title: Submilisievert ultralow-dose CT colonography using iterative reconstruction technique: a feasibility study.
abstract: BACKGROUND
  Computed tomography (CT) colonography is a well established modality for the examination of symptomatic patients as well as in screening. Recent technical advances in improving image quality by iterative reconstruction contribute to the reduction of the radiation dose which is a major concern in CT imaging.
  
  
  OBJECTIVE
  To evaluate image quality of ultralow-dose submilisievert CT colonography using hybrid iterative reconstruction technique.
  
  
  METHODS
  Sixteen patients underwent contrast-enhanced CT colonography with standard protocol in supine position and ultralow-dose protocol in prone position. Ultralow-dose datasets were reconstructed with filtered back projection and an advanced hybrid iterative reconstruction technique. Two radiologists independently evaluated 96 colonic segments for image quality in the endoluminal view and axial thin sections. Colonic distension, smoothness of colonic wall and distortion of folds in the endoluminal view, sharpness of colonic wall delineation, perceived image noise, and presence of photon starvation artifact were rated on a five-point scale. Intraluminal noise expressed as standard deviation of Hounsfield density was measured in all segments.
  
  
  RESULTS
  The mean radiation dose was 0.42 mSv and 5.48 mSv in prone and supine scans, respectively. All distended segments were rated evaluable in standard dose and ultralow-dose series reconstructed with the iterative reconstruction technique, whereas in 61% segments image quality was rated poor or unacceptable in ultralow-dose series where filtered back projection was used with worst ratings in the rectum and the sigmoid colon.
  
  
  CONCLUSIONS
  This pilot study shows that iterative reconstruction technique is a feasible method to decrease the radiation dose from CT colonography for both positions below 1mSv. Further investigations of larger scale need to be done to clarify, whether such a low radiation dose would influence the detection of polyps.
authors.affiliation: Department of Radiology, First Faculty of Medicine of Charles University, Prague, Czech Republic lambert@mudr.org.
authors.forename: Lukas
authors.initials: L
authors.lastname: Lambert
authors.affiliation: Department of Radiology, First Faculty of Medicine of Charles University, Prague, Czech Republic.
authors.forename: Jan
authors.initials: J
authors.lastname: Danes
authors.affiliation: Department of Radiology, First Faculty of Medicine of Charles University, Prague, Czech Republic.
authors.forename: Jiri
authors.initials: J
authors.lastname: Jahoda
authors.affiliation: Department of Radiology, First Faculty of Medicine of Charles University, Prague, Czech Republic.
authors.forename: Martin
authors.initials: M
authors.lastname: Masek
authors.affiliation: Department of Radiology, 2nd Faculty of Medicine of Charles University and Motol University Hospital, Prague, Czech Republic.
authors.forename: Jiri
authors.initials: J
authors.lastname: Lisy
authors.affiliation: Department of Imaging Methods, St. Anne's University Hospital, Brno, Czech Republic.
authors.forename: Petr
authors.initials: P
authors.lastname: Ourednicek
mesh_terms: D000368:Aged; D023881:Colonography, Computed Tomographic / Q000379:methods*; D003287:Contrast Media; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007410:Intestinal Diseases / Q000000981:diagnostic imaging*; D008297:Male; D010865:Pilot Projects; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D014283:Triiodobenzoic Acids
chemical_list: D003287:Contrast Media; D014283:Triiodobenzoic Acids; C054871:ioversol
keywords: Colonography; colon; computed tomography; iterative reconstruction; low-dose; polyp