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Cbct
This document provides an overview of cone beam computed tomography (CBCT) including its history, components, principles, and applications in dentistry. Some key points: - CBCT was first introduced in the 1990s and provides 3D imaging with lower radiation dose than medical CT. It works by generating a cone-shaped X-ray beam and using a detector to record attenuation data, which is then reconstructed into 3D images. - Components include an X-ray generator, image sensor, and software for image reconstruction. Images are stored in DICOM format. - Advantages include rapid scan time, interactive display modes, and ability to view structures in multiple planes. Disadvantages include potential artifacts and inability to view
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Cbct
- 1. Dr.Rabab Khursheed Cone Beam ComputoTomography
- 2. Contents • What isCBCT? • History • Why 3D? • How does CBCT work? • Principles of CBCT Components used Field of view voxel scan time resolution Dicom file • Artifacts • Advantages and disadvantages • Applications in dentistry • Applications in Orthodontics
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- 4. • Its isthe most significant technological advancement in maxilla facial imaging • It is a form of xray computed tomography • X rays are divergent forming a cone
- 5. History • Cone beamtechnology was first introduced in the European market in 1996 by QR s.r.l. (NewTom 9000) and into the US market in 2001 • October 25, 2013, during the "Festival della Scienza" in Genova, Italy, the original members of the research group:AttilioTacconi, Piero Mozzo, Daniele Godi and Giordano Ronca received an award for the cone-beam CT invention. Hatcher DC -Operational principles of cone beam computed tomography JADA oct 2010
- 6. "Prima Immagine Cone-Beam-1994-07-01-3"by Daniele Godi - Own work.
- 7. Why 3D? • 3D visualization of manifested disease/deformation/malocclusion • diagnostic accuracy • Better understanding • To the point treatment planning
- 8. How does CBCTwork? Xray source Detector Raw data Rotates Records after attenuation by patient tissues Reconstructed by complex algorithms
- 12. Components used • X-raygenerator • Image sensor • Image reconstruction
- 13. X-ray generator • Highvoltage generator which modifies incoming voltage and current to provide the x ray tube with the power needed to produce an x ray beam of desired peak kilo voltage (kVp) and current (mA) • X ray tube- anode cathode tube envelop tube housing • Collimator Size of the anode matters.smaller the size of the anode intensity of the x ray increases
- 14. • Exposure factorscan be controlled manually or automatically • Scout images • KvP 60 to 90 • mA 6 to 10 • Pulsed or continuous x ray generation • 180 or 360 degree rotation of the x ray generator and sensor
- 15. Image sensor • PSP(photo stimulable phosphorus plates) • CCD sensors • FPD (flat panel detector) direct indirect A sensor which has smaller pixel size has better resolution . One pixel can be 0.007 to 0.3mm size. A sensor which has a higher bit rate, can identify more areas of black and white .
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- 18. Field of view •Collimation of x ray beam by adjustment of FOV limits the radiation to one ROI • These depend on the detector size and shape, beam projection geometry and the ability to collimate or not • It is desirable to limit the field size to the smallest volume that can accommodate the region of interest.
- 20. Region of interestbeyond FOV? • Obtaining data from two or more separate scans and superimposing and overlapping the regions of the CBCT data using refrence points, • A software is used to stich or blend the images together • Disadvantage being scanning the regions of interest double times so increase in doage of radiation.
- 23. Voxel • The spatialresolution is determined by individual volume elements called voxels. • These are cubic in nature equal in all dimensions • The principle determinant of voxel size is the pixel size of the detector. Detectors with smaller pixel size capture fewer xray photons per voxel and result in more noise. • To balance it out a good scanner has higher dosage of radiation
- 25. Grayscale • The abilityof a cbct scan to display differences in attenuation. • This parameter is called bit depth of the system and determines the number of shades of grey available to display the attenuation. • All current CBCT machines have 12 bit detectors and are capable of identifying 4096 shades of gray . A 16 bit detector can identify 65,536 shades of grey, but this would mean the file sizes and image processing time would increase by folds.
- 26. Exposure settings • ALARAprinciple • Can controlled either automatic or manual adjustment of kVp or mA • Scout exposure- high energy x rays can be avoided by taking an initial scout exposure, the amount of electrons generated by the patient is registered on the sensor and the exposure settings are adjusted.
- 27. • Can bepulsed or continuous . • Rotation of 180 degrees or 360 degrees
- 28. Scan time • Averagetime for one cbct scan may vary from 7-30 seconds.This is the scan time including the initial scout image scan • It also varies if half a rotation or a full circle rotation is used. • Standard scan- 3-4 seconds, lower resolution , reduced scan time.
