title: Reducing the Radiation Dose for CT Colonography: Effect of Low Tube Voltage and Iterative Reconstruction.
abstract: OBJECTIVE
  The purpose of this study was to assess the effect of a low-tube-voltage technique and iterative reconstruction (IR) on the radiation dose and image quality of computed tomography colonography (CTC).
  
  
  METHODS
  We studied 30 patients (14 women and 16 men; mean age, 64.5 ± 13.1 years; range, 39-90 years) with colorectal cancer referred for surgical treatment. All underwent CTC with fecal tagging under a standard 120-kVp protocol in the supine position and a 100-kVp protocol in the prone position. The 120-kVp images were reconstructed with filtered back projection (FBP). The 100-kVp images were postprocessed using FBP and a hybrid type of IR (adaptive iterative dose reduction 3D). The effective radiation dose (ED), image noise, and contrast-to-noise ratio (CNR) were compared among the three protocols. The visual image quality was scored on a four-point scale.
  
  
  RESULTS
  The mean ED was significantly lower under the 100-kVp protocol than the 120-kVp protocol, resulting in a 27% radiation dose decrease (3.5 ± 2.0 vs 2.5 ± 1.5 mSv; P < .01). Image noise decreased by 48%, and the mean attenuation of tagged fluid increased from 452 to 558 HU on images acquired at 100 kVp with IR compared to that in the 120-kVp protocol; these differences were significant. The mean CNR was significantly higher under the 100 kVp with IR than the other two protocols. We found no significant differences in the visual scores for diagnostic utility between the 100 kVp with IR and the 120 kVp with FBP protocol (P = .10).
  
  
  CONCLUSIONS
  Low-tube-voltage CTC reduced the radiation dose by approximately 27% while maintaining the image quality.
authors: Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, 1-1-1 Honjyo, Chuo-ku, Kumamoto 860-8556, Japan.
authors: Sadahiro
authors: S
authors: Yamamura
authors: Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, 1-1-1 Honjyo, Chuo-ku, Kumamoto 860-8556, Japan. Electronic address: seisei0430@nifty.com.
authors: Seitaro
authors: S
authors: Oda
authors: Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, 1-1-1 Honjyo, Chuo-ku, Kumamoto 860-8556, Japan.
authors: Masanori
authors: M
authors: Imuta
authors: Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, 1-1-1 Honjyo, Chuo-ku, Kumamoto 860-8556, Japan.
authors: Daisuke
authors: D
authors: Utsunomiya
authors: Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, 1-1-1 Honjyo, Chuo-ku, Kumamoto 860-8556, Japan.
authors: Morikatsu
authors: M
authors: Yoshida
authors: Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, 1-1-1 Honjyo, Chuo-ku, Kumamoto 860-8556, Japan.
authors: Tomohiro
authors: T
authors: Namimoto
authors: Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, 1-1-1 Honjyo, Chuo-ku, Kumamoto 860-8556, Japan.
authors: Hideaki
authors: H
authors: Yuki
authors: Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, 1-1-1 Honjyo, Chuo-ku, Kumamoto 860-8556, Japan.
authors: Masafumi
authors: M
authors: Kidoh
authors: Department of Medical Physics, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.
authors: Yoshinori
authors: Y
authors: Funama
authors: Department of Gastroenterological Surgery, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.
authors: Hideo
authors: H
authors: Baba
authors: Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, 1-1-1 Honjyo, Chuo-ku, Kumamoto 860-8556, Japan.
authors: Yasuyuki
authors: Y
authors: Yamashita
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D023881:Colonography, Computed Tomographic / Q000295:instrumentation / Q000379:methods*; D015179:Colorectal Neoplasms / Q000000981:diagnostic imaging; D003287:Contrast Media; D003973:Diatrizoate; D003974:Diatrizoate Meglumine; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D056888:Patient Positioning; D016684:Prone Position; D011446:Prospective Studies; D011829:Radiation Dosage; D059629:Signal-To-Noise Ratio; D016683:Supine Position
chemical_list: D003287:Contrast Media; D003973:Diatrizoate; D003974:Diatrizoate Meglumine
keywords: CT colonography; image quality; iterative reconstruction; low tube voltage; radiation dose