title: Noninvasive mapping of water diffusional exchange in the human brain using filter-exchange imaging.
abstract: We present the first in vivo application of the filter-exchange imaging protocol for diffusion MRI. The protocol allows noninvasive mapping of the rate of water exchange between microenvironments with different self-diffusivities, such as the intracellular and extracellular spaces in tissue. Since diffusional water exchange across the cell membrane is a fundamental process in human physiology and pathophysiology, clinically feasible and noninvasive imaging of the water exchange rate would offer new means to diagnose disease and monitor treatment response in conditions such as cancer and edema. The in vivo use of filter-exchange imaging was demonstrated by studying the brain of five healthy volunteers and one intracranial tumor (meningioma). Apparent exchange rates in white matter range from 0.8±0.08 s(-1) in the internal capsule, to 1.6±0.11 s(-1) for frontal white matter, indicating that low values are associated with high myelination. Solid tumor displayed values of up to 2.9±0.8 s(-1). In white matter, the apparent exchange rate values suggest intra-axonal exchange times in the order of seconds, confirming the slow exchange assumption in the analysis of diffusion MRI data. We propose that filter-exchange imaging could be used clinically to map the water exchange rate in pathologies. Filter-exchange imaging may also be valuable for evaluating novel therapies targeting the function of aquaporins.
authors: Department of Medical Radiation Physics, Lund University, Lund, Sweden. markus.nilsson@med.lu.se
authors: Markus
authors: M
authors: Nilsson
authors: Jimmy
authors: J
authors: Lätt
authors: Danielle
authors: D
authors: van Westen
authors: Sara
authors: S
authors: Brockstedt
authors: Samo
authors: S
authors: Lasič
authors: Freddy
authors: F
authors: Ståhlberg
authors: Daniel
authors: D
authors: Topgaard
mesh_terms: D000328:Adult; D000465:Algorithms; D001923:Brain Chemistry; D060833:Cellular Microenvironment / Q000502:physiology*; D004058:Diffusion; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water