Cone Beam Computed Tomography.pptx

Moderator
Prof (Dr) Vidya Ajila
Department of Oral Medicine and Radiology
Presenter
Dr. Anand shankar sarkar

 Introduction
 History
 Terminologies
 CBCT vs CT
 Types of CBCT Equipment
 Basic Principles and Imaging technique
 Artefacts

 Imaging Guidelines
 CBCT in Prosthodontics
 CBCT in Endodontics
 CBCT in Periodontics
 CBCT in Orthodontics
 CBCT in Maxillofacial surgery
 CBCT in Otolaryngology
 Limitations
 Conclusion
 References

 Radiology is essential in dentistry for determining the presence and extent of
disease.
 It also has a role in treatment planning, monitoring disease progression and in
assessing treatment efficacy.
ORALAND MAXILLOFACIAL RADIOLOGY
‘A Speciality of denstistry and discipline of radiology concerned with the production and interpretation
of images and data produced by all modalities of radiant energy that are used for the diagnosis and
management of diseases, disorders and conditions of the oral and maxillofacial region’

 In conventional X-ray imaging an object is irradiated by photons generated from an X-ray
source and the transmitted photons are registered on a photographic plate.
 Since the X-ray attenuation of the irradiated object is proportional to its electron density,
the X-ray intensity transmitted after traversing a region of lower density is greater than
the X-ray intensity transmitted after traversing a region of higher density.
 The contrast of the radiographic image has been applied for diagnostic purpose.
Need for a THREE
DIMENSIONAL
Imaging modality

 Cone beam imaging technology is the three dimensional imaging modality specially
designed for the maxillofacial region, commonly referred to as cone beam computed
tomography (CBCT).
 The terminology “cone beam” refers to the conical shape of the beam that scans the
patient in a circular path around the vertical axis of the head, in contrast to the fan-
shaped beam and more complex scanning movement of multidetector-row computed
tomography (MDCT) commonly used in medical imaging.

Wilhelm C Roentgen, Professor of Physics in Wurzburg, Bavaria, discovered X-rays during his
experiments with cathode rays
Another mathematical advancement that Hounsfield built on is the “Algebraic Reconstruction
Technique,” which was formulated by Polish mathematician Stefan Kaczmarz
The mathematical basis for CT was first discovered by Radon called “Radon transform”
1895
1937
1917
CT was invented in 1972 by British engineer Godfrey Hounsfield of EMI Laboratories, England
and by South Africa-born physicist Allan Cormack of Tufts University.
1972

Dedicated head CT scanner - "Siretom“ produced by circa 1974
An early volumetric CT predecessor of CBCT, the dynamic spatial reconstructor, was developed by
Robles RA in by the Biodynamics Research Unit at the Mayo Clinic.
Late
1970s
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.

CBCT prototypes based on C-arms were demonstrated as early as 1983.
The technology transfer of CBCT to dentistry.
Attilio Tacconi and Piero Mozzo, developed a CBCT system for the maxillofacial region that was
designed and produced by QR, Inc of Verona, Italy.
1983
1995
NewTom DVT 9000 became the first commercial CBCT unit marketed specifically to the dental
market. (Europe).
1999
The Food and Drug Administration (FDA) approved the first CBCT unit for dental use in the United
States — the NewTom DVT 9000 (Quantitative Radiology srl, Verona, Italy).
March
8,
2001
FDA granted approval for production of CBCT by various manufactures
2003

 Tomography
 Method of producing three dimensional images of internal structures, imaging sections or
sectioning through the use of any kind of penetrating wave. The device used in tomography
is called tomograph where as the image produced is called a tomogram.
 Hounsfield units (HU)
 Quantitative measure of the radiolucency of different materials in a CAT scan. Hounsfield
units allow us to differentiate the relative densities of various biological structures. The
Hounsfield scale ranges from air at -1000 HF, through water at 0 HF, up to +1000 HF for
cortical bone, +400 for cancellous bone, and 2000-3000 for metallic structures.

 DICOM :
 Digital imaging and communications in medicine.
 This is a standardized format given by the ACR/NEMA (American College of
Radiology/National Electrical Manufacturers Association) to allow the digital transfer
of data between various diagnostic-imaging equipment and software.
 Gray scale :
 The ability of a CBCT scan to display differences in attenuation. This parameter is
called bit depth of the system and determines the number of shades of gray available
to display the attenuation

 Pixel :
 Picture + Element. Pixel represents the smallest single component of an image on a
two-dimensional grid.
 Voxel :
 Volumetric form of pixel. The voxel adds the third dimension (3-D) to the digital
image by adding the z-axis (depth) to the x-axis (width) and the y-axis (height).
Stacks of these volumetric boxes of data allow 360 degrees of virtual manipulation
of imaged objects.

 Attenuation :
 The property of reduction of the intensity of an x-ray beam as it traverses matter.
 Attenuation coefficient :
 Measure of the quantity of radiation attenuated by a given thickness of an absorbing
material.
 The linear attenuation coefficient :
 Symbolized by the Greek letter µ, is the fractional change in x ray intensity according to
the thickness of the attenuating material because of interactions in a given material.
 Frame Rate:
 Speed with which the images are acquired.

 Field of view :
 Area of interest to be covered during the scanning procedure.
 Small field of view (also referred to as limited or focused fields of view): scan height and
width less than 5 cm.
 Medium field of view (also referred to as dentoalveolar field of view): scan height 5–15
cm.
 Large field of view (also referred to as craniofacial field of view): scan height greater than
15 cm.

