Relaxation times and microstructures

Fenrich, F. R.; Beaulieu, Christian; Allen, Peter S.

doi:10.1002/nbm.685

Cited by 62 publications

(90 citation statements)

References 45 publications

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“…Multiple T 2 components are observed in nerve and white matter and they are often assigned to individual water compartments (see review by Fenrich et al 79 and references within). Parallel ADC, perpendicular ADC, and their anisotropy were independent of spin-echo time (70-450 ms) in the in vitro olfactory, trigeminal and optic nerves of the garfish.…”

Section: Mgmentioning

confidence: 99%

“…88 The similarity between the three distinct garfish nerves precluded a correlation between the number of diffusion components and the identifiable individual water compartments, as is often performed with T 2 analyses of nerve. 79 To evaluate whether or not there was additional information (i.e. about water compartmentation) in the diffusion curves of the garfish nerves (Fig.…”

Section: -85mentioning

confidence: 99%

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The basis of anisotropic water diffusion in the nervous system – a technical review

2002

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Anisotropic water diffusion in neural fibres such as nerve, white matter in spinal cord, or white matter in brain forms the basis for the utilization of diffusion tensor imaging (DTI) to track fibre pathways. The fact that water diffusion is sensitive to the underlying tissue microstructure provides a unique method of assessing the orientation and integrity of these neural fibres, which may be useful in assessing a number of neurological disorders. The purpose of this review is to characterize the relationship of nuclear magnetic resonance measurements of water diffusion and its anisotropy (i.e. directional dependence) with the underlying microstructure of neural fibres. The emphasis of the review will be on model neurological systems both in vitro and in vivo. A systematic discussion of the possible sources of anisotropy and their evaluation will be presented followed by an overview of various studies of restricted diffusion and compartmentation as they relate to anisotropy. Pertinent pathological models, developmental studies and theoretical analyses provide further insight into the basis of anisotropic diffusion and its potential utility in the nervous system.

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Section: Mgmentioning

confidence: 99%

Section: -85mentioning

confidence: 99%

The basis of anisotropic water diffusion in the nervous system – a technical review

2002

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“…The tissues with a majority of short T 2 components can be subdivided into cortical bone, dentine and enamel (very short T 2 and always a zero signal with conventional sequences), as well as other tissues with T 2 components that are not quite as short and that show a low signal (but not always a zero signal) with conventional sequences. The many tissues with a minority of short T 2 components, such as skeletal muscle, have these components present in low concentrations, typically of about 1-20% (45).…”

Section: Mr Properties Of Tissuementioning

confidence: 99%

Clinical ultrashort echo time imaging of bone and other connective tissues

2006

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The background underpinning the clinical use of ultrashort echo time, SPRITE and other pulse sequences for imaging bone and other connective tissues with short T 2 is reviewed. Features of the basic physics relevant to UTE imaging are described, including the consequences when the radiofrequency pulse duration is of the order of T 2 so that rotation of tissue magnetization into the transverse plane is incomplete. Consequences of the broad linewidth of short T 2 components are also discussed, including partial saturation by off-resonance fat suppression pulses as well as those used in multislice and multiecho imaging. The need for rapid data acquisition of the order of T 2 is explained. The basic two-dimensional UTE pulse sequence with its half excitation pulse and radial imaging from the centre of k-space is described, together with options that suppress fat and/or reduce the signal from long T 2 components. The basic features of SPRITE and other sequences with very short TE are described. Image interpretation is discussed. Clinical features of the imaging of cortical bone, tendons, ligaments, menisci, periosteum and the spine are illustrated. The source of the short T 2 signal in these tissues is predominantly collagen and water tightly bound to collagen. Short T 2 components in all of these tissues are detectible and may show high signals. Possible future developments are outlined, as are technical limitations of clinical magnetic resonance systems.

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“…This results in high signal-to-noise ratio ͑SNR͒ demands to robustly fit the model. 24,25 As a result, we have developed an additional approach, which we call inversion-recovery prepared REXSY ͑IR-REXSY͒.…”

Section: ͑13͒mentioning

confidence: 99%

Development, simulation, and validation of NMR relaxation-based exchange measurements

Dortch

Horch

Does

2009

The Journal of Chemical Physics

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Two-dimensional ͑2D͒ nuclear magnetic resonance correlation experiments have recently been proposed as a means for studying exchange in porous media. Most notable of these is the T 2 − T 2 relaxation exchange spectroscopy ͑REXSY͒ experiment. Unfortunately, quantifying exchange with this method requires a relatively long, three-dimensional acquisition. To reduce acquisition times, novel 2D methods for quantifying exchange were developed. For each method, model equations were derived ͑for an arbitrary N-pool system͒, tested via simulation studies, and validated via experimental studies in an aqueous urea model system. Results indicate that the novel methods outperform REXSY-in terms of uncertainty per unit time for the fitted exchange rate-for certain model systems. The relative merits of each method are discussed in the text.

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Relaxation times and microstructures

Cited by 62 publications

References 45 publications

The basis of anisotropic water diffusion in the nervous system – a technical review

The basis of anisotropic water diffusion in the nervous system – a technical review

Clinical ultrashort echo time imaging of bone and other connective tissues

Development, simulation, and validation of NMR relaxation-based exchange measurements

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