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craniofacial imaging-Recent advances

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craniofacial imaging-Recent advances

  1. 1. 3
  2. 2. Ortho radio diagnosis 4
  3. 3. 5
  4. 4. Ortho radio diagnosis clinician is to apply his skills the boundaries of these The real task for the and his techniques within biologic limits. 6
  5. 5. Comprehensive Diagnosis Study cast Analysis Functional Analysis Roentgeno- Cephalometric Analysis Radiographic Analysis Photographi c Analysis
  6. 6. History Nothing materializes as if by magic overnight. Even Roentgen’s discovery depended upon the development and application of three converging thoughts ; Movement of the electrons in a conductor. Phenomena by which materials exert attractive or repulsive forces on other materials. Complete absence of air. ELECTRICITY VACUUM MAGNETISM
  7. 7. Discovery of X-Rays  While experimenting and searching for the invisible light rays on a low pressure Crookes tube, to his surprise a fluorescence screen covered with Barium Platino cyanide started to glow brightly. The screen was on a table some distance away. Wilhem Conrad Roentgen November 8th 1895
  8. 8.  While investigating he accidentally placed his hand between the tube and the fluorescent screen, to be surprised by seeing a faint image of the bones of his hand on the screen.  Tracing back the rays to their source, he found out that the rays were produced, whenever and wherever the cathode rays encountered matter.
  9. 9. His curuosity dint end here..,  He proceeded to make 1st radiograph of human body; he placed his wife’s hand and exposed it for 15 minutes. Anna Bertha
  10. 10.  He termed these rays as “ X- Rays ’’ after the mathematical symbol for the unknown – X, the American way.  These rays were ultimately called as Roentgen Rays.
  11. 11. Early pioneers of oral radiology: Otto Walkhoff, Germany  Took first dental radiograph in1896.  He placed a photographic glass plate in his mouth for 25 minutes to expose to X-Ray beam and obtained the image of crowns of maxillary and mandibular teeth. William Morton and Kells -  Made the first dental radiographs in America.
  12. 12. Later…  An autopowered X-Ray was used by physicians at the turn of the century.  The early X-Ray machine was small enough to be portable, and its tube could be operated on a car battery. Wires leading through a bedroom window.
  13. 13. which radiograph to Prescribe ? According to AOO for a orthodontic treatment a minimum of lateral cephalogram, opg and 3 anterior IOPAs are essential.
  14. 14. Pt presents with orthodontic problem Is the Pt a candidate for orthodontic Rx Obtain lateral Cephalogram Evaluate the pt individual radiographi c needs   Is the Pt heavily restored or exhibits PDL problems   Obtain OPG, Ant IOPAs Obtain complete mouth survey (IOPAs & bitewing) AJODO -1992
  15. 15. Does the Pt have a severe facial asymmetry Does Pt have significant TMJ signs & symptoms If growing, growth modulation or subjecting for surgery Diagnose and treat the patient Obtain TMJ tomograms Obtain hand wrist radiograph Obtain PA Cephalogram   
  16. 16. “An unobstructed or complete view of a region in every direction” Is based on the principle of the reciprocal movement of an X- Ray source and an image receptor around a central point or plane called image layer. PANORAMIC IMAGING
  17. 17.  It is a technique for producing a single tomographic image of the facial structures that include, both the maxillary and mandibular dental arches and their supporting structures.
  18. 18. 20 The 4 Diagnostic regions in OPG Dentoalveolar region Maxillary regionMandibular region TMJ, including retromaxillary region
  19. 19. INTERPRETING: 1) Condylar process and temperomandibular joint 2) Coronoid process 3) Ramus 4) Body and angle
  20. 20. The maxilla can be divided into different major sites for examination: 1) Cortical boundary of the maxilla, including the posterior border and the alveolar ridge 2) Pterygomaxillary fissure 3) Maxillary sinuses, Zygomatic complex, including inferior and lateral orbital rims, zygomatic process of maxilla. Ortho radio diagnosis
  21. 21. 1) Nasal cavity and conchae 2) Temperomandibular joint
  22. 22.  The maxillary sinuses are well visualized on panoramic images.  The borders are entirely outlined with cortical bone, roughly symmetric, and comparable in radiographic density. The borders should be present and intact.
  23. 23. 1) Palatoglossal air space 2) Nasopharyngeal air space 3) Glossopharyngeal air space
  24. 24.  The tongue arching across the film under the hard palate  lip markings  The nasal septum,  Ear lobes,  Nose, and Nasolabial folds.
