title: Preliminary results: prospective clinical study to assess image-based iterative reconstruction for abdominal computed tomography acquired at 2 radiation dose levels.
abstract: OBJECTIVE
  The objective of this study was to compare image quality for abdominal computed tomographic (CT) images acquired at 200 and 50 mA s and reconstructed with image-based iterative reconstruction.
  
  
  METHODS
  In this institutional review board-approved prospective study, 22 patients (mean [SD] age, 64.3 [14.4] years; male-female ratio, 12:10) gave informed consent for acquisition of additional abdominal CT images on 64-slice multi-detector CT (MDCT) (Siemens Definition Flash). Standard-dose images were acquired at 200 quality reference mA s, whereas low-dose images were acquired at 50 mA s (all series: 120 kV; 5-mm section thickness; pitch, 0.9:1). The low-dose images were reconstructed with a nonlinear 3-dimensional iterative image reconstruction (3D-IIR) (SafeCT; MedicVision, Tirat Carmel, Israel) (4 settings, namely, A1, A2, A3, and A4) and were assessed by 3 abdominal radiologists for lesion detection, image noise, and visibility of small structures. CATPHAN 500 was scanned at the respective doses to obtain noise spectral density and modulation transfer function.
  
  
  RESULTS
  Subjective image noise was unacceptable at 50-mA s filtered back projection and improved to average in 50-mA s A1 and minimal or no noise in 50-mA s A4. However, the visibility of small structures was similar to standard-dose filtered back projection images on 50-mA s A2. Objective image noise was reduced to 66% for the 50-mA s 3D-IIR images (9.08 [2.3]/26.75 [6.8]). The modulation transfer function curve demonstrated resolution improvement in the low-dose images with the 3D-IIR technique, whereas the noise spectral density curve confirmed noise suppression in the 50-mA s 3D-IIR images.
  
  
  CONCLUSIONS
  Three-dimensional iterative image reconstruction helps to lower image noise without affecting the visibility of small structures at "moderate" settings. Diagnostically acceptable abdominal CT examinations can be acquired at 75% lower-radiation dose with the help of the image-based iterative reconstruction technique.
authors.affiliation: From the *Department of Radiology, Massachusetts General Hospital, Boston, MA; and †Center for Medical Image Science and Visualization, Linköpings universitet/US, Linköping, Sweden.
authors.forename: Sarvenaz
authors.initials: S
authors.lastname: Pourjabbar
authors.forename: Sarabjeet
authors.initials: S
authors.lastname: Singh
authors.forename: Anand K
authors.initials: AK
authors.lastname: Singh
authors.forename: Rocio P
authors.initials: RP
authors.lastname: Johnston
authors.forename: Anuradha S
authors.initials: AS
authors.lastname: Shenoy-Bhangle
authors.forename: Synho
authors.initials: S
authors.lastname: Do
authors.forename: Atul
authors.initials: A
authors.lastname: Padole
authors.forename: Michael A
authors.initials: MA
authors.lastname: Blake
authors.forename: Anders
authors.initials: A
authors.lastname: Persson
authors.forename: Mannudeep K
authors.initials: MK
authors.lastname: Kalra
mesh_terms: D003287:Contrast Media; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D007479:Iopamidol; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D011446:Prospective Studies; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D011860:Radiography, Abdominal; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D007479:Iopamidol