Computed tomography (CT) of the chest at less than 1 mSv: an ongoing prospective clinical trial of chest CT at submillisievert radiation doses with iterative model image reconstruction and iDose4 technique. 
To assess lesion detection and diagnostic confidence of computed tomography (CT) of the chest performed at less than 1 mSv with 2 iterative reconstruction (IR) techniques.  Ten patients gave written informed consent for the acquisitions of images at submillisievert dose (0.9 mSv), in addition to clinical standard-dose (SD) chest CT (2.9 mSv).  Submillisievert images were reconstructed with iDose and iterative model reconstruction (IMR).  Two radiologists assessed lesion detection, margins, diagnostic confidence, and visibility of small structures.  Objective noise and noise spectral density were measured.  Lesion detection was identical for standard-dose filtered back projection (FBP), submSv iDose, and submSv IMR.  Lesion margins were better seen for 30% of detected lung lesions with submSv IMR compared to standard-dose FBP and submSv iDose (P < 0.05).  Visibility of abdominal structures, and diagnostic confidence with submSv iDose and submSv IMR were similar to standard-dose FBP.  There was 21% to 64% noise reduction with submSv IMR and 1% to 15% higher noise with iDose compared to standard-dose FBP (P < 0.0001).  Submillisievert IMR improves delineation of lesion margins compared to standard-dose FBP and submSv iDose.