  25. 25. 1. Teeth number, position and anatomy should be evaluated. 2. Tooth germ positions. 3. Atypical sequence of eruption. 4. Ectopic tooth germs. 5. Over retained primary teeth. 6. Supernumerary teeth.
  26. 26. 7. Pathological root formation. 8. Root resorption. 10. Bone loss, bony pockets. 11. Third molars – orientation, configuration of roots and its relationship to the surrounding structures. 12. Endodontic obturations, crowns, and other fixed restorations, should be noted.
  27. 27. Advantages Disadvantages
  28. 28. 30 Lateral Cephalogram
  29. 29. Ortho radio diagnosis  Although the cephalometric radiograph in standard lateral projection was introduced into orthodontics during 1930s, the method has become routine in recent years.  Today cephalometric analysis has firmly taken place in dentofacial diagnostic procedures.
  30. 30. uses 1. Assessement of the facial skeleton 2. Relationship of the jaw bases 3. Relationship of the axial inclination of incisors 4. Assessment of the soft tissue morphology 5. Growth pattern and direction 6. Localization of the malocclusion 7. Treatment possibilities and limitations.
  31. 31. Cephalometrics is used in three major areas:  Morphological Analysis: By evaluating the sagittal and vertical relations of dentition, facial skeleton and soft tissue profile.  Growth Analysis: By taking two or more cephalograms at different time intervals and comparing the changes.  Treatment Analysis: By evaluating alterations during and after therapy.
  32. 32. Tongue Position: Root: It is usually flat in cases of mouth breathing. In all other cases slight contact of the tongue usually occurs with soft palate. Dorsum: Is high in Class II malocclusion and in deepbite cases. Tip: Is retracted in cases of Class II div 1 malocclusions. In openbite, tip is forward.
  33. 33. The changes in the position of the tongue relate closely to the different types of malocclusion. In Class III the tongue is flat and lies downward and forward. And With Class II tongue is backward.
  34. 34. 36 POSTERIOR ANTERIOR VIEW
  35. 35.  The X-Ray passes in a posterior anterior direction through the skull.  A cassette is positioned vertically in a holding device.  Frontal view is particularly important in cases of dentoalveolar & facial asymmetry, crossbites and functional mandibular displacements.
  36. 36. Uses To detect developmental abnormalities like facial asymmetries. Used to examine the skull for presence of disease, trauma, developmental abnormalities. Used to detect progressive change in the mediolateral dimensions of the skull. It offers good visualization of facial structures including frontal, ethmoidal sinus, nasal fossa and orbits.
  37. 37.  Both the dental midline and skeletal midline is not matching in rest and occlusion. LATEROGNATHY  Here at rest dental midline is matching but in occlusion there is shift of the mandible. LATEROCLUSION At rest At occlusion
  38. 38. 40 Suhana Tabasum 7/F
  39. 39.  Transcranial Projection  Transpharyngeal Projection  Transorbital Projection
  40. 40. Film placement: The cassette is placed flat against the patient’s ear & centered over the TMJ of interest, parallel to the sagittal plane.
  41. 41. Diagnostic information:  Transcranial projection is useful for identifying gross osseous changes on the lateral aspect of the joint only.  We can see the position of the head of the condyle within the fossa, the shape of the glenoid fossa & articular eminence. Closed mouth Open mouth
  42. 42. Film Placement:  The cassette is placed flat against the patient's ear and is centered to the external auditory meatus parallel to the sagittal plane.  Open mouth position.
  43. 43. Structures Shown:  Sagittal view of the medial pole of the condylar head and neck, usually taken in the open mouth position.  This view is effective for visualizing erosive changes of the condyle.
  44. 44. Film Position:  The film is positioned behind the patient's head at an angle of 45° to the sagittal plane & perpendicular to the X-ray beam. Position of Patient:  The patient head is bend 100 down so that canthomeatal line is horizontal.  Here patient mouth is opened maximally to avoid superimposition of the articular eminence.
  45. 45. Diagnostic information:  The entire mediolateral dimension of the articular eminence, condylar head & condylar neck is visible, so is particularly useful for visualizing condylar neck fractures.
  46. 46. Limitations of the 2D images 1. A conventional headfilm is a 2D representation of a 3D object. 2. Cephalometric analyses are based on the assumption of a perfect superimposition of the right and left sides about the mid sagittal plane.
  47. 47. 3. A significant amount of external error, known as radiographic projection error, is associated with image acquisition. a) Magnification b) Distortion c) Patient positioning 4. In cephalometry, errors are most likely in locating the landmarks due to the lack of well defined outlines, hard edges and shadows.
  48. 48. 52 Change is the only CONSTANT. In orthodontics there are many ADVANCES taken place, especially in the area of Craniofacial Imaging.
