Comparison of lung nodule image quality using two adaptive statistical iterative reconstruction algorithms in chest CT:a phantom study / 实用放射学杂志

ABSTRACT

Objective To compare the values of the lung nodule image quality by using two adaptive statistical iterative reconstruction (ASIR)in a chest phantom CT imaging study.Methods Non-enhanced CT of chest phantom with routine dose was obtained on both GE Discovery CT and Revolution CT.The scan parameters included tube voltage of 120 kVp,a noise index of 14 HU,slice thickness of 5 mm.All scans were reconstructed with FBP and different percentages of (20%－100% ASIR)when using Discovery CT,and different percentages of ASIR-V (20%－100% ASIR-V)when using Revolution CT.The CT attenuation values and SD (the SD represented image noise)of the subcutaneous uniform tissue were measured at the level of thoracic entry,trachea carina and hepatic portal.Based on the standard FBP(FBPs )algorithm,the image noise reduction rate of reconstructed images using different iterative percentage of standard algorithms ASIR and ASIR-V(ASIRs and ASIR-Vs )were compared.The paired t test was used to compare the noise of ASIRs and ASIR-Vs images under the same iterative percentage.The subj ective image quality was independently evaluated by two experienced radiologists,Kappa test was used to evaluate consistency,Wilcoxon test was used to compare subjective scores.Results For all ASIRs and ASIR-Vs images,the objective image noise of subcutaneous uniform tissue decreased along with increasing percentage.Comparison with the average noises of CT image reconstructed with the FBPs algorithm,the image noise reconstructed with ASIRs from 20% to 1 00% were reduced by 1 1.0 6%－48.9 7%,while the image noise reconstructed with ASIR-Vs from 20% to 100% were reduced by 17.06%－79.50%.The image noise of different percentage ASIR-Vs was significantly lower than that of same percentage ASIRs between 40% and 1 00% (P＜0.05 ).In terms of subj ective image evaluation,all ASIR1 and ASIR-V1 reconstructions had good diagnostic acceptability.Two readers scored good or moderate consistency in each iterative reconstruction of each lung nodule.Nodules of smaller size and less dense were more likely to have score differences.The 60%ASIR1 showed significantly superior visibility of lung nodules when compared to other percentages (P＜0.05).60% and 80% ASIR-V1 series showed significantly superior visibility of lung nodules when compared to the 60% ASIR1 and ASIR-V1 of other percentages (P＜0.05).Conclusion In routine dose non-enhanced chest CT, ASIR-V shows greater potential in reducing image noise and improves lung nodule image quality when compared to the same level ASIR algorithm. Combining both the obj ective and subj ective evaluation of images,reconstructed with 60% and 80% ASIR-V in the non-enhanced chest CT image is recommended for the observation and evaluation of pulmonary nodules.