Small FOV CBCT units
A small FOV means that high-resolution images with a spatial resolution down to 0.076 mm
isotropic voxel size can be achieved at very low exposure to ionizing radiation and without
extensive reconstruction times that would be expected with larger FOV systems due to the
greater file sizes to be processed.
A small FOV reduces the volume examined, and for which the practitioner is responsible to
interpret. Small FOV systems concentrate on the dental arches or individual
temporomandibular joints, the structures in which the average dentist is most familiar.
Only a limited area is imaged.
Cannot be used for imaging maxillofacial pathologies and trauma.

 CBCT systems can be categorized according to the orientation of the patient during
image acquisition, the scan volume irradiated, or the clinical functionality.
Patient Positioning
 Depending on the system employed, CBCT can be performed in three possible
positions:
1. Sitting
2. Standing
3. Supine.

 Equipment that requires the patient to be supine has a larger physical footprint and
may not be readily accessible for patients with physical disabilities.
 Standing units may not be able to be adjusted to a height to accommodate
wheelchair bound patients.
 Seated units are the most comfortable; however fixed seats may not allow ready
scanning of physically disabled or wheelchair bound patients.
 As scan times are often similar to or greater than those used with panoramic
imaging, The most factor other than patient orientation is the head restraint
mechanism used.

Scan Volume
 The dimensions of the FOV, or scan volume, are primarily dependent on the detector
size and shape, beam projection geometry, and the ability to collimate the beam.
 The shape of the FOV can be either a cylinder or spherical.
 Collimation of the primary X-ray beam limits x-radiation exposure to the region of
interest (ROI).
 Field size limitation ensures that an optimal FOV can be selected for each patient
based on disease presentation and the region designated to be imaged.

 Based on available or selected scan volume height, the use of units can be designed
as follows:
1. localized region (also referred to as focused, small field or, limited field)—
approximately 5 cm or less,
2. Single arch—5 cm to 7 cm,
3. Inter-arch—7 cm to 10 cm,
4. Maxillofacial—10 cm to 15 cm,
5. Craniofacial—greater than 15 cm.

Multimodality
 Hybrid multimodal systems combine digital panoramic radiography with a relatively
small-to medium-FOV CBCT system.
 This combination is now priced at a level similar to upper-level digital panoramic
radiographic systems.
 Cost of CBCT detectors is highly dependent on size. The ProMax 3D CBVT (Planmeca Oy,
Helsinki, Finland) was the first to incorporate a small FOV 3D sensor to their ProMax
digital panoramic line, which can be also be retrofitted to any of the prior ProMax digital
models.
 Examples of other hybrid units are the Veraviewepocs 3D (J. Morita, Corporation, Kyoto,
Japan), the Picasso Trio (Vatech/E. Woo Corporation, Korea), and the Kodak Dental
Imaging 9000 DS (Kodak Dental Imaging/Practiceworks Atlanta, GA, USA)

NewTom
3G.
Accuitomo 170
Scanora
3Dx
CS 9300 (Carestream
Health, Rochester, NY).
Orthophos
XG 3D
(Sirona USA,
Charlotte,
NC).

i-CAT FLX (Imaging
Sciences
International,
Hatfield, PA)
NewTom 5G,
Italy
The SkyView CBCT
scanner
(MyRay, Imola, Italy)
Planmeca – Promax
3D (Finland)

Imaging Modalities Effective Dose
Panoramic film 3-11 μS
Lateral cephalography 5-7 μS
PA cephalograph 5-7 μS
Occlusal film 5 μS
Full mouth series 30-80 μS
TMJ series 20-30 μS
CBCT Small FOV 48-652μS
CBCT Large FOV 68-1073 μS
MDCT 534-2100μS

 Patient to be placed stationary between the x ray
source and detector.
 The rotating platform to which an X-ray source
and detector are present rotates at 360 degrees
around the patient.
 Data will be acquisited based on a translate-
rotate parallel beam geometry wherein pencil
beams of X-rays were directed at a detector
opposite the source and the transmitted
intensity of photons incident on the detector was
measured.
 Raw images will be processed and obtained on
the viewing console.
Basic Imaging technique

Components of CBCT image production
(1) Acquisition configuration
(2) Image detection
(3) Image reconstruction
(4) Image display

X-ray Generation
 The X-ray generators used in CBCT operates in a range of 80–120 kVp.
 Focal spot dimension of 0.5–0.8 mm similar to CT machines.
 The tube current is generally much lower than CT.
X-ray Detection
 Two systems are currently used in CBCT.
 Image intensifiers/charge-coupled device (II/CCD) and flat panel detectors (FPDs).

II/Charge-coupled Device
They consist of an X-ray image intensifier,
proper optics and complementary metal
oxide semiconductor (CMOS) or CCD
camera.
The II/CCD detectors are large and bulky
and most frequently result in circular-basis
image areas rather than
rectangular/cylindrical volumes.
The main disadvantages of II/CCD detectors
are geometric distortion and blurring.
FPD
FPD consists of an array of
hydrogenated amorphous silicon thin-
film transistors or CMOS arrays.
The silicon matrix is covered by a X-
ray scintillator layer, which results in
an indirect X-ray detection process.
X-rays are detected indirectly by
means of a scintillator such as
thallium-doped cesium .
X ray / Image Detectors

Department of Oral Medicine and
Radiology
Moderator
Presenter

CCD Vs FPD
Baba R, Konno Y, Ueda K, Ikeda S. Comparison of flat-panel detector and image-
intensifier detector for cone-beam CT. Computerized medical imaging and graphics.
2002 May 1;26(3):153-8.

