title: The impact of iterative reconstruction on image quality and radiation dose in thoracic and abdominal CT.
abstract: OBJECTIVE
  To compare the image quality and radiation dose between iterative reconstruction (IR) and standard filtered back projection (FBP) in CT of the chest and abdomen.
  
  
  METHODS
  Thoracic CT was performed in 50 patients (38 male, 12 female; mean age, 51 ± 23 yrs; range, 7-85 yrs) and abdominal CT was performed in 50 patients (36 male, 14 female; mean age, 62 ± 13 yrs; range, 20-85 yrs), using IR as well as FBP for image reconstruction. Image noise was quantitatively assessed measuring standard deviation of Hounsfield Units (HU) in defined regions of interest in subcutaneous tissue. Scan length and Computed Tomography Dose Index (CTDI) were documented. Scan length, image noise, and CTDI of both reconstruction techniques were compared by using paired tests according to the nature of variables (McNemar test or Student t test). Overall subjective image quality and subjective image noise were compared.
  
  
  RESULTS
  There was no significant difference between the protocols in terms of mean scan length (p>0.05). Image noise was statistically significantly higher with IR, although the difference was clinically insignificant (13.3 ± 3.0 HU and 13.6 ± 3.0 HU for thoracic CT and 11.5 ± 3.1 HU and 11.7 ± 3.0 HU for abdominal CT, p<0.05). There was no significant difference in overall subjective image quality and subjective image noise. The radiation dose was significantly lower with IR. Volume-weighted CTDI decreased by 64% (6.2 ± 2.5 mGy versus 17.1 ± 9.5 mGy, p<0.001) for thoracic CT and by 58% (7.8 ± 4.6 mGy versus 18.5 ± 8.6 mGy, p<0.001) for abdominal CT.
  
  
  CONCLUSIONS
  Our study shows that in thoracic and abdominal CT with IR, there is no clinically significant impact on image quality, yet a significant radiation dose reduction compared to FBP.
authors.affiliation: Division of General Radiology, Department of Radiology, Medical University of Graz, Auenbruggerplatz 9, 8036 Graz, Austria.
authors.forename: Peter I
authors.initials: PI
authors.lastname: Kalmar
authors.affiliation: Institute for Medical Informatics, Statistics and Documentation, Medical University of Graz, Auenbruggerplatz 2, 8036 Graz, Austria.
authors.forename: Franz
authors.initials: F
authors.lastname: Quehenberger
authors.affiliation: Division of General Radiology, Department of Radiology, Medical University of Graz, Auenbruggerplatz 9, 8036 Graz, Austria.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Steiner
authors.affiliation: Division of General Radiology, Department of Radiology, Medical University of Graz, Auenbruggerplatz 9, 8036 Graz, Austria.
authors.forename: Andre
authors.initials: A
authors.lastname: Lutfi
authors.affiliation: Division of General Radiology, Department of Radiology, Medical University of Graz, Auenbruggerplatz 9, 8036 Graz, Austria.
authors.forename: Dennis
authors.initials: D
authors.lastname: Bohlsen
authors.affiliation: Division of General Radiology, Department of Radiology, Medical University of Graz, Auenbruggerplatz 9, 8036 Graz, Austria.
authors.forename: Emina
authors.initials: E
authors.lastname: Talakic
authors.affiliation: Division of General Radiology, Department of Radiology, Medical University of Graz, Auenbruggerplatz 9, 8036 Graz, Austria.
authors.forename: Eva Maria
authors.initials: EM
authors.lastname: Hassler
authors.affiliation: Division of General Radiology, Department of Radiology, Medical University of Graz, Auenbruggerplatz 9, 8036 Graz, Austria. Electronic address: helmut.schoellnast@medunigraz.at.
authors.forename: Helmut
authors.initials: H
authors.lastname: Schöllnast
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D058996:Quality Improvement; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D011860:Radiography, Abdominal; D013902:Radiography, Thoracic; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: Computed tomography; Filtered back projection; Iterative reconstruction