  49. 49. 53 “Imaging beyond imagination”
  50. 50. 1. In terms of spatial distribution of the picture elements. 2. In terms of different shades of grays of each of the pixels. The term digital refers to the numeric format of the image content. Images Conventional ANALOG PROCESS Contemporary DIGITAL PROCESS
  51. 51. What is an Analog image ? An analog image, such as a radiographic film, has virtually an infinite number of elements, with each element represented by a continuous gray scale. What is a digital image ? A digital image is a matrix of square pieces, or picture elements (pixels), that form a mosaic pattern from which the original image can be reconstructed for visual display.
  52. 52. Characteristics of digital images  A digital image is composed of picture elements (pixels) that are arranged in a 2-dimensional rectangular grid.  A pixel is the smallest element of a digitized image. Radiographic images generally use gray color with an intensity value between 8 bits (0 to 256 shades of gray).
  53. 53.  Image resolution refers to the degree of sharpness of the image. Resolution is determined by the number of pixels per given length of an image (pixels/mm), the number of gray levels per pixel (bits).
  54. 54. PRINCIPLE OF DIGITAL IMAGING Normal X-ray Digital X-ray Silver halide grains in x- ray films perceived as different shades of gray by the human eye due to varying densities Silver halide grains are replaced by small light- sensitive electronic sensors which produce an electric signal depending on the voltage recorded by the sensor.
  55. 55. CONVENTIONAL (ANALOG) DIGITAL CEPHALOGRAM
  56. 56. CONVENTIONAL DIGITAL OPG IOPA
  57. 57. INDIRECT DIRECT a) Scanner b) Photostimulable Phosphor plate (PSP) a) Charged Coupled Device (CCD) b) Complementary metal oxide semiconductor (CMOS) c) Charge injection device. (CID) METHODS OF IMAGE ACQUISITION
  58. 58. • X-ray source • Intraoral sensor • Computer It is used to digitize, process and store information received from the sensor within 5 – 10 sec and display image on computer screen. Radiovisiography
  59. 59. Image enhancement: 1. Adjusted image is an improved version of the original one. 2. Most image enhancement operations are applied to make the image visibility more appealing. 3. This can be enhanced by increasing contrast, optimizing brightness. 4. Brightness & contrast 5. Color 6. Digital subtraction radiography
  60. 60. Color:  Most digital systems currently provide opportunities for color conversion of gray scale images also called pseudo-color.  Neither diagnostically nor educationally useful.
  61. 61. 1. About 50% - 70% less radiation than conventional radiography 2. Immediate picture 3. Image improvable with image processing 4. Elimination of darkroom, film, and chemical processing 5. Reduce cost of daily maintenances 6. Easy to share by digital networking 7. Easy to store. 8. Easy for client education. BENEFITS OF DIGITAL RADIOGRAPHY
  62. 62. 1) Expensive. 2) Spare parts are expensive. 3) System, network, and database safety and security. 4) Potential training needs. 5) Cross infection. DRAWBACKS OF DIGITAL RADIOGRAPHY
  63. 63. Computers With Tiny Carbon Tubes On Silicon Chips  It includes use of extremely tiny carbon 'nanotubes' instead of copper conductors to interconnect parts within integrated circuits (ICs).  One advantage of using carbon nanotube within integrated circuits is that these interconnects have the ability to conduct very high currents, more than a million amperes of current.
  64. 64. Digital subtraction radiography:  Subtraction in digital radiography is another image enhancement method.  When 2 images of the same area in the mouth are registered and the image intensities of the corresponding pixels are subtracted, a uniform difference image is produced.
  65. 65.  The 1st image can be subtracted from the 2nd one to identify changes that may have occurred during a certain time period.  If there is a changes seen between pre and follow up examination, these changes show up as loss or gain of hard tissues.
  66. 66.  In order for subtraction radiography to be diagnostically useful, it is imperative that the both the radiographs taken at different intervals must be reproducible.  BUT IT IS VIRTUALLY IMPOSSIBLE. Some form of mechanical standardization if done, it may reduce the reliance on image processing and will generally produce better results.
  67. 67. Ortho radio diagnosis 71 XERORADIOGRAPH Y
  68. 68.  It is a technique of making dry radiographs by a totally photoelectric process, using metal plates coated with a semiconductor, such as selenium.  Special features- 1. Prononced edge enhancement. 2. High contrast. 3. A choice of positive & negative displays. 4. Good detail. 5. Does not require silver halide crystal containing films, hence no dark room processing. 6. Reduced patient exposure.
