Measuring small compartmental dimensions with low-q angular double-PGSE NMR: The effect of experimental parameters on signal decay

Shemesh, Noam; Özarslan, Evren; Basser, Peter J.; Cohen, Yoram

doi:10.1016/j.jmr.2009.01.004

Cited by 64 publications

(99 citation statements)

References 42 publications

(92 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…22 can be employed to obtain accurate estimates of small compartmental dimensions. 23 In a different study, it was predicted that when all gradient orientations were kept parallel to each other in a multi-PFG acquisition with an even number of gradient pulse pairs, increasing the gradient strength would yield peculiar features such as zero crossings that are robust to the heterogeneity of the specimen. 7 These predictions were validated experimentally.…”

Section: Introductionmentioning

confidence: 99%

A general framework to quantify the effect of restricted diffusion on the NMR signal with applications to double pulsed field gradient NMR experiments

Özarslan

Shemesh

Basser

2009

The Journal of Chemical Physics

Self Cite

102

160

View full text Add to dashboard Cite

Based on a description introduced by Robertson, Grebenkov recently introduced a powerful formalism to represent the diffusion-attenuated NMR signal for simple pore geometries such as slabs, cylinders, and spheres analytically. In this work, we extend this multiple correlation function formalism by allowing for possible variations in the direction of the magnetic field gradient waveform. This extension is necessary, for example, to incorporate the effects of imaging gradients in diffusion-weighted NMR imaging scans and in characterizing anisotropy at different length scales via double pulsed field gradient ͑PFG͒ experiments. In cylindrical and spherical pores, respectively, two-and three-dimensional vector operators are employed whose form is deduced from Grebenkov's results via elementary operator algebra for the case of cylinders and the Wigner-Eckart theorem for the case of spheres. The theory was validated by comparison with known findings and with experimental double-PFG data obtained from water-filled microcapillaries.

show abstract

Section: Introductionmentioning

confidence: 99%

A general framework to quantify the effect of restricted diffusion on the NMR signal with applications to double pulsed field gradient NMR experiments

Özarslan

Shemesh

Basser

2009

The Journal of Chemical Physics

Self Cite

102

160

View full text Add to dashboard Cite

show abstract

“…In the short mixing time regime, interesting diffusion-diffraction phenomena can be produced [32][33][34][35][36], and angular dependencies can provide insight into pore sizes as shown experimentally first by Koch and Finsterbusch [37,38] and then by others [39][40][41]; however, by analyzing the displacement correlation tensor [42], the short τ m angular DDE experiment aiming to measure compartment sizes was found by Jespersen to be equivalent to a time-dependent SDE experiment [43]. By contrast, in the long mixing time regime, the second order term in the displacement correlation tensor, from which sizes are measured, is decoupled from µA, making its measurement much less complicated [25,31].…”

Section: Introductionmentioning

confidence: 93%

Axon Diameters and Myelin Content Modulate Microscopic Fractional Anisotropy at Short Diffusion Times in Fixed Rat Spinal Cord

Shemesh

2018

Front. Phys.

Self Cite

View full text Add to dashboard Cite

Mapping tissue microstructure accurately and noninvasively is one of the frontiers of biomedical imaging. Diffusion Magnetic Resonance Imaging (MRI) is at the forefront of such efforts, as it is capable of reporting on microscopic structures orders of magnitude smaller than the voxel size by probing restricted diffusion. Double Diffusion Encoding (DDE) and Double Oscillating Diffusion Encoding (DODE) in particular, are highly promising for their ability to report on microscopic fractional anisotropy (µFA), a measure of the pore anisotropy in its own eigenframe, irrespective of orientation distribution. However, the underlying correlates of µFA have insofar not been studied. Here, we extract µFA from DDE and DODE measurements at ultrahigh magnetic field of 16.4T with the goal of probing fixed rat spinal cord microstructure. We further endeavor to correlate µFA with Myelin Water Fraction (MWF) derived from multiexponential T 2 relaxometry, as well as with literature-based spatially varying axon diameter. In addition, a simple new method is presented for extracting unbiased µFA from three measurements at different b-values. Our findings reveal strong anticorrelations between µFA (derived from DODE) and axon diameter in the distinct spinal cord tracts; a moderate correlation was also observed between µFA derived from DODE and MWF. These findings suggest that axonal membranes strongly modulate µFA, which-owing to its robustness toward orientation dispersion effects-reflects axon diameter much better than its typical FA counterpart. µFA varied when measured via oscillating or blocked gradients, suggesting selective probing of different parallel path lengths and providing insight into how those modulate µFA metrics. Our findings thus shed light into the underlying microstructural correlates of µFA and are promising for future interpretations of this metric in health and disease.