- 29. Resolution • The abilityof an image to differentiate between two closely placed objects. • Two types- spatial resolution contrast resolution • Spatial resolution – the ability to visualize the difference between two objects of different radio density • Contrast resolution – ability to differentiate two objects of the same color type.
- 30. DICOM file Cbct producestwo data products • The volumetric image data from the scan • Image report generated by the operator All of these images are svae in the DICOM (digital imaging and communication in medicine) format. This is the international standards organization – refrenced standard for all diagnostic imaging Includes x ray, visible light images and ultrasound
- 31. Artifacts Any distortion orerror in the image that is unrelated to the subject being studied. Occurs at the interface of the material with a completely different radiological property from the subject being imaged • Inherent artifacts • Procedure related artifacts • Introduced artifacts
- 32. Inherent artifacts Can resultfrom limitations in physical processes involved in the accusation of the CBCT data.the beam projection geometry of the CBCT , reduced trajectory rotational arcs and image reconstruction methods produce the following three types of artifacts • Scatter • Partial volume averaging • Cone beam effect
- 33. • Scatter resultsfrom x ray photons that are diffracted from their original path after interaction with matter • The scattered photons that are captured by the sensors contribute to over all image degradation called ‘quantum noise’
- 34. • Partial volumeaveraging happens when the selected voxel size of the scan is larger than the object being imaged. • Boundaries in the resultant image may have a step appearance or homogeneity of pixel intensity level. • Selection of the smallest accusation voxel can reduce this
- 35. • Cone beameffect is a potential source of artifacts , especially in the peripheral portions of the scan volume. • Because of the divergence of the x ray beam as it rotates around the patient in a horizontal plane, structures at the top and bottom of the image are exposed only when the xray source is on the opposite side of the patient. • This results in large image distortion and streak artifacts and peripheral noise. • This is minimized by the incorporation by manufacturers of various forms of cone beam reconstruction. • Clinically it can be reduced by placing the ROI in the horizontal plane of the xray beam.
- 36. Procedure related artifacts •When very few basis images are taken or the time between the images are too long, undersampaling of the object can occur.this leads to aliasing artifacts or striations in the image. • Scanner related artifacts can also appear as a circular projection.This could be due to the misalignment of the xray source to the detector
- 39. Introduced artifacts • Beamhardening • Cupping artifact • Extinction or missing value artifact As an xray beam passes through an object , lower energy photons are absorbed in preference to higher energy photons.This is called beam hardening , which results in two types of artifacts , i. Distortion of metallic structures as a result of differential absorption known as the cupping artifact ii. Streaks and dark bands which when present between two dense objects create extinction or missing artifacts. In clinical practice it is advised to reduce the field of view, modify patient position, or separate the dental arches to avoid scanning regions susceptible to beam hardening
- 42. Effective radiation dosage •FOV>15 cm – 52 to 1073 µSv • FOV 10 to 15cm – 61 to 603 µSv • FOV of < 10 cm- 18 to 333 µSv • Multislice CT -426-1600 µSv • Panaromic – 6-50 µSv • Cephalogram- 2 -10 µSv • IOPA- 2-8 µSv AAOMR
- 45. Patient selection criteria •the ALARA principal must always be applied. • There should be justification of the exposure to the patient so that the total diagnostic benefits are greater than the individual determinant the radiation may cause. • Should be used only when a periapical or an opg cannot provide necessary information for patient diagnosis and treatment planning.
