Basic Principles of Cone Beam Computed Tomography Kenneth Abramovitch, DDS, MS, Dwight D. Rice, DDS  Dental Clinics  Volume 58, Issue 3, Pages 463-484 (July 2014) DOI: 10.1016/j.cden.2014.03.002 Copyright © 2014 Elsevier Inc. Terms and Conditions

Fig. 1 Standard anatomic planes of imaging used for multiplanar reconstructions in cone beam computed tomography (CBCT) and multidetector-row computed tomography. (Modified from Washington CM, Leaver DT. Principles and practice of radiation therapy. Philadelphia: Mosby; 2004.) Dental Clinics 2014 58, 463-484DOI: (10.1016/j.cden.2014.03.002) Copyright © 2014 Elsevier Inc. Terms and Conditions

Fig. 2 (A) NewTom 3G. This supine CBCT scanner was one of the first commercially available units in North America. It was replaced by units that scanned patients seated with the head in an upright position. (B) The Accuitomo 170 (J. Morita USA, Irvine, CA). (C) The Scanora 3Dx (Soredex, Milwaukee, WI). (D) The CS 9300 (Carestream Health, Rochester, NY). (E) The Orthophos XG 3D (Sirona USA, Charlotte, NC). (F) The i-CAT FLX (Imaging Sciences International, Hatfield, PA). (G) The NewTom 5G in patient entry (left) and patient scan (right) positions. This unit is currently manufactured by QR srl, Verona, Italy. (H) The SkyView CBCT scanner (MyRay, Imola, Italy) in patient entry (left) and patient scan (right) chair positions. Dental Clinics 2014 58, 463-484DOI: (10.1016/j.cden.2014.03.002) Copyright © 2014 Elsevier Inc. Terms and Conditions

Fig. 2 (A) NewTom 3G. This supine CBCT scanner was one of the first commercially available units in North America. It was replaced by units that scanned patients seated with the head in an upright position. (B) The Accuitomo 170 (J. Morita USA, Irvine, CA). (C) The Scanora 3Dx (Soredex, Milwaukee, WI). (D) The CS 9300 (Carestream Health, Rochester, NY). (E) The Orthophos XG 3D (Sirona USA, Charlotte, NC). (F) The i-CAT FLX (Imaging Sciences International, Hatfield, PA). (G) The NewTom 5G in patient entry (left) and patient scan (right) positions. This unit is currently manufactured by QR srl, Verona, Italy. (H) The SkyView CBCT scanner (MyRay, Imola, Italy) in patient entry (left) and patient scan (right) chair positions. Dental Clinics 2014 58, 463-484DOI: (10.1016/j.cden.2014.03.002) Copyright © 2014 Elsevier Inc. Terms and Conditions

Fig. 3 (A) Cylindrical shape and measurement characteristics of the field of view (FOV) for CBCT. (B) The different FOV option sizes from the Vatech CBCT (Vatech America, Fort Lee, NJ). Many CBCT units now have the capability of scanning a range of FOV sizes. Dental Clinics 2014 58, 463-484DOI: (10.1016/j.cden.2014.03.002) Copyright © 2014 Elsevier Inc. Terms and Conditions

Fig. 4 Basis-image capture for a hypothetical CBCT rotational scan of the cervical spine. Two basis-image capture sequences are depicted in this diagram as the machine rotates counterclockwise from Position 1 to Position 2. An arrow depicts the counter-clockwise rotation. CBCT scans routinely capture in the range of 100 to 600 basis images per rotational scan. (Modified from Zhen X, Yan H, Zhou L, et al. Deformable image registration of CT and truncated cone beam CT for adaptive radiation therapy. Phys Med Biol 2013;58(22):7979–93.) Dental Clinics 2014 58, 463-484DOI: (10.1016/j.cden.2014.03.002) Copyright © 2014 Elsevier Inc. Terms and Conditions

Fig. 5 Examples of multiplanar reconstructions. The upper example (A) is constructed by One Volume viewer software (J. Morita USA). The lower (B) reconstruction is by CS 3D Imaging Software (Carestream Health, New York). Dental Clinics 2014 58, 463-484DOI: (10.1016/j.cden.2014.03.002) Copyright © 2014 Elsevier Inc. Terms and Conditions

Fig. 6 Examples of secondary reconstructions from various CBCT software programs. (A) Two-dimensional (2D) panoramic reconstruction. Although a CBCT scan is not indicated solely for panoramic imaging, many imaging software packages can reconstruct panoramic images from the storage data. (B) Implant planning with 2D reconstructions and a tracing of the mandibular nerve. (C) Implant planning with 2D/3-dimensional (3D) reconstructions. (D) Bilateral reconstructions of the temporomandibular joints in coronal and sagittal sections. (E) Sagittal reconstruction without (top) and with (bottom) Airway Measurement tool from InVivo 5.2 imaging software (Anatomage, San Jose, CA). When the airway is traced in the airway measurement window, the program wizard computes the volume of the airway space. Threshold values for compromised airway volumes have not yet been determined for this software. Dental Clinics 2014 58, 463-484DOI: (10.1016/j.cden.2014.03.002) Copyright © 2014 Elsevier Inc. Terms and Conditions

