CBCT units can be categorized according to patient positioning, field of view, clinical functionality, and detector type. Clinicians should consider all these. cone-beam computed tomography (CBCT) specifically dedicated to imaging the maxillofacial region . image noise. CBCT: TECHNICAL FUNDAMENTALS . Ann-Marie DePalma, RDH, reviews some of the basics about CBCT, or cone- beam computed tomography, to facilitate your discussions with.
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The introduction of cone beam computed tomography CBCT devices, changed the basucs oral and maxillofacial radiology is practiced. CBCT was embraced into the dental settings very rapidly due to its compact size, low cost, low ionizing radiation exposure when compared to medical computed tomography.
Alike medical CT, 3 dimensional evaluation of the maxillofacial region with minimal distortion is offered by the CBCT. This article provides an overview of basics of CBCT technology and reviews the specific application of CBCT technology to oral and maxillofacial region with few illustrations. The discovery of X — rays in by Sir Wilhelm Conrad Roentgen was an incredible era in the history of medicine.
Diagnostic imaging over the last few decades, turned basicw to be much more refined owing to addition bssics various imaging technology with complex physical principles. Threedimensional imaging 3D evolved to meet the demands of advanced technologies in delivering the treatment and at the same time responsible for the evolution of new treatment strategies. Considering the limitations superimpositions, distortions etc. Hounsfield, in introduced computerized transverse axial scanning 1 which lead to introduction of Computed Tomography CT.
However the high cost, limited access, and high radiation exposure, were the main drawbacks for under utilization of CT in dentistry. The cost effective technology of CBCT, led to speedy ingress into the field of dentistry with demand for commitment of dental professionals and dental educators to explore the applications of CBCT technology.
The purpose of this review is to provide an insight into 3D imaging with CBCT technology, its basic concepts, advantages, disadvantages and applications in dentistry with few illustrations. Conventional CT equipment using a fan shaped X ray beam captures a series of axial plane slices or from a continuous spiral motion over the axial plane.
Depending upon manufacturers, the scanning time of CBCT equipment varies from nearly 5 to 40 seconds. The captured 2D images are instantaneously conveyed to the computer, which reconstructs them, using modified Feldkamp algorithm into the anatomical volume for viewing at 1: The data is in the Digital Imaging and Communications in Medicine DICOM format, which enables ease of telecommunication and usage with other third party imaging software.
CBCT, Principle of basis image acquisition where in X-ray source and Image receptor reciprocate basicw patient — degrees to acquire —2D cephalometric images Basis images. Image acquisition and display modes.
Most of the CBCT equipment comes with userfriendly viewing software containing basic 3D imaging tools. Third party software are accessible at a wide range of price, which provide extensive tools to analyze and do treatment plans.
Besides these, third party software are used to prepare surgical guides, virtual study prototypes, and laser generated resin models, easing the process of diagnosis, treatment plan and delivery of the treatment 56.
The utmost hands-on benefit of CBCT in dental imaging is the facilitation to interact with the data and create images imitating those generally employed in clinical settings for example panoramic, cephalometric, or bilateral multiplanar projections of the temporomandibular joint. These reconstructed views, consecutively interpreted, judged, and measured for diagnostic and treatment-planning purposes Figure 3.
The CBCT provides following display modes apart from basic orthogonal views, as explained below 789 Nonorthogonal slicing Figure 3e 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 MPR. 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.
This enables to trace the jaw arch to display a trace view, providing acquainted panorama like view Figure 3f. Cross-sectional oblique coronal view: This function creates a set of successive cross-sectional images Figure 3g bawics 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.
This function enables to display the thickened MPR slices by adding up adjacent voxels Cct 3h. However, they can be negatively affected by the superimposition of multiple structures analogous to 2D imaging. This function enables one to selectively display voxels within a data set to visualize volume. Direct volume rendering and indirect volume rendering are the two frequently used tools with this function. Direct volume rendering involves picking an arbitrary threshold of voxel values, below or above which all gray values are excluded.
Numerous techniques are available; however, the most commonly used is maximum intensity projection MIP. MIP displays an image Figure 3i with the voxels, which have highest density values within a particular thickness. Voxel values that are below an arbitrary threshold are excluded.
MIP images are ideal for locating impacted teeth, for TMJ assessment, for assessment of fractures, for craniofacial analysis, for surgical follow-up, and for visualization of soft tissue calcifications. Two kinds of views are possible: IVR is ideal for visualization and analysis of craniofacial conditions and determination of relationships of various anatomic features, such as the inferior alveolar canal to the mandibular third molar. High radiation dose, cost, availability, longer scanning time, poor resolution and difficulty in interpretation have led to restricted use of CT in dentistry.
Few of these problems can be overcome with CBCT, which provides a number of potential advantages for Oral and Maxillofacial imaging, compared with conventional CT This procedure fulfils the individual needs, reduces unnecessary exposure to the patient and minimizes scattered radiation that would degrade cbcy quality. CBCT machines provide isotropic voxels i. Although CT voxel surfaces can be as small as 0.
This sub-millimeter resolution of CBCT is precise enough for measurements in oral and maxillofacial applications fulfilling the need of exactness required for implant site assessment and orthodontic analysis 9 The single rotation, which is used in CBCT technology to acquire basis images for 3D imaging usually requires scan time ranging from basicx to 40 seconds comparable to panoramic radiography.
This short scanning time is advantageous in plummeting the artifacts owing to patient movement CBCT delivers an equivalent patient radiation dose of 5 to 74 times that of a panoramic X – ray or 3 to 48 days of background radiation 15 CBCT offers significant dose reductions of between Display modes unique to maxillofacial imaging: Besides providing interrelated images in orthogonal planes CBCT data sets can be segmented nonorthogonally MPR to provide oblique, curved planar reformation distortion free simulated panoramic images and, serial cross sectional reformation Figure 3all of which can be utilized to accentuate precise anatomic structures and diagnostic functions.