Incident X ray Beam
X ray is converted light
Electron Beam is formed
Electron beam is converted to light
Intensity of light is adjusted and
converted to electrical signals
Read out of the image
Phosphor
Screen
Photocathod
e
CMOS/CCD
Camera
STEPS
IN
IMAGE
DETECTION
IN
II/CCD

Incident X ray Beam
X ray is converted to visible light in
photodiode array
Electrical charge is produced,
proportional to the energy of the
incident x ray beam.
Electron charge is received and stored
Actual readout process is started
Read out of the image
Scintillator
Photodiode
Detection
elements
STEPS
IN
IMAGE
DETECTION
IN
FPD
Thin film
transistor

The x-ray tube and the flat-panel
detector are aligned and joined
together in an imaging gantry which
turns around the patient in a single,
partial or complete rotation scan and
record the digital data as data
volume.

Image Reconstruction
 Image reconstruction in CT is a mathematical operation that converts attenuation
values per voxel from X-ray projection data to grayscale images.
 There are essentially two categories of reconstruction methods.
 Operations based on filtered back projection (FBP) - type of analytical reconstruction
that is widely used because of their computational efficiency and numerical stability.
Different FBP-based methods have been developed for all generations of CT data-
acquisition geometries for CBCT large-area detectors.
Analytical reconstruction
techniques

 These algorithms have recently been introduced in CT imaging, because they have
many advantages compared with conventional FBP techniques.
 Important physical factors, including focal spot and detector geometry, photon
statistics, X-ray beam spectrum and scattering, can be more accurately incorporated
into iterative reconstruction, yielding lower image noise and higher spatial resolution
compared with FBP.
 Iterative reconstruction may also show a significant dose reduction.
 In CBCT scanners, no control over the reconstruction method is provided to the
operator.
Iterative reconstruction
techniques

Preprocessing stage
After the multiple planar projection images are acquired, these images must be corrected for
inherent pixel imperfections, variations in sensitivity across the detector, and uneven exposure.
Reconstruction stage
The corrected images are converted into a special representation called a sinogram - a composite image from
multiple projection images.
The horizontal axis of a sinogram represents individual rays at the detector, whereas the vertical axis
represents projection angles. If there are 300 projections, the sinogram will have 300 rows. This process of
generating a sinogram is referred to as the Radon transformation. The resulting image comprises multiple
sine waves of different amplitude, as individual objects are projected onto the detector at continuously
varying angles.
Stages of Image Reconstruction

Sinogram Formation (Conversion and
Correction)
Weighting the projection Data
Filtering of the Projected Data
Back projection of weighted Data
Reconstruction of image from the
projected data
BASIC
IMAGE
RECONSTRUCTION
PROCESS

Image stitching
 Two or More consecutive scans are acquired, which are then merged (i.e. stitched) into one
image.
 This can be carried out to combine two or more Small or Medium FOVs.
 Stitching of the image could be carried out through simple overlap or through automatic
matching of the images using image registration.
Acquisition
Configuration
Image
Detection
Image
Reconstruction
Image Display

Image Display
 The volumetric data of CBCT is displayed in the monitor/viewing console after data
acquisition and can be viewed interactively.
 The default presentation offered by most visualization software is usually as a series of
two-dimensional (2D) inter-relational images at a thickness defaulted to the native
resolution in three orthogonal planes (axial, sagittal and coronal).
 CBCT imaging acquisition and visualization are usually performed on the same
computer/workstation.
 Display software provides a number of visualization options, each directed toward
highlighting specific components of the volumetric data set.
 The obtained data set can be reformatted and enhanced using third party softwares.

Multiplanar reformatting
 After reconstruction process a 3D matrix is created that can be viewed as a series of
2D cross-sectional images – axial (slices from top to bottom), sagittal (left to right)
and coronal (anterior to posterior) views.
 Such MPR modes include oblique, curved planar reformation and serial transplanar
reformation (providing cross-sections).

 Oblique slicing:
 Nonorthogonal slicing of the CBCT images at any angle is possible because of the isotropic
nature of the datasets to provide non-axial 2-D planar images referred to as multiplanar
reformations.
 This function creates 2D images at any angle by cutting across a set of axial images, which
help in evaluating particular structures (Impacted teeth, TMJ).
 Curved slicing:
 This enables to trace the jaw arch to display a trace view, providing acquainted panorama like
view.

 Cross-sectional view:
 This function creates a set of successive cross-sectional images perpendicular to curved slice
with the option of selecting the thickness and spacing.
 Such images are valuable in the evaluation of morphometric characteristics of alveolar bone
for implant placement, the relationship of impacted mandibular third molar with mandibular
canal, condylar surface and shape in the symptomatic TMJ or pathological conditions affecting
the jaws.

Ray sum or ray casting
 Increasing the number of adjacent voxels in the display of any multiplanar image it gets
‘‘thickened’’.
 This process creates an image slab that represents a specific volume of the patient and is
referred to as a ray sum.
 By using full thickness perpendicular ray sum images we can generate simulated projections
such as lateral cephalometric images.

Three-dimensional volume rendering
 Allow the visualization of 3 dimensional data through integration of large volumes of
adjacent voxels and selective display.
(a) Indirect volume rendering - a complex process, requiring selecting the intensity or density
of the grayscale level of the voxels to be displayed within an entire data set and provides a
volumetric surface reconstruction with depth.

(b) Direct volume rendering - most common direct volume rendering technique is
maximum intensity projection (MIP).
 MIP visualizations are accomplished by evaluating each voxel value along an
imaginary projection ray from the observer’s eyes within a particular volume of
interest and then representing only the highest value as the display value.

