title: Reducing CT radiation exposure with organ effective modulation: A retrospective clinical study.
abstract: OBJECTIVE
  To evaluate the effect of Organ Effective Modulation (OEM) on objective and subjective image quality as well as the radiation dose needed for thoracoabdominal computed tomography (CT).
  
  
  METHODS
  This retrospective study included 196 consecutive patients who were referred to our institution for enhanced thoracoabdominal CT on a specific scanner. Patients were divided into two groups: those for whom OEM was used and those for whom it was not used. For the non-OEM group, the tube current was controlled with an angular-longitudinal modulation technique. All CT examinations were performed with adaptive iterative dose reduction with 3D processing (AIDR-3D). The radiation dose was compared between the two groups. Objective image noise was measured in several regions at the thoracic and abdominal level. Subjective image quality was assessed by two radiologists for image noise, artifacts, sharpness, and overall diagnostic acceptability at the chest, abdomen, and pelvis.
  
  
  RESULTS
  The CTDIvol was 8.3% lower in the OEM group and high-BMI patients tended to have higher dose reductions. Image noise was not significantly different at the thoracic level, except for the ventral air space, which showed more noise in the OEM group. At the abdominal level, the OEM group showed less noise in every region, only demonstrating a significant difference in the posterior segment of the right hepatic lobe. Subjective image quality assessment indicated more artifacts in the thoracic ventral air space in the OEM group, whereas all other items including the overall diagnostic acceptability showed no statistical differences between the two groups.
  
  
  CONCLUSIONS
  OEM can reduce the radiation dose by approximately 8% without affecting the diagnostic acceptability of the image compared to angular-longitudinal modulation, especially in patients with a high BMI.
authors: Department of Radiology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan. Electronic address: hakai-tky@umin.ac.jp.
authors: Hiroyuki
authors: H
authors: Akai
authors: Department of Radiology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
authors: Shigeru
authors: S
authors: Kiryu
authors: Department of Radiology, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
authors: Eisuke
authors: E
authors: Shibata
authors: Department of Radiology, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
authors: Eriko
authors: E
authors: Maeda
authors: Department of Radiology, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
authors: Jiro
authors: J
authors: Sato
authors: Department of Radiology, New Tokyo Hospital, 1271 Wanagaya, Matsudo City, Chiba 270-2232, Japan.
authors: Nobuo
authors: N
authors: Tomizawa
authors: Division of Advanced Medicine Promotion, The Advanced Clinical Research Center, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo, 108-8639, Japan.
authors: Masanori
authors: M
authors: Nojima
authors: Department of Radiology, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
authors: Kuni
authors: K
authors: Ohtomo
mesh_terms: D000005:Abdomen / Q000000981:diagnostic imaging; D016477:Artifacts; D015992:Body Mass Index; D003287:Contrast Media; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods / Q000706:statistics & numerical data; D008297:Male; D010388:Pelvis / Q000000981:diagnostic imaging; D011829:Radiation Dosage; D000069079:Radiation Exposure / Q000706:statistics & numerical data*; D011856:Radiographic Image Enhancement / Q000379:methods*; D011860:Radiography, Abdominal / Q000379:methods* / Q000706:statistics & numerical data; D013902:Radiography, Thoracic / Q000379:methods* / Q000706:statistics & numerical data; D015203:Reproducibility of Results; D012189:Retrospective Studies; D036542:Tomography, Spiral Computed / Q000379:methods* / Q000706:statistics & numerical data
chemical_list: D003287:Contrast Media
keywords: CT; Image quality; Radiation exposure