Quantitative analysis of metal artefacts of dental implant in CBCT image by correlation analysis to micro-CT: A microstructural study.

OBJECTIVES: Quantification of dental implant metal artefacts in CBCT images using correlation analysis of trabecular microstructural parameters from CBCT and micro-CT, and analysis of the effect of varying the angular position of the subject. METHODS: Polyurethane synthetic bone blocks were first scanned without implants by micro-CT and CBCT. Two dental implants were then placed parallel in the bone blocks and these specimens were scanned by CBCT with different alpha angles. Three volumes of interest (VOI) were set for further analysis. Six microstructural parameters were measured: trabecular thickness (Tb(Th)), trabecular spacing (Th(Sp)), bone volume per total volume (BV/TV), bone surface per total volume (BS/TV), connectivity density (CD) andfractal dimension (FD). Micro-CT measurements were used as a gold standard for CBCT. Spearman correlation coefficients for each microstructural parameter from CBCT and micro-CT were calculated and compared using Steiger's Z test. RESULTS: Without the implants, in VOI(1), the Spearman correlation coefficients of Tb(Th), Tb(Sp), BV/TV, BS/TV, CD and FD were 0.599, 0.76, 0.552, 0.566, 0.664 and 0.607, respectively. With the implants, the correlation coefficients decreased sharply in VOI(1). As the alpha angle increased from zero to 90 degrees , the correlation coefficients increased and became significant. Similar results appeared in VOI(2). In contrast, in VOI(3), the correlation coefficient decreased as the alpha angle increased. CONCLUSIONS: Metal artefacts were successfully quantified using microstructural parameters in terms of the image quality of the CBCT. Changes in alpha angle affected the quality of the CBCT image.