Image Quality
 Four fundamental parameters of image quality.
Spatial resolution
Contrast
Noise
Artefacts

Spatial resolution
 The spatial resolution of an imaging system is its ability to discriminate objects of
different attenuation at small separation distances.
 It is typically described as the spatial frequency (measured in line pairs per
centimeter) that can be discriminated with a 10% detection of true contrast.
Example :
If 20 lines are seen in a 1 cm of image, then spatial resolution is 20.
More the lp – More the Spatial resolution
Normal Eye of Observers can distinguish about 6 lp/mm without benefit of
magnification.
Intraoral film is capable of providing more than 20 lp/mm of resolution.
CBCT sensors are capable of proving about 0.6 and 2.8 lp/mm

Temporal resolution
 It refers to the ability of an imaging system to discriminate sequentially acquired
projection data separated by small time intervals. With higher temporal resolution,
more projection datasets can be acquired over a fixed gantry rotation interval, thus
improving contrast resolution.
Contrast resolution
 Contrast resolution describes the ability of an imaging system to discriminate
differences in tissue attenuation, as measured in HU.
 The low-contrast detectability in CBCT systems depends on both the dynamic range
and temporal resolution of the detector as well as x-ray scatter and quantum noise.

Low High
Why resolution is
important ?

Image Noise
Quantum noise
 caused by the inherent random nature of the interactions happening during X-ray
production and attenuation
Electronic noise
 caused by the conversion and transmission of the detector signal.
Image Noise refers to the random variability in voxel
values in an image.

High
Low
The scatter-to-primary ratios are
about 0.01 for single-ray CT,
0.05–0.15 for fan-beam and
spiral CT,
About 0.4–2.0 in CBCT.

Artefacts in CBCT Imaging
Beam related
Artefacts
Patient related
Artefacts
Scanner related
Artefacts
Foreign objects
Beam Hardening
Cone Beam
related Faults
Scatter
Photon
Depression
Exponential
edge gradient
effect
Image Noise and
Poor soft tissue
Contrast
Factors deteriorating the image in CBCT
Other deterioration
factors

 Department of Oral Medicine and
Radiology
Presenter
Moderator

From experimental as well as clinical research, it can be
seen that great variability of GVs can exist on CBCT
images owing to various reasons that are inherently
associated with this technique (i.e. the limited field size,
relatively high amount of scattered radiation and
limitations of currently applied reconstruction algorithms).
Pauwels R, Jacobs R, Singer SR, Mupparapu M. CBCT-based bone quality
assessment: are Hounsfield units applicable?. Dentomaxillofacial Radiology. 2015
Jan;44(1):20140238.

Single projection images, known as “basis” images, are acquired at
certain degree intervals, which are similar to lateral cephalometric
radiographic images, each slightly offset from one another.
The series of such basis projection images is referred to as the
projection data, on which software programs incorporating
sophisticated algorithms are applied to generate a 3D volumetric
data set, which can be used to provide primary reconstruction
images in all three orthogonal planes (axial, sagittal, and coronal).
Kumar M, Shanavas M, Sidappa A, Kiran M. Cone beam computed tomography-know
its secrets. Journal of international oral health: JIOH. 2015 Feb;7(2):64.

Artefacts
 Image artefacts can be defined as regions in the image that are aberrant, that is, do
not correspond to the real object, and are deterministic (i.e. non-random) with respect
to the projection data.
 In CT, the term artifact is applied to any systematic discrepancy between the CT
numbers in the reconstructed image.

 The most prominent artifacts seen in CBCT images are beam hardening artifacts.
 Beam hardening artifact is seen because the mean energy of beam increases as the
lower energy photons are absorbed more in comparison to higher energy photons.
 Highly absorbing materials such as metal function as a filter positioned within the
object and they absorb the low energy photons.
 This shows effects in the distortion of metallic structures as a result of disturbance in
the reconstruction process.
Beam hardening artifact

Caused by : Heavy Metallic restorations,
Metal posts in the root canals, etc..
Manufacture’s method of minimizing: By using
filtration, calibration correction, and beam
hardening correction software.
Operator’s method of minimizing : Avoid
including potential areas to cause beam
hardening within the FOV, Increasing the kVp

Cupping artifacts
It occurs when x-rays passing through the center of a large object
become harder than those passing through the edges of the
Object such as metal due to the greater amount of material the
beam has to penetrate. Because the beam becomes harder in the
center of the object, the resultant profile of the linear attenuation
coefficients appears as a "cup".
They are seen as a distortion of metallic structures as a
result of differential absorption
Streaks and dark bands
They can be seen between two dense objects.
More prominently seen in the axial planes and 3D
reconstruction images

The cone beam projection geometry and the image reconstruction method produce three
types of artifacts:
 Partial volume averaging: It occurs when the selected voxel resolution of the scan is
greater than the spatial or contrast resolution of the object to be imaged. Partial volume
averaging artifacts occur in regions where surfaces are rapidly changing in the z direction
(e.g. in the temporal bone).
 Cone beam effect: This type of artifact is seen in the peripheral portions of the scan and
is seen because of the divergence of X-rays in those areas. The outcome of cone beam
effect is image distortion, streaks, and peripheral noise.
Cone-shaped beam-related
faults

 Under sampling
 This is a type of aliasing artifact. It is seen when
very few basis projections are provided for the
reconstruction.

Exponential edge-gradient effect
 This effect is caused because of the sharp edges
of the metallic crown borders producing high
contrast, as it reduces the computed density
value.
 As sharp edges of high contrast may commonly
occur in the oral cavity, e.g. at metallic crown
borders, this artifact also has to be considered in
dental CBCT.
Exponential edge-gradient effect (EEGE) with
typical thin lines tangent to sharp edges
(arrows) in the direction of the beam.

