27.1
The following basic termonologies are essential to three dimensional digital imaging language.
Term |
Definition |
| Cone Beam Computed Tomography (CBCT) | Computer-assisted digital imaging in dentistry; this imaging technique uses a cone-shaped x-ray beam to acquire information and present it in three dimensions |
| Cone Beam Volume Tomography (CBVT) | Computer-assisted digital imaging in dentistry; used interchangeably with cone beam volume imaging (CBVI); terms used to differentiate this procedure from medical computed tomography (CT) |
| DICOM Data | The universal format for handling, storing and transmitting three-dimensional images; the acronym refers to Digital Imaging and Communications in Medicine |
| Field Of View (FOV) | The area that can be captured when performing imaging procedures; With CBCT imaging, region of interest of the patient anatomy |
| Multiplanar reconstruction (MPR) | The reconstruction of raw data into images when imported into viewing software to create three anatomic planes of the body |
| Plane, axial | A horizontal plane that divides the body into superior and inferior parts; runs parallel to the ground |
| Plane, coronal | A vertical plane that divides the body into anterior and posterior sides; runs perpendicular to the ground |
| Plane, sagittal | A vertical plane that divides the body into right and left sides; runs perpendicular to the ground |
| Resolution, contrast | The number of gray scale colors available to be chosen for each pixel in the image |
| Resolution, spatial | A measurement of pixel size in multiplanar reconstruction |
| Three-dimensional digital imaging | An image that demonstrates structures in three dimensions |
| Three-dimensional volume rendering | A three-dimensional shape that is created from two-dimensional images |
| Voxel | The smallest element of a three-dimensional image; also referred to as volume element or three-dimensional pixel |
Fundamentals
Three-dimensional digital imaging is a method designed to evaluate the oral-maxillofacial complex. It is named three-dimensional because it uses a cone-shaped x-ray beam to acquire three-dimensional information. The source of radiation rotates around the head of the patient, and the area of interest is termed “field of view” (FOV).
DICOM images allow a practitioner to see the field of view in three dimensions. They are viewed in three planes: Axial, coronal, and sagittal. When viewed together, images are referred to as “multiplanar reconstructed images,” and they can be shared amongst dental professionals.
HARP Act Regarding the Use of the Three-Dimensional Digital Imaging
5.2 (1) A member of the following classes of persons is exempt from the prohibition in subsection 5 (1) of the Act with respect to the operation of a CT scanner, other than a dental CT scanner, for the irradiation of a human being, as long as subsection (2) is complied with:
- A legally qualified medical practitioner.
- A member of the College of Medical Radiation and Imaging Technologists of Ontario.
- A person who is a member of a class of persons set out in Item 1 or 6 in Column 1 of Table 1 provided that the person only operates the CT scanner under the supervision of a person set out opposite that item in Column 2 of Table 1. Reg. 173/11, s. 2; O. Reg. 359/19, s. 2. (2)
The exemption under subsection(1) only applies when the irradiation is prescribed by, a legally qualified medical practitioner;
a) a member of the Royal College of Dental Surgeons of Ontario who holds
b.) specialty certificate of registration authorizing the practice of the specialty of Oral and Maxillofacial Surgery;
5.3 A member of the following classes of persons is exempt from the prohibition in subsection 5 (1) of the Act with respect to the operation of a dental CT scanner for the irradiation of a human being, as long as subsection (2) is complied with:
- A member of the Royal College of Dental Surgeons of Ontario who holds a specialty certificate of registration authorizing the practice of the specialty of Oral and Maxillofacial Radiology.
- A member of the Royal College of Dental Surgeons of Ontario in compliance with the standards of practice set out in the document dated April 18, 2011 and entitled “Standard of Practice – Dental CT Scanners” that is published by the Royal College of Dental Surgeons of Ontario and approved by the Council of that College.
- A member of the College of Medical Radiation and Imaging Technologists of Ontario who is under the supervision of a person described in paragraph 1 or 2.
- A person who is a member of a class of persons set out in Item 2 in Column 1 of Table 1 provided that the person only operates the CT scanner under the supervision of a person set out opposite that item in Column 2 of Table 1 who is also a person described in paragraph 1 or 2. O. Reg. 173/11, s. 2; O. Reg. 359/19, s. 3.(2) The exemption under subsection (1) only applies, (a) with respect to a dental CT scanner that is installed and operated in a facility that is designated under subsection 23 (2) of the Act, and that is a dental facility operated by a dentist; and (b) when the irradiation is prescribed by a person described in paragraph 1 or 2 of subsection (1). O. Reg. 173/11, s. 2
Computed Tomography (CT) – dentist (registered with RCDSO) qualifications – additional training required, permitting and approval (Ministry of Health (MOH) & Royal Colleges of Dental Surgeons of Ontario (RCDSO)) for a dental facility in Ontario to operate
Dentist must wear a dosimeter badges
Only DDS is qualified to acquire CT imaging a DA and DH are not allowed to press the acquisition button
Equipment
Specialized equipment is needed for three-dimensional digital imaging. A CBCT machine is comparable in size to a panoramic machine where a patient sits, stands, or is placed in a supine position and in one rotation, radiation and receptor capture field of view. The radiation that exits the patient is received by a solid-state flat panel detector and becomes raw data that are sent to the computer. The number of manufacturers producing CBCT technology in dentistry is growing rapidly.
A computer accepts raw data and converts them into a stack of axial images. The technique is completed during the data reconstruction process and the computer has separate viewing software to import DICOM images.
Viewing software allows dental practitioners to view axial, coronal, and sagittal images, and each CBCT machine has its own proprietary viewing software, but many 3rd party DICOM viewing software are available with additional features.
Common Uses
Common uses for three-dimensional digital imaging include the following:
- Greatly improve interpretation, diagnosis, and treatment planning of dental care
- Implant placement
- Extraction or exposure of impacted teeth
- Definition of anatomic structures
- Endodontic assessment
- Airway and sinus analysis
- Evaluation of temporomandibular joint disorders
- Orthodontic evaluation
- Evaluation of lesions and abnormalities
- Trauma evaluation
- Comprehensive examination and interpretation should be completed and documented with the overall health of the patient in mind
