Filter-exchange PGSE NMR determination of cell membrane permeability

Åslund, Ingrid; Nowacka, Agnieszka; Nilsson, Markus; Topgaard, Daniel

doi:10.1016/j.jmr.2009.07.015

Cited by 98 publications

(135 citation statements)

References 36 publications

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“…where k sf and k fs are the forward and reverse exchange rates between the slow and the fast compartment, and f 0 f (0) is the fast fraction immediately after the filter (9). Due to mass balance, k sf and k fs are related to the fractions according to f s k sf ¼ f f k fs .…”

Section: Filter Exchange Imagingmentioning

confidence: 99%

“…However, water exchange takes place between the compartments, either directly through the lipid bilayer or facilitated through so-called aquaporins (AQP) (6,7). The exchange rate is proportional to the cell membrane permeability to water (8,9), which is important for cell volume regulation (10) and for conditions involving edema such as tumors, infection, and stroke (11,12). In aggressive tumors, AQP upregulation has been demonstrated (13)(14)(15).…”

Section: Introductionmentioning

confidence: 99%

“…With increased diffusion time, effects from exchange increase the attenuation for high b-values, whereas effects from restriction reduce it (18). For higher specificity to exchange, a double-diffusion encoding (DDE) sequence can be employed (9,19). Filter exchange imaging (FEXI) is a DDE-based method implemented for clinical use that yields the apparent exchange rate (AXR) (20).…”

Section: Introductionmentioning

confidence: 99%

“…The AXR is sensitive to changes in membrane permeability (9,20), and has been measured in the healthy human brain and a meningioma brain tumor (21). In fixed monkey brain, a tensor-based AXR analysis has been explored (22).…”

Section: Introductionmentioning

confidence: 99%

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Optimal experimental design for filter exchange imaging: Apparent exchange rate measurements in the healthy brain and in intracranial tumors

Lampinen

Szczepankiewicz

Westen

et al. 2017

Magnetic Resonance in Med

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Purpose: Filter exchange imaging (FEXI) is sensitive to the rate of diffusional water exchange, which depends, eg, on the cell membrane permeability. The aim was to optimize and analyze the ability of FEXI to infer differences in the apparent exchange rate (AXR) in the brain between two populations. Methods: A FEXI protocol was optimized for minimal measurement variance in the AXR. The AXR variance was investigated by test-retest acquisitions in six brain regions in 18 healthy volunteers. Preoperative FEXI data and postoperative microphotos were obtained in six meningiomas and five astrocytomas. Results: Protocol optimization reduced the coefficient of variation of AXR by approximately 40%. Test-retest AXR values were heterogeneous across normal brain regions, from 0.3 6 0.2 s À1

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Section: Filter Exchange Imagingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Optimal experimental design for filter exchange imaging: Apparent exchange rate measurements in the healthy brain and in intracranial tumors

Lampinen

Szczepankiewicz

Westen

et al. 2017

Magnetic Resonance in Med

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“…Furthermore, DDE has been used to estimate molecular exchange between compartments. Åslund et al [9], based on the work of Callaghan and Furó [8], developed filter exchange spectroscopy (FEXSY). FEXSY showed that exchange rates can be assessed in a sample with well-defined compartments (yeast suspension).…”

Section: Introductionmentioning

confidence: 99%

Experimental validation of a bias in apparent exchange rate measurement

Ulloa

Methot

Koch

2017

Current Directions in Biomedical Engineering

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Double diffusion encoding (DDE) MRI is a technique in which two diffusion weighted periods are applied between excitation and acquisition. This allows to acquire structural information (as pore size and shape) and molecular exchange between compartments, in terms of apparent exchange rate (AXR). However, it has not been well investigated yet whether the diffusion restriction underlying DDE size estimation may compromise AXR results.Numerical simulations for impermeable spheres have shown that in case of small pores (diameter < 10 µm) the restriction effect may be neglected. Yet, for larger pores, the restriction effect can be relevant and needs to be considered in the analysis of experiments.Here, we present experiments performed on a 3 T clinical MRI system using a water-in-oil emulsion in which no exchange between compartments is expected. The results show that a nonzero apparent exchange rate may be estimated in a sample with impermeable pores. This shows that, as predicted in simulations, the restriction effect affects the AXR results. The use of perpendicular diffusion gradients may be a solution for this problem in isotropic samples.

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Apparent exchange rate mapping with diffusion MRI

Lasič

Nilsson

Lätt

et al. 2011

Magnetic Resonance in Med

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114

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Water exchange through the cell membranes is an important feature of cells and tissues. The rate of exchange is determined by factors such as membrane lipid composition and organization, as well as the type and activity of aquaporins. A method for noninvasively estimating the rate of water exchange would be useful for characterizing pathological conditions, e.g., tumors, multiple sclerosis, and ischemic stroke, expected to be associated with a change of the membrane barrier properties. This study describes the filter exchange imaging method for determining the rate of water exchange between sites having different apparent diffusion coefficients. The method is based on the filter-exchange pulsed gradient spin-echo NMR spectroscopy experiment, which is here modified to be compatible with the constraints of clinical MR scanners. The data is analyzed using a modelfree approach yielding maps of the apparent exchange rate, here being introduced in analogy with the concept of the apparent diffusion coefficient. Proof-of-principle experiments are performed on microimaging and whole-body clinical scanners using yeast suspension phantoms. The limitations and appropriate experimental conditions are examined. The results demonstrate that filter exchange imaging is a fast and reliable method for characterizing exchange, and that it has the potential to become a powerful diagnostic tool. Magn Reson Med 66:356-365,

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Filter-exchange PGSE NMR determination of cell membrane permeability

Cited by 98 publications

References 36 publications

Optimal experimental design for filter exchange imaging: Apparent exchange rate measurements in the healthy brain and in intracranial tumors

Optimal experimental design for filter exchange imaging: Apparent exchange rate measurements in the healthy brain and in intracranial tumors

Experimental validation of a bias in apparent exchange rate measurement

Apparent exchange rate mapping with diffusion MRI

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