The Kärger vs bi-exponential model: Theoretical insights and experimental validations

Nicolas Moutal; Markus Nilsson; Daniel Topgaard; Denis Grebenkov

doi:10.1016/j.jmr.2018.08.015

The Kärger vs bi-exponential model: Theoretical insights and experimental validations

J Magn Reson. 2018 Nov:296:72-78. doi: 10.1016/j.jmr.2018.08.015. Epub 2018 Aug 31.

Authors

Nicolas Moutal¹, Markus Nilsson², Daniel Topgaard², Denis Grebenkov³

Affiliations

¹ PMC, CNRS - Ecole Polytechnique, F-91128 Palaiseau, France. Electronic address: nicolas.moutal@polytechnique.edu.
² Physical Chemistry, Lund University, P.O.B. 124, SE-22100 Lund, Sweden.
³ PMC, CNRS - Ecole Polytechnique, F-91128 Palaiseau, France. Electronic address: denis.grebenkov@polytechnique.edu.

PMID: 30223153
DOI: 10.1016/j.jmr.2018.08.015

Abstract

We revise three common models accounting for water exchange in pulsed-gradient spin-echo measurements: a bi-exponential model with time-dependent water fractions, the Kärger model, and a modified Kärger model designed for restricted diffusion, e.g. inside cells. The three models are compared and applied to experimental data from yeast cell suspensions. The Kärger model and the modified Kärger model yield very close results and accurately fit the data. The bi-exponential model, although less rigorous, has a natural physical interpretation and suggests a new experimental modality to estimate the water exchange time.

Keywords: Bi-exponential model; Kärger model; PGSE; Permeability; Water exchange; Yeast cells.