Photon deprivation
 This is a result of severe beam hardening, generally seen next to titanium
implants or other heavy metal restorations. Due to the high density of
metallic restorations, sufficient photons do not reach the detector and a
complete void exists in the image, which is known as photon starvation.
 Photon deprivation effects can present as apparent "pseudo" fracture on axial
images.
Cone beam related artefacts are Corrected by the manufacturer : By Use of
efficient reconstruction algorithms

 Scattering is caused by those photons that are diffracted from their original path after
interaction with matter.
 Most of the scattered radiation is produced omnidirectionally and is recorded by pixels
on the cone beam area detector, which does not reflect the actual attenuation of the
object within a specific path of the X-ray beam.
 The resultant outcome increases the image noise and reduces contrast.
Amount of Scatter ∝ Reconstruction error
Scatter
Scatter refers to the off-axis low-energy radiation
that is generated in the patient during image acquistion

 Patient motion can cause faulty registration of
data, which appears as unsharpness or double
image in the reconstructed image.
 If an object moves during the scanning process,
the reconstruction process does not account for
that move.
Patient related Artefact

 Caused by : Patient movement - The lines along which the back projection do not correspond
to the lines along which the attenuation had been recorded, because the object has moved
during the acquisition, leading to misregistration / double images.
 Operator’s method for minimization : By using a head restraint, Using a scan time as short as
possible.

 These artifacts typically present as circular or
concentric rings centered on the location of the
axis of rotation.
Caused by : malfunction of the detector due to faulty
calibration or imperfections in scanner detection.
Minimized by : Correction of Calibration
Scanner related Artefact

 The bite block may cast a shadow as per its shape and size, which may be confused
as a foreign object.
 Metal foreign objects such as nose rings, earrings, clips, etc. can cast a shadow as a
result of beam hardening.
Caused by : Presence of Foreign objects in the imaging field.
Operator’s method of minimizing : Instruct the patient to remove possible foreign
objects in the imaging field.
Foreign objects related Artefact

 “Missing value artifacts”
 If the object under study contains highly absorbing material, (e.g., gold prosthesis),
then the signal recorded in the detector pixels behind that material may be close to
zero or actually zero.
 A typical gold crown may be estimated to have at least 2–3 mm of thickness (when
considering that the X-rays have to pass through both sides of it). This results in
absorption of the mean energy of 90–97%.
 Consequently, no absorption can be computed and severe artifacts are induced as
these zero entries are back projected into the volume.
Caused by : High absorbing materials.
Method of minimizing : Postprocessing image filters can help to correct raw data.
Extinction Artefacts

 Aliasing in CBCT lies in the divergence of the
cone beam.
 In each projection, the voxels close to the source
will be traversed by more recorded “rays” than
those close to the detector.
 This causes aliasing which represents itself as
line patterns (moire patterns), commonly
diverging toward the periphery of the
reconstructed volume.
Aliasing Artefacts

Review the patient’s medical and dental history along with performing a thorough clinical exam.
Documentation of these procedures and justification that the excess radiation will result in a benefit
outweighing the radiation risk must be included in the patient’s chart prior to prescribing a scan.
Determine if standard 2D radiographic images show or do not show the area in question to the extent they
need.
Have basic knowledge and education in CBCT imaging to understand what the scan will or will not show.
“ ADA recommends using evidence-based articles and continuing education courses to understand cone beam
CT basics”
For Dental professionals ordering CBCT Scans

Prior to installing a CBCT unit, a health physicist should be consulted to determine the desired location of
the machine has adequate shielding based on the machine perimeters (kVp, mA, and exposure times).
The health physicist will also ensure that the office is in compliance with federal and/or state radiation
regulations
After a CBCT unit is installed, proper training and education on safe use when performing scans must be
achieved by all dental professionals who will be operating the machine. Adequate performance of quality
control program including an evaluation interval to determine the machine is operating at the specified
settings.
The CBCT unit must be operated by either a licensed practitioner or certified radiologic operator. This will be
different for every state/country. In certain states and countries, a CBCT may be either classified as a dental x-
ray unit or a medical x-ray unit.
For Dental offices and/or imaging centers that have a CBCT
The imaging site should always be in compliance with ALARA principles.
Offices with a cone beam CT unit should be continually learning about cone beam CT and radiation safety.
Technology is consistently changing and the applications of this technology are also changing. An office must
stay current to determine the best possible way to manage this new technology so as to aid in its patient care.

The referring practitioner is responsible to interpret the findings of the entire scan and generate a report of
the findings. The practitioner is held to the same level as a board certified oral and maxillofacial radiologist.
The scan should be interpreted by an oral and maxillofacial radiologist to aid the referring practitioner, an
issue of licensure and malpractice insurance coverage needs to be determined.
For Interpretation of CBCT Scans
All CBCT scans should be evaluated by a dentist with training and education in CBCT interpretation. The entire
captured CBCT scan must be interpreted and all findings put in the patient’s chart.
It is the responsibility of the referring dentist to inform the patient of the findings both normal and abnormal.

Lechuga L, Weidlich GA. Cone beam CT vs. fan beam CT: a comparison of image
quality and dose delivered between two differing CT imaging modalities. Cureus. 2016
Sep 12;8(9).

Summarized results from Elstrøm, et al., Garayoa, et al., and Kan, et al. showing the
preferable system for various aspects

 Replacement by dental implants demands accurate assessment of the implant site for the
successful implant placement and to avoid injury to vital structures.
 Currently CBCT is the ideal choice of imaging, that has brought down implant failures by
rendering accurate information about vital structures, height and width of the planned implant
site, bone density and profile of the alveolus, while delivering low radiation exposure.
Prosthodontics & Oral Implantology
In 2000, the American Academy of Oral and Maxillofacial Radiology (AAOMR) published a
position paper on the role of imaging in dental-implant treatment planning.
“After reviewing the current literature, AAOMR recommends that some form of cross-
sectional imaging be used for implant cases and that conventional cross-sectional
tomography be the method of choice for gaining this information for most patients receiving
implants.”

