Optimizing the reconstruction filter in cone-beam CT to improve periodontal ligament space visualization: An in vitro study

Abstract

PurposeEvaluation of alveolar bone is important in the diagnosis of dental diseases. The periodontal ligament space is difficult to clearly depict in cone-beam computed tomography images because the reconstruction filter conditions during image processing cause image blurring, resulting in decreased spatial resolution. We examined different reconstruction filters to assess their ability to improve spatial resolution and allow for a clearer visualization of the periodontal ligament space.Materials and MethodsCone-beam computed tomography projections of 2 skull phantoms were reconstructed using 6 reconstruction conditions and then compared using the Thurstone paired comparison method. Physical evaluations, including the modulation transfer function and the Wiener spectrum, as well as an assessment of space visibility, were undertaken using experimental phantoms.ResultsImage reconstruction using a modified Shepp-Logan filter resulted in better sensory, physical, and quantitative evaluations. The reconstruction conditions substantially improved the spatial resolution and visualization of the periodontal ligament space. The difference in sensitivity was obtained by altering the reconstruction filter.ConclusionModifying the characteristics of a reconstruction filter can generate significant improvement in assessments of the periodontal ligament space. A high-frequency enhancement filter improves the visualization of thin structures and will be useful when accurate assessment of the periodontal ligament space is necessary.

The accuracy of periapical radiography and cone beam computed tomography in measuring periodontal ligament space: Ex vivo comparative micro‐CT study

“…The irregular morphology of the PDL in artificial phantoms and the filling of the PDL space with water might have caused this result. Authors found that a development filter improved the partial resolution and allowed for better measurement of the PDL space (15). In our study, the CBCT images were sharp and the number of PDL spaces with clearer boundaries were high and built-in enhancement tools were used when deemed necessary.…”

“…Another study reported a natural PDL space width of 0.14-0.24 mm (23). Studies evaluating the visualisation of the PDL have generally developed in vitro phantom models to simulate the PDL cavity and surrounding tissues (15)(16)(17).…”

“…For periodontal assessment, the FOV should be limited to the area of interest to prevent exposing the patient to unnecessary radiation. However, it is difficult to clearly visualise small areas, such as the PDL space in the CBCT image due to blurring of the image, which causes a reduction in mechanical resolution (15). The authors previously compared CBCT with conventional intraoral radiographs for PDL space assessment on phantom jaws with artificial PDL cavities as a model (15)(16)(17).…”

“…However, it is difficult to clearly visualise small areas, such as the PDL space in the CBCT image due to blurring of the image, which causes a reduction in mechanical resolution (15). The authors previously compared CBCT with conventional intraoral radiographs for PDL space assessment on phantom jaws with artificial PDL cavities as a model (15)(16)(17). Currently, rapid advancements in technology have allowed the development of micro-computed tomography (MCT), which has the potential to examine dental structures at the micron level with ultrahigh radiation doses in vitro.…”

“…In another study (15), axial images of different artificial phantoms were evaluated using CBCT, and MCT was used as a reference similar to our study. In the CBCT images (highest voxel = 0.1 mm), reconstruction filters were used to allow observers to clearly see the boundaries of the PDL cavity.…”