Influence of windowing and metal artefact reduction algorithms on the volumetric dimensions of five different high-density materials: a cone-beam CT study

Abstract

Objective: To assess the influence of windowing and metal artefact reduction (MAR) algorithms on the volumetric dimensions of high-density materials using two CBCT systems. Methods: Four cylinders of amalgam, cobalt-chromium, gutta-percha, titanium and zirconium, were manufactured and their physical volumes (PV) were measured. A polymethyl methacrylate phantom containing the cylinders was submitted to CBCT acquisitions with Picasso Trio and OP300 units with their MAR enabled and disabled. The tomographic volume (TV) of all the cylinders was obtained by semi-automatic segmentation using two windowing adjustments: W1—large window width and upper window level; W2—narrow window width and low window level. Volumetric distortion was expressed as the difference between TV and PV. Statistics comprised intraclass correlation coefficient (ICC) and analysis of variance (ANOVA) for repeated measures with Tukey post hoc test (α = 5%). Results: The ICC values ​​indicated excellent reproducibility of TV. Gutta-percha and titanium resulted in the smallest volumetric distortion. Using W1 provided less volumetric distortion for almost all experimental conditions (p < 0.05). Activating MAR algorithm of Picasso Trio underestimated gutta-percha and titanium TV (p < 0.05) and was inefficient in significantly reducing the volumetric distortion of the other materials (p > 0.05). Disabling MAR algorithm of OP300 resulted in smaller volumetric distortion for almost all experimental conditions (p < 0.05). Conclusions: The TV of gutta-percha and titanium were closer to the PV. In general, the MAR algorithms of both systems were inefficient in significantly reducing the volumetric distortion of high-density materials. We encourage the use of large window width and upper window level to evaluate high-density materials.

Comparison of the amount of artifacts induced by zirconium and titanium implants in cone-beam computed tomography images

“…Artifacts are visualized structures formed in the image through the data reconstruction process that do not represent the subject being studied [ 1 , 7 ]. Factors involved in inducing the artifacts can be classified as follows: 1) artifacts caused by the physical structure of the CBCT system, such as the mathematical format used in the 3-dimensional reconstruction, 2) artifacts related to the image acquisition, such as patient movement, exposure settings including milliamperage (mA) and peak kilovoltage (kVp), and presence of high-density elements [ 5 , 8 – 10 ].…”

Know your way around acute unenhanced CT during global iodinated contrast crisis: a refresher to ED radiologists

“…Without iodinated contrast, CT becomes significantly limited because of low inherent contrast between different types of soft tissues [ 19 ]. Adjusting the window width and level settings, aka “windowing,” is a process used to adjust the grey tones in CT images during their visualization, with the aim to adjust window width and level for optimum tissue contrast for lesion detection [ 20 ]. Different areas of anatomy or organ systems are interpreted using different window level and width settings, and generally accepted default settings are available for examination [ 21 ].…”

Impact of the blooming artefact on dental implant dimensions in 13 cone-beam computed tomography devices

“…Conversely, the implant diameter was overestimated for almost all images acquired with the small-FOV standard protocol. This increase may be related to some factors, such as spatial resolution (i.e., partial volume effect and other sources of blurring), contrast resolution (e.g., histogram distribution), filter and cut-off value used during reconstruction, beam hardening, and photon starvation [3,4,12]. Also, when comparing the medium FOV with small-FOV protocols at standard resolution, in a few cases, the medium FOV performed better and this can be possibly attributed to the reduced interference from the exomass, which are the structures located outside of the FOV but still between the X-ray source and the receptor [18].…”

“…Because the delineation between a dental implant and the surrounding bone may be faded, previous studies have demonstrated the positive influence of image brightness and contrast (B&C) adjustments on the dimensional representation of different high-density materials [11,12]; the visualization of such adjustments may vary amongst CBCT devices, depending on the severity of the artefact and the effective contrast resolution.…”