title: Reducing the radiation dose for CT colonography using adaptive statistical iterative reconstruction: A pilot study.
abstract: OBJECTIVE
  The purpose of our study was to evaluate the feasibility of preserving image quality during CT colonography (CTC) using a reduced radiation dose with adaptive statistical iterative reconstruction (ASIR).
  
  
  METHODS
  A proven colon phantom was imaged at standard dose settings (50 mAs) and at reduced doses (10-40 mAs) using six different ASIR levels (0-100%). We assessed 2D and 3D image quality and noise to determine the optimal dose and ASIR setting. Eighteen patients were then scanned with a standard CTC dose (50 mAs) in the supine position and at a reduced dose of 25 mAs with 40% ASIR in the prone position. Three radiologists blinded to the scanning techniques assessed 2D and 3D image quality and noise at three different colon locations. A score difference of > or = 1 was considered clinically important. Actual noise measures were compared between the standard-dose and low-dose acquisitions.
  
  
  RESULTS
  The phantom study showed image noise reduction that correlated with a higher percentage of ASIR. In patients, no significant image quality differences were identified between standard- and low-dose images using 40% ASIR. Overall image quality was reduced for both image sets as body mass index increased. Measured image noise was less with the low-dose technique using ASIR.
  
  
  CONCLUSIONS
  The results of this pilot study show that the radiation dose during CTC can be reduced 50% below currently accepted low-dose techniques without significantly affecting image quality when ASIR is used. Further evaluation in a larger patient group is warranted.
authors.affiliation: Department of Radiology, Mayo Clinic, Scottsdale, AZ 85259, USA.
authors.forename: Kristina T
authors.initials: KT
authors.lastname: Flicek
authors.forename: Amy K
authors.initials: AK
authors.lastname: Hara
authors.forename: Alvin C
authors.initials: AC
authors.lastname: Silva
authors.forename: Qing
authors.initials: Q
authors.lastname: Wu
authors.forename: Mary B
authors.initials: MB
authors.lastname: Peter
authors.forename: C Daniel
authors.initials: CD
authors.lastname: Johnson
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D023881:Colonography, Computed Tomographic / Q000379:methods*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D056888:Patient Positioning; D019047:Phantoms, Imaging; D010865:Pilot Projects; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted