Object Localization and CBCT in Dentistry PDF

12/22/2023 Dr. Noha El-kersh Lecturer of oral & maxillofacial radiology 1 2D imaging 2 1 12/22/2023 3 Approaches for object localization • Right angle technique • Tube shift technique • = Buccal Object rule • =Clark’s rule • 3D imaging modality CT/CBCT 3 1)Right angle technique 5 2 ...

12/22/2023 Dr. Noha El-kersh Lecturer of oral & maxillofacial radiology 1 2D imaging 2 1 12/22/2023 3 Approaches for object localization • Right angle technique • Tube shift technique • = Buccal Object rule • =Clark’s rule • 3D imaging modality CT/CBCT 3 1)Right angle technique 5 2 12/22/2023 --The periapical radiograph localizes the impacted canine in the mesiodistal and superoinferior dimensions, the maxillary occlusal radiograph provides information in the buccolingual dimensions. --The combined information allows the clinician to locate the impacted tooth in all three dimensions, which is necessary for planning the surgical approach to expose the canine crown for subsequent orthodontic tooth movement. 6 7 3 12/22/2023 2) Tube shift technique = Buccal Object rule =Clark’s rule Horizontal shift (SLOB) 8 The application of this principle can be easily remembered by the acronym  SLOB: same lingual, opposite buccal 9 4 12/22/2023 (A) A radiopaque object on the lingual surface of the mandible (black dot) may appear apical to the second premolar. (B) When another radiograph is made of this region angulated from the mesial, the object appears to have moved mesially with respect to the second premolar apex (“same lingual” in the acronym SLOB). 10 (A) An object on the buccal surface of the mandible may appear apical to the second premolar. (B) When another radiograph is made of this region angulated from the mesial, the object appears to have moved distally with respect to the second premolar 11 5 12/22/2023 The tooth is positioned palataly 12 Localization by vertical shift Objects that move with the central ray are located behind The canine is palataly positioned 13 6 12/22/2023 14 What is Computed Tomography? Computed tomography (CT), considered by many to be among the top five innovations in medicine. The word “tomography” is derived from the Greek words “tomos” (slice) and “graphe” (drawing)—CT produces images of sections of the body. 15 7 12/22/2023 A Brief History on Computed Tomography: ▪1979 Godfrey Hounsfield shares Nobel Prize in Medicine with Alan Cormack who developed the image reconstruction mathematics used in CT imaging •Current Full body CT takes about 20 seconds 16 17 8 12/22/2023 Medical-Grade CT scans were associated with many disadvantages including : - Availability - Cost - Radiation exposure to the patient 18 CBCT 19 9 12/22/2023 CBCT It uses a conical beam and it gives all the information of a CT but, at 1/8th the radiation dose and at a lower cost. C= CONE B= BEAM C= COMPUTED T= Tomo –Graphy Tomo= section Graphy= representation 20 21 10 12/22/2023 CONE-BEAM CT vs MSCT 22 CONE-BEAM CT vs MSCT 1. 2. 3. Cone shaped x-ray beam Only one or two 360 degree rotations Low radiation dose 1. 2. 3. 2D fan shaped x-ray beam Hundreds of rotations High radiation dose 23 11 12/22/2023 ➢The scanning software collects the data and reconstructs it, producing what is termed a digital volume or raw data or DICOM files with file extension of “dcm” Digital Imaging and Communication in Medicine (the universal format for 3-dimensional images in the medical field ) ➢The digital volume data can then be manipulated and visualized with specialized software. For example: Ondemand, Anatomage, Icat, Bluesky, Romexis, Dolphin,etc… 28 12/22/2023 29 29 12 12/22/2023 Image display 30 Orthogonal planes 31 13 12/22/2023 Principles of CBCT imaging 32 3D module 33 14 12/22/2023 3D module 34 Dental volume reconstruction (DVR module) 35 15 12/22/2023 Dental volume reconstruction (DVR module) 36 Cross section views 37 16 12/22/2023 Cross section views 38 38 CBCT terminology Always describe CT findings as densities, • (hyperdense) • (hypodense) • (isodense) -Higher the density the whiter it is (towards bone)……hyperdense -Lower the density the darker it is (towards air)…….hypodense -Brain here is the reference density and thus isodense 39 17 12/22/2023 CBCT terminology Pixel Picture element 40 CBCT terminology Voxel Volume element In CBCT terminology voxel is used instead of pixel, since it is referring to volume and not to a 2-dimensional space 41 18 12/22/2023 Spatial Resolution Voxel size • 0.4 x 0.4 x 0.4 mm • 0.3 x 0.3 x 0.3 mm • 0.2 x 0.2 x 0.2 mm • 0.1 x 0.1 x 0.1 mm • 0.08 x 0.08 x 0.08 mm • 0.07 x 0.07 x 0.07 mm Size Resolution The smaller the voxel the better the image resolution. 42 CBCT terminology Field of view(FOV) 29 --- 860 µSv 43 19 12/22/2023 APPLICATIONS of CBCT in dentistry 44 1) IMPLANT SITE ASSESMENT 1) Provides cross section view of alveolar bone height, width, and angulations 2) Measures accurate distance from vital structure such as inferior alveolar canal in mandible and maxillary sinus 45 20 12/22/2023 Measures relative bone density 46 Misch Classification 47 21 12/22/2023 How to decide the implant size? by keeping in mind the safety distance to different vital structures 48 COMPUTER-GUIDED SURGERIES 49 22 12/22/2023 Workflow for guided implant surgery 50 2) Endodontic Applications 1) Diagnosis of periapical pathology 2) Assessment of improper endodontic treatment 3)Canal morphology 4) Evaluation of root fractures and trauma 51 23 12/22/2023 52 52 3) ORTHODONTICS 1. Used in identification of root resorption 2. Display of position of impacted or supernumerary teeth 3. Relation to adjacent structure 53 24 12/22/2023 4) MAXILLOFACIALPATHOSIS • Useful in assessment of trauma • Visualizing the extent and degree of involvement of any lesion in the oral cavity or the maxillofacial region 54 Images can be viewed in axial coronal and sagittal planes 55 25 12/22/2023 Limitations of CBCT 1) Poor soft tissue contrast- 56 Limitations of CBCT 2) Beam hardening (Metal) artifacts The presence of metallic objects such as filling or metallic crowns produce streak artifacts. 57 26 12/22/2023 58 Thank you 58 27