title: Detecting physiological systems with laser speckle perfusion imaging of the renal cortex.
abstract: Laser speckle perfusion imaging (LSPI) has become an increasingly popular technique for monitoring vascular perfusion over a tissue surface. However, few studies have utilized the full range of spatial and temporal information generated by LSPI to monitor spatial properties of physiologically relevant dynamics. In this study, we extend the use of LSPI to analyze renal perfusion dynamics over a spatial surface of ~5 × 7 mm of renal cortex. We identify frequencies related to five physiological systems that induce temporal changes in renal vascular perfusion (cardiac flow pulse, respiratory-induced oscillations, baroreflex components, the myogenic response, and tubuloglomerular feedback) across the imaged surface and compare the results with those obtained from renal blood flow measurements. We find that dynamics supplied from global sources (cardiac, respiration, and baroreflex) present with the same frequency at all locations across the imaged surface, but the local renal autoregulation dynamics can be heterogeneous in their distribution across the surface. Moreover, transfer function analysis with forced blood pressure as the input yields the same information with laser speckle imaging or renal blood flow as the output during control, intrarenal infusion of N(ω)-nitro-L-arginine methyl ester to enhance renal autoregulation, and intrarenal infusion of the rho-kinase inhibitor Y-27632 to inhibit vasomotion. We conclude that LSPI measurements can be used to analyze local as well as global renal perfusion dynamics and to study the properties of physiological systems across the renal cortex.
authors.affiliation: Department of Biomedical Engineering, Worcester Polytechnic Institute, Worcester, MA 01609, USA.
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Scully
authors.forename: Nicholas
authors.initials: N
authors.lastname: Mitrou
authors.forename: Branko
authors.initials: B
authors.lastname: Braam
authors.forename: William A
authors.initials: WA
authors.lastname: Cupples
authors.forename: Ki H
authors.initials: KH
authors.lastname: Chon
mesh_terms: D000465:Algorithms; D000577:Amides / Q000494:pharmacology; D000818:Animals; D017704:Baroreflex / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D025461:Feedback, Physiological; D006339:Heart Rate / Q000502:physiology; D006706:Homeostasis / Q000502:physiology; D007091:Image Processing, Computer-Assisted; D007672:Kidney Cortex / Q000098:blood supply / Q000502:physiology*; D007678:Kidney Glomerulus / Q000502:physiology; D007684:Kidney Tubules / Q000502:physiology; D007834:Lasers; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D052250:Nitric Oxide Synthase Type III / Q000037:antagonists & inhibitors; D055420:Perfusion Imaging / Q000379:methods*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D020318:Rats, Long-Evans; D012079:Renal Circulation / Q000502:physiology*; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors
chemical_list: D000577:Amides; D004791:Enzyme Inhibitors; D047428:Protein Kinase Inhibitors; D011725:Pyridines; C108830:Y 27632; D052250:Nitric Oxide Synthase Type III; D054460:rho-Associated Kinases; D019331:NG-Nitroarginine Methyl Ester
keywords: laser speckle imaging; myogenic response; renal autoregulation; tubuloglomerular feedback