- 46. Required characteristics foran ideal CBCT image for diagnosis • Good density and contrast • Sharpness • Good resolution • Accuracy of image • Free of artifacts • Free of noise
- 47. Advantages • Rapid scantime • Beam limitation • Image accuracy • Reduction in patient radiation dose when compared to medical ct • Interactive display modes • Multiplanar reformatting • 3 dimensional volume rendering • Better images with good spatial resolution • Economical, comfortable and safe Disadvantages • Scatter • Artifacts • Motion artifacts due to increased scan time • Scan volume in sufficiency • Poor contrast resolution, thus soft tissue cannot be viewd • Image noise is detrimental
- 48. European SEDENTEXCT guidelinesfor CBCT (2012)
- 49. Principals 1.History and clinical examination 2.Benefits should outweigh risks 3.New informationto aid the patient 4.Not be repeated routinely 11.Quality assurance programs for setting up each CBCT facility 6.Diagnosis with lower radiation imaging is questionable 5.Reffering dentists must provide sufficient information to radiologists 12.Aids to accurate positioning must always be used 10.Resolution compatible with adequate diagnosis yet low radiation should be used. 7.Thourough clinical evaluation report should be made 9.Use small volume doses where you can 8.Should not be done for soft tissue assessment
- 50. 13.ALL new installations should undergo critical examination for safety 14.CBCT machines should undergo regular routine tests 16.Adequate practical and theoretical training for all those involved 15.European guidleines for radiation protecyion for staff 20.For non dentoalveolar areas, the evaluation should be done by a radiologist 17.Continuing education and training 19.Small FOV for dentoalveolar regions and teeth 18.Dentists who are not previously trained , should be trained
- 51. Justified referrals • Localisedapplications of CBCT for the developing dentition • Generalized application of CBCT for the developing dentition • Dental caries diagnosis • Periodontal assessment • Assessment of periapical disease • Endodontics • Dental trauma • Implant dentistry • Bony pathosis • Facial trauma • Orthognathic surgery • Temporomandibular joint
- 52. • Segmental mandibulectomy •Alveolar fractures • Airway assessment • Root canal volume • 3 D cephalometry
- 54. Limitations • Periapical lesions •Caries • Periodontal problems related to pdl or gingiva • Soft tissue assessment • Very small lesions (smaller than voxel size) • Fractures of the tooth • Root canals, accessory canals • Assessing bone density • Artifacts • High scan time can cause motion artifacts
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- 57. INDIA UNIT MODEL MANUFACTURER NEWTOM3G/NEWTOMVGi QR,Inc ,Italy ACCUITOMO 3D ACCUITOMO- TOMOGRAPH/VERAVIEWPACS 3D J-MORITA,JAPAN KODAK KODACK 9000/9500/9300 CBCT CARESTREAM HEALTH GALILEOS GALILEOS SINORA DENTAL SYSTEMS, GERMANY PROMAX 3D CBCT PLANMECAOY, FINLAND
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- 62. Accuracy and reliabilityof cone-beam computed tomography measurements: Influence of head orientation ,Amr Ragab Et al , AJODO 2011
- 63. Comparison of transverseanalysis between posteroanterior cephalogram and cone-beam computed tomography by Kyung-Min Lee et al , Angle Orthod. 2014
- 64. Three-dimensional monitoring ofroot movement during orthodontic treatment, Robert et al ,Am J Orthod Dentofacial Orthop 2015
- 65. Accurate registration ofcone-beam computed tomography scans to 3-dimensional facial Photographs, Kyung-Yen Nahm, Am J Orthod Dentofacial Orthop 2014
- 66. Accuracy of cone-beamcomputed tomography in detecting alveolar bone dehiscences and fenestrations, Liangyan Sun et al Am J Orthod Dentofacial Orthop 2015
- 67. Impact of cone-beamcomputed tomography on orthodontic diagnosis and treatment planning, Ryan J et al Am J Orthod Dentofacial Orthop 2013
- 68. Diagnostic accuracy of2 cone-beam computed tomography protocols for detecting arthritic changes in temporomandibular joints , SumitYadav, Am J Orthod Dentofacial Orthop 2015
- 69. Incidental findings arisingwith cone beam computed tomography imaging of the orthodontic patient, Sheelagh et al , Angle Orthodontist, Vol 81, No 2, 2011
- 70. Conclusion This technique hugelyexpands the fields for diagnosis and treatment possibilities, not to forget many more research frontiers as well.however CBCT should be used with careful consideration ,it should not be used where 2D imaging suffices.
- 71. • White andPharrow , oral radiology edition 7, 2014 • European SEDENTEXCT guidelines for CBCT (2012) • ICRP – international commission on radiological protection 2007 publication • American academy of oral and maxillofacial radiology 2009 • Prima Immagine Cone-Beam-1994-07-01-3" by Daniele Godi - Own work • Hatcher DC -Operational principles of cone beam computed tomography JADA oct 2010 References
- 72. • Incidental findingsarising with cone beam computed tomography imaging of the orthodontic patient, Sheelagh et al ,Angle Orthodontist,Vol 81, No 2, 2011 • Diagnostic accuracy of 2 cone-beam computed tomography protocols for detecting arthritic changes in temporomandibular joints , SumitYadav,Am J Orthod Dentofacial Orthop 2015 • Impact of cone-beam computed tomography on orthodontic diagnosis and treatment planning, Ryan J et al Am J Orthod DentofacialOrthop 2013 • Accuracy of cone-beam computed tomography in detecting alveolar bone dehiscences and fenestrations, Liangyan Sun et al Am J Orthod DentofacialOrthop 2015 • Accurate registration of cone-beam computed tomography scans to 3-dimensional facial Photographs, Kyung-Yen Nahm, Am J Orthod DentofacialOrthop 2014 References
- 73. • Three-dimensional monitoringof root movement during orthodontic treatment, Robert et al ,Am J Orthod Dentofacial Orthop 2015 • Comparison of transverse analysis between posteroanterior cephalogram and cone-beam computed tomography by Kyung- Min Lee et al , Angle Orthod. 2014 • Accuracy and reliability of cone-beam computed tomography measurements: Influence of head orientation ,Amr Ragab Et al , AJODO 2011
- 74. • ScarfeWC, FarmnaAG, Sukovic P. Clinical applications of cone beam tomography in dental practice. J Can Dent Assoc. 2006;72:75–80. • Ludlow JB, Ivanovic M. Comparative dosimetry of dental CBCT devices and 64-slice CT for oral and maxillofacial radiology. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2008;106:106–114 • Upadhyay M,Yadav S, Patil S. Mini-implant anchorage for en-masse retraction of maxillary anterior teeth: a clinical cephalometric study. Am J Orthod Dentofacial Orthop. 2008; 134:803–810.
