title: Contrast Dose and Radiation Dose Reduction in Abdominal Enhanced Computerized Tomography Scans with Single-phase Dual-energy Spectral Computerized Tomography Mode for Children with Solid Tumors.
abstract: BACKGROUND
  Contrast dose and radiation dose reduction in computerized tomography (CT) scan for adult has been explored successfully, but there have been few studies on the application of low-concentration contrast in pediatric abdominal CT examinations. This was a feasibility study on the use of dual-energy spectral imaging and adaptive statistical iterative reconstruction (ASiR) for the reduction of radiation dose and iodine contrast dose in pediatric abdominal CT patients with solid tumors.
  
  
  METHODS
  Forty-five patients with solid tumors who had initial CT (Group B) and follow-up CT (Group A) after chemotherapy were enrolled. The initial diagnostic CT scan (Group B) was performed using the standard two-phase enhanced CT with 320 mgI/ml concentration contrast, and the follow-up scan (Group A) was performed using a single-phase enhanced CT at 45 s after the beginning of the 270 mgI/ml contrast injection using spectral mode. Forty percent ASiR was used for the images in Group B and monochromatic images with energy levels ≥60 keV in Group A. In addition, filtered back-projection (FBP) reconstruction was used for monochromatic images <60 keV in Group A. The total radiation dose, total iodine load, contrast injection speed, and maximum injection pressure were compared between the two groups. The 40 keV and 60 keV spectral CT images of Group A were compared with the images of Group B to evaluate overall image quality.
  
  
  RESULTS
  The total radiation dose, total iodine load, injection speed, and maximum injection pressure for Group A were decreased by 19%, 15%, 34.4%, and 18.3%, respectively. The optimal energy level in spectral CT for displaying the abdominal vessels was 40 keV. At this level, the CT values in the abdominal aorta and its three branches, the portal vein and its two branches, and the inferior vena cava were all greater than 340 hounsfield unit (HU). The abdominal organs of Groups A and B had similar degrees of absolute and relative enhancement (t = 0.36 and -1.716 for liver, -0.153 and -1.546 for pancreas, and 2.427 and 0.866 for renal cortex, all P> 0.05). Signal-to-noise ratio of the abdominal organs was significantly lower in Group A than in Group B (t = -8.11 for liver, -7.83 for pancreas, and -5.38 for renal cortex, all P< 0.05). However, the subjective scores for the 40 keV (FBP) and 60 keV (40% ASiR) spectral CT images determined by two radiologists were all> 3, indicating clinically acceptable image quality.
  
  
  CONCLUSIONS
  Single-phase, dual-energy spectral CT used for children with solid abdominal tumors can reduce contrast dose and radiation dose and can also maintain clinically acceptable image quality.
authors.affiliation: Imaging Center, Beijing Children's Hospital, Capital Medical University, Beijing 100045, China.
authors.forename: Tong
authors.initials: T
authors.lastname: Yu
authors.affiliation: Imaging Center, Beijing Children's Hospital, Capital Medical University, Beijing 100045, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Gao
authors.affiliation: Imaging Center, Beijing Children's Hospital, Capital Medical University, Beijing 100045, China.
authors.forename: Zhi-Min
authors.initials: ZM
authors.lastname: Liu
authors.affiliation: Imaging Center, Beijing Children's Hospital, Capital Medical University, Beijing 100045, China.
authors.forename: Qi-Feng
authors.initials: QF
authors.lastname: Zhang
authors.affiliation: Imaging Center, Beijing Children's Hospital, Capital Medical University, Beijing 100045, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Imaging Center, Beijing Children's Hospital, Capital Medical University, Beijing 100045, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Jiang
authors.affiliation: Imaging Center, Beijing Children's Hospital, Capital Medical University, Beijing 100045, China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Peng
mesh_terms: D000005:Abdomen / Q000000981:diagnostic imaging; D002648:Child; D002675:Child, Preschool; D003287:Contrast Media; D005260:Female; D006801:Humans; D008297:Male; D009369:Neoplasms / Q000000981:diagnostic imaging*; D011856:Radiographic Image Enhancement / Q000379:methods; D011860:Radiography, Abdominal; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media