A Prospective Evaluation of Dose Reduction and Image Quality in Chest CT Using Adaptive Statistical Iterative Reconstruction

OBJECTIVE. The purpose of this study was to compare the subjective image quality, image noise, and radiation dose of chest CT images reconstructed with a 30% blend of iterative reconstruction and 70% conventional filtered back projection (FBP) with those of images generated with 100% FBP. SUBJECTS AND METHODS. Clinically indicated chest CT examinations of 292 consecutively registered patients were prospectively alternately assigned to two scanners on which different reconstruction techniques were used: adaptive statistical iterative reconstruction (ASIR) blended with FBP and 100% FBP. Both acquisitions were performed with dose modulation (noise index, 25 for ASIR and 21 for FBP). Patient demographics and habitus were recorded. Two radiologists blinded to the reconstruction algorithm independently scored subjective image quality on a 3-point Likert scale and measured image noise and radiation dose. RESULTS. Compared with FBP images, ASIR images had significantly lower subjective image quality (p = 0.01), less image noise (p = 0.02), and less radiation dose (p < 0.0001). The CT dose index of the ASIR cohort (11.3 +/- 51) was significantly lower than that of the 100% FBP cohort (15.4 +/- 6.3) (p < 0.0001). Interobserver agreement on subjective image quality was excellent for both ASIR and FBP (Cronbach alpha, 0.92, p < 0.0001; Cronbach alpha, 0.85, p < 0.0001). CONCLUSION. In clinically indicated chest CT examinations, ASIR images had better image quality and less image noise at a lower radiation dose than images acquired with a conventional FBP reconstruction algorithm.