Editor's Notes
- #5 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 tomograpohy is called tomograph where as the image produced is called a tomogram.
- #6 Was actually developed for angiography in 1980
- #8 We live in a 3 dimensional world with 3 dimensional people yet we comfortably depend on 2 d images and systems to plan intricate diagnosis and treatment plans
- #9 Any kind of computed tomography consists of an x ray source and detector mounted on a rotating gantry .during rotation of the gantry , the xray source produces radiation while the receptor records the residual x rays after attenuation by the patients tissues.these recordings constitute the raw data that is reconstructed by computer based on complex alogrithms to generate cross sectional images. These basis images are similar to cephalometric images except each one is a little offset from the other.
- #10 CT first scans in slices the reconstructs
- #11 CBCT scans the whole Region of interest, then slices it ..
- #13 1895 roengen
- #14 An x-ray machine is essentially a camera. Instead of visible light, however, it uses X-rays to expose the film. X-rays are like light in that they are electromagnetic waves, but they are more energetic so they can penetrate many materials to varying degrees. When the X-rays hit the film, they expose it just as light would. Since bone, fat, muscle, tumors and other masses all absorb X-rays at different levels, the image on the film lets you see different (distinct) structures inside the body because of the different levels of exposure on the film.
- #15 Center of rotation lies within the center of the object being imaged
- #16 Ccd sensors, the area odf focus is less and requires stiching of the image. Binary system of ???
- #17 One scan can produce about 500 -600 images.each image is known as a basis projection .not only lateral projections, but also antero posterior.
- #19 Minimizes scattered radiation.
- #24 Reducing object to detector distance and increasing object to source distance also gives good resolution but obviously produces magnification of the image Smallrer Fov have larger voxels and better images.
- #25 Pixel- voxel- Accuracy of linear measurements from cone-beam computed tomography-derived surface models of different voxel sizes Janalt Damstra Am J Orthod Dentofacial Orthop 2010,0.25 and 0.4 did not make a difference
- #27 As low as reasonably achievable
- #28 Sensor needs some time to get processed as an image so there is a lag time where there is no registration of the x ray beam , this can be avoided by pulsed. Machines that have an option of pulsed exposure also have longer lifes than the other
- #29 People who could benefit with a lesser scan time- children, a person who cannot stand still.
- #30 The ability of the image to revale fine detail .This is dependent on the pixel size. Cbct has poor contrast resolution.
- #35 For example a voxel of 1mm may contain both bone and adjacent soft tissue , in this case the displayed pixel is not of either bone nor soft tissue .it becomes an average of the brightness of the different tissues.
- #40 Cupping artifacts from beam hardening occur when x-rays passing through the center of a large object become harder than those passing through the edges of the object 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"
- #43 American academy of oral and maxillofacial radiology ICRP 2007 CHART
- #45 1 micro serviet euals 100 milirem , therefore to produce any problems we have to reach above 1000 milirems , 10000 micro serviets..
- #46 European sedentex guidlinesssss 2012
- #50 ICRP – international commission on radiological protection
- #52 They need us to do more good than harm
- #53 Letter to the author airway assessment in 2015 in response to schendel et als article about osp , he stated that the airway is not always static and can change in a person the very next day Moonyung lee 2015 angle orthod newly defined landmarks
- #56 Melissa 2015 angle orthod –only 5% chances of perforating a root
- #65 Mimics software
- #66 Holdaway and park and burstone Facial asymmetry
- #67 Cbct over estimates the amount
- #68 Los angeles, straight c white showed just how important it was to take a cbct when there was an unerupted tooth or severe root resorption
- #69 Accuitomo CBCT scanner, Kyoto japan , small and large leasions