Potential dose reduction and image quality improvement in chest CT with a photon-counting CT compared to a new dual-source CT

Purpose

To compare potential dose reduction and quality improvement in chest CT images with Photon-Counting CT (PCCT) versus a Dual-Source CT (DSCT).

Methods

Acquisitions on phantoms were performed on a DSCT and a PCCT at 5 dose levels (9.5/7.5/6.0/2.5/0.4 mGy). Noise power spectrum (NPS) and task-based transfer function (TTF) were calculated to assess noise magnitude and noise texture (f_av) and spatial resolution (f₅₀), respectively. Computed detectability indexes (d′) modelled the detection of 2 chest lesions: subsolid pulmonary nodules (SPN) and high-contrast pulmonary nodules (HCN). Two radiologists subjectively assessed the quality of chest images on an anthropomorphic phantom.

Results

For all dose levels, noise magnitude was significantly lower with PCCT than with DSCT (−44.7 ± 3.0 %; p < 0.05). Identical outcomes were found for noise texture (f_av; −6.2 ± 0.5 %; p < 0.05). f₅₀ values were significantly higher with DSCT than with PCCT from 9.5 to 6 mGy for iodine insert (p < 0.05) and from 7.5 to 2.5 mGy for air insert (p < 0.05), but similar for both inserts at other dose levels. For all dose levels, d’ values were significantly higher with PCCT than DSCT (71.9 ± 5.4 % for HCN and 65.6 ± 13.5 % for SPN). From 9.5 to 2.5 mGy, the potential dose reduction was −59.0 ± 3.9 % for both lesions with PCCT compared to DSCT. Chest images were rated satisfactory for clinical use by the radiologists with both CTs for all dose levels, except at 0.4 mGy.

Conclusion

Noise magnitude and detectability of chest lesions were better with PCCT than with the DSCT. PCCT may offer great potential for dose reduction in patients undergoing chest CT examinations.