title: Pixel-by-pixel mean transit time without deconvolution.
abstract: BACKGROUND
  Mean transit time (MTT) within a kidney is given by the integral of the renal activity on a well-corrected renogram between time zero and time t divided by the integral of the plasma activity between zero and t, providing that t is close to infinity. However, as the data acquisition of a renogram is finite, the MTT calculated using this approach might result in the underestimation of the true MTT. To evaluate the degree of this underestimation we conducted a simulation study.
  
  
  METHODS
  One thousand renograms were created by convoluting various plasma curves obtained from patients with different renal clearance levels with simulated retentions curves having different shapes and mean transit times.
  
  
  RESULTS
  For a 20 min renogram, the calculated MTT started to underestimate the MTT when the MTT was higher than 6 min. The longer the MTT, the greater was the underestimation. Up to a MTT value of 6 min, the error on the MTT estimation is negligible.
  
  
  CONCLUSIONS
  As normal cortical transit is less than 2 min, this approach is used for patients to calculate pixel-to-pixel cortical mean transit time and to create a MTT parametric image without deconvolution.
authors.affiliation: Department of Nuclear Medicine, University Hospital Ghent, Ghent, Belgium. andre.dobbeleir@skynet.be
authors.forename: Andre A
authors.initials: AA
authors.lastname: Dobbeleir
authors.forename: Amy
authors.initials: A
authors.lastname: Piepsz
authors.forename: Hamphrey R
authors.initials: HR
authors.lastname: Ham
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007668:Kidney / Q000000981:diagnostic imaging* / Q000378:metabolism*; D008657:Metabolic Clearance Rate; D008954:Models, Biological; D011866:Radioisotope Renography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D019275:Radiopharmaceuticals