  69. 69.  In this technique instead of conventional film, selenium coated photoreceptor plate with uniformly distributed electrostatic charge is used as the image receptor.  The charged plate is held in a light-tight cassette in a plastic bag and is exposed to x- ray.  The X-rays beam is left as a charged pattern on the plate. Selenium plate Selenium plate ++ ++ + + + X-Ray exposure Charged pattern on the plate Selenium plate Lines of forces ++ ++ + + + ++++++++++++++++ Selenium plate Toner distribution of charges
  70. 70. uses 1. Mammography. 2. Sialography. 3. Height of the alveolar crest is better visualized. 4. Periodontal and periapical assessment. 5. Caries seen more readily. 6. Tmj tomography.
  71. 71. Ortho radio diagnosis
  72. 72.  The graphical information contained within the cephalogram is transformed into numbers (digits) that the computer can store, retrieve and manipulate.  3 possible approaches may be used to perform a cephalometric analysis - Digitization
  73. 73. 1 • Manual tracing 2 • COMPUTER AIDED ANALYSIS • Computer aided- landmarks are located manually & digitized into a computer system, then the computer completes the analysis 3 • COMPLETELY AUTOMATED. • Cephalogram is scanned into the computer first, computer automatically locates landmark and performs ceph analysis.
  74. 74. Two methods – 1) DIGITIZING TABLET – it is a peripheral computer device that has 2 parts, tablet (writing surface) & stylus. Data input can be 2 modes - POINT AND STREAM MODE. 2) DIRECTLY ON THE SCREEN - Here the image is fed directly into the computer, and the mouse is clicked to identify the landmark points. Once digitization is complete, any analysis can be performed in seconds
  75. 75. Ortho radio diagnosis
  76. 76. Spatial spectroscopy – Image pixels that are in regions of high intensity gradient are identified as edges, & these edges are assumed to be object boundries:  it involves 4 steps – 1) Remove noise 2) label pixels according to edginess 3) Connect pixels and label edges 4) Find landmarks based on position or relationship to a labeled edge. 3 • COMPLETELY AUTOMATED • Cephalogram is scanned into the computer first, computer automatically locates landmark and performs ceph analysis.
  77. 77. Signal to noise ratio • The useful signal for any imaging system needs to be compared with backround noise. • In analog film – backround noise is comparable to the base density and fog. • Signal noise ratio improves with increased radiation dose for all systems.
  78. 78. 83
  79. 79.  Introduced in medicine in early 70’s – Godfrey Hounsfield. Tomography means an image of layer of tissue, and a computer is necessary to generate the pictures; hence the name – COMPUTED TOMOGRAPHY
  80. 80. Equipment - Scanner (movable X ray table + gantry) - Computer system - Display console
  81. 81. An image of a layer within the body is produced while the images of the structures above and below that layer are made invisible by blurring. PRINCIPLE
  82. 82. Remnant radiation of this beam is detected by scintillation crystal. Analog signal is then fed into computer Digitized and analysed by mathematical algorithm Data is reconstructed as an axial tomographic image.
  83. 83. AXIAL SAGITTAL CORONAL
  84. 84. To acquire a volume of data, 2 scanning modes are possible- 1) SEQUENTIAL – the table with the patient is positioned and the attenuation data are acquired. Then the table is moved to a next position, and a new acquisition is made. 2) SPIRAL – the table moves from the initial position to the end position while the X-Ray attenuation data are acquired.
  85. 85.  Single slice CT – From an X-Ray source, a fan beam X- Ray is emitted through the imaged object towards a single array of detectors.  Multiple slice CT – Multiple slices can be produced using adjacent detector arrays.
  86. 86. 9 1
  87. 87. Ortho radio diagnosis
  88. 88.  Conventional radiography has the following short comings, 1. Difficulty in assessing position (buccal/palatal) 2. Difficulty in assessing level and extent of resorption of adjacent teeth
  89. 89. CT scan was advised  Can determine the exact position of an impacted tooth.  Clear serial sections may be taken at graduated depth.  This technique allows the elimination of superimposition of other structures.
  90. 90. Position for axial section Position for coronal section
  91. 91. 96 AXIAL Ortho radio diagnosis Right left Right left
  92. 92. Right left
  93. 93. 98 CORONAL Ortho radio diagnosis RightleftRightleft
  94. 94.  It completely eliminates the superimpositions of images of structures outside the area of interest.  High contrast resolution - it can differentiate b/w the tissues of less then 1%.  Geometric accuracy.  Tissue Characterization.  Digital image processing. Expensive Radiation dose.
  95. 95. Limitations of CT Scan However, even though the images are obtained at different planes, the analysis by the orthodontist is still limited. The images are seen as 2 dimensional on film and computer screen.
