title: Glomerular filtration rate measured by using triphasic helical CT with a two-point Patlak plot technique.
abstract: OBJECTIVE
  To determine the accuracy of the two-point Patlak plot in the calculation of glomerular filtration rate (GFR).
  
  
  METHODS
  Fifty patients without acute renal disorder were included. GFR was calculated by using a two-point Patlak plot technique. The computed tomography (CT) protocol consisted of a plain examination followed by two contrast material-enhanced examinations in the arterial and portovenous phase. Each examination included the entire kidneys and was performed after injection of 120 mL iopromide and 300 mg of iodine per milliliter given per 75 kg of body weight. All examinations were performed with a standard abdominal protocol. Section thickness was 4 x 2.5 mm, and table advance was 12.5 mm. Bolus triggering commenced 10 seconds after the start of contrast medium injection. Twelve dynamic scans were obtained with reduced tube current every 3 seconds to obtain sufficient arterial input function data. Correction for hematocrit level was made by using the unenhanced attenuation of the aorta. As a reference method, plasma clearance of the contrast medium injected for CT was calculated from three iodine plasma concentration measurements obtained 3, 4, and 5 hours after injection. Linear correlation was performed.
  
  
  RESULTS
  GFR was calculated from CT data in 48 patients. Two patients were excluded because of breathing errors. Mean GFR was 80 mL/min (range, 17-153 mL/min) as measured with iopromide plasma clearance and 82 mL/min (range, 28-148 mL/min) as measured with CT. Linear correlation between the two methods was r = 0.889; GFR calculated with the two-point Patlak plot was equal to 15 plus 0.83 times GFR (plasma clearance). The mean difference between GFRs as determined with the two methods was -1.2 mL/min (95% CI: -27.1, 24.6).
  
  
  CONCLUSIONS
  Total GFR can be measured accurately with minimally extended triphasic CT in patients without acute renal disorder by using a two-point Patlak plot technique.
authors.affiliation: Department of Diagnostic Radiology, Justus-Liebig Universität Giessen, Klinikstr 36, 35385 Giessen, Germany.
authors.forename: Nils
authors.initials: N
authors.lastname: Hackstein
authors.forename: Cornelia
authors.initials: C
authors.lastname: Wiegand
authors.forename: Wigbert Stefan
authors.initials: WS
authors.lastname: Rau
authors.forename: Alexander Claus
authors.initials: AC
authors.lastname: Langheinrich
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007674:Kidney Diseases / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D007677:Kidney Function Tests / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed