Diffusion NMR spectroscopy

Abstract

MR offers unique tools for measuring molecular diffusion. This review focuses on the use of diffusionweighted MR spectroscopy (DW-MRS) to non-invasively quantitate the translational displacement of endogenous metabolites in intact mammalian tissues. Most of the metabolites that are observed by in vivo MRS are predominantly located in the intracellular compartment. DW-MRS is of fundamental interest because it enables one to probe the in situ status of the intracellular space from the diffusion characteristics of the metabolites, while at the same time providing information on the intrinsic diffusion properties of the metabolites themselves. Alternative techniques require the introduction of exogenous probe molecules, which involves invasive procedures, and are also unable to measure molecular diffusion in and throughout intact tissues. The length scale of the process(es) probed by MR is in the micrometer range which is of the same order as the dimensions of many intracellular entities. DW-MRS has been used to estimate the dimensions of the cellular elements that restrict intracellular metabolite diffusion in muscle and nerve tissue. In addition, it has been shown that DW-MRS can provide novel information on the cellular response to pathophysiological changes in relation to a range of disorders, including ischemia and excitotoxicity of the brain and cancer.

Diffusion tensor spectroscopy (DTS) of human brain

“…Diffusion ordered spectroscopy (DOSY) has demonstrated enormous potential in the fields of chemistry and biochemistry (1); however, the investigation of metabolite diffusion (molecules other than water) in vivo has lagged behind due to technical challenges, such as limited signal-to-noise ratio, poor spatial resolution, pulse sequence availability, significant post-processing, lengthy acquisition times, and limited brain coverage. Despite these challenges, the pursuit of metabolite diffusion in diseased tissue is worthwhile since it may yield insights into changes in the underlying intra-cellular environment with disease (2)(3)(4)(5).…”

Diffusion-weighted Line-scan Echo-planar Spectroscopic Imaging Technique to Reduce Motion Artifacts in Metabolite Diffusion Imaging

“…[1][2][3][4] Many studies have used diffusion-weighted spectroscopy (DWS) especially to investigate changes in metabolite diffusion at ischemia 5 -9 and properties of metabolite diffusion that differ from those of water. 10 -15 However, only a few studies have employed diffusionweighted spectroscopic imaging (DWSI).…”

Daydreaming about Our Metaphorical Tool Belt

“…4 We would seem to be in an era of increased emphasis on quantification, and this technique may eventually lend itself nicely to that paradigm. DW-MR imaging has been studied in nervous system and musculoskeletal tissues, 4 and in normal and disease states, including ischemia and neoplasia. 4 Some of the metabolites studied include glucose and lactate.…”

“…[2][3][4][5] Arguably well-summarized in the abstract of a review by Nicolay and colleagues in NMR in Biomedicine in 2001, this research tool allows one to "noninvasively quantitate the translational displacement of endogenous metabolites in intact mammalian tissues." 4 We would seem to be in an era of increased emphasis on quantification, and this technique may eventually lend itself nicely to that paradigm. DW-MR imaging has been studied in nervous system and musculoskeletal tissues, 4 and in normal and disease states, including ischemia and neoplasia.…”

“…DW-MR imaging has been studied in nervous system and musculoskeletal tissues, 4 and in normal and disease states, including ischemia and neoplasia. 4 Some of the metabolites studied include glucose and lactate. 3 In the current article, 1 Zheng and colleagues apparently sought to establish any effects of aging on baseline measures and then to also evaluate ischemia effects, if any.…”