title: Whole-organ CT perfusion of the pancreas: impact of iterative reconstruction on image quality, perfusion parameters and radiation dose in 256-slice CT-preliminary findings.
abstract: BACKGROUND
  This study was performed to assess whether iterative reconstruction can reduce radiation dose while maintaining acceptable image quality, and to investigate whether perfusion parameters vary from conventional filtered back projection (FBP) at the low-tube-voltage (80-kVp) during whole-pancreas perfusion examination using a 256-slice CT.
  
  
  METHODS
  76 patients with known or suspected pancreatic mass underwent whole-pancreas perfusion by a 256-slice CT. High- and low-tube-voltage CT images were acquired. 120-kVp image data (protocol A) and 80-kVp image data (protocol B) were reconstructed with conventional FBP, and 80-kVp image data were reconstructed with iDose(4) (protocol C) iterative reconstruction. The image noise; contrast-to-noise ratio (CNR) relative to muscle for the pancreas, liver, and aorta; and radiation dose of each protocol were assessed quantitatively. Overall image quality was assessed qualitatively. Among 76 patients, 23 were eventually proven to have a normal pancreas. Perfusion parameters of normal pancreas in each protocol including blood volume, blood flow, and permeability-surface area product were measured.
  
  
  RESULTS
  In the quantitative study, protocol C reduced image noise by 36.8% compared to protocol B (P<0.001). Protocol C yielded significantly higher CNR relative to muscle for the aorta, pancreas and liver compared to protocol B (P<0.001), and offered no significant difference compared to protocol A. In the qualitative study, protocols C and A gained similar scores and protocol B gained the lowest score for overall image quality (P<0.001). Mean effective doses were 23.37 mSv for protocol A and 10.81 mSv for protocols B and C. There were no significant differences in the normal pancreas perfusion values among three different protocols.
  
  
  CONCLUSIONS
  Low-tube-voltage and iDose(4) iterative reconstruction can dramatically decrease the radiation dose with acceptable image quality during whole-pancreas CT perfusion and have no significant impact on the perfusion parameters of normal pancreas compared to the conventional FBP reconstruction using a 256-slice CT scanner.
authors.affiliation: Department of Radiology, Huashan Hospital, Fudan University, Shanghai, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Xie
authors.forename: Juan
authors.initials: J
authors.lastname: Wu
authors.forename: Ying
authors.initials: Y
authors.lastname: Tang
authors.forename: Yafang
authors.initials: Y
authors.lastname: Dou
authors.forename: Sijie
authors.initials: S
authors.lastname: Hao
authors.forename: Feijia
authors.initials: F
authors.lastname: Xu
authors.forename: Xiaoyuan
authors.initials: X
authors.lastname: Feng
authors.forename: Zonghui
authors.initials: Z
authors.lastname: Liang
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D010179:Pancreas / Q000000981:diagnostic imaging* / Q000528:radiation effects; D055420:Perfusion Imaging / Q000379:methods*; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D014057:Tomography, X-Ray Computed / Q000009:adverse effects / Q000379:methods*