Feasibility of low-dose CT with spectral shaping and third-generation iterative reconstruction in evaluating interstitial lung diseases associated with connective tissue disease: an intra-individual comparison study

To investigate the feasibility of low-dose CT (LDCT) with tin filtration and third-generation iterative reconstruction (IR) in evaluating interstitial lung diseases associated with connective tissue disease (CTD-ILD). Fifty-three consecutive adult patients with CTD-ILD underwent regular-dose chest CT (RDCT) at 110 kVp followed by LDCT with tin-filtered 100 kVp. RDCT was reconstructed with filtered back projection (FBP) and advanced modeled iterative reconstruction (ADMIRE); LDCT was reconstructed with ADMIRE. Image noise, streak artifact, image quality, and visualization of normal and abnormal CT features were evaluated and compared among RDCT-ADMIRE, RDCT-FBP, and LDCT-ADMIRE groups. The mean radiation dose of LDCT was reduced to 20% of RDCT. Objective image noise of RDCT-ADMIRE (38.08 ± 6.37 HU), LDCT-ADMIRE (51.68 ± 9.06 HU), and RDCT-FBP (62.09 ± 10.95 HU) increased progressively (p < 0.001 in any two pairs). RDCT-ADMIRE significantly improved subjective image noise, streak artifact, and overall image quality compared with RDCT-FBP and LDCT-ADMIRE (all p < 0.001), while no significant difference was noted between the latter two groups. All abnormal lung structures were better scored in RDCT-ADMIRE compared with those in RDCT-FBP (all p < 0.001). LDCT-ADMIRE was inferior to RDCT-FBP in visualizing peripheral bronchi and vessels as well as reticulation (all p < 0.001); other normal and abnormal structures were similar between the two groups. LDCT with tin filtration and third-generation IR was applicable in evaluating ILD lesions of CTD. Image quality was significantly improved after applying ADMIRE algorithm to CT protocols. • Optimization of CT radiation dose is a clinical concern in patients with connective tissue disease. • Spectral shaping and third-generation iterative reconstruction emerge as promising techniques in reducing radiation dose and acquiring desired image quality of CTD-ILD patients. • The third-generation iterative reconstruction algorithm can optimize visualization of ILD patterns in low-dose CT.