3D Cone Beam Imaging in Dental Practices

Abstract

Cone Beam Imaging is increasingly being considered as an important source of three dimensional (3D) imaging in orthodontics ever since it was introduced back in 1998. This manuscript has been designed to highlight the applications of cone beam imaging, its background, efficiency and its scope over the years. Although its advantages are more over the routine radiography cases, and its ever increasing popularity, there are a few disadvantages that exist under the surface and this manuscript tends to explore that as well. Similarly, there are some dentists who use it frequently while some refuse to use it in the office. All such scenarios have been evaluated in this research manuscript.

Keywords: radiography, orthodontics, cone beam CT, computed, tomography, dental practices, instrumentation

3D Cone Beam Imaging in Dental Practices

For quite a while now, the use of advanced imaging for most dental practitioners has been limited due to the considerations of radiation doses, availability and cost. However, after the introduction of Cone Beam Imaging with the help of Computed Tomography, the opportunities for multi-planar imaging have made their way for applications in maxillofacial regions.

Introduction to 3D Cone Beam Imaging

Cone beam imaging is based on volumetric tomography, in which an extended two-dimensional digital array is used in combination with a three-dimensional x-ray beam and an area detector. The technology uses a single scan of 360 degrees in which the detector and x-ray source move around the head of the patient in a synchronization, which is fixed in a stable position with the help of a head holder. At specific intervals of degrees, basis images or the single projection images are acquired by the device. These basis images resemble the lateral cephalometric radiographic pictures, and the series of these images is termed as the projection data (Lofthag-Hansen, Thilander-Klang, & Kerstin, 2011). Different software are then used to employ back-filtered projection to these images in order to generate a 3D set of volumetric data, which is then used to provide reconstruction images in the coronal, sagittal and axial planes (Noo, 2010).

Although the principle of cone beam imaging has been into applications for the last two decades, the recent availability of powerful computers, high-quality detector systems and affordable x-ray tubes have given way to more commercial usage of this technology. Ever since the introduction of first cone beam imaging back in 2001 as NewTom QR DVT 9000 (Benavides, et al., 2012), a lot of systems have been introduced in the market. All of these systems can be categorized on the basis of their detection system. For maxillofacial applications, most of these units used a charge-coupled device and an image intensifier tube. Only recently, a flat panel imager was brought into applications which consisted of a scintillator made up of cesium iodide and an amorphous silicon thin film transistor (Shah, Mann, Tornai, Richmond, & Zentai, 2014; Stratemann, Huang, Maki, Miller, & Hatcher, 2014). These systems generated lesser noise and did not need the preprocessing for the reductions of geometric distortions present in the configuration of detectors.

Applications of Cone Beam Imaging in Clinical Dental Practice

Cone beam imaging technology is suitable for usage in clinical dental practice due to its size, unlike the conventional computed tomography scanners that are expensive and large to maintain and purchase (Poeschl, et al., 2013). In dental practices where space is at a premium, dose considerations and costs are taken under consideration and the scanning scope is limited to the head, cone beam imaging systems become quite popular.

All cone beam imaging technology units provide sagittal, coronal and axial images, with basic enhancement options of magnification, zoom and visual adjustments, have the capability of cursor-driven measurement and annotation additions. Other enhancements include color ranges and contrast levels within the frame window. Values of cone beam imaging technology imaging in post-operative assessment of craniofacial fractures (Wortche, et al., 2014; Mischkowski, et al., 2014), TMJ assessments (Honda, et al., 2014; Tsiklakis, Syriopoulos, & Stamatakis, 2014; Kijima, et al., 2014), surgical assessment of pathology and implant planning (Weitz, et al., 2011; Maret, et al., 2014; Liang, et al., 2010) have been evaluated into applications. Similarly, cone beam imaging technology has also been found into popular applications in the field of orthodontics for the assessment of development and growths (Stratemann S. , Huang, Maki, Hatcher, & Miller, 2011), with popularity increasing evermore at the West Coast of the United States.

Advantages of Cone Beam Imaging

Cone beam imaging technology is highly suitable for the craniofacial area as it provides clear images of bones and contrasted structures. There are a number of advantages for cone beam imaging technology over the conventional computed tomography which include:

Limitation of X-Ray Beam

With the reduction of the size of irradiated area to the area of interest by the collimation of primary x-ray beam, the amount of radiation dose is greatly reduced. Most units can be adjusted to scan the beam perfectly allowing the scan of entire craniofacial complex whenever necessary.

Accuracy of Images

In the conventional computed tomography, the voxels are rectangular and anisotropic, whereas the voxels in cone beam imaging are square and isotropic. This allows the units to produce high quality images varying from as high as 0.4mm down to as few as 0.125mm of resolution.

Rapid Scan Time

Since all the images are acquired within a single rotation, the scan time is rapid and comparable to the medical spiral systems ranging from 10 seconds to 70 seconds. The reduction in scan time also reduces the probability of motion artifacts (Suomalainen, Vehmas, Kortesniemi, Robinson, & Peltola, 2014).

Reduction in Doses

Different reports indicate that the effective radiation dose is reduced greatly in conic beam imaging systems as compared to conventional computed tomographic systems. The average dosage of the conventional systems is reduced up to 98% in the cone beam imaging systems (Tyndall & Kohltfarber, 2012; Pauwels, et al., 2012; Tyndall, et al., 2012).

Reduced Image Artifacts

Cone beam imaging technology images produce low image artifacts due to the suppressed algorithms and increased number of projections, especially in the reconstructions designed secondarily for observing teeth and jaws (Miles, 2013).

Conclusion

The rapid commercialization and development of cone beam imaging technology has undoubtedly increased the access of dental practitioners to 3D radiographic procedures dedicated to imaging the maxillofacial region in the clinical dental practice. Cone beam imaging technology imaging provides sub-millimeter, high quality images with spatial resolution and short scanning times ranging between ten seconds to a minute, defining it as a convenient source of diagnostic procedures.

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