title: Effect of pre-enhancement set point on computed tomographic perfusion values in normal liver and metastases to the liver from neuroendocrine tumors.
abstract: OBJECTIVE
  The objective of this study was to assess the effects of pre-enhancement set point (T1) positioning on computed tomographic perfusion (CTp) parameter values.
  
  
  METHODS
  The CTp data from 16 patients with neuroendocrine liver metastases were analyzed with distributed parameter modeling to yield tissue blood flow (BF), blood volume, mean transit time, permeability, and hepatic arterial fraction for tumor and normal liver, with displacements in T1 of ±0.5, ±1.0, ±2.0 seconds, relative to the reference standard. A linear mixed-effects model was used to assess the displacement effects.
  
  
  RESULTS
  Effects on the CTp parameter values were variable: BF was not significantly affected, but T1 positions of ≥+1.0 second and -2.0 seconds or longer significantly affected the other CTp parameters (P ≤ 0.004). Mean differences in the CTp parameter values versus the reference standard for BF, blood volume, mean transit time, permeability, and hepatic arterial fraction ranged from -5.0% to 5.2%, -12.7% to 8.9%, -12.5% to 8.1%, -5.3% to 5.7%, and -12.9% to 26.0%, respectively.
  
  
  CONCLUSIONS
  CTp parameter values can be significantly affected by T1 positioning.
authors.affiliation: From the Departments of *Diagnostic Radiology, †Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, TX; ‡CT Research, GE Healthcare, Waukesha, WI; Departments of §Gastrointestinal Medical Oncology, and ∥Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, TX.
authors.forename: Chaan S
authors.initials: CS
authors.lastname: Ng
authors.forename: Adam G
authors.initials: AG
authors.lastname: Chandler
authors.forename: James C
authors.initials: JC
authors.lastname: Yao
authors.forename: Delise H
authors.initials: DH
authors.lastname: Herron
authors.forename: Ella F
authors.initials: EF
authors.lastname: Anderson
authors.forename: Chusilp
authors.initials: C
authors.lastname: Charnsangavej
authors.forename: Brian P
authors.initials: BP
authors.lastname: Hobbs
mesh_terms: D000328:Adult; D000368:Aged; D001783:Blood Flow Velocity; D005260:Female; D006801:Humans; D008099:Liver / Q000098:blood supply* / Q000000981:diagnostic imaging*; D008113:Liver Neoplasms / Q000098:blood supply* / Q000000981:diagnostic imaging* / Q000556:secondary; D008297:Male; D008875:Middle Aged; D018358:Neuroendocrine Tumors / Q000473:pathology*; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*