title: Quantification of water compartmentation in cell suspensions by diffusion-weighted and T(2)-weighted MRI.
abstract: When studying water diffusion in biological systems, any specific signal attenuation curve may be reproduced by a broad range of mathematical functions. Our goals were to quantify the diffusion and T(2) relaxation properties of water in a simple biological system and to study the changes that occur in osmotically stressed cells. Human breast cancer cells were incubated in isotonic or hypotonic osmotic buffers. Diffusion-weighted and T(2)-weighted magnetic resonance images were acquired during sedimentation over 12 h. Diffusion-weighted imaging (DWI) data were analyzed with a biexponential fit, the Kärger model for exchange between two freely diffusing populations and the Price-modified Kärger model accounting for restricted diffusion in spherical geometry. We found that only the Price model provided an accurate quantitative description for water diffusion in both cell systems, independent of acquisition parameters, over the entire density range. Model-derived cell radii, intracellular volume fractions and transmembrane water exchange times were in good agreement with results calculated from light microscopy and with model-free exchange times. T(2) data indicated two populations in fast exchange, with volume fractions clearly different from DWI populations. Hypotonic stress led to higher slow apparent diffusion coefficient, longer T(2) and lower membrane permeability. The tortuosity in a hypotonic cell suspension complied with the Wang model for spherical geometry. Quantitative characterization of biological systems is obtainable by DWI, using appropriate modeling, accounting for water restriction and exchange between compartments.
authors.affiliation: Advanced Technology Center, Sheba Medical Center, Tel-Hashomer 52621, Israel.
authors.forename: Yiftach
authors.initials: Y
authors.lastname: Roth
authors.forename: Aharon
authors.initials: A
authors.lastname: Ocherashvilli
authors.forename: Dianne
authors.initials: D
authors.lastname: Daniels
authors.forename: Jesus
authors.initials: J
authors.lastname: Ruiz-Cabello
authors.forename: Stephan E
authors.initials: SE
authors.lastname: Maier
authors.forename: Arie
authors.initials: A
authors.lastname: Orenstein
authors.forename: Yael
authors.initials: Y
authors.lastname: Mardor
mesh_terms: D001834:Body Water / Q000378:metabolism*; D001943:Breast Neoplasms / Q000378:metabolism*; D004058:Diffusion; D038524:Diffusion Magnetic Resonance Imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted; D016018:Least-Squares Analysis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D013535:Suspensions
chemical_list: D013535:Suspensions