  96. 96.  The CT images can be manipulated to undergo a three- dimensional reconstruction of the image by a procedure called INTERPOLATION.  The original voxel - rectangular units, should be dimensionally altered into multiple cuboidal voxels.
  97. 97.  Creation of these new cuboidal voxels allows the image to be reconstructed in any plane without loss of resolution.  The final image can be fed through a computer aided design system and viewed on a computer screen.
  98. 98. Steps :- 1. Image which is obtained consists of individual pixels along with the face of the volume called VOXEL . 2. Cuboid voxels can be created from the original rectangular voxel by INTERPOLATION.
  99. 99. 104 Magnetic Resonance Imaging Ortho radio diagnosis
  100. 100. MECHANISM OF MRI  The theory of MRI is based on the magnetic properties of an atom.  Atomic nuclei spin about their axis much as the earth spins about its axis.  In nuclei in which protons and neutrons are evenly paired, the spin of each nucleon cancels that of another, producing a net spin of zero.  Where as the nucleus of the element hydrogen contains a single, unpaired proton and therefore acts as a magnetic field.
  101. 101. 106 N S
  102. 102.  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.
  103. 103. 108 N S Externally applied magnetic field Higher energy state Lower energy state
  104. 104.  Energy in the form of an electromagnetic wave in the radiofrequency range from an antenna coil is directed to tissue.  Those protons that have a larger frequency matching that of the electromagnetic wave absorb energy and shift or rotate away from the direction induced by the magnet.
  105. 105.  After removing the application of an radiofrequency signal, 2 events occur simultaneously- 1) The radiation of energy is released from the body. T1 relaxation time 2) Return of the nuclei to their original state. T2 relaxation time  This energy is detected by the sensors and used to construct the MR image by computer.
  106. 106.  When images are displayed, intense signals show as and weak ones as and intermediate as shades of gray.  Cortical bone and teeth with low presence of hydrogen are poorly imaged and appear black.
  107. 107.  Indications  Assessing diseases of the TMJ  Cleft lip and palate  Tonsillitis and adenoiditis  Cysts and infections  Tumors  Contraindications  Patients with cardiac pacemakers.  Patients with cerebral metallic aneurysm clips.  Stainless steel and other metals produce artifacts.
  108. 108. Advantages  Magnetic forces - does not produce any biological side effects.  Non invasive technique and can be used in most patients. Short comings  Inability to identify ligament tears or perforations  Cannot be used in patients suffering from claustrophobia.
  109. 109. The limiting factor in the use of MRI in Orthodontics Apart from economic cost, the functional modality of MRI depends on the presence of large numbers of hydrogen nuclei in the tissues being imaged. Because hard tissues such as bone, enamel and dentin contain few if any free hydrogen nuclei, the use of this diagnostic tool is restricted in orthodontics to the visualization of the cartilaginous components of temperomandibular joint.
  110. 110. 115 Ortho radio diagnosis
  111. 111.  For 3D imaging, 3D CT imaging is needed to volumetrically measure the patient’s anatomy.  However for cephalometric analysis, the availability of 2D lateral and frontal is beneficial to indicate landmarks accurately and repeatably in a 3D scene. Ortho radio diagnosis
  112. 112.  To avoid extra radiation dose, and to achieve this geometric relationship, lateral and frontal cepahlograms are computed from the CT data.  In this way an unlimited number of virtual X-Ray images of the skull can be computed.  To compute an virtual image, a bundle of parallel rays are cast through the CT volume.
  113. 113.  The orientation of the virtual X-Ray image plane is perpendicular to the bundle of rays. Therefore, this X-Ray image can be added to the 3D scene as a textured rectangle. Virtual cephalogram computed from the CT volume
  114. 114. Pre op -, mandibular asymmetry with chin deviated to Rt. ( Early loss of right condylar process )
  115. 115. Pre op 3D surface hard tissue representation Linked frontal & lateral virtual ceph Right Left
  116. 116. Virtual planning of a reverse L – osteotomy in the right ramus was planned. Planning for reconstruction of right condylar process & placement of unilateral distractor & osteotomy of coronoid process
  117. 117. Post distraction – 1 week after distractor removal Lengthening of the vertical ramus and improvement in chin projection, and increase in Anterior and Posterior facial height.
  118. 118. 124 Teleradiography Ortho radio diagnosis
  119. 119.  Electronic transmission of radiologic images from one location to another for the purpose of interpretation, consultation or both.  Teleradiology system allow direct digital or digitized film images to be transmitted to distant locations, where they can be viewed and downloaded to hard copy for reading and interpretation.  Transmission of images requires that the image files be in a digital format.
