Imaging Sci Dent.  2020 Mar;50(1):23-30. 10.5624/isd.2020.50.1.23.

Does the metal artifact reduction algorithm activation mode influence the magnitude of artifacts in CBCT images?

• Fontenele
• Nascimento EHL
• Santaella
• Freitas DQ

• KMID: 2471842
• DOI: http://doi.org/10.5624/isd.2020.50.1.23

Abstract

PURPOSE
This study was conducted to assess the effectiveness of a metal artifact reduction (MAR) algorithm activated at different times during cone-beam computed tomography (CBCT) acquisition on the magnitude of artifacts generated by a zirconium implant.
MATERIALS AND METHODS
Volumes were obtained with and without a zirconium implant in a human mandible, using the OP300 Maxio unit. Three modes were tested: without MAR, with MAR activated after acquisition, and with MAR activated before acquisition. Artifacts were assessed in terms of the standard deviation (SD) of gray values and the contrast-to-noise ratio (CNR) in 6 regions of interest with different distances (10 to 35 mm, from the nearest to the farthest) and angulations (70° to 135°) from the implant region.
RESULTS
In the acquisitions without MAR, the regions closer to the implant (10 and 15 mm) had a higher SD and lower CNR than the farther regions. When MAR was activated (before or after), SD values did not differ among the regions (P>0.05). The region closest to the implant presented a significantly lower CNR in the acquisitions without MAR than when MAR was activated after the acquisition; however, activating MAR before the acquisition did not yield significant differences from either of the other conditions.
CONCLUSION
Both modes of MAR activation were effective in decreasing the magnitude of CBCT artifacts, especially when the effects of the artifacts were more noticeable.

Keyword

Artifacts; Cone-Beam Computed Tomography; Dental Implant; Zirconium

MeSH Terms

Artifacts*
Cone-Beam Computed Tomography
Dental Implants
Humans
Mandible
Zirconium
Dental Implants
Zirconium

Figure

• 

  Fig. 1 Examples of cropped axial images of the control and zirconium groups in various metal artifact reduction (MAR) conditions: without MAR, MAR after acquisition, and MAR before acquisition.

• 

  Fig. 2 A. A line is drawn through the center of the implant and parallel to the long axis of the mandibular body on the right side, and then a perpendicular line (90°) to that line is drawn. Considering the position of this perpendicular line, 4 additional lines are drawn, differing 20° between each other; 2 posterior (110° and 130°) and 2 anterior (70° and 50°) lines. B. After establishing these lines, circles centered on the dental implant are drawn with different radii (10 mm, 15 mm, 20 mm, 25 mm, 30 mm, and 35 mm). C. In the regions between intersections of the lines and circles, square regions of interest (ROIs) (2 mm×2 mm) are established. In addition, an ROI of the same size is established in the ERB block located in the anterior region of the mandible, serving as a control ROI.

• 

  Fig. 3 The magnitude of artifacts is evaluated by grouping the regions of interest located in the same circle. In this way, 6 different regions are established.

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