Diagnostic accuracy of state-of-the-art MDCT scanners without gantry tilt in patients with oral and oropharyngeal cancer

Abstract

Purpose: Current CT-protocols for staging oral and oropharyngeal cancer include primary transversal slices and secondary tilted slices to avoid artifact-producing regions of dental metalwork. Some of the latest MDCT scanners do not allow gantry tilt. Hence, we assessed the relevance of secondary tilted slices in tumor staging.

Materials and methods: Scans of a tiltable 64-row MDCT-scanner of 82 patients with oral or oropharyngeal cancer were retrospectively and independently evaluated twice by three readers: once using the primary transversal scans only, and once taking the transversal and secondary tilted scans into account. Tumor diameters and TN-stage were determined with both methods. Artifacts on transversal scans were analyzed using a 3-point-ranking-scale.

Results: Image quality was impaired by severe artifacts in 24% of transversal slices of the oral cavity and in 12% of the oropharynx. The three readers detected an average of 57.7 ± 2.1 of 82 tumors (70%) on transversal CT slices. An average of 6.3 ± 0.6 more tumors (8%) were detected when transversal studies were evaluated in conjunction with secondary tilted slices, leading to a significantly (p=0.0156-0.0313) increased average detection rate of 64.0 ± 2.0 tumors (78%). Moreover, secondary tilted slices led to a correction of underestimated tumor stages in up to six patients (7.3%).

Conclusion: Tilted slices that avoid artifact-producing regions of dental metalwork significantly improve the reader's sensitivity and are of incremental value for staging of oral and oropharyngeal cancers.