Ridge Morphology
 Buccolingual ridge pattern cannot be viewed on 2D radiographs, but CBCT provides
with advantage of appreciating the type of alveolar ridge pattern present.
 Cross-sectional images - appearance of ridge patterns, loss of cortical plates,
undulating concavities, etc.
Evaluation of proximity to Vital structures
 CBCT aids in pre and post surgical evaluation of implants for assessement of the
proximity of the implant to vital structures such as Mental foramen, Inferior alveolar
Nerve Canal, Maxillary Sinus, Nasal Cavity.
Angulation and Position of the Implant

CBCT Guided Implant Surgery
 Type and size of the planned implants, its position within the bone, its relationship to
the planned restoration and adjacent teeth and/or implants, and its proximity to vital
structures can be determined before performing surgery.
 This is possible with integration of CBCT scans with CAD/CAM technology and 3 D
Printing.
 Computer generated surgical guides can be fabricated from the virtual treatment plan.
 These surgical guides are used by the implantologist to place the planned implants in
the patient’s mouth in the same position as in the virtual treatment plan, allowing more
accurate and predictable implant placement and reduced patient morbidity.

Virtual Implant Placement
Fabrication of Surgical Guides

1 : Panoramic radiography should be used as the imaging modality of choice for
initial evaluation.
2: Use intraoral periapical radiography to supplement the preliminary information
from panoramic radiography.
3: Do not use cross-sectional imaging including CBCT as an initial diagnostic
imaging examination.
4: The radiographic examination of any potential implant site should include cross-
sectional imaging orthogonal to the site of interest.
5: CBCT should be considered as the imaging modality of choice for preoperative
cross-sectional imaging of potential implant sites.

6: CBCT should be considered when clinical conditions indicate a need for augmentation
procedures or site development before placement of dental implants, Assessment of
impacted teeth in the field of interest, Evaluation of prior traumatic injury.
7: CBCT imaging should be considered if bone reconstruction and augmentation procedures
have been performed to treat bone volume deficiencies before implant placement..
8: In the absence of clinical signs or symptoms, use intraoral periapical radiography for the
postoperative assessment of implants. Panoramic radiographs may be indicated for cases
with multiple implants.
9: Use cross-sectional imaging immediately postoperatively only if the patient presents with
implant mobility or altered sensation, especially if the fixture is in the posterior mandible.
10: Do not use CBCT imaging for periodic review of clinically asymptomatic implants.

 Department of Oral Medicine and Radiology
Presenter
Moderator

 CBCT have made it the choice for exploring and handling Trauma, Imaging of midfacial and
orbital fractures including dentoalveolar fractures, post fracture evaluation.
 Examination of the precise location and extension of pathologies such as odontogenic and
non-odontogenic tumors, cysts of the jaws, Osteomyelitis, etc.
 Pathologic calcifications (e.g., tonsilloliths, lymph nodes, salivary gland stones) can be
recognized in terms of location and distinguished from possibly noteworthy calcifications,
such as those occurring in carotid artery.
 Pre operative assessment and localization of impacted teeth and odontomes.
 3 D printed models derived from CBCT Scans can be used in simulation of surgeries / mock
surgeries especially in orthognathic surgery cases.
 3D reconstructions – Aid in patient education.
Oral and Maxillofacial Surgery

 CBCT images are also employed for pre- and post-surgical evaluation of bone graft
receiver sites and to assess osteonecrotic changes of the jaws like medication-
related osteonecrosis of the jaw.
 The morphologic appearances and degree of lesions in the para nasal air sinuses are
predominantly well seen, although CBCT imaging does not provide suitable soft
tissue contrast.
 CBCT derived images are helpful for pre-treatment assessments of patients with
obstructive sleep apnea and to conclude suitable surgical method.

Paramedian fracture mandible – not visible
on panoramic radiograph
Coronal view (CBCT) sections taken in the
paramedian area – visible fracture line.

Fracture of the Maxillary sinus – Multiplanar orthogonal slicing.

Multiple comminuted fractures involving
NOE.

 CBCT is a very useful tool in diagnosing apical lesions
 CBCT used as a tool to assess whether the lesion was of endodontic or non-endodontic origin.
 CBCT superior to 2-D radiographs in detecting fractured roots.
 Inflammatory root resorptions.
 Extent of Cervical caries/abrasion.
 Tooth morphology and complex root canal morphologies. (Ex : Dens invaginatus, denticles)
 Multiplanar sections of CBCT is helpful in locating fractured or separated root canal instruments
within the root canal.
Endodontics

• Identification of potential accessory canals in teeth with suspected complex morphology based on conventional imaging.
• Identification of root canal system anomalies and determination of root curvature.
• Diagnosis of dental periapical pathosis in patients who present with non-specific clinical signs and symptoms, who have
poorly localized symptoms associated with an untreated or previously endodontically treated tooth with no evidence of
pathosis identified by conventional imaging and in cases where anatomic superimposition of roots or areas of the
maxillofacial skeleton is required to perform task-specific procedures.
• Diagnosis of non-endodontic origin pathosis in order to determine the extent of the lesion and its effect on surrounding
structures.
• Intra-or post-operative assessment of endodontic treatment complications, such as overextended root canal obturation
material, separated endodontic instruments, calcified canal identification and localization of perforations.
• Diagnosis and management of dentoalveolar trauma, especially root fractures, luxation and/or displacement of teeth and
alveolar fractures.
• Localization and differentiation of external and internal root resorption or invasive cervical resorptions.

Cervical Resorption
IOPA Sagittal/CS Axial Section

Periodontology
 Precise measurement of intra-bony defects.
 Analysis of Buccal and Lingual Cortices.
 Evaluate of furcation involvement, dehiscence, fenestration defects, and
periodontal cysts.
 Assessment of postsurgical consequences of regenerative periodontal treatment.
 3 D Reconstructions – Patient education about bone loss and periodontal status.

