title: In vivo MR imaging of pulmonary perfusion and gas exchange in rats via continuous extracorporeal infusion of hyperpolarized 129Xe.
abstract: BACKGROUND
  Hyperpolarized (HP) (129)Xe magnetic resonance imaging (MRI) permits high resolution, regional visualization of pulmonary ventilation. Additionally, its reasonably high solubility (>10%) and large chemical shift range (>200 ppm) in tissues allow HP (129)Xe to serve as a regional probe of pulmonary perfusion and gas transport, when introduced directly into the vasculature. In earlier work, vascular delivery was accomplished in rats by first dissolving HP (129)Xe in a biologically compatible carrier solution, injecting the solution into the vasculature, and then detecting HP (129)Xe as it emerged into the alveolar airspaces. Although easily implemented, this approach was constrained by the tolerable injection volume and the duration of the HP (129)Xe signal.
  
  
  RESULTS
  Here, we overcome the volume and temporal constraints imposed by injection, by using hydrophobic, microporous, gas-exchange membranes to directly and continuously infuse (129)Xe into the arterial blood of live rats with an extracorporeal (EC) circuit. The resulting gas-phase (129)Xe signal is sufficient to generate diffusive gas exchange- and pulmonary perfusion-dependent, 3D MR images with a nominal resolution of 2×2×2 mm(3). We also show that the (129)Xe signal dynamics during EC infusion are well described by an analytical model that incorporates both mass transport into the blood and longitudinal relaxation.
  
  
  CONCLUSIONS
  Extracorporeal infusion of HP (129)Xe enables rapid, 3D MR imaging of rat lungs and, when combined with ventilation imaging, will permit spatially resolved studies of the ventilation-perfusion ratio in small animals. Moreover, EC infusion should allow (129)Xe to be delivered elsewhere in the body and make possible functional and molecular imaging approaches that are currently not feasible using inhaled HP (129)Xe.
authors.affiliation: Department of Radiology, Duke University Medical Center, Durham, North Carolina, United States of America.
authors.forename: Zackary I
authors.initials: ZI
authors.lastname: Cleveland
authors.forename: Harald E
authors.initials: HE
authors.lastname: Möller
authors.forename: Laurence W
authors.initials: LW
authors.lastname: Hedlund
authors.forename: John C
authors.initials: JC
authors.lastname: Nouls
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Freeman
authors.forename: Yi
authors.initials: Y
authors.lastname: Qi
authors.forename: Bastiaan
authors.initials: B
authors.lastname: Driehuys
mesh_terms: D000818:Animals; D003198:Computer Simulation; D005112:Extracorporeal Circulation / Q000379:methods*; D008168:Lung / Q000098:blood supply* / Q000187:drug effects / Q000502:physiology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008954:Models, Biological; D010477:Perfusion; D011659:Pulmonary Gas Exchange / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012119:Respiration / Q000187:drug effects; D012815:Signal Processing, Computer-Assisted; D014978:Xenon / Q000008:administration & dosage* / Q000494:pharmacology*; D014979:Xenon Isotopes
chemical_list: D014979:Xenon Isotopes; D014978:Xenon