title: Non-invasive quantification of cerebral blood flow for rats by microPET imaging of 15O labelled water: the application of a cardiac time-activity curve for the tracer arterial input function.
abstract: OBJECTIVE
  In-vivo quantitative cerebral blood flow (CBF) measurement using positron emission tomography (PET) has typically employed invasive arterial blood sampling procedure to determine the arterial input function (AIF). The present study was performed to provide a non-invasive quantitative CBF measurement technique for rats using a dedicated animal PET.
  
  
  METHODS
  CBF was measured in 10 male rats (Fischer 344, 247-290 g) under alpha-chloralose anesthesia (30 mg x kg . h, intravenous infusion) by dynamic PET imaging employing the intravenous bolus injection of H2(15)O. Unlike other conventional PET methods, no arterial blood sampling was employed. Instead, a cardiac time-activity curve (TAC) obtained from the dynamic PET imaging was used to determine the AIF. For the validation of this technique, CBF was also measured by calculating the washout rate of the tracer (H2(15)O) following an intracarotid bolus injection. CBF measurements by two independent methods were done while modulating and maintaining the body temperature at two different levels (32+/-1 and 37+/-1 degrees C by the rectal temperature). Two methods were compared by the linear regression analysis.
  
  
  RESULTS
  CBF (ml x 100 g x min) values (mean+/-SD) were 45.2+/-6.05 (intravenous) and 47.4+/-8.64 (intracarotid) at the hypothermic condition (32 degrees C), and 55.1+/-4.88 (intravenous) and 54.4+/-4.60 (intracarotid) at the normothermic condition (37 degrees C). There was a good agreement between the two methods (r=0.70).
  
  
  CONCLUSIONS
  Our cardiac TAC analysis technique for small animals can be used for the non-invasive quantification of CBF using the PET-based in-vivo imaging technique.
authors.affiliation: Research Imaging Center, University of Texas Health Science Center at San Antonio, USA. yees@uthscsa.edu
authors.forename: Seong-Hwan
authors.initials: SH
authors.lastname: Yee
authors.forename: Paul A
authors.initials: PA
authors.lastname: Jerabek
authors.forename: Peter T
authors.initials: PT
authors.lastname: Fox
mesh_terms: D000818:Animals; D001921:Brain / Q000098:blood supply* / Q000000981:diagnostic imaging* / Q000378:metabolism; D002536:Cerebral Arteries / Q000000981:diagnostic imaging / Q000378:metabolism / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D010104:Oxygen Radioisotopes / Q000493:pharmacokinetics; D049268:Positron-Emission Tomography / Q000379:methods* / Q000662:veterinary*; D011865:Radioisotope Dilution Technique; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D051381:Rats; D011916:Rats, Inbred F344; D014867:Water / Q000378:metabolism
chemical_list: D010104:Oxygen Radioisotopes; D019275:Radiopharmaceuticals; D014867:Water