  120. 120. TRANSMISSION OF IMAGES Digital images may be saved in a variety of file formats. Commonly used are - TIFF – tagged image format file. WAN- wide area network. IP - Internet protocol. JPEG – joint photographic expert group.
  121. 121. Transmission and receiving console system Staff monitoring the transmission system.
  122. 122. 128 RAPID PROTOTYPING (RPT)
  123. 123. Prototype; Derived from Latin - "first form"  Rapid Prototyping is a method in which the part is created by a layer-additive process.  By using a specialized software a 3-D CAD model is obtained.  Then the RP machine constructs the part layer by layer until a solid replica of the CAD model is generated.
  124. 124.  Rapid prototyping takes virtual designs (from CAD model), which transforms them into cross sections, and then create each cross section in physical space, one after the next until the model is finished.  It is a WYSIWYG process where the virtual model and the physical model correspond almost identically. WYSIWYG acronym for What You See Is What You Get.
  125. 125. Techniques in Rapid Prototyping 131 Most commercially available RP machines use one of six techniques. They are: 1. Stereolithography (STL) 2. Laminated object manufacture (LOM) 3. Selective laser sintering (SLS) 4. Fused deposition modeling (FDM) 5. Solid ground curing (SGC) 6. 3-D ink jet printing
  126. 126. Basic steps in Prototyping 1. CAD model creation 2. Conversion to STL format 3. Slice the STL format 4. Layer by layer construction 5. Clean & finish
  127. 127. Pre treatment – elevation in palatal mucosa
  128. 128. Image from STL file after elimination of all the tissues and structures
  129. 129. Findings from prototype models  Crown of canine was tipped toward the palate  Was 2.1mm away from the root of maxillary right lateral incisor  Root apex was over the apex of maxillary right first premolar  The model was used as an aid during surgical exposure.
  130. 130. Advantages  Diagnosis & treatment planning  Communication with patients  Surgical access made easier Disadvantages  Exposure to CT radiation  Conventional radiographs still required for records  The COST
  131. 131. Digigraph Equipment -  Computer system  Video camera with light source  Sonic digitizing probe with receptor microphones and  Patient seat with a head holder.  With digigraph, any point can be located in 3 planes of space.
  132. 132. Head holder  More comfortable  Ear rods and forehead clamp. Attached video monitor Images, text, numerical data can be displayed, stored, modified using a light pen or computer keyboard
  133. 133.  Digitizing handpiece with removable, sterilizable tips  Landmark location is recorded in 3 dimensional coordinates (x,y,z)  The time it takes the sound to reach each of the microphones determines the landmark location.
  134. 134. Digitization 142  4 microphones are arranged strategically above the Pt’s head. A sound emitting probe is placed on various landmarks directly on the Patient’s head.  Each landmark is recorded by emitting a sound.  The computer calculates the exact position of landmark in 3D by analyzing the sound arriving at each microphone. Ortho radio diagnosis
  135. 135. With the Pt in position, lateral and frontal cephalometric points are easily digitized.
  136. 136. 144 Ortho radio diagnosis
  137. 137. The 2 principle differences that distinguishes CBCT from traditional CT are – 1) The type of imaging source detector complex. 2) Method of data acquisition. 14 Ortho radio diagnosis
  138. 138. 146 • X-Ray source is a high output rotating anode generator. • Uses a fan shape X- Ray beam. • Image sensors used solid state detectors arranged in a 360 degree array around patient. • In contrast to CT it uses a low energy fixed anode tube similar to that used for OPG machines. • Uses a cone shaped X- Ray beam. • The image sensors used are special image intensifier & solid state sensor.
  139. 139.  CBCT uses 1 rotation sweep of the patient. Image data can be collected for a complete maxillofacial volume or limited area of interest.  Scan times vary from 10 – 90 sec.  Dose is also reduced.
  140. 140. Possible Fields of View Include (A) 3 Inches, (B) 6 Inches, (C) 9 Inches, And (D) 12 Inches.
  141. 141. • Extended FOV scanning incorporating the craniofacial region is difficult to incorporate into cone-beam design because of the high cost of large-area detectors. • The expansion of scan volume height has been accomplished by one unit (iCAT Extended Field of View model) by the software addition of two rotational scans to produce a single volume with a 22-cm height.
