Water compartments in the myelinated nerve. III. Pulsed NMR result

Vasilescu, V.; Katona, Eva; Simplăceanu, Virgil; Demco, Dan E.

doi:10.1007/bf01932339

Cited by 91 publications

(90 citation statements)

References 5 publications

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“…For example, multiple component relaxation of water in nerve was reported in 1969 1 and again in 1978. 2 Similar data from muscle were published in 1972 3 and 1974. 4 Efforts to exploit the information contained within the deviation from a single exponential, in order to gain information about the heterogeneous structure, are similarly long standing, and they extend well beyond biological systems into materials and geological science.…”

Section: Introductionsupporting

confidence: 72%

Relaxation times and microstructures

2001

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A discussion is presented of the evaluation of multiple relaxation components from water protons in biological tissue. The principal focus is to draw attention to the way in which limitations in the raw NMR data, such as signal-to-noise ratio, data sampling density and acquisition window width, affect the precision and resolution in the processed multiple component solution of the return to thermal equilibrium. The second issue discussed is the interpretation of these multiple components in terms of microstructural compartments of the biological sample and, thirdly, we outline some of the successes in determining regional and pathological variations in microstructure in the human body in-vivo, using the technique of multiple relaxation components.

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Section: Introductionsupporting

confidence: 72%

Relaxation times and microstructures

2001

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“…These three central clusters, shown in black in Fig. 1, represented 88% of the total signal and were attributed to the three nerve-water components seen in several previous studies (2,4,12,13). Spurious components with T 2 Ϸ 1 ms or Ͼ 500 ms were considered artifacts and ignored from further processing.…”

Section: Resultsmentioning

confidence: 97%

“…Neural tissue is known to exhibit multiexponential T 2 relaxation behavior, which is believed to reflect separate microanatomic water compartments in slow exchange (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11). In particular, water trapped within and in between the membrane layers that form myelin (myelin-water, for short) is thought to give rise to a characteristic short-lived component of transverse magnetization.…”

mentioning

confidence: 99%

Selective excitation of myelin water using inversion–recovery‐based preparations

Travis

Does

2005

Magnetic Resonance in Med

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T 1 and T 2 relaxation of excised frog sciatic nerve water was characterized at 7 T. Based on these findings, optimal timings for multiple inversion-recovery magnetization preparations were determined to selectively excite the so-called myelinwater T 2 component. Subsequent double inversion-recovery and triple inversion-recovery preparations were used in combination with CPMG acquisitions to experimentally determine optimal timings and effect of the preparation. Using double inversion-recovery, optimal timings were found to excite magnetization that is predominantly (Ϸ93%) derived from the myelin-water component. Greater selectivity (Ϸ96%) was found by extending the preparation to triple inversion-recovery, at the price of decreasing SNR by a factor of Ϸ 2. Magn Reson Med 54:743-747, 2005.

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“…[17][18][19] The strength of the MR signal used to measure the apparent diffusion of water in tissue is determined by the relaxation of protons in each compartment, the restrictions to diffusion in each compartment, and the ability for water protons to exchange between compartments through cellular membranes. Changes in the measured diffusion ellipsoid, and hence p and q, can potentially arise from changes in proton relaxation, 20 diffusion, 21,22 and compartmental volumes, 19 which are known to occur in pathological conditions such as stroke.…”

Section: Green Et Al Increased Anisotropy In Acute Strokementioning

confidence: 99%

Increased Anisotropy in Acute Stroke

Green

Peña

Price

et al. 2002

Stroke

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Background and Purpose-The increase in fractional anisotropy (FA) in acute stroke has yet to be explained. Using an engineering methodology known as pq diagrams, we sought to explain the increase in FA by describing changes in the total magnitude of the diffusion tensor (L) as well as the isotropic (p) and anisotropic (q) components. Methods-Diffusion tensor imaging was performed in 10 patients with stroke Ͻ27 hours old. The diffusion tensor was decomposed into the p and q components and plotted to describe the diffusion trajectories. FA was also calculated and compared. Results-There was significant and consistent reduction in p, q, and L (p: mean, Ϫ50.0%; range, Ϫ36.6% to Ϫ64.5%; q: mean, Ϫ50.8%; range, Ϫ30.8% to Ϫ72.8%; L: mean, Ϫ50.3%; range, Ϫ37.0% to Ϫ65.1%). There were inconsistent changes in FA (mean, Ϫ0.5%; range, Ϫ44.9% to ϩ45.0%). Five patients had elevated FA due to proportionately higher loss of L than q. Conclusions-Changes in FA only occur when there is a change in the ratio of q/L. Acute elevation of FA occurred in the context of a larger reduction in L than q. The elevation in FA occurs in the context of a reduction in the anisotropic tensor and therefore is a consequence of ratio-metric measurement. This appears to clarify the reported increase in FA in terms of alterations in the shape of the apparent diffusion tensor. pq diagrams appear to offer improved resolution of acute diffusion changes in ischemia.

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Water compartments in the myelinated nerve. III. Pulsed NMR result

Cited by 91 publications

References 5 publications

Relaxation times and microstructures

Relaxation times and microstructures

Selective excitation of myelin water using inversion–recovery‐based preparations

Increased Anisotropy in Acute Stroke

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