 Localization of Ectopic, Impacted and Supernumerary Teeth.
 Assessment of Root Resorption, Both from Ectopically Erupting Teeth as Result of
Orthodontic Treatment Side Effect.
 Quantitative and Qualitative measurement of Bony Dimensions in All Three Planes of
Space.
 Evaluation of facial asymmetry.
 Evaluation of Pre and Post treatment assessment of arches.
 Evaluation of Cleft lip and Palate.
 Airway Analysis.
 Evaluation of Temporomandibular Joint.
Orthodontics

1. Decision to order a CBCT scan should be based on the patient’s history, clinical examination and the
presence of an appropriate clinical condition and assure the benefits to diagnosis and/or the treatment plan
outweigh the potential risks of exposure to radiation, especially in the case of a child or young adult.
2. Use CBCT only when the clinical question for which imaging is required cannot be answered adequately by
lower dose conventional dental radiography or alternate non-ionizing imaging modalities.
3. Do not use CBCT solely to facilitate the placement of orthodontic appliances such as aligners and computer
bent wires or to produce virtual orthodontic models.
4. Design CBCT protocols to be task specific and to incorporate the imaging goal for the patient’s specific
presenting circumstances. The protocol includes considerations of exposure (mA and kVp), minimum, image-
quality parameters (e.g. number of basis images, resolution), and restriction of the field of view (FOV) to
visualize adequately the region of interest.
5. Do not perform a CBCT, if only 2D projected images derived from CBCT are to be used for diagnostic
purposes.

 One of the significant part of forensic dentistry is age estimation in which CBCT can be used
efficiently.
 Enamel is generally resistant to alterations beyond normal wear and tear; conversely, the
pulp dentinal complex displays physiologic and pathological changes with progressing age.
Characteristically, to create skeleton for sex determination, personal identification.
 Digital forensic facial reconstruction algorithms verify these changes, extraction and
sectioning of teeth if necessary, which is not always a practicable choice. CBCT, however,
affords a non-invasive substitute.
 Evaluation of Maxillofacial can develop an array of facial profile based on the bony anatomy.
Forensic Applications

 Use of CBCT in an otolaryngology is to identify less complicated disease conditions
quickly, cheaply and with lower radiation dose compared to a MDCT examination.
 Sinusitis, a common inflammatory disease involving the maxillofacial skeleton, is
often of odontogenic origin. (Imaging of Sino nasal pathology in relation to
dentition)
 CBCT not only provides diagnostic information of the status of extension of
periapical lesions into the maxillary sinuses but also provides reliable information on
the septa of the sinus and presence of exostoses.
Otolaryngology
Lata et al. (2018) – Opinion of ENT Specialists on CT Vs
CBCT Diagnosis
(1) Same as CT: 58 (53.1%)
(2) Less than CT: 27 (25%)
3) More than CT: 25 (21.9%)

 Paranasal Sinus Imaging, Sinonasal pathologies and Tooth Relations
 Pre- Endoscopic sinus surgery
 Maxillofacial and Nasal Trauma
 Temporal Bone Pathologies
 Middle/Inner Ear Malformation
 Cochlear Implant Visualization
 Ossicular Chain Malformations
 Obstructive Sleep Apnoea
 Airway Imaging
 Naso Lacrimal Gland - CBCT with Dacryocystography with some iodine contrast
media for lachrymal canaliculi and sac is used to check blockade in nasolacrimal duct.

3 D Stereophotogrammetry
Stereophotogrammetry is based on photographing objects by a pair of
configured cameras and combining photos taken from two different
directions to create 3D models.
CBCT Scanners with improved photographing aids in the assessment of
soft tissue asymmetries.

Improved Resolution.
Faster Scanning compared to the current CBCT Scanners.
Reduced Motion artefacts.

 CBCT TECHNOLOGY already in clinical usage includes:
1. 3 –Dimensional printing of implant stents using CAD/CAM.
2. CBCT use in orthodontic analysis –skeletal analysis,dental analysis
using anato-models,facial soft tissue analysis.
3. CBCT for facial reconstruction.
4. Surgical simulation and sleep apnoea management.
5. Surface acquisition technology|virtual patient
6. Intra-oral scanning and CBCT – complex and advanced orthodontic
procedures.

 Future advances in CBCT technology includes:
1. Improved x-ray tube ,detector design efficiency and function.
2. Larger variation in field of view, including single tooth imaging.
3. Improvements in post processing reconstruction algorithms and
merging dual energy photo scans to limit metal artifacts.
4. Enhanced software application like merging intraoral/facial scans
with CBCT and single tooth imaging.
5. Simulate treatment strategy ,procedures and outcome.
6. Merging robotic dynamic navigation tools with CBCT technology.

Hardware Improvements :
Improved Algorithms for noise reduction.
Improved Quality of sensors.
Beam Configuration and Beam Geometry.
Software Improvements :
Artefact Reduction softwares.
Softwares for cephalometric analysis of facial skeleton. (Dolphin, NemoCeph)
Software for demonstration of Visual Treatment Objectives.

SOFTWARE MANUFACTURER USES
CS 3D CARESTREAM DENTAL, NY, USA USER FRIENDLY,
IMAGE
MANIPULATTION
DOLPHIN 3D DOLPHIN IMAGING, CA, USA CEPHALOMETRIC
ANALYSIS
EASY GUIDE KEYSTONE DENTAL, MA, USA USER FRIENDLY,
IMAGE
MANIPULATTION
PROCERA SOFTWARE NOBEL BIOCARE, USA IMPLANTS
PLANMECA ORTHOSTUDIO PLANMECA OY, FINLAND ORTHODONTIC

Contrast-enhanced cone-beam computed tomography (CBCT) imaging is used for
evaluating neurovascular stents and their relationship to the parent artery or vascular
pathologies such as arteriovenous malformations (AVMs) and dural arteriovenous
fistulas (dAVFs) in the context of surrounding anatomical structures.
Used in Neurovascular Imaging of Brain Parenchyma.

