To evaluate improved spatial resolution/critical structure visualization for temporal bone imaging using a photon-counting-detector (PCD) CT system.*Methods and Materials Patients referred for clinically indicated temporal bone CT were scanned on a conventional energy-integrating detector (EID) CT using our routine clinical protocol (120 kV, comb-based ultra-high-resolution (ultra-HR), CTDIvol = 55 mGy) and an investigational PCD-CT system (SOMATOM Count Plus, Siemens Healthineers, 120 kV, non-comb-based HR, CTDIvol = 35.7 mGy). CT images were reconstructed in axial, coronal and Poschl planes using the smallest available slice thickness (0.4 mm for EID-CT, 0.2 mm for PCD-CT). Images were reconstructed using Ur77 (EID-CT) and Hr84 (PCD-CT) kernels to maximize spatial resolution at acceptable noise levels. Two radiologists blindly evaluated randomized and paired EID-CT and PCD-CT images, and scored PCD-CT against EID-CT. Critical structures (round window, incudomallear joint, modiolus, oval window, scutum and incudostapedial joint, as well as ossicular prosthesis when present) were individually scored for spatial resolution/visualization, and a final overall score given for statistical evaluation. Image scoring was performed using a 5-point Likert scale (1 = inferior resolution with degraded visualization, 2 = slightly inferior resolution without affecting visualization, 3 = equivalent resolution and visualization, 4 = slightly superior resolution without affecting visualization, 5 = superior spatial resolution with improved visualization). Wilcoxon rank-sum test was used for statistical analysis, and descriptive analyses (mean and median scores) were performed for individual critical structures.*Results A total of 13 patients were enrolled. CT images were reconstructed separately for left and right sides, yielding 26 image sets for evaluation. Despite a 35% decrease in the CT dose, HR images from PCD-CT were significantly preferred over EID-CT (p < 0.0001) with a mean overall score of 4.62 (individual median score of 5 for PCD-CT from both readers).*Conclusions Reduced dose PCD-CT demonstrated significantly better spatial resolution/visualization for temporal bone structures compared to conventional EID-CT.*Clinical Relevance/Application Substantially better visualization of critical structures within the temporal bone from PCD-CT may yield superior diagnostic capabilities in evaluation of the inner ear.

A total of 13 patients were enrolled. CT images were reconstructed separately for left and right sides, yielding 26 image sets for evaluation. Despite a 35% decrease in the CT dose, HR images from PCD-CT were significantly preferred over EID-CT (p < 0.0001) with a mean overall score of 4.62 (individual median score of 5 for PCD-CT from both readers).

Substantially better visualization of critical structures within the temporal bone from PCD-CT may yield superior diagnostic capabilities in evaluation of the inner ear.