Cone Beam Computed Tomography (CBCT)

• Cone Beam Computed Tomography (CBCT) is a medical imaging technique using X-rays.
• It creates detailed 3D images, focusing on bones and soft tissues
• CBCT is primarily used in dentistry, oral surgery, and orthodontics
• It has applications in ENT (Ear, Nose, and Throat) and maxillofacial surgery

How CBCT Works

• CBCT uses a cone-shaped X-ray beam, unlike traditional CT scanners with fan-shaped beams.
• The cone-shaped beam rotates around the patient, capturing multiple images.
• A single scan involves positioning the patient in the scanner and rotating the X-ray machine 360 degrees.
• This captures data from different angles to create high-resolution images.
• Captured 2D images (X-ray slices) are processed by computer software.
• The 2D images are reconstructed into 3D images or models of the examined area.

CBCT Features

• Creates three-dimensional images, offering a detailed view of anatomical structures compared to 2D X-rays.
• Allows high-resolution images for precise diagnoses and treatment planning, especially in dentistry and oral surgery.
• Uses lower radiation than conventional CT scanners, making it safer for repeated imaging in dental treatments.
• CBCT scans are faster than traditional CT scans, typically taking only a few minutes to complete.

Image Quality

• Pixel is the unit of measurement for the quality of a normal (2D) image.
• A 2D image comprises small squares, and the more of them there are, the better the resolution.
• Voxel measures the quality of a 3D image; Voxels are cubes arranged next to each other, on top of each other, etc.
• Tomography relies on slicing.
• Tomo = Slicing
• The more and smaller the pixels of image = the Higher the resolution

Image Types

• 2D Periapical X-rays and 3D CBCTs are options.
• CBCT allows movement in all directions of an image.
• CBCT allows for the ability to disassemble a structure within the image.

Axial Slices

• Axial slices refer to cross-sectional images taken in the axial plane (transverse plane) of the body.
• CT and CBCT divide the body in horizontal slices.
• Axial slices represents a thin section that is captured from top to bottom, or superior to inferior.

Hounsfield Unit

• The Hounsfield Unit (HU) is a scale used in CT (Computed Tomography) imaging.
• It measures the density of tissues and materials.
• It enables quantifying how different tissues absorb X-rays, with each type of tissue appearing as different shades of gray.
• The Hounsfield scale assigns a numerical value to each tissue.
• This helps radiologists differentiate between tissues and structures.
• CT and CBCT images are captured in 2D slices, then are reconstructed in 3D using a algorithm

CT scanner

• A CT scanner rotates around the patient and takes multiple 2D cross-sectional slices.
• The slices are also called "images" of the body.
• Data is captured using a fan-shaped X-ray beam.
• Each slice captures a thin layer of the body, which are then stacked to represent different layers.
• CBCT uses a cone-shaped X-ray beam
• CBCT captures multiple angles of a scanned area, typically around the head and neck or the maxillofacial region.
• Data from 2D slices are sent to a computer system.
• The computer reconstructs a 3D image using mathematical algorithms (mathematical tomography).
• Algorithms treat 2D slices like layers or building blocks, forming a 3D volume when stacked.

Conventional panorama

• Tomography of panorama is Mechanical.
• A rotating X-ray machine captures detailed images.
• Creates a broad image that includes structures from both sides of the face (Right & Left).
• Panorama images display mesiodistal dimensions
• Panorama images do NOT display Right & left, or Buccolingual dimensions
• CBCT displays Buccolingual dimensions
• Panorama images magnify images
• It is difficult to assess the Actual Size of something in a panorama
• Panorama images can may have distorted or unclear areas, which can hinder diagnosis.
• CBCT images are able to determine of the thickeness of the maxilla/mandible

Panoramic vs CBCT Images

• Conventional panoramic images cannot accurately determine the true thickness of bone (Mandible or maxilla).
• CBCT Reformatted panorama provides the ability to measure the thickness of the bone.
• CBCT Reformatted panorama Utilizes customization of panorama.
• CBCT tracing creates an accurate depiction of the arch, and identifies the ammount of bone to work with.

Type of Tomography

• CBCT offers Volume elements (2D Images) from multiple angles
• Conventional panorama is Mechanical
• CBCT images are 2D images of multiple angles.
• CBCT uses a Cone-shaped X-ray beam.
• CT images use Fan-shaped X-ray beam
• CBCT machines use Area detector, CT machines use Line(s) of detectors
• CBCT images use Single Rotation, CT images use Axial Rotations
• The voxel are isotropic with CBCT (they are equal in all 3 dimensions ) Actual Size 1:1, Voxel are anisotropic (not equal in size - longest dimensions is in the axial slice) with CT

CBCT vs CT

• CBCT images scan the Craniofacial region (Head & Nick) only, CT scans the whole Body
• CBCT images use a Higher scatter beam
• CBCT machines are Compact (used in dental clinics), CT machines are Large
• CBCT machines are Convenient, while CT machines are less so
• CBCT images have Poor soft tissue Resolution, good soft tissue Resolution due to High X-ray output with CT

Field of View

• The FOV determines the extent of anatomical structures included in the image.
• FOV size can vary, from imaging the entire head or jaw to a focused region (like a single tooth).
• The smaller the area, the less the dose, and the higher quality of the image
• Small area results in a low dose and a higher quality image faster
• A large area results in a a higher dose and a lower quality image slower

Example Applications of Varying the FOV

• Large FOV: Used to image the entire craniofacial region for complex cases such as jaw fractures, TMJ disorders, or sinus imaging.
• Medium FOV: Used in orthodontics to analyze the alignment of teeth and jaw structure, or assess bone structure for dental implants.
• Small FOV: Commonly used in endodontics (root canal procedures) or for single-tooth imaging, wherever focus is important.
• A scout image is a preliminary image taken before the actual imaging scan.
• The scout is used to define the scan range, and give an overview of the area to be scanned.

Image

• The order of field of view from largest to smallest is: Scout > Maxillofacial > Biarch > Arch > Quadrant > Segment

Digital Images

• DICOM is the file type of the images sent from the radiology professional
• The DICOM Viewer is the program used to view the images
• The images can be sent via CD
• Examples of DICOM Viewers include - BlueSky plan - Planmeca Romexis

Display Parameters

• Density = degree of blackness of the processed radiograph
• Contrast = range of densities on the radiograph
• [ the difference between black, grey and white ]
• Sharpness = the ability to produce sharp outlines of objects
• Resolution= the ability of an imaging system to distinguish between small structures or details within the body, a critical factor in determining the clarity and quality of the image

3D Volume Rendering

• An essential technique in modern dental imaging and maxillofacial surgery.
• Converts 2D slice data into a 3D model
• Allows clinicians view and assess complex anatomical structures from different angles
• This results in more accurate diagnoses and treatment planning

Cuts

• Axial: Horizontal cut with movement from up and down to view Anterior & posterior – left & right
• Coronal: Vertical cut with its movement from Anterior to posterior to view vertical dimensions (UP& Down) of Right & left sides
• Sagittal (Named after sagittal suture of parietal bone): Vertical cut its movement from Right to Left to view Anterior & posterior - vertical dimensions (UP& Down)
• In medical imaging cross-section cuts in refer to slices of an object, body, or structure made perpendicular at specific planes (axial, sagittal, .coronal)

Image types

• Assesment requires Bucco lingual width
• Cross-section cuts = Bucco lingual cuts (perpendicular cut on arch not oblique cuts, because oblique cuts are not at the actual size )
• For Implant purpose all cuts are cross sectional