Low-dose ultrahigh-resolution PCCT enhances subsolid nodule characterization.

Purpose: To characterize invasion-associated CT features in pulmonary subsolid nodules using low-dose ultrahigh-resolution (UHR) photon-counting CT (PCCT) images and evaluate UHR's diagnostic superiority over standard high-resolution (HR) images.

Methods: Patients with subsolid lung adenocarcinoma were recruited for chest scan on PCCT to obtain UHR and standard HR images between November 2023 and May 2024. Nodule characteristics were visually assessed and histogram features were extracted from each nodule. Image quality and radiation dose at previous energy-integrating detector CT (EID-CT) of 30 patients were compared with those of PCCT. Differences between UHR and standard HR, PCCT and EID-CT were compared using paired McNemar-test or paired Wilcox-test.

Results: One hundred and eighty-four patients with 203 subsolid nodules were collected including 77 precursors, 77 minimally invasive adenocarcinoma (MIA) and 49 IA. UHR significantly outperformed standard HR in revealing CT findings including larger nodular diameter and solid-component diameter, more frequency of heterogeneous attenuation, lobulation, bubble-like sign, air bronchogram, pleural indentation and vascular sign (all P < 0.05). Additionally, UHR images exhibited significantly greater value in histogram-derived parameters compared to standard HR images (all P < 0.05), except for "Median," "Minimum." Furthermore, the radiation dose in PCCT was half of that in EID-CT (effective dose: 1.32 ± 0.27 vs. 3.85 ± 1.65/mSv, P < 0.001. CDTI_vol: 2.97 ± 0.53 vs. 6.90 ± 2.97/mGy, P < 0.001), with image quality significantly better in PCCT.

Conclusion: The UHR protocol on PCCT provides a magnified perspective to reveal CT characteristics of invasive growth in subsolid LUAD, previously undetectable on standard HR images, achieving halved radiation dose and better image quality than EID-CT.