Ultrahigh-resolution CT scan of the temporal bone

Objective: Ultrahigh-resolution CT (U-HRCT) provides better spatial resolution than conventional multi-detector row CT (ConvCT) and could be expected to identify microstructures with its 0.25-mm collimation, 1792 channels and 160 detector rows, 0.4 × 0.5 mm focus size, and a 1024 matrix. The aim of the study was to evaluate key anatomic structures in temporal bone using U-HRCT comparing it to ConvCT. Materials and methods: A total of 30 patients (14 males and 16 females; age range, 8–82 years; median 49 years) underwent both U-HRCT and ConvCT. All CT images were obtained with 0.5 mm section thickness and a 512 × 512 matrix, and field of view of 80 mm. Transverse scans were acquired in a plane parallel to the orbitomeatal plane in the helical mode with 120 kV. Images of the 30 temporal bones of unaffected side were reviewed by two independent neuroradiologists who rated the visibility of key anatomic structures for both U-HRCT and ConvCT. The ratings between U-HRCT and ConvCT were compared using Wilcoxon matched-pairs signed rank test. The interobserver agreement on the rating of stapedius tendon was evaluated using weighted κ statistics. Results: Excellent interobserver agreement was shown for U-HRCT (κ = 0.920), whereas good agreement was obtained for ConvCT (κ = 0.733). According to both observers, stapedius tendon was more clearly visualized using U-HRCT than ConvCT (p < 0.0001). All other anatomic structures were well visualized using both CT scanners. Conclusion: The anatomy of temporal bone is more conspicuous on U-HRCT than on ConvCT because of its ultra-high-resolution detector. U-HRCT may provide beneficial information for determining surgical indication or procedures.