Improved Image reconstruction algorithms are incorporated into CBCT imaging.
For Image Guided Radio therapy.

Portable
Used for Intra Operative Applications
Intraoperative imaging aids in the
radiographic surgical assessment of the
repair and fixation in the operating room,
The use of intraoperative CBCT/CT can
reduce the need for a second surgery, as the
inadequacies of the surgery being performed
can identified by CT imaging in the OT.
The advent of intraoperative imaging
methods have minimized the need for
revision surgeries and thereby morbidity and
ultimately improved clinical outcome

xCAT ENT CBCT –XORAN TECHOLOGIES

 CBCT is a technical advancement of CT imaging that uses a cone beam acquisition
geometry and FPD to provide relatively low-dose imaging with high isotropic spatial
resolution acquired with a single gantry revolution.
 Efficient use of the X-ray beam in CBCT imaging produces a relatively low x-ray tube
power requirement, which, along with flat panel detection and limited anatomic
coverage, has facilitated the production of compact CBCT scanners suitable for use in an
office-based setting.
 There is a Scope for further research on improving the limitations of CBCT, such as
improvisation of the contrast resolution, reduction of image noise, Standardization of HU
and exposure parameters.

 Schulze, R., Heil, U., Gross, D., Bruellmann, D., Dranischnikow, E., Schwanecke,
U., & Schoemer, E. (2011). Artefacts in CBCT: a review. Dento maxillo facial
radiology, 40 5, 265-73 .
 Bhoosreddy AR, Sakhavalkar PU. Image deteriorating factors in cone beam
computed tomography, their classification, and measures to reduce them: A
pictorial essay . J Indian Acad Oral Med Radiol 2014;26:293-7.
 Nagarajappa AK, Dwivedi N, Tiwari R. Artifacts: The downturn of CBCT image. J
Int Soc Prev Community Dent. 2015 Nov-Dec;5(6):440-5.
 Brüllmann D, Schulze RK. Spatial resolution in CBCT machines for
dental/maxillofacial applications-what do we know today? Dentomaxillofac
Radiol. 2015;44(1):20140204.
 Prashant P Jaju. CONE BEAM COMPUTED TOMOGRAPHY A Clinician’s Guide to
3D Imaging. Ist Edition. Jaypee Publishers. New Delhi.
References

 White S. C.,Pharoah, M. J. Oral radiology: Principles and interpretation. St.
Louis, Mo: Mosby/Elsevier. 2009
 Venkatesh E, Elluru SV. Cone beam computed tomography: basics and
applications in dentistry. Journal of istanbul University faculty of Dentistry.
2017;51(3 Suppl 1):S102.
 Pavan Kumar T, Sujatha S, Yashodha Devi BK, Nagaraju Rakesh SV. Basics of
CBCT Imaging. J Dent Orofac Research. 2013;13(1):49-55.
 Abramovitch K, Rice DD. Basic principles of cone beam computed tomography.
Dent Clin North Am. 2014 Jul 1;58(3):463-84.
 Maret D, Vergnes JN, Peters OA, Peters C, Nasr K, Monsarrat P. Recent Advances
in Cone-beam CT in Oral Medicine. Curr Med Imaging. 2020;16(5):553-564.
 Lechuga L, Weidlich GA. Cone beam CT vs. fan beam CT: a comparison of image
quality and dose delivered between two differing CT imaging modalities. Cureus.
2016 Sep 12;8(9).

 Venkatesh E, Elluru SV. Cone beam computed tomography: basics and
applications in dentistry. J Istanb Univ Fac Dent. 2017 Dec 2;51(3 Suppl
1):S102-S121.
 Jacobs R, Salmon B, Codari M, Hassan B, Bornstein MM. Cone beam computed
tomography in implant dentistry: recommendations for clinical use. BMC Oral
Health. 2018 May 15;18(1):88.
 Alshehri AD, Alamri HM, Alshalhoob MA, Arabia S. CBCT applications in
dental practice: A literature review. Oral and maxillofacial surgery.
2010;36(26.86).
 .P. Sarment, A.M. Christensen, The use of cone beam computed tomography in
forensic radiology, Journal of Forensic Radiology and Imaging (2014).
 Lata S, Mohanty SK, Vinay S, Das AC, Das S, Choudhury P. "Is Cone Beam
Computed Tomography (CBCT) a Potential Imaging Tool in ENT Practice?: A
Cross-Sectional Survey Among ENT Surgeons in the State of Odisha, India.
Indian J Otolaryngol Head Neck Surg. 2018 Mar;70(1):130-136.
 Erten O, Yılmaz BN. Three-Dimensional Imaging in Orthodontics. Turk J
Orthod. 2018 Sep;31(3):86-94.

 White S. C.,Pharoah, M. J. Oral radiology: Principles and interpretation;
2nd south asia edition, St. Louis, Mosby/Elsevier. 2019
 Pauwels R, Jacobs R, Singer SR, Mupparapu M. CBCT-based bone
quality assessment: are Hounsfield units applicable?.
Dentomaxillofacial Radiology. 2015 Jan;44(1):20140238.
 Kumar M, Shanavas M, Sidappa A, Kiran M. Cone beam computed
tomography-know its secrets. Journal of international oral health:
JIOH. 2015 Feb;7(2):64.
 Cone Beam CT and 3D imaging: A Practical Guide,Caruso P; 2014; Kindle
Edition;Springer’s publishers.
 IAOMR position paper on CBCT ; extracted online from IAOMR website.

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