title: Microstructural Analysis of Peripheral Lung Tissue through CPMG Inter-Echo Time R2 Dispersion.
abstract: Since changes in lung microstructure are important indicators for (early stage) lung pathology, there is a need for quantifiable information of diagnostically challenging cases in a clinical setting, e.g. to evaluate early emphysematous changes in peripheral lung tissue. Considering alveoli as spherical air-spaces surrounded by a thin film of lung tissue allows deriving an expression for Carr-Purcell-Meiboom-Gill transverse relaxation rates R2 with a dependence on inter-echo time, local air-tissue volume fraction, diffusion coefficient and alveolar diameter, within a weak field approximation. The model relaxation rate exhibits the same hyperbolic tangent dependency as seen in the Luz-Meiboom model and limiting cases agree with Brooks et al. and Jensen et al. In addition, the model is tested against experimental data for passively deflated rat lungs: the resulting mean alveolar radius of RA = 31.46 ± 13.15 μm is very close to the literature value (∼34 μm). Also, modeled radii obtained from relaxometer measurements of ageing hydrogel foam (that mimics peripheral lung tissue) are in good agreement with those obtained from μCT images of the same foam (mean relative error: 0.06 ± 0.01). The model's ability to determine the alveolar radius and/or air volume fraction will be useful in quantifying peripheral lung microstructure.
authors.affiliation: Department of Neuroradiology, Heidelberg University, Heidelberg, Germany.|Department of Radiology, German Cancer Research Center, Heidelberg, Germany.
authors.forename: Felix T
authors.initials: FT
authors.lastname: Kurz
authors.affiliation: Department of Experimental Physics 5, Würzburg University, Würzburg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Kampf
authors.affiliation: Department of Radiology, German Cancer Research Center, Heidelberg, Germany.
authors.forename: Lukas R
authors.initials: LR
authors.lastname: Buschle
authors.affiliation: Department of Radiology, German Cancer Research Center, Heidelberg, Germany.
authors.forename: Heinz-Peter
authors.initials: HP
authors.lastname: Schlemmer
authors.affiliation: Department of Neuroradiology, Heidelberg University, Heidelberg, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Heiland
authors.affiliation: Department of Neuroradiology, Heidelberg University, Heidelberg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Bendszus
authors.affiliation: Department of Neuroradiology, Heidelberg University, Heidelberg, Germany.|Department of Radiology, German Cancer Research Center, Heidelberg, Germany.
authors.forename: Christian H
authors.initials: CH
authors.lastname: Ziener
mesh_terms: D000818:Animals; D040761:Biomimetic Materials; D004058:Diffusion; D020100:Hydrogels; D007700:Kinetics; D008297:Male; D008954:Models, Biological; D057054:Molecular Imaging; D011650:Pulmonary Alveoli / Q000166:cytology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D020100:Hydrogels