title: CPMG relaxation rate dispersion in dipole fields around capillaries.
abstract: Transverse relaxation rates for Carr-Purcell-Meiboom-Gill (CPMG) sequences increase with inter-echo time in presence of microscopic magnetic field inhomogeneities due to nuclear spin diffusion. For a weak field approximation that includes diffusion effects, the CPMG relaxation rate shift for proton diffusion around capillaries in muscle tissue can be expressed in terms of a frequency correlation function and the inter-echo time. The present work provides an analytical expression for the local relaxation rate shift that is dependent on local blood volume fraction, diffusion coefficient, capillary radius, susceptibility difference and inter-echo time. Asymptotic regions of the model are in agreement with previous modeling results of Brooks et al., Luz et al. and Ziener et al. In comparison with simulation data, the model shows an equal or better accuracy than established approximations. Also, model behavior coincides with experimental data for rat heart and skeletal muscle. The present work provides analytical tools to extract sub-voxel information about uniform capillary networks that can be used to study capillary organization or micro-circulatory remodeling.
authors.affiliation: Heidelberg University Hospital, INF 400, D-69120 Heidelberg, Germany; German Cancer Research Center, E010 Radiology, INF 280, D-69120 Heidelberg, Germany. Electronic address: felix.kurz@med.uni-heidelberg.de.
authors.forename: F T
authors.initials: FT
authors.lastname: Kurz
authors.affiliation: University of Würzburg, Dept. of Experimental Physics 5, Am Hubland, D-97074 Würzburg, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Kampf
authors.affiliation: German Cancer Research Center, E010 Radiology, INF 280, D-69120 Heidelberg, Germany.
authors.forename: L R
authors.initials: LR
authors.lastname: Buschle
authors.affiliation: Heidelberg University Hospital, INF 400, D-69120 Heidelberg, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Heiland
authors.affiliation: German Cancer Research Center, E010 Radiology, INF 280, D-69120 Heidelberg, Germany.
authors.forename: H-P
authors.initials: HP
authors.lastname: Schlemmer
authors.affiliation: Heidelberg University Hospital, INF 400, D-69120 Heidelberg, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Bendszus
authors.affiliation: Heidelberg University Hospital, INF 400, D-69120 Heidelberg, Germany; German Cancer Research Center, E010 Radiology, INF 280, D-69120 Heidelberg, Germany.
authors.forename: C H
authors.initials: CH
authors.lastname: Ziener
mesh_terms: D000818:Animals; D002196:Capillaries / Q000502:physiology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D008955:Models, Cardiovascular; D008962:Models, Theoretical; D009132:Muscles / Q000098:blood supply*; D011522:Protons; D051381:Rats; D066253:Vascular Remodeling / Q000502:physiology
chemical_list: D011522:Protons
keywords: CPMG sequence; Capillary; Correlation function; Muscle tissue; Susceptibility effects; Transverse relaxation