Specialized Radiographic technique for the use in the maxilofacial area

1. Specialized radiographic
technique
Prof. Dr. Naglaa Shawki El Kilani
Prof And Head Of Department Of Oral Medicine,
Perio, Diagnosis And Oral Radiology
Head Of Laser Centre
Faculty Of Dental Medicine, Al AzharUniversity.

2. Tomography

3. Each tomogram shows the tissues in
that section sharply defined and in
focus (the focal plane).
While structures outside the plane of
interest are blurred through the
process of motion unsharpness.
 Sections are usually in either the
sagittal or coronal planes .
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5. Thus, The objective of tomography is
to blur the images of structures not
located in the focal plane both as much
and as uniformly as possible.
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6. Tomographic motion
There are at least five types of
tomographic movement: linear, circular,
elliptical, hypocycloidal, and spiral .
Mechanically, the simplest tomographic
motion is linear.
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8. The image quality of linear tomograms
has several deficiencies compared with
tomograms produced by other types of
movement.
These are:
1. Streaks, called false images or parasite
lines
2. Inconsistent magnification,
dimensional instability, and non
uniform densities
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10. If sharper tomographic images of more
uniform density, consistent magnification,
and dimensional stability are required, a
multidirectional tomographic motion is
necessary.
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Linear tomography Spiral tomography

13. Computed Tomography

14. In 1972 Godfrey Hounsfield announced the
invention of a revolutionary imaging
technique, which he referred to as
computerized axial transverse scanning.
With this technique he was able to produce
an axial cross sectional image of the head
using a narrowly collimated, moving beam of
x rays.
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16. Main indications in the head and
neck
Investigation of intracranial disease
Investigation of suspected intracranial and
spinal cord damage following trauma to the
head and neck .
Assessment of fractures involving:
 - The orbits and naso-ethmoidal complex
 - The cranial base - The cervical spine .
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17. Tumor staging
- benign and malignant tumours, affecting:
- The maxillary antra
- The base of the skull
- The pterygoid region
- The pharynx
Tumors and tumor –like ;intrinsic and extrinsic
to the salivary glands .
Investigation of the TMJ .
 Preoperative assessment of alveolar bone
height and thickness before inserting implants.
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19. PRINCIPLE
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20.  The detectors measure the intensity of the
X ray beam emerging from the patient and
convert this into digital data which is stored
and manipulated by the computer.
This numerical information is converted
into a grey scale representing different tissue
densities, allowing a visual image to be
generated.
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21. CT image is a digital image,
reconstructed by computer, which
mathematically manipulates the
transmission data obtained from
multiple projections.
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22. As each pixel has a definite volume, is
referred to as a voxel.
Each voxel is given a CT number or
Hounsfield unit between + 1000 and
-1000, depending on the amount of
absorption within that block of tissue.
 Each CT number is assigned a different
degree of grayness, allowing a visual image
to be constructed and displayed on a
television screen.
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29. Three dimensional reformatted C.T:
Advances in computer software now
enable digital data to be displayed three-
dimensionally using a variety of software
methods.
Three-dimensional reformatting can be
performed either on the CT scan computer
itself, usually as an optional software
addition, or as part of a dedicated image-
processing workstation.
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31. Advantages CT over conventional
tomography
 Very small amounts, and differences, in X-ray absorption can
be detected, allowing:
- Imaging of hard and soft tissues
- Excellent differentiation between different
types of tissue, both normal and diseased .
Axial tomographic sections are obtainable .
Tomographic sections in the coronal and sagittal planes can be
reconstructed from information obtained in the axial plane .
Images can be enhanced by the use of IV contrast media,
providing additional information.
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32. Disadvantages
The equipment is very expensive .
Facilities are not widely available .
Very thin (1.5 - 3 mm), contiguous or overlapping
axial slices are required for image reconstruction in
other planes with a resultant high dose of radiation
to the patient .
Metallic objects such as fillings produce marked
streak artifacts across the CT image.
There are inherent risks associated with IV
contrast agents .
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33. Cone beam Computed
Tomography

