Standardized method to quantify the variation in voxel value distribution in patient-simulated CBCT data sets

Area of Science:

• Dental Radiology
• Medical Imaging Physics

Background:

• Cone-beam computed tomography (CBCT) is crucial in dental diagnostics.
• Assessing the stability and reproducibility of CBCT image quality over time is essential for reliable diagnosis and treatment planning.

Purpose of the Study:

• To propose a standardized method for evaluating voxel value distribution variations in simulated CBCT datasets.
• To investigate the impact of time between exposures (TBE) on these variations.
• To introduce the Aarhus measurement of reproducibility (AMORe) for quality assurance.

Main Methods:

• Six different CBCT units were tested using a human skull phantom with a titanium implant.
• Volumetric data were acquired across two sessions with varying TBE (15 and 30 minutes) between exposures.
• Voxel-by-voxel subtractions were performed to calculate mean grey shade variation for each unit and session.

Main Results:

• Significant mean grey shade variations were observed, particularly in subtraction set-up 2 (27-447 shades).
• The highest variation in subtraction set-up 1 occurred with the NEW5 unit between the initial and subsequent datasets.
• The introduced AMORe metric ranged from 0 to 64 across the tested units.

Conclusions:

• Discrepancies in voxel value distribution exist between initial and subsequent CBCT examinations.
• Time between exposures (TBE) did not demonstrate a predictable influence on CBCT-derived voxel value variations.
• The AMORe metric offers a potential tool for CBCT quality assurance.