Cone beam computed tomography is a quite modern and recent technology in dental medicine. You will see it on this slide here. First looking at it, it seems to be quite similar to a panoramic view, but it has other features as you will learn now. During this rotation, the field of interest, or the region of interest, is at the centre, fixed at the centre, and the gantry is rotating around that. During this rotation, normally around to up to 1, images are taken, so a lot of images.
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Cone beam computed tomography is a quite modern and recent technology in dental medicine. You will see it on this slide here. First looking at it, it seems to be quite similar to a panoramic view, but it has other features as you will learn now.
During this rotation, the field of interest, or the region of interest, is at the centre, fixed at the centre, and the gantry is rotating around that. During this rotation, normally around to up to 1, images are taken, so a lot of images.
Those are called basis images, and they will be very important later on. The imaging can be performed in a sitting, in a standing, or also in a supine position, depending on the device. This is Accuitomo device. Here you sit, and you also see the rotating gantry which is rotating around the head. The head is the centre of interest. What is different from a medical computed tomography to a dental cone beam computed tomography?
The cone beam, as you see on the image on the left, enables us to take an image with one rotation, which is in contrast to CT imaging where the slice, or the fan beam actually leaves us to take an image of a head by doing a lot, or multiple rotations.
Voxel can be of different sizes. They can be about 0. And those together, they composite an image, and this image is normally a cylinder.
And we also have spherical volumes, but normally we use cylindrical volumes. As you see here, those cylindrical volumes can be small, on the left, they can be in a medium range, but they also can be in a large or maxillofacial range. But all those volumes are here to depict different areas of interest within the maxillofacial region.
An alveolar range of about a few teeth, or the maxilla and the mandible, if we talk about maxillofacial surgical approaches. Just to give you a little bit more visualisation of those cylinders, I have here put some glass cylinders with the picked typical cylindrical volumes used for CBCT imaging.
They range here in this image from 4 by 4, on far-right down to 10 by 10, which is quite a large field of view on the far-left upper right. Well, now we have those basis images. What do we do with those basis images? We need those in the computer to calculate a volume that we can look at. So, this takes time, and this depends on variables such as hardware, software, but also on other issues. And then when we have actually computerized these basis images into basis projections, then we can look at those.
And those are normally axial, sagittal, and coronal cuts of the region that we screened. So just to give you an example here, we have on the left, a sagittal, on the middle, a coronal, and on the right, an axial cut. We can also look on the diagnose image data sets on multiplanar reformations. These are actually virtual slices we cut into the maxilla, or into the mandible, and then we have cuts, actually coronal cuts along this axis that we draw, which is a little bit similar to an elderly CT prints that we used before all was digital.
And last but not least, we can also produce 3D volume data sets. Surface-rendered images, volume-rendered images, which are good for presenting those data sets to our patients. But might also be helpful when we process images for, for example, surgical purposes. We have one problem at hand, CBCT is not perfect, and one of the biggest problems is actually artifacts. Some artifacts are acquisition artifacts.
That means physical properties make that these artifacts are actually visible in our images. Typically we see cupping, beam hardening, and scattering. And specifically when you have metallic objects, it can become quite difficult to actually diagnose an image. And when they move, we can have slight artifacts like you see on the right. Often these are double-cortical projections. But it can also be as severe as seen on the right here, and they can be so severe that actually a CBCT image can not be used for further diagnosis.
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Computed Tomography (CT) Scanning
At the end of the course, participants will be able to: Demonstrate detailed knowledge of anatomy of the tooth-bearing portions of maxilla and mandible Understand artefacts that may occur in CBCT images Determine the location and orientation of impacted teeth and relationship to ID canal, maxillary sinus and other adjacent structures Correlate CBCT scans with conventional 2D radiographs Handle CBCT datasets for various clinical applications Use radiological terminology to describe abnormalities Describe important diseases including malignancy affecting the dento-alveolar regions Write CBCT interpretation reports for the dento-alveolar regions Identify when to refer cases for a second opinion or over-read Format The course combines theoretical and practical aspects of radiological interpretation. Participants will be given a chance to practise many clinical case studies which will work develop their confidence in the handling of datasets and interpretation of findings. The small group teaching format will enable each participant to gain personal tutor attention and enable them to progress at their own pace. Laptop computers will be provided to minimise disruption. More and more dentists are using them to diagnose complex clinical problems.
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