Clinical applications of conebeam imaging
Cone-beam CT is an exciting new addition to the imaging armamentarium which can be utilized to investigate the head and neck. It has the potential to transform practically all aspects of dental imaging. It offers an alternative to the need for complicated interpretative reasoning currently used, for example, in parallax techniques for location of unerupted teeth. For ectopic, palatally placed maxillary canines parallax techniques have been shown to have a sensitivity of 69%, using a vertical technique, and 88% for horizontal parallax, but for buccally displaced canines these sensitivity figures both drop to 63%.2 In view of these figures and with the advent of cone-beam imaging, which gives so much more detail, perhaps the dose/benefit ratio needs to be reappraised. The 3-D nature of the data obtained allows easy visualization of structures in the complex maxillofacialenvironment. The potential scope of clinical applications for cone-beam imaging is vast and currently has been shown to be particularly useful in the following dental and maxillofacial areas:
Advantages of cone-beam imaging
Cone-beam imaging is wellmatched for the craniofacial area, in particular for evaluating bone and dental hard tissue. As these units have been custom designed for this region, unlike conventional CT, the software has beenspecifically produced to simplify obtaining the most useful views using pre-set parameters. In addition, most have been developed to work with other propriety maxillofacial imaging software, such as SimPlant (Materialise, Leuven, Belgium) and Nobel Biocare (Sweden) for implant planning. Also, compared to conventional CT, there are a number of significant advantages.
Dose reduction: published data for conebeam CT indicate an effective radiation dose between 0.035 and 0.10 mSv,5 which is up to a 98% reduction compared to conventional CT (effective dose for CT of mandible and maxilla being 0.4 mSv − Newcastle University Trust Hospitals data*) and equivalent to approximately a full mouth series of periapicals or 3−10 standard dental panoramic tomograms (*Dose calculated by Julie Willis, Medical Physics Department, Newcastle upon Tyne Hospitals using a programme produced by Imaging performance of CT scanners
X-ray beam limitation: reducing the size of the irradiated area by collimation of theprimary x-ray beam to the area of interest minimizes the radiation dose. Most scanners can be adjusted to scan specific small regions or to include the entire craniofacial complex, depending on the required task.
Rapid scan times: because all the basis images are acquired in a single rotation, scan time is quick, varying between 10 and 40 seconds. Fast scan times also result in fewer artefacts, such as those due to patient movement. These scan times are comparable to conventional dental panoramic imaging and those of modern
helical CT units.
Image accuracy: the volumetric dataset comprises a 3-D block of smaller cuboid units, known as voxels, each representing a specific degree of x-ray absorption. The size of these voxels determines the resolution of the image. In conventional CT, the voxels are anisotropic, ie rectangular cubes, where the longest dimension of the voxel is the axial slice thickness and is determined by slice pitch, a function of gantry motion. Although CT voxel surfaces can be as small All cone beam units provide voxel resolutions that are isotropic, ie equal in all three dimensions. This produces sub-millimetre resolutions (often exceeding the highest grade multislice CT) ranging from 0.4 mm to as low as 0.125 mm.1 In conventional CT of the oral region, the presence of metallic dental restorations causes a problem due to streak artefact, which can significantly degrade the image. Cone beam imaging also produces streak artefact but to a much lesser extent and consequently provides superior quality images of oral structures.
This a new technology for CTG Healthcare and we are now offering it to all our dental customers. Cone-beam Computed Tomography is an exciting addition to the imaging armamentarium which can be utilized to investigate the head and neck. It has the potential to transform practically all aspects of dental imaging. This is such an exciting advancement for CTG Healthcare. The Dental CT (3D) can measure every detail of the patients jaw in three dimensions. This gives us a chance to understand the exact situation of dental implant placement place. Available now at CTG Healthcare.
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