Higher Computed Tomography (CT) Scan Resolution Improves Accuracy of Patient-specific Mandibular Models When Compared to Cadaveric Gold Standard

Abstract

3D-printed patient-specific anatomical models are becoming an increasingly popular tool for planning reconstructive surgeries to treat oral cancer. Currently there is a lack of information regarding model accuracy, and how the resolution of the computed tomography (CT) scan affects the accuracy of the final model. The primary objective of this study was to determine the CT z-axis resolution necessary in creating a patient specific mandibular model with clinically acceptable accuracy for global bony reconstruction. This study also sought to evaluate the effect of the digital sculpting and 3D printing process on model accuracy. This was a cross-sectional study using cadaveric heads obtained from the Ohio State University Body Donation Program. The first independent variable is CT scan slice thickness of either 0.675, 1.25, 3.00, or 5.00mm. The second independent variable is the three produced models for analysis (unsculpted, digitally sculpted, 3D printed). The degree of accuracy of a model as defined by the root mean square (RMS) value, a measure of a model's discrepancy from its respective cadaveric anatomy. All models were digitally compared to their cadaveric bony anatomy using a metrology surface scan of the dissected mandible. The RMS value of each comparison evaluates the level of discrepancy. One-way ANOVA tests (P<.05) were used to determine statistically significant differences between CT scan resolutions. Two-way ANOVA tests (P<.05) were used to determine statistically significant differences between groups. CT scans acquired for 8 formalin-fixed cadaver heads were processed and analyzed. The RMS for digitally sculpted models decreased as slice thickness decreased, confirming that higher resolution CT scans resulted in statistically more accurate model production when compared to the cadaveric gold standard. Furthermore, digitally sculpted models were significantly more accurate than unsculpted models (P<.05) at each slice thickness. Our study demonstrated that CT scans with slice thicknesses of 3.00mm or smaller created statistically significantly more accurate models than models created from slice thicknesses of 5.00mm. The digital sculpting process statistically significantly increased the accuracy of models and no loss of accuracy through the 3D printing process was observed.