title: Assessment of chest CT at CTDIvolless than 1 mGy with iterative reconstruction techniques.
abstract: OBJECTIVE
  To assess the image quality of chest CT reconstructed with image-based iterative reconstruction (SafeCT; MedicVision®, Tirat Carmel, Israel), adaptive statistical iterative reconstruction (ASIR; GE Healthcare, Waukesha, WI) and model-based iterative reconstruction (MBIR; GE Healthcare, Waukesha, WI) techniques at CT dose index volume (CTDIvol) <1 mGy.
  
  
  METHODS
  In an institutional review board-approved study, 25 patients gave written informed consent for acquisition of three reduced dose (0.25-, 0.4- and 0.8-mGy) chest CT after standard of care CT (8 mGy) on a 64-channel multidetector CT (MDCT) and reconstructed with SafeCT, ASIR and MBIR. Two board-certified thoracic radiologists evaluated images from the lowest to the highest dose of the reduced dose CT series and subsequently for standard of care CT.
  
  
  RESULTS
  Out of the 182 detected lesions, the missed lesions were 35 at 0.25, 24 at 0.4 and 9 at 0.8 mGy with SafeCT, ASIR and MBIR, respectively. The most missed lesions were non-calcified lung nodules (NCLNs) 25/112 (<5 mm) at 0.25, 18/112 (<5 mm) at 0.4 and 3/112 (<4 mm) at 0.8 mGy. There were 78%, 84% and 97% lung nodules detected at 0.25, 0.4 and 0.8 mGy, respectively regardless of iterative reconstruction techniques (IRTs), Most mediastinum structures were not sufficiently seen at 0.25-0.8 mGy.
  
  
  CONCLUSIONS
  NCLNs can be missed in chest CT at CTDIvolof <1 mGy (0.25, 0.4 and 0.8 mGy) regardless of IRTs. The most lung nodules (97%) were detected at CTDIvolof 0.8 mGy. The most mediastinum structures were not sufficiently seen at 0.25-0.8 mGy. Advances in knowledge: NCLNs can be missed regardless of IRTs in chest CT at CTDIvolof <1 mGy. The performance of ASIR, SafeCT and MBIR was similar for lung nodule detection at 0.25, 0.4 and 0.8 mGy.
authors.affiliation: 1 Department of Radiology, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Atul
authors.identifier: http://orcid.org/0000-0002-3917-4871
authors.initials: A
authors.lastname: Padole
authors.affiliation: 1 Department of Radiology, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Subba
authors.initials: S
authors.lastname: Digumarthy
authors.affiliation: 1 Department of Radiology, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Efren
authors.initials: E
authors.lastname: Flores
authors.affiliation: 2 Department of Radiology, Brigham and Women's Hospital, Boston, MA, USA.
authors.forename: Rachna
authors.initials: R
authors.lastname: Madan
authors.affiliation: 1 Department of Radiology, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Shelly
authors.initials: S
authors.lastname: Mishra
authors.affiliation: 1 Department of Radiology, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Amita
authors.initials: A
authors.lastname: Sharma
authors.affiliation: 1 Department of Radiology, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Mannudeep K
authors.initials: MK
authors.lastname: Kalra
mesh_terms: D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D013902:Radiography, Thoracic / Q000379:methods*