title: Reducing abdominal CT radiation dose with adaptive statistical iterative reconstruction technique.
abstract: OBJECTIVE
  To assess radiation dose reduction for abdominal computed tomography (CT) examinations with adaptive statistical iterative reconstruction (ASIR) technique.
  
  
  METHODS
  With institutional review board approval, retrospective review of weight adapted abdominal CT exams were performed in 156 consecutive patients with ASIR and in 66 patients with filtered back projection (FBP) on a 64-slice MDCT. Patients were categorized into 3 groups of <60 kg (n = 42), 61 to 90 kg (n = 100), and >or=91 kg (n = 80) for weight-based adjustment of automatic exposure control technique. Remaining scan parameters were held constant at 1.375:1 pitch, 120 kVp, 55 mm table feed per rotation, 5 mm section thickness. Two radiologists reviewed all CT examinations for image noise and diagnostic acceptability. CT dose index volume, and dose length product were recorded. Image noise and transverse abdominal diameter were measured in all patients. Data were analyzed using analysis of variance.
  
  
  RESULTS
  ASIR allowed for an overall average decrease of 25.1% in CT dose index volume compared with the FBP technique (ASIR, 11.9 +/- 3.6 mGy; FBP, 15.9 +/- 4.3 mGy) (P < 0.0001). In each of the 3 weight categories, CT examinations reconstructed with ASIR technique were associated with significantly lower radiation dose compared with FBP technique (P < 0.0001). There was also significantly less objective image noise with ASIR (6.9 +/- 2.2) than with FBP (9.5 +/- 2.0) (P < 0.0001). For the subjective analysis, all ASIR and FBP reconstructed abdominal CTs had optimal or less noise. However, 9% of FBP and 3.8% of ASIR reconstructed CT examinations were diagnostically unacceptable because of the presence of artifacts. Use of ASIR reconstruction kernel results in a blotchy pixilated appearance in 39% of CT sans which however, was mild and did not affect the diagnostic acceptability of images. The critical reproduction of visually sharp anatomic structures was preserved in all but one ASIR 40% reconstructed CT examination.
  
  
  CONCLUSIONS
  ASIR technique allows radiation dose reduction for abdominal CT examinations whereas improving image noise compared with the FBP technique.
authors.affiliation: Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA.
authors.forename: Priyanka
authors.initials: P
authors.lastname: Prakash
authors.forename: Mannudeep K
authors.initials: MK
authors.lastname: Kalra
authors.forename: Avinash K
authors.initials: AK
authors.lastname: Kambadakone
authors.forename: Homer
authors.initials: H
authors.lastname: Pien
authors.forename: Jiang
authors.initials: J
authors.lastname: Hsieh
authors.forename: Michael A
authors.initials: MA
authors.lastname: Blake
authors.forename: Dushyant V
authors.initials: DV
authors.lastname: Sahani
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D016477:Artifacts; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011829:Radiation Dosage; D011860:Radiography, Abdominal / Q000379:methods*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*; D055815:Young Adult