These features are very essential considering the intricate oral and maxillofacial anatomy. Measurements calculated on the screen are free basiccs distortion and magnification. Furthermore, true 3D visualization of the dataset including ray sum, Basivs and 3D computer vasics models Figure 3 are available 10 Availability of artifact suppression algorithms and increasing number of projections have led to low level of metal artifact, mainly in secondary reconstructions intended for seeing the jaws and teeth The clarity of CBCT images is affected by artifacts, noise, and poor soft tissue contrast.
An artifact is any distortion or error in the image that is unrelated to the subject being studied. This impairs CBCT image quality and limit adequate visualization of structures in the dento-alveolar region. Artifacts can be due to beam hardening results in cupping artifact and streaks and dark bandsPatient-related artifacts Patient motion resulting in unsharpness of the reconstructed imageScanner-related artifacts circular or ringshaped and cone beam—related artifacts partial volume averaging, undersampling, and cone-beam effect Image noise is due to large volume being irradiated during CBCT scanning resulting in heavy interactions with tissues producing scattered bascs, which in turn leads to nonlinear attenuation by the detectors.
This additional x-ray detection is called noise and contributes to image degradation Poor soft tissue contrast: Three factors cbvt the contrast resolution of CBCT, which include increased image noise, the divergence of the x-ray beam and numerous inherent flat-panel detector-based artifacts 23 Since then, a number of CBCT machines have been introduced into the market and the information of some of these has been summarized in the Table 1.
Radiographic examination is essential in diagnosis and treatment planning in dentistry. Apart from compressing three-dimensional anatomy of the area being radiographed into a two-dimensional image, 2D imaging possesses unique inherent limitations including magnification, distortion, and superimpositiontogether leading to misrepresentation of structures CBCT produces 3D images useful for many oral and maxillofacial situations Figure 5 that can guide in diagnosis and assessment of disease severity, planning and delivery of treatment, and follow-up.
Missing teeth replacement by dental implants demands accurate assessment of the implant site for the successful implant placement and to avoid injury to contiguous vital structures.
Most commonly 2D radiographs and in specific cases, conventional CT were employed for assessment of the implant site. Currently CBCT is the ideal choice Figure 6which 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 2526 Furthermore, a surgical guide is prepared which provides accurate guidance for placement of the proposed implants 25 Unlike Hounsfield unit HU numbers derived from conventional CT, the bone density numbers from CBCT are not accurate and cannot be correlated with HU units considering the image acquisition methods employed in CBCT machines; as a result, bone density numbers derived from this technology cannot be established over a group of CBCT cbt or individuals Fbct lines on the axial and panoramic images indicate the location of the cross-sections.
Apart from information of bone quality and dimensions, the cross-sections reveal the amount of lingual undercut and location of the inferior alveolar canal green. Oral and Maxillofacial Surgery: Because of extensive dbct of CBCT, more dentists are utilizing these to assess oral and maxillofacial injury Figure 7. Considering the limitations of 2D images like structural superimpositions, Baskcs permits precise measurement of surface distances These advantages of CBCT have made it the choice for exploring and handling midfacial and orbital fractures including dentoalveolar fractures Figure 8post fracture evaluation, interoperative visualization of the maxillofacial bones, and intraoperative navigation throughout procedures 31 Intraoperative ability has also been assessed in mandibular fracture fixation CBCT is being used to examine the precise location and extension of pathologies odontogenic and non-odontogenic tumors, cysts of the jaws Figure 9 and Figure 10 as well as osteomyelitis Figure 11 34 MPR is very useful in evaluating dentoalveolar fractures, which are easily missed on 2D imaging.
The present CBCT scan reveals dentoalveolar fracture associated with maxillary anterior teeth in different display modes. The cross-sections revealing expansion and perforation of facial and palatal cortical plates due to radicular bwsics. CBCT scan- Panoramic view AAxial views Bcrossections C and IVR reveal radiographic features sequestration, altered density of trabecular bone, cortical expansion, compression of the mandibular canal of a case of chronic osteomyelitis.
Axial view A showing buccolingual positioning of crown and root of impacted third molar. Panoramic view B and C revealing relationship of third molar with mandibular canal and second molar. Set of cross sections D revealing the relationship with the mandibular canal. Panoramic AAxial B views and C crossections reveal iatrogenic injury accidental sectioning of distal root of second molar, yellow arrow during third molar removal.
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 38 The cbcg appearances and degree of lesions in the para nasal air sinuses are predominantly well seen e.
CBCT derived images are helpful for pre-treatment assessments of patients with obstructive sleep apnea Figure 15 and to conclude suitable surgical method Applications in orthodontics CBCT offers superimposition free images that are self-corrected for magnification, with a practical 1: Some of the orthodontic uses include assessment of palatal bone thickness, skeletal growth patterns, dental age estimation, visualization of impacted teeth tooth inclination and torque, determining available alveolar bone width for buccolingual movement of teeth, upper airway assessment, and for planning orthognathic and facial orthomorphic surgeries 424344 ccbt, 45.
The availability of software like Dolphin and In Vivo Dental together with CBCT images for cephalometric analysis has turned out to be the best means for assessing facial growth, age, airway function, and disturbances in tooth eruption.
CBCT provides pictorial guides for safe placement of miniimplants, evading accidental and irreparable injury to the vital structures 46 Applications in TMJ disorders: CBCT imaging offers multiplanar and possibly three-dimensional images of the condyle and surrounding structures to enable analysis of TMJ and function Figure