title: Hepatic CT perfusion measurements: a feasibility study for radiation dose reduction using new image reconstruction method.
abstract: OBJECTIVE
  To assess the effects of image reconstruction method on hepatic CT perfusion (CTP) values using two CT protocols with different radiation doses.
  
  
  METHODS
  Sixty patients underwent hepatic CTP and were randomly divided into two groups. Tube currents of 210 or 250 mA were used for the standard dose group and 120 or 140 mA for the low dose group. The higher currents were selected for large patients. Demographic features of the groups were compared. CT images were reconstructed by using filtered back projection (FBP), image filter (quantum de-noising, QDS), and adaptive iterative dose reduction (AIDR). Hepatic arterial and portal perfusion (HAP and HPP, ml/min/100ml) and arterial perfusion fraction (APF, %) were calculated using the dual-input maximum slope method. ROIs were placed on each hepatic segment. Perfusion and Hounsfield unit (HU) values, and image noises (standard deviations of HU value, SD) were measured and compared between the groups and among the methods.
  
  
  RESULTS
  There were no significant differences in the demographic features of the groups, nor were there any significant differences in mean perfusion and HU values for either the groups or the image reconstruction methods. Mean SDs of each of the image reconstruction methods were significantly lower (p<0.0001) for the standard dose group than the low dose group, while mean SDs for AIDR were significantly lower than those for FBP for both groups (p=0.0006 and 0.013). Radiation dose reductions were approximately 45%.
  
  
  CONCLUSIONS
  Image reconstruction method did not affect hepatic perfusion values calculated by dual-input maximum slope method with or without radiation dose reductions. AIDR significantly reduced images noises.
authors.affiliation: Division of Radiology, Kobe University Hospital, Department of Radiology, Kobe University Graduate School of Medicine, 7-5-2 Kusunokicho, Chuoku, Kobe 650-0017, Japan. noriyuki@med.kobe-u.ac.jp
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Negi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yoshikawa
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Ohno
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Somiya
authors.forename: Toshinori
authors.initials: T
authors.lastname: Sekitani
authors.forename: Naoki
authors.initials: N
authors.lastname: Sugihara
authors.forename: Hisanobu
authors.initials: H
authors.lastname: Koyama
authors.forename: Tomonori
authors.initials: T
authors.lastname: Kanda
authors.forename: Naoki
authors.initials: N
authors.lastname: Kanata
authors.forename: Tohru
authors.initials: T
authors.lastname: Murakami
authors.forename: Hideaki
authors.initials: H
authors.lastname: Kawamitsu
authors.forename: Kazuro
authors.initials: K
authors.lastname: Sugimura
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008113:Liver Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D055420:Perfusion Imaging / Q000379:methods*; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*