  142. 142. IMAGE DISPLAY • The availability of CBCT technology provides the dental clinician with a great choice of image display formats. • The volumetric data set is a compilation of all available voxels and, for most CBCT devices, it is presented to the clinician on screen as secondary reconstructed images in three orthogonal planes (axial, sagittal, and coronal), usually at a thickness defaulted to the native resolution
  143. 143. STANDARD DISPLAY MODES OF CBCT VOLUMETRIC DATA. (A) VOLUMETRIC 3D REPRESENTATION OF HARD TISSUE SHOWING THE THREE ORTHOGONAL PLANES IN RELATION TO THE RECONSTRUCTED VOLUMETRIC DATA SET; EACH ORTHOGONAL PLANE HAS MULTIPLE THIN-SLICE SECTIONS IN EACH PLANE. (B) REPRESENTATIVE AXIAL IMAGE. (C) REPRESENTATIVE SAGITTAL IMAGE, AND (D) REPRESENTATIVE CORONAL IMAGE
  144. 144. Types of CBCT machines
  145. 145. Available CBCT Imaging Systems – Worldwide Unit Model(s) Manufacturer/Distributor Accuitomo 3D Accuitomo - XYZ Slice View Tomograph/Veraviewpacs 3D J. Morita, Japan AUS: Henry Schein Halas Galileos Galileos Sirona Dental Systems, Germany AUS: Sirona Dental Systems Hitachi CB MercuRay / CB Throne Hitachi Medical Systems, Japan AUS: Unknown iCAT i-CAT* / Platinum Imaging Sciences Int'l, USA AUS: Body Logic Australia ILUMA Ultra Cone Beam CT Scanner MTEC Imaging, USA/Kodak AUS: Currently unavailable KaVo 3D exam * Announced at IDS 2007 KaVo, Germany AUS: Currently unavailable Newtom 3G / NewTom VG/5G QR, Inc. Verona, Italy AUS: Inline Systems Picasso Series Trio / Pro / Master E-Woo Technology, Korea AUS: Integradent PreXion 3D TeraRecon Inc., USA AUD: Currently unavailable Promax 3D Planmeca OY, Helsinki, Finland AUS: Henry Schein Halas Scanora 3D CBCT Soredex , Helsinki, Finland AUS: Currently unavailable SkyView 3D Panoramic Imager My-Ray Dental Imaging, Italy AUS: Currently
  146. 146. FOV 8 cm x 8 cm FOV 16 cm x 4 cm FOV 16 cm x 6 cm upper jaw TMJ FOV 16 cm x 6 cm lower jaw FOV 16 cm x 8 cm FOV 16 cm x 10 cm FOV 16 cm x 11 cm FOV 16 cm x 13 cm FOV 23 cm x 17 cm
  147. 147. 3D Facial photo • Planmeca ProFace® is an exclusive 3D facial photo system available for all of Planmeca 3D X-ray units. • This integrated system produces a realistic 3D facial photo and CBCT image in a single imaging session. • can also take a separate 3D face photo without exposing your patient to any radiation.
  148. 148. Create a 2D photo series automatically Pre and post-operative comparisons Measure distances and relationships between bone and soft tissue Superimpose images for comparison Deviate images for instant viewing of changes
  149. 149. Impacted Canines • In the past, orthodontists have used the tube shift technique to compare two periapical radiographs taken at different beam angles to determine the facial/lingual position of the impacted canine. • This same lingual, opposite buccal rule is helpful in determining whether the impacted canine is labial or lingual to the incisor roots; however, the degree of displacement is difficult to determine • These 3D images are beneficial in determining the proximity of adjacent incisor and premolar roots. • Which can be invaluable in determining the ease of uncovering and bonding and the vector of force that should be used to move the tooth into the arch with a lesser chance of adjacent root resorption
  150. 150. Root Resorption • Most root resorption involved in orthodontic treatment can be readily viewed on periapical radiographs. • However, resorption that occurs on the facial or lingual side of the tooth is difficult to ascertain and quantify with this 2D view. • CBCT scanning allows for better viewing of resorption on either of these surfaces. • Removal of the deciduous canine adjacent to the impacted permanent canine has been shown to be effective if accomplished early.
  151. 151. Fractured Root
  152. 152. Orthodontic Temporary Anchorage Device Placement • CBCT images allow more accurate and dependable views of the interradicular relationships than panoramic radiographs. • These images allow not only more successful placement but also better treatment planning of where these TADs should be placed so that proper force vectors can be used during orthodontic treatment. • CBCT data can be used to construct placement guides for positioning mini-implants between the roots of adjacent teeth in anatomically difficult sites. • The quality of the bone in the proposed placement sites can be evaluated before insertion of the mini-implants. • Quantifying the thickness of the palatal bone can aid in determining the size and location of any TADs that may be treatment planned for the palate.