show abstract

“…In recent years, several approaches have been proposed to quantify non-Gaussian [31][32][33][34][35] and AD processes in heterogeneous systems [8,13,14,[18][19][20][36][37][38][39][40][41]. In this paper, for the first time, we show and compare anomalous subdiffusive Mα maps together with anomalous pseudo-superdiffusion Mγ and conventional MD maps obtained from the same samples (controlled phantom and excised brain tissues).…”

Section: Resultsmentioning

confidence: 97%

Spatio-temporal anomalous diffusion imaging: results in controlled phantoms and in excised human meningiomas

Capuani

Palombo

Gabrielli³

et al. 2013

Magnetic Resonance Imaging

View full text Add to dashboard Cite

Recently, we measured two anomalous diffusion (AD) parameters: the spatial and the temporal AD indices, called γ and α, respectively, by using spectroscopic pulse gradient field methods. We showed that γ quantifies pseudo-superdiffusion processes, while α quantifies subdiffusion processes. Here, we propose γ and α maps obtained in a controlled heterogeneous phantom, comprised of packed micro-beads in water and in excised human meningiomas. In few words, α maps represent the multi-scale spatial distribution of the disorder degree in the system, while γ maps are influenced by local internal gradients, thus highlighting the interface between compartments characterized by different magnetic susceptibility. γ maps were already obtained by means of AD stretched exponential imaging and α-type maps have been recently achieved for fixed rat brain with the aim of highlighting the fractal dimension of specific brain regions. However, to our knowledge, the maps representative of the spatial distribution of α and γ obtained on the same controlled sample and in the same excised tissue have never been compared. Moreover, we show here, for the first time, that α maps are representative of the spatial distribution of the disorder degree of the system. In a first phase, γ and α maps of controlled phantom characterized by an ordered and a disordered rearrangement of packed micro-beads of different sizes in water and by different magnetic susceptibility (Δχ) between beads and water were obtained. In a second phase, we investigated excised human meningiomas of different consistency. Results reported here, obtained at 9.4 T, show that α and γ maps are characterized by a different image contrast. Indeed, unlike γ maps, α maps are insensible to (Δχ) and they are sensible to the disorder degree of the microstructural rearrangement. These observations strongly suggest that AD indices α and γ reflect some additional microstructural information which cannot be obtained using conventional diffusion methods based on Gaussian diffusion. Moreover, α and γ maps obtained in excised meningiomas seem to provide more microstructural details above those obtained with conventional DTI analysis, which could be used to improve the classification of meningiomas based on their consistency.

show abstract

Measuring small compartmental dimensions with low-q angular double-PGSE NMR: The effect of experimental parameters on signal decay

Cited by 64 publications

References 42 publications

A general framework to quantify the effect of restricted diffusion on the NMR signal with applications to double pulsed field gradient NMR experiments

A general framework to quantify the effect of restricted diffusion on the NMR signal with applications to double pulsed field gradient NMR experiments

Axon Diameters and Myelin Content Modulate Microscopic Fractional Anisotropy at Short Diffusion Times in Fixed Rat Spinal Cord

Spatio-temporal anomalous diffusion imaging: results in controlled phantoms and in excised human meningiomas

Contact Info

Product

Resources

About