Résumé
•Photon-counting CT decreases image noise and improves detectability of simulated chest lesions compared to dual-source CT.•The improvements brought about by the PCCT will enhance the quality of Ultra low-dose chest CT images.•The use of Ultra low-dose chest CT images with a high diagnostic image quality is essential for lung cancer screening.
To compare the image quality obtained with an energy-integrating detector CT (EID-CT) and a photon-counting CT (PCCT) in ultra-low dose (ULD) chest CT protocols for three patient morphology configurations.
ULD-CT acquisitions were performed at Sn100 kV on PCCT and EID-CT using an image quality phantom. Different phantom sections were used to simulate standard, overweight and obese patients and the ULD levels were adapted to each section: 0.4, 0.8 and 1.6 mGy, respectively. Noise power spectrum (NPS) and task-based transfer function (TTF) were computed to assess noise magnitude, noise texture and spatial resolution, respectively. Detectability indexes (d′) were computed to model the detection of a high-contrast solid nodule (HCN).
At all dose levels, noise magnitude values were significantly lower with PCCT than with EID-CT (−8.9 ± 0.4 %; p < 0.05). Values of average NPS spatial frequencies were significantly higher (p < 0.05) with PCCT (0.446 ± 0.010 mm−1) than with EID-CT mode (0.323 ± 0.011 mm−1). For the air insert, TTF values at 50 % were significantly lower for PCCT (0.719 ± 0.045 mm−1) than with EID-CT (0.916 ± 0.030 mm−1) at 1.6 mGy but similar for other dose levels (p < 0.05). For the simulated chest lesion, d′ values were significantly higher (p < 0.05) with PCCT than with EID-CT. The improvements in d′ values was 23.6 ± 5.5 % for HCN.
Compared with EID-CT, using PCCT makes it possible to reduce noise, improve noise texture and, above all, improve the detection of simulated high-contrast thoracic lesion in ULD CT protocols.