by conventional
methods.
Fig: Swelling in the left maxillary sinus diagnosed
with Brown tumor

57. TMJ
CT helps identify the bony
changes in the TMJ like
destruction of the condylar
head, wearing of articular
elements, traumatic lesions
within and outside the
capsule.
Advantageous over
arthrography as it is a painless
procedure with superior
resolution.
Figure 2: Coronal CT scan view showing
obliteration of left interarticular space of
TMJ.

59. CONCLUSION
CT scan 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.
CT scan has made a major impact on the practice of
dentistry, particularly in oral and maxillofacial diagnosis,
surgery and management of a wide variety of oral lesions.
Advances in computer softwares already allow 3 D
visualization and conclusion of anatomy and pathology,
but further improvement in clinical performance is
expected.

60. References
• Oral radiology, 1st south asian edition, white and pharoah
• Oral radiology, 6e, White and Pharoah
• Fundamentals of Diagnostic Radiology, 4e, Brant, William and Helms
• Handbook of biomedical Instrumentation, R S khandpur
• Lippincott Radiology
• Computed Tomography - Special Applications Edited by Dr. Luca Saba
• ww.contempclindent.org/article.asp
• serc.carleton.edu/research_education/geochemsheets/techniques/CT.
html
• http://pocketdentistry.com/
• http://arcadiacachamber.org/hospitals-ct-scanner-state-of-art/