34. It was designed with the purpose of improving the
limitations of CT equipment:
1. The high radiation doses,
2. The time taken to carry out the exploration
3. The cost of the equipment.
Moreover, the cone-beam CT device, which is compact, can
be used effectively in the dental clinic.
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35. Cone Beam CT
The equipment employs a
cone-shaped x-ray beam
(rather than the FAN)
Beam scans the head in 360
degrees.
Raw data are reconstructed
to form images
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38. CBCT
the computer then collect the information into tiny
cubed or voxels (typically 0.4 mm x 0.4mm ).
 Individual voxels are much smaller than in medical
CT.
The voxel sizes in newer machines are even smaller
(0.15mm x 0.15mm x 0.15 mm) so improving image
resolution
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39. CBCT
Special detector
◦ image intensifier tube/ Charged couple
device (IIT/ CCD)
◦ flat panel detectors
Flat panel detectors have high resolution
and inexpensive, but they require more
radiation
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40. Field of view
Collimation of x ray beam by adjustment of FOV
limits the radiation to one ROI
It is desirable to limit the field size to the smallest
volume that can accommodate the region of
interest.
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42. Large FOV
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43. Medium FOV
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44. Focused FOV
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45. Focused (Stitched) FOV
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47. Advantages of CBCT
Short scan time
Image accuracy with high resolution
Reduced radiation dose
Interactive display modes
Multiplanar reformation
3D volume rendering
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49. Limitation of CBCT
Image noise because of large area to be
imaged cause more scatter radiation.
Poor soft tissue contrast.
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50. Application of CBCT in Dental field
Dental Implant
Maxillofacial surgery
Temporomandibular joint
Orthodontics
Disease
Cleft palate
Endodontic application
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51. Dental implants
CBCT, combined with customized software,
provide the necessary 3-D information. This
allows determination of the optimal implant size
and location considering surgical, anatomic,
and prosthodontic issues.
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52. Cone beam radiography
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53. Temporomandibular joint: (a)
corrected lateral and (b) frontal views
demonstrating smooth cortical outlines
of the mandibular
condyle and mandibular fossa of
temporal bone. The position of the
condyle within the fossa, concentric, is
normal. Images made with the 3DX
Accuitomo (J. Morita USA., Inc., 9
Mason, Irvine, CA). NAGLAA S. EL KILANI

54. Orthodontics
Pharyngeal air way space and soft tissue
relationship can be provided by CBCT.
CBCT can detect teeth impaction easily.
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56. Three-dimensional monitoring of root movement during orthodontic
treatment, Robert et al ,Am J Orthod Dentofacial Orthop 2015
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57. Accuracy of cone-beam computed tomography in detecting alveolar
bone dehiscences and fenestrations, Liangyan Sun et al Am J Orthod
Dentofacial Orthop 2015
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58. Disease
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59. Ameloblastoma. An 18-year-old male. Data acquired using an iCAT CBCT machine.
Images are reformatted in OnDemand 3-D, a third-party software. (a) Sagittal view of
the right mandible showing a large multilocular lesion and inferior displacement of the
third molar. (b) Coronal section through the angle of the mandible. Compared to the
normal left side, the right side shows expansion in buccolingual aspect and lower
border of the mandible. The third molar is next to the buccal cortical plate. (c) A 3-D
reconstruction of the involved area, showing the thinning and perforation of the
cortical plates. The superimposing structures (vertebra, hyoid bone)
are subtracted by segmentation.
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60. Cleft palate
CBCT showed 3D relations of the defect and
bone thickness around the existing teeth in
proximity to the cleft.
The volume of the graft material needed for
repair could be estimated by volumetric analysis.
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61. Cleft palate
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63. Endodontic application
Diagnosis of endodontic pathosis
Canal morphology
Assessment of pathosis of non-endodontic
origin
Evaluation of root fractures and trauma
Analysis of external and internal root resorption
and invasive cervical resorption
Pre-surgical planning
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64. Diagnosis of endodontic pathosis and Assessment of
pathosis of non-endodontic origin
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65. Canal morphology
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66. Trauma
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67. Analysis of external and internal root resorption and
invasive cervical resorption
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68. Pre-surgical planning
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69. Magnetic resonance imaging
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70. Magnetic resonance imaging (MRI) uses
non ionizing radiation from the
radiofrequency (RF) band of the
electromagnetic spectrum.
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71. To produce an MR image, the patient is
placed inside a large magnet, which
induces a relatively strong external
magnetic field.
This causes the nuclei of many atoms in
the body, including hydrogen, to align
themselves with the magnetic field.
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Principle:

