Influence of anatomical position on beam hardening and photon starvation artifacts caused by different high-density materials in CBCT.

OBJECTIVE: To evaluate the effect of different anatomical positions on the formation of beam hardening and photon starvation artifacts produced by different high-density materials in cone-beam computed tomography (CBCT). MATERIALS AND METHODS: Titanium (Ti), zirconia (Zr), and cobalt-chromium (Co-Cr) cylinders were inserted into a polymethyl methacrylate (PMMA) phantom under 4 experimental settings, combining number of cylinders (1 or 2) and their anatomical position (anterior or posterior). CBCT images were acquired using two devices (OP300 and Eagle3D). Five axial slices were selected from each exam, and circular regions of interest were defined. Mean of gray values (MGV) and noise were measured, and absolute difference between test and control regions (|ΔMGV|) expressed artifact intensity. MGV, noise, and |ΔMGV| results were compared according to anatomical position using the analysis of variance (α = 0.05). RESULTS: The anterior position in the OP300 showed higher MGV and |ΔMGV| for most materials and higher noise for Ti and Co-Cr. In the Eagle3D, anterior position showed higher MGV for Zr and Co-Cr. Noise and |ΔMGV| were higher in the posterior position for all materials. CONCLUSIONS: Anatomical positioning of high-density materials within the devices' projection geometry influences artifact behavior, although this effect is device-dependent.