Comparing the detectability of pulmonary nodules on two ultra-high resolution CT scanners: a preliminary phantom study.

OBJECTIVES: To objectively and subjectively compare the detectability of pulmonary nodules on an ultra-high-resolution CT (UHR-CT) scanner equipped with energy-integrating detectors and a photon-counting CT (PCCT) in UHR mode. MATERIALS AND METHODS: ), respectively. Detectability indices (d') were computed to model the detection of three chest nodules. Five radiologists subjectively evaluated their confidence in detecting these nodules available on the anthropomorphic phantom. RESULTS: values were higher with PCCT than with UHR-CT. d' values increased as the dose increased with PCCT, and the opposite was found with UHR-CT. Confidence in nodule detection was considered clinically sufficient at all dose levels for high-contrast solid nodules at 7.5 and 2.5 mGy for subsolid nodules, and only for PCCT at 7.5 mGy for low-contrast nodules. CONCLUSION: Under UHR conditions, pulmonary nodule detectability strongly depends on the dose level and reconstruction parameters. High-contrast nodule detection can be performed at all dose levels with both CT systems, but reconstruction strategies must be optimized for low-contrast nodule detection. KEY POINTS: Do the performance of UHR-CT and PCCT scanners improve the detectability of pulmonary nodules? PCCT showed dose-invariant noise texture and higher effective spatial resolution, whereas UHR-CT relied on dose-dependent noise suppression, producing smoother images and reduced spatial frequency. High-contrast nodule detection can be performed at all dose levels with both CT systems, particularly at ultra-low dose levels, but reconstruction strategies must be optimized for low-contrast nodule detection.