Fig. 6 Examples of secondary reconstructions from various CBCT software programs. (A) Two-dimensional (2D) panoramic reconstruction. Although a CBCT scan is not indicated solely for panoramic imaging, many imaging software packages can reconstruct panoramic images from the storage data. (B) Implant planning with 2D reconstructions and a tracing of the mandibular nerve. (C) Implant planning with 2D/3-dimensional (3D) reconstructions. (D) Bilateral reconstructions of the temporomandibular joints in coronal and sagittal sections. (E) Sagittal reconstruction without (top) and with (bottom) Airway Measurement tool from InVivo 5.2 imaging software (Anatomage, San Jose, CA). When the airway is traced in the airway measurement window, the program wizard computes the volume of the airway space. Threshold values for compromised airway volumes have not yet been determined for this software. Dental Clinics 2014 58, 463-484DOI: (10.1016/j.cden.2014.03.002) Copyright © 2014 Elsevier Inc. Terms and Conditions

Fig. 6 Examples of secondary reconstructions from various CBCT software programs. (A) Two-dimensional (2D) panoramic reconstruction. Although a CBCT scan is not indicated solely for panoramic imaging, many imaging software packages can reconstruct panoramic images from the storage data. (B) Implant planning with 2D reconstructions and a tracing of the mandibular nerve. (C) Implant planning with 2D/3-dimensional (3D) reconstructions. (D) Bilateral reconstructions of the temporomandibular joints in coronal and sagittal sections. (E) Sagittal reconstruction without (top) and with (bottom) Airway Measurement tool from InVivo 5.2 imaging software (Anatomage, San Jose, CA). When the airway is traced in the airway measurement window, the program wizard computes the volume of the airway space. Threshold values for compromised airway volumes have not yet been determined for this software. Dental Clinics 2014 58, 463-484DOI: (10.1016/j.cden.2014.03.002) Copyright © 2014 Elsevier Inc. Terms and Conditions

Fig. 7 (A) Sagittal temporomandibular joint reconstruction from projection data processed from a full quota of basis images in the projection data set. (B) Sagittal temporomandibular joint reconstruction from a shorter exposure scan that has fewer basis images in the projection data and resulting volumetric data set. There is less detail and contrast resolution in the resulting image display than with projection data from a full quota of basis images used for construction of the volumetric data set. Dental Clinics 2014 58, 463-484DOI: (10.1016/j.cden.2014.03.002) Copyright © 2014 Elsevier Inc. Terms and Conditions

Fig. 8 Two CBCT scanners from Sirona USA. The Galileos (top) has a charge-coupled image-intensifier detector. The Orthophos XG 3D unit (bottom) has the smaller flat-panel detector. The detectors are demarcated with dotted outlines. Differences between the two are described in the text. Dental Clinics 2014 58, 463-484DOI: (10.1016/j.cden.2014.03.002) Copyright © 2014 Elsevier Inc. Terms and Conditions

Fig. 9 Distortion patterns produced by image detectors. (A) Grid type X is the type of grid-distortion pattern produced by the image-intensifier detector that affects the image construction and is subsequently noted in the image display. There is distortion of the image grid when moving away from the center. (B) With flat-panel detectors (ie, grid type Y) the image receptor area receiving the signal from the flat-panel detector’s scintillator is flat. Therefore, even at more distant areas from the center of the grid, there is minimal to no distortion of the grid pattern. Dental Clinics 2014 58, 463-484DOI: (10.1016/j.cden.2014.03.002) Copyright © 2014 Elsevier Inc. Terms and Conditions

Fig. 10 Comparative reconstructions of two different scans of the same posterior left maxillary quadrant from a scanner with a flat-panel detector (left) and one from a charge-coupled device image intensifier (right). The improved image quality and the higher signal-to-noise ratio are noted in the left image. (Courtesy of Dr Bruno Azevedo, Western University, Pomona, CA.) Dental Clinics 2014 58, 463-484DOI: (10.1016/j.cden.2014.03.002) Copyright © 2014 Elsevier Inc. Terms and Conditions

Fig. 11 Beam hardening and streak artifact in CBCT image reconstructions. (A) Axial section with dental implant in #18 region highlighted by black arrow. (B) Beam-hardening artifact is indicated by red arrows. The green arrows depict streak artifact. (C) The locations of cross-sectional and parasagittal reconstructions are shown. (D) The effect of beam hardening simulating peri-implantitis and alveolar bone defects in the cross-sectional and parasagittal reconstructions. (E) The effect of streak artifact creating the outline of a “ghost” implant (as well as other radiopaque streak outlines) in the cross-sectional reconstruction. The streak artifact makes it more difficult to discern the validity of the cortical bone outlines. (Courtesy of Dr. Gerald Marlin, Washington, DC.) Dental Clinics 2014 58, 463-484DOI: (10.1016/j.cden.2014.03.002) Copyright © 2014 Elsevier Inc. Terms and Conditions