72. Application of a radiofrequency pulse
can induce resonance in particular sets
of nuclei.
Release of energy occurs as the RF
pulse is turned off is detected by a
receiving coil and converted to an
electric signal which provides data for a
digital image.
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75. The rate or frequency of precession is
called the resonant or Larmor frequency.
The Larmor frequency is specific for the
nuclear species and depends on the
strength of the external magnetic field.
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76. As soon as the radio waves (the resonant
RF pulse) are turned off, two events occur
simultaneously:
The radiation of energy and the return of
the nuclei to their original spin state at a
lower energy. This process is called
relaxation
 The energy loss is detected as a signal,
which is called free induction decay (FID).
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77. The strength of returned signal is directly
proportional to;
The strength of the static magnetic field
The number of hydrogen nuclei
(protons) present in the tissue (proton
density) in a sample of tissue
The degree to which hydrogen is bound
within a molecule.
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78. The antenna does not separate the
individual signals coming from different
tissues; rather, they are summed to form a
complex FID signal.
The Fourier transform separates the
complex FID signal from the different tissues
into its various frequency components.
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81. Main indications of MRI in the head and
neck
Assessment of intracranial lesions involving
particularly the posterior cranial fossa, the
pituitary and the spinal cord .
Tumour staging-evaluation of the site, size and
extent of soft tissue tumours and tumour-like
lesions, involving - The salivary glands - The
pharynx – The larynx
Investigation of the TMJ to show the hard and
soft tissue components of the joint including
the disc.
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84. Advantages over CT
 Ionizing radiation is not used.
No adverse effects from MRI have ''Yet been
demonstrated.
 High-resolution images can be reconstructed in all
planes .
 Excellent differentiation between soft tissues is
possible and between normal and abnormal tissues
ie: High contrast sensitivity of MRI to tissue
differences.
There is no need for enhancement of images
using intravenous contrast media with their
associated risks.
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85. Disadvantages
Cortical bone is not imaged, signal
obtainable only from bone marrow .
It is contraindicated in patients with
certain types of surgical clips and
cardiac pacemakers .
Scanning time is long and thus more
demanding on the patient .
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86. Metallic objects, e.g. endotracheal
tubes need to be replaced by plastic .
Equipment is very expensive .
The very powerful magnets pose
problems with sitting of equipment .
Facilities are not widely available
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87. Radio nucleotide imaging
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88. Film radiography, CT, MRI, and
diagnostic ultrasonography are
considered morphologic imaging
techniques
That is, each requires some specific
structural difference or anatomic
change for information to be recorded
by an image receptor.
However, human diseases can exist
with no specific anatomic changes.
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89. Changes that are seen may simply be
later effects of some biochemical process
that remains undetected until physical
symptoms develop.
 Radionuclide imaging (or functional
imaging) provides the only means of
assessing physiologic change that is a
direct result of biochemical alteration.
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90. PRINCIPLERadioisotope imaging uses radioactive
compounds that have an affinity for
particular tissues; so-called target tissues.
These radioactive compounds are injected
into the patient, concentrated in the target
tissue
Their radiation emissions are then detected
and imaged, usually using a gamma camera.
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93. This investigation allows the function
and/or the structure of the target tissue
to be examined under both static and
dynamic conditions.
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94. Nuclear medicine versus conventional radiography:
Patient rather than the machine is the source of
radiation.
The detection instrumentation is different.
The sensitivities of nuclear medicine procedures
are great.
However its specifity is low
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95. Main indications for isotope imaging in the head and
neck
Investigation of salivary gland function.
Tumour staging-assessment of the sites and
extent of bone metastases .
Evaluation of bone grafts .
Assessment of continued growth in condylar
hyperplasia .
Investigation of the thyroid .
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96. Advantages over conventional radiography
Target tissue function is investigated .
 All similar target tissues can be examined
during one investigation, e.g. the whole
skeleton can be imaged during one bone scan
.
 Computer analysis and enhancement of
results is available.
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97. Disadvantages
 Image resolution is poor-often only minimal
information is obtained on target tissue
anatomy .
The radiation dose to the whole body can be
relatively high .
 Images are not usually disease-specific .
Some investigations take several hours.
Facilities are not widely available
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