  153. 153. Asymmetry Evaluation • It can be difficult to evaluate the bony asymmetry of orthodontic patients using cephalometric and panoramic radiographs. • Direct measurements can be made of these structures with CBCT imaging by comparing the right and left sides. • Software companies are adding the ability to extract (segment) the mandible or maxilla from the CBCT image and evaluate the bone independent of the other structures. • In addition, the unilateral nature of posterior cross bites can be diagnosed more specifically. • A determination of an asymmetric maxilla or mandible can be accomplished more easily by viewing and measuring the bones in 3D.
  154. 154. TMJ Degenerative Changes • Conventional tomography has been used extensively for the evaluation of TMJ hard tissues; however, technique sensitivity and the length of the examinations made it a less attractive diagnostic tool for the dental practitioner. • CBCT images of the TMJ have been shown to provide greater reliability and accuracy than tomographic or panoramic views in detecting condylar erosions. • With temporomandibular dysfunction continuing to be a haunting pathology in some orthodontic cases, it is important to view the anatomy of these patients’ joints carefully before, during, and after orthodontic treatment. • Current software solutions allow the visualization of TMJ osseous elements isolated (segmented) from other surrounding structures.
  155. 155. Soft Tissue • Frontal photographs are used to judge symmetry, but without numerous views from different angles, it is difficult to gain a good feel of facial symmetry. • Using the soft tissue data gathered in the CBCT scan, it is possible to rotate and tilt the head in an infinite number of positions to evaluate symmetry of the soft tissue. • It is difficult to gain a good view of the nose with some CBCT machines because this area is at the edge of the image package. • Recently, various companies have offered photographic imaging packages to coordinate with the CBCT data, using multiple camera locations.
  156. 156. Airway • Using lateral cephalometric radiographs, the orthodontist may evaluate the airway in a 2D manner. • Many studies have been accomplished and various analyses established in this way. • All this evaluation, however, is limited by the fact that we are looking at a flat projection seen in a sagittal or coronal plane. • A 3D view of the airway can be readily available with CBCT imaging.
  157. 157. CBCT airway view displaying the volume of the airway and sinuses. The most constricted region has been located and the minimum axial area calculated
  158. 158. ADVANTAGES • Ray sum or ray casting • Multiplanar reformation • Interactive display modes unique to maxillofacial imaging • Reduced patient radiation dose compared to conventional CT • Image accuracy • Beam limitation • Rapid scan time
  159. 159. DISADVANTAGES 1. It is definitely more expensive than classic two-dimensional radiologic investigations. 2. The dose of ionising radiation generated is greater than in a pantomography investigation. 3. Any movement artefacts affect the whole data set and the whole image rather than just one part. 4. It provides limited resolution of deeper (inner) soft tissues, and MRI and classic CT are better for soft-tissue imaging. 5. It has low contrast range (dependent on the type of x-ray detector). 6. It has increased noise from scattered radiation and concomitant loss of contrast resolution.
  160. 160. LIMITATIONS • Noise and contrast • Image noise • Poor soft tissue contrast
  161. 161.  Orthodontic imaging has come a long way since the “PLASTER ERA” during the times of E.H Angle and Calvin case when plaster was recording medium for dentition as well as facial form.  With advent of impression material, radiographic and photographic film – the orthodontic patient evolved into “FILM ERA”. Despite their limitations, these methods have served orthodontists well as research tools, diagnostic aids and medico-legal records.
  162. 162. We are now in “DIGITAL ERA” in which digital technologies are being used to resolve previous limitations. Continuing evolution in orthodontic imaging and treatment of patients is such that these techniques will be key to future orthodontic practice.
  163. 163. 1) Oral radiology principle & interpretation. White and Pharoah – 5th edition. 2) Craniofacial imaging, 2nd chapter. Graber Vanarsdall & Vig – 4th edition. 3) 3D Cephalometry. Swennen, Schutyser & Hausamen. 4) Color atlas of Radiology. - Klaus and H.F. Wolf. 5) Radiographic cephalometry – Alexander Jacobson. 1st and 2nd edition. 6) Basics of radiography & radiology – Eric whaites. 7) Color atlas, orthodontic diagnosis – T.Rakosi, Irmtrud jonas & T.M.Graber.
  164. 164. 7) Current status and feature needs in craniofacial imaging – orthodontic craniofacial research -2003. 8) Digital imaging in dentistry -DCNA 2000. 9) An algorithm for ordering Pre treatment orthodontic radiographs – AJODO 1992. 10) Rapid prototyping as a tool for diagnosis & treatment planning - AJODO 2006. 11)Automatic computerized radiographic identification of ceph landmarks. AJODO-1998. 12) Reliability of digital cephalometric landmark identification – SEMI IN ORTHOD 2005.

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