MR microscopy of multicomponent diffusion in single neurons

Grant, Samuel C.; Buckley, David L.; Gibbs, S. Julian; Webb, Andrew; Blackband, Stephen J.

doi:10.1002/mrm.1306

Cited by 89 publications

(73 citation statements)

References 24 publications

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“…A slight (though not significant) increase of the ADC with echo time in cortical areas was reported in (34). Another study (31) reported an ϳ30% increase of the ADC with echo times between 24 msec and 100 msec. Assuming slow exchange and an intra-/extracellular fraction of 80%/20%, Buckley et al (32) predicted that the intracellular T 2 would need to be about 20 msec to explain the results.…”

Section: Discussionmentioning

confidence: 89%

“…Other in vivo studies indicate short T 2 components in human cortex (28) and in rat cortex (29) at 2.0 T. High field studies on single neurons demonstrate that short T 2 in cytoplasm, in the range 29 -42 msec (30,31), is associated with low diffusion in cytoplasm of 0.23 ϫ 10 -3 mm 2 /second (30). These single neuron studies use NMR microscopy so that the regional diffusion and relaxation constants were found directly and not as a result of fitting a model to the compound signal.…”

Section: Discussionmentioning

confidence: 95%

See 1 more Smart Citation

Microstructural changes in ischemic cortical gray matter predicted by a model of diffusion‐weighted MRI

Vestergaard‐Poulsen

Hansen

Østergaard

et al. 2007

Magnetic Resonance Imaging

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Purpose: To understand the diffusion attenuated MR signal from normal and ischemic brain tissue in order to extract structural and physiological information using mathematical modeling, taking into account the transverse relaxation rates in gray matter. Materials and Methods:We fit our diffusion model to the diffusion-weighted MR signal obtained from cortical gray matter in healthy subjects. Our model includes variable volume fractions, intracellular restriction effects, and exchange between compartments in addition to individual diffusion coefficients and transverse relaxation rates for each compartment. A global optimum was found from a wide range of parameter permutations using cluster computing. We also present simulations of cell swelling and changes of exchange rate and intracellular diffusion as possible cellular mechanisms in ischemia. Results:Our model estimates an extracellular volume fraction of 0.19 in accordance with the accepted value from histology. The absolute apparent diffusion coefficient obtained from the model was similar to that of experiments. The model and the experimental results indicate significant differences in diffusion and transverse relaxation between the tissue compartments and slow water exchange. Our model reproduces the signal changes observed in ischemia via physiologically credible mechanisms. Conclusion:Our modeling suggests that transverse relaxation has a profound influence on the diffusion attenuated MR signal. Our simulations indicate cell swelling as the primary cause of the diffusion changes seen in the acute phase of brain ischemia.

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Section: Discussionmentioning

confidence: 89%

Section: Discussionmentioning

confidence: 95%

Microstructural changes in ischemic cortical gray matter predicted by a model of diffusion‐weighted MRI

Vestergaard‐Poulsen

Hansen

Østergaard

et al. 2007

Magnetic Resonance Imaging

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“…Since then, studies aimed at improving our ability to image tissue microstructure have focused on understanding cellular-level diffusion properties by MR microscopy in an effort to inform modeling [79][80][81][82][83][84][85], and modeling aimed at extracting specific cytoarchitectural measures [86,87]. A common limitation of these methods is the requirement for strong gradients.…”

Section: Future Directions For the Fast Kurtosis Techniquesmentioning

confidence: 99%

Recent Developments in Fast Kurtosis Imaging

Hansen

Jespersen

2017

Front. Phys.

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Diffusion kurtosis imaging (DKI) is an extension of the popular diffusion tensor imaging (DTI) technique. DKI takes into account leading deviations from Gaussian diffusion stemming from a number of effects related to the microarchitecture and compartmentalization in biological tissues. DKI therefore offers increased sensitivity to subtle microstructural alterations over conventional diffusion imaging such as DTI, as has been demonstrated in numerous reports. For this reason, interest in routine clinical application of DKI is growing rapidly. In an effort to facilitate more widespread use of DKI, recent work by our group has focused on developing experimentally fast and robust estimates of DKI metrics. A significant increase in speed is made possible by a reduction in data demand achieved through rigorous analysis of the relation between the DKI signal and the kurtosis tensor based metrics. The fast DKI methods therefore need only 13 or 19 images for DKI parameter estimation compared to more than 60 for the most modest DKI protocols applied today. Closed form solutions also ensure rapid calculation of most DKI metrics. Some parameters can even be reconstructed in real time, which may be valuable in the clinic. The fast techniques are based on conventional diffusion sequences and are therefore easily implemented on almost any clinical system, in contrast to a range of other recently proposed advanced diffusion techniques. In addition to its general applicability, this also ensures that any acceleration achieved in conventional DKI through sequence or hardware optimization will also translate directly to fast DKI acquisitions. In this review, we recapitulate the theoretical basis for the fast kurtosis techniques and their relation to conventional DKI. We then discuss the currently available variants of the fast kurtosis techniques, their strengths and weaknesses, as well as their respective realms of application. These range from whole body applications to methods mostly suited for spinal cord or peripheral nerve, and analysis specific to brain white matter. Having covered these technical aspects, we proceed to review the fast kurtosis literature including validation studies, organ specific optimization studies and results from clinical applications.

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“…The latter is being pursued by diffusion studies on isolated brain slices [13,14], excised spinal cords [15] and a new red blood cell ghost model [16] on the 750 MHz instrument. SNR is also a paramount issue in our continuing microimaging and spectroscopy studies of isolated single neurons [17,18]. Even though these studies were performed to date at fields of up to 600 MHz, SNR improvements provided by even higher fields increase our ability to explore multicompartmental diffusion within the single cell [16] and to localize subcellular regions for spectroscopic examination [17] under a variety of perturbations.…”

Section: Microimaging and Microcoilsmentioning

confidence: 99%

“…SNR is also a paramount issue in our continuing microimaging and spectroscopy studies of isolated single neurons [17,18]. Even though these studies were performed to date at fields of up to 600 MHz, SNR improvements provided by even higher fields increase our ability to explore multicompartmental diffusion within the single cell [16] and to localize subcellular regions for spectroscopic examination [17] under a variety of perturbations. So far, bench tests and preliminary MR studies demonstrate no significant problems in constructing RF microcoils (solenoids having diameters of less than 1 mm) at 750 MHz.…”

Section: Microimaging and Microcoilsmentioning

confidence: 99%

Progress in high field MRI at the University of Florida

Beck

Plant

Grant

et al. 2001

MAGMA

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In this article we report on progress in high magnetic field MRI at the University of Florida in support of our new 750MHz wide bore and 11.7T/40cm MR instruments. The primary emphasis is on the associated rf technology required, particularly high frequency volume and phased array coils. Preliminary imaging results at 750MHz are presented. Our results imply that the pursuit of even higher fields seems warranted.

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MR microscopy of multicomponent diffusion in single neurons

Cited by 89 publications

References 24 publications

Microstructural changes in ischemic cortical gray matter predicted by a model of diffusion‐weighted MRI

Microstructural changes in ischemic cortical gray matter predicted by a model of diffusion‐weighted MRI

Recent Developments in Fast Kurtosis Imaging

Progress in high field MRI at the University of Florida

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