title: Comparing kidney perfusion using noncontrast arterial spin labeling MRI and microsphere methods in an interventional swine model.
abstract: OBJECTIVE
  The purpose of this study was to assess the ability of a flow-sensitive alternating inversion recovery-arterial spin labeling (FAIR-ASL) technique to track renal perfusion changes during pharmacologic and physiologic alterations in renal blood flow using microspheres as a gold standard.
  
  
  METHODS
  Fluorescent microsphere and FAIR-ASL perfusion were compared in the cortex of the kidney for 11 swine across 4 interventional time points: (1) under baseline conditions, (2) during an acetylcholine and fluid bolus challenge to increase perfusion, (3) initially after switching to isoflurane anesthesia, and (4) after 2 hours of isoflurane anesthesia. In 10 of the 11 swine, a bag of ice was placed on the hilum of 1 kidney at the beginning of isoflurane administration to further reduce perfusion in 1 kidney.
  
  
  RESULTS
  Both ASL and microspheres tracked the expected cortical perfusion changes (P < 0.02) across the interventions, including an increase in perfusion during the acetylcholine challenge and decrease during the administration of isoflurane. Both techniques also measured lower cortical perfusion in the iced compared with the non-iced kidneys (P ≤ 0.01). The ASL values were systematically lower compared with microsphere perfusion. Very good correlation (r = 0.81, P < 0.0001) was observed between the techniques, and the relationship appeared linear for perfusion values in the expected physiologic range (microsphere perfusion <550 mL/min/100 g) although ASL values saturated for perfusion >550 mL/min/100 g.
  
  
  CONCLUSIONS
  Cortical perfusion measured with ASL correlated with microspheres and reliably detected changes in renal perfusion in response to physiologic challenge.
authors.affiliation: Department of Medical Physics, Wisconsin Institute for Medical Research, University of Wisconsin-Madison, 1111 Highland Ave, Madison, WI 53705, USA.
authors.forename: Nathan S
authors.initials: NS
authors.lastname: Artz
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Wentland
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Sadowski
authors.forename: Arjang
authors.initials: A
authors.lastname: Djamali
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Grist
authors.forename: Songwon
authors.initials: S
authors.lastname: Seo
authors.forename: Sean B
authors.initials: SB
authors.lastname: Fain
mesh_terms: D000818:Animals; D001158:Arteries; D005260:Female; D007668:Kidney / Q000098:blood supply*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D008863:Microspheres; D010477:Perfusion; D011237:Predictive Value of Tests; D012079:Renal Circulation; D015203:Reproducibility of Results; D013113:Spin Labels; D013223:Statistics as Topic; D034421:Sus scrofa; D013552:Swine
chemical_list: D013113:Spin Labels