title: MR imaging of apparent 3He gas transport in narrow pipes and rodent airways.
abstract: High sensitivity makes hyperpolarized (3)He an attractive signal source for visualizing gas flow with magnetic resonance (MR) imaging. Its rapid Brownian motion, however, can blur observed flow lamina and alter measured diffusion rates when excited nuclei traverse shear-induced velocity gradients during data acquisition. Here, both effects are described analytically, and predicted values for measured transport during laminar flow through a straight, 3.2-mm diameter pipe are validated using two-dimensional (2D) constant-time images of different binary gas mixtures. Results show explicitly how measured transport in narrow conduits is characterized by apparent values that depend on underlying gas dynamics and imaging time. In ventilated rats, this is found to obscure acquired airflow images. Nevertheless, flow splitting at airway branches is still evident and use of 3D vector flow mapping is shown to reveal surprising detail that highlights the correlation between gas dynamics and lung structure.
authors.affiliation: Pacific Northwest National Laboratory, MSIN P7-58, Richland, WA 99352, USA. kevin.minard@pnl.gov
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Minard
authors.forename: Richard E
authors.initials: RE
authors.lastname: Jacob
authors.forename: Gernot
authors.initials: G
authors.lastname: Laicher
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Einstein
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Kuprat
authors.forename: Richard A
authors.initials: RA
authors.lastname: Corley
mesh_terms: D000818:Animals; D003198:Computer Simulation; D003287:Contrast Media / Q000493:pharmacokinetics; D006371:Helium / Q000493:pharmacokinetics*; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007554:Isotopes / Q000493:pharmacokinetics; D008168:Lung / Q000033:anatomy & histology* / Q000378:metabolism*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008954:Models, Biological; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D003287:Contrast Media; D007554:Isotopes; D019275:Radiopharmaceuticals; D006371:Helium