What Drives Metal Artifacts in CBCT? A Comparative Study of Detector Types and Metallic Object Configurations

Area of Science:

• Dental Imaging
• Medical Physics
• Radiology

Background:

• Metallic artifacts are a significant limitation in cone beam computed tomography (CBCT) imaging.
• The widespread use of dental metals necessitates understanding artifact reduction strategies.
• CBCT system design, particularly detector configuration, may influence artifact severity.

Purpose of the Study:

• To compare the impact of aligned versus lateral offset detectors on metal artifact formation in CBCT.
• To evaluate how different metallic materials and their placement affect artifact severity.
• To determine the influence of the number of metallic objects on artifact generation.

Main Methods:

• An in vitro study using a human skull phantom with various metallic objects (titanium, chrome-cobalt, amalgam).
• Scans were performed using four CBCT systems (two aligned, two offset detectors).
• Artifact severity was quantified using mean gray value (MGV) and standard deviation (SD) in defined regions of interest (ROIs).

Main Results:

• Aligned detectors demonstrated significantly reduced artifact severity (higher MGV, lower SD) compared to offset detectors (p < 0.001).
• Amalgam restorations produced the most severe artifacts, while cobalt-chromium showed the highest variability.
• Artifact severity increased with the number of metallic objects and when objects were positioned on the same side as the region of interest.

Conclusions:

• Detector type, metal composition, and object characteristics significantly impact CBCT metal artifact formation.
• Utilizing aligned detectors and considering object properties can mitigate artifacts.
• Optimizing CBCT parameters is crucial for enhancing diagnostic image quality in the presence of dental restorations.