Position and variation in the number of high-density objects influence the expression of volumetric alteration artifacts in cone-beam computed tomographic images.

Purpose: This study aimed to evaluate whether the position and number of high-density objects within the field of view (FOV) affect the volumetric alteration (VA) artifact in cone-beam computed tomography (CBCT) images.

Materials and methods: Four cylinders, each made of either cobalt-chromium, titanium, or zirconium, were placed in a phantom for acquisitions using the OP300 Maxio (Instrumentarium Dental, Tuusula, Finland) and Eagle (Dabi Atlante S/A Indústrias Médico Odontológicas, Ribeirão Preto, Brazil) CBCT systems. The cylinders were arranged in 7 different combinations based on their position and number within the FOV. Two oral radiologists segmented the volumes of the cylinders, and VA was calculated as the difference between the tomographic and physical volumes. Statistical analyses included the intraclass correlation coefficient (ICC) and multiway analysis of variance with Tukey's post-hoc test (α=5%).

Results: VA was observed under all experimental conditions. The factors region (anterior/posterior), combination (1 to 7), and material (cobalt-chromium, titanium, or zirconium) significantly influenced VA (P<0.05). In general, the presence of 3 cylinders within the FOV reduced VA (P<0.05). Although the effect of a cylinder's position varied with the CBCT system, VA typically increased in the posterior region (P<0.05). Additionally, titanium exhibited the lowest VA for both CBCT systems (P<0.05).

Conclusion: The presence of 3 high-density objects within the FOV reduced VA in CBCT images, whereas positioning an object in the posterior region generally increased its measured volume.