In addition, the SQ spectra have intensities that are larger than expected based on the intensities of the DQF spectra. This excess intensity corresponds to 23 Na that experiences very small C Q.
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Therefore, we conclude that there may be at least three discrete types of environments or compartments, one isotropic and two anisotropic, contributing to the 23 Na line shapes. This model does not account for the possibility that there are sodium ions that experience widely different local environments whose distribution does not resemble a bell-shaped concentration distribution. More importantly, in such models it is difficult to allow for an additional simultaneous distribution of T 2 values.
Since in the disc tissue the T 2 's are clearly different for the different compartments, as we pointed out above, our model needs to allow for a strong correlation between C Q and T 2. We have therefore fit our spectra to a model consisting of a number of distinct types of compartments, each defined by a single set of C Q , T 2f , and T 2s values, which were found by least-squares curve fitting to calculated spectra employing a steepest-descent iterative approach. It was further necessary to introduce an extra inhomogeneous line broadening of about 1 ppm to the theoretical lineshapes as well as small chemical shift differences between the compartments.
We ascribe these to magnetic-susceptibility effects in the spatially inhomogeneous samples. The broadening and shift parameters were optimized in the curve fitting process. Examples of the fits for the 15 y. The values obtained for the relaxation times, the residual quadrupolar couplings and the relative concentrations for all four samples are presented in Table 2.
It should be noted that the assignment of the T 2s values to specific anisotropic sites is ambiguous. The calculated spectra were obtained using the parameters given in Table 2. The NMR spectra indicate that there are at least three types of compartments with different dynamic behavior of the sodium ions as characterized by C Q , T 2f and T 2s. As mentioned above, these graphs should be viewed as simplified representations of the more realistic many-compartment distribution profiles.
Based on this limited preliminary set of samples it is obviously not possible to draw general conclusions about the way disc degeneration is affecting the distribution of spectroscopic parameters obtained using 23 Na DQF NMR. However, the large variations in the distribution profiles among these four samples indicate that the 23 Na DQF analysis may serve as a powerful characterization method.
Several striking features are apparent in Figure 7.
Introduction
The distribution of C Q values for the 15 y. Upon aging the distribution becomes significantly broader. We also see incremental widening of the distribution when comparing the 79 y. The last column of Table 2 lists the product of C Q and T 2f , which allows for correlations between the two parameters to be easily identified. It is seen that in the majority of the anisotropic compartments the product C Q T 2f is between 0.
The current observations indicate that 23 Na DQF NMR can be developed into a sensitive probe of disc degeneration, although specific interpretations of the spectral characteristics in terms of biochemical and biophysical structure are still beyond our capabilities at this time.
Continued application of DQF experiments to study spinal disc degeneration holds potential for gaining fundamental biophysics information about the disc tissue. But even without detailed attention paid to the lineshapes at this stage of the investigation, we found that the buildup curves of the signal intensities illustrate a potential way of using 23 Na DQF as a diagnostic technique.
O thanks the natural sciences and engineering research council of Canada for financial support. National Center for Biotechnology Information , U. Author manuscript; available in PMC Nov Ooms , 1 Marco Cannella , 2 Alexander J.
The application of 23Na DQF NMR spectroscopy for the study of spinal disc degeneration
Author information Copyright and License information Disclaimer. The publisher's final edited version of this article is available free at Magn Reson Med. See other articles in PMC that cite the published article. Abstract Degenerative disc disease is an irreversible process that leads to a loss of mechanical integrity and back pain in millions of people. Introduction Spinal disc degeneration is a leading cause of back pain for millions of people.
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Experimental The spectra were acquired of annulus fibrosus and nucleus pulposus samples harvested from 15 and 79 year old y. Table 1 Samples used in this study and some of the experimental features of the NMR spectra. Open in a separate window. Results NMR spectra as a function of creation time Representative spectra acquired using the DQF pulse sequence for the four samples are presented in Figure 1. Annulus 1 53 0 0. Annulus 1 43 0 2.
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It was found that values as large as 80 Hz did not affect the fit. Discussion The NMR spectra indicate that there are at least three types of compartments with different dynamic behavior of the sodium ions as characterized by C Q , T 2f and T 2s. Degeneration of the Intervertebral Disc. Takegoshi Magic-angle turning with double acquisition J. Magnetic Resonance, ; doi: Takegoshi Determination of nuclear quadrupolar parameters using singularities in field-swept NMR patterns The Journal of Chemical Physics, ; doi: Meier, Matthias Ernst Quantification and compensation of the influence of pulse transients on symmetry-based recoupling sequences Journal of Magnetic Resonance, ; doi: Wittmann, Kazuyuki Takeda, Beat H.
Annual Reports on NMR Spectroscopy: Volume 56
Takegoshi Susceptibility cancellation of a microcoil wound with a paramagnetic-liquid-filled copper capillary J. Takegoshi, A statistical approach for analyzing the development of 1 H multiple-quantum coherence in solids Phys. This work has been done in collaboration with Dr. General Analytic Approach J. Takegoshi Homo- and heteronuclear two-dimensional covariance solid-state NMR spectroscopy with a dual-receiver system Phys. This work has been led by Prof. Yoji Kobayashi, Olivier J. This work has been done by Yuichi Masuda, a former posdoc in our lab and presently an assistant professor in Tohoku University, in collaboration with a group headed by Prof.
This work has been done in collabolation with Dr.
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In this work we discuss statistical data processing, namely, Phase Standard Deviation and Phase Covariance, which can complement the conventional approach of signal averaging. Takegoshi Post-processing of individual signals for de-noising J. Takegoshi Noise reduction by dynamic signal preemphasis J. Kitagawa 2H-decoupling-accelerated 1H spin diffusion in dynamic nuclear polarization with photoexcited triplet electrons J.
In this work we propose how to actively compensate amplitude and phase transients simultaneously. Kitagawa Total compensation of pulse transients inside a resonator J. Shoji group Gumma Univ.