title: Dose-modified 256-MDCT of the abdomen using low tube current and hybrid iterative reconstruction.
abstract: OBJECTIVE
  To evaluate the performance of hybrid iterative reconstruction technique (h-IRT) on image quality (IQ) in abdominal dose-modified (DM) scans in phantom and in patients in comparison to filtered back projection (FBP).
  
  
  METHODS
  An anthropomorphic phantom was scanned using various kVp (80-140) and mAs (25-100) settings. Images were reconstructed with FBP and h-IRT levels (1-6). In 69 adults (59.6 ± 13.54 years; 20 male, 49 female), DM computed tomography (CT) scans were performed using 120 kVp and 100-120 mAs. In 25/69, 5-mm FBP and h-IRT (levels 1-4 and 5) images were analyzed to validate IQ. The subsequent 44/69 had FBP and h-IRT (level 4) images reconstructed. Two readers evaluated 188 image series for IQ, noise, and artifacts. Objective and subjective data were analyzed using t-test and Wilcoxon signed-rank test, respectively. In 46/69 patients, prior dose CT was available for dose comparison.
  
  
  RESULTS
  In the phantom, noise reduction ranged from 12% (h-IRT level 1) to 50% (level 6). In patients, h-IRT level 4 images were rated diagnostic in 69/69 exams but DM-FBP images were found nondiagnostic in 20/69 patients. The size-specific dose estimate (SSDE) was reduced by 55% in the dose-modified CT group, (SSDE:4.55 ± 1.15 mGy) over the prior dose protocol (SSDE:10.21 ± 3.5 mGy, P < .0001).
  
  
  CONCLUSIONS
  h-IRT improved IQ in abdominal DM-CT scans in phantom and in patients. Dose improvements were greater in smaller patients than larger ones.
authors.affiliation: Division of Abdominal Imaging and Intervention, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Boston, MA 02115.
authors.forename: Jorge M
authors.initials: JM
authors.lastname: Fuentes-Orrego
authors.forename: Koichi
authors.initials: K
authors.lastname: Hayano
authors.forename: Avinash R
authors.initials: AR
authors.lastname: Kambadakone
authors.forename: Peter F
authors.initials: PF
authors.lastname: Hahn
authors.forename: Dushyant V
authors.initials: DV
authors.lastname: Sahani
mesh_terms: D003287:Contrast Media; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography / Q000379:methods*; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D011860:Radiography, Abdominal / Q000379:methods*
chemical_list: D003287:Contrast Media
keywords: Radiation dose; abdomen; computed tomography; image quality; iterative reconstruction