Sensitivity‐Enhanced Natural‐Abundance Silicon‐29 Magnetic Resonance Imaging

Wong, Alan; Sakellariou, Dimitrios

doi:10.1002/cphc.201100432

Cited by 3 publications

(4 citation statements)

References 20 publications

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“…Finally, although these ideas were initially developed in the field solid-state NMR they are also applicable in the realm of magnetic resonance imaging of rotating samples 3,4 including recent work by Sakellariou and coworkers. 5…”

Section: Discussionmentioning

confidence: 99%

“…In magnetic resonance imaging, a separation of modulated and unmodulated frequency contributions while a sample rotates in a magnetic field gradient can be used to reconstruct a three-dimensional image of the sample within the rotor. [3][4][5] Since the seminal work of Dixon, 6 various methods for separating the modulated and unmodulated contributions to a transition frequency in a rotating sample have been proposed. The central idea behind these methods is a recognition that the signal phase contributions from both rotor-modulated and unmodulated frequencies, which are parametrically dependent on the same time variable, can be separated by splitting their evolution into orthogonal time dimensions.…”

Section: Introductionmentioning

confidence: 99%

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Sideband separation experiments in NMR with phase incremented echo train acquisition

Walder

Dey

Kaseman

et al. 2013

The Journal of Chemical Physics

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A general approach for enhancing sensitivity of nuclear magnetic resonance sideband separation experiments, such as Two-Dimensional One Pulse (TOP), Magic-Angle Turning (MAT), and Phase Adjust Spinning Sidebands (PASS) experiments, with phase incremented echo-train acquisition (PIETA) is described. This approach is applicable whenever strong inhomogeneous broadenings dominate the unmodulated frequency resonances, such as in non-crystalline solids or in samples with large residual frequency anisotropy. PIETA provides significant sensitivity enhancements while also eliminating spectral artifacts would normally be present with Carr-Purcell-Meiboom-Gill acquisition. Additionally, an intuitive approach is presented for designing and processing echo train acquisition magnetic resonance experiments on rotating samples. Affine transformations are used to relate the two-dimensional signals acquired in TOP, MAT, and PASS experiments to a common coordinate system. Depending on sequence design and acquisition conditions two significant artifacts can arise from truncated acquisition time and discontinuous damping in the T2 decay. Here we show that the former artifact can always be eliminated through selection of a suitable affine transformation, and give the conditions in which the latter can be minimized or removed entirely.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Sideband separation experiments in NMR with phase incremented echo train acquisition

Walder

Dey

Kaseman

et al. 2013

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…The rotor was then sealed with a Teflon plug (see Figure 2) and capped with a specially designed fluteless cap that enables stable spinning at low MAS frequencies, [24] as is common for STRAFI-MAS experiments. [20,21,22] The sample was then cooled to approximately 105 K and spun at 143 Hz with a stability of ±1 Hz. The STRAFI-MAS images were acquired using a 2.35 μs 1 H 90° pulse, a 2 ms contact time, 1 H decoupling during t 1 and t 2 , and 3.75 and 7.5 μs 31 P 90 and 180° pulses.…”

Section: Methodsmentioning

confidence: 99%

“…Although this gradient is continuously oriented along the "z" direction, the sample rotation in an MAS probe can be used to reorient the sample such that the gradient is sequentially aligned along all three Cartesian directions. [19,20,21,22] The pulse sequence diagram for the twodimensional (2D) cross-polarization (CP) stray-field imaging (STRAFI)-MAS experiment is shown in Figure 1. It can be seen that, in the rotor frame, the direction of the gradient is modulated such that it is aligned along three orthogonal directions every 120° of rotation (or 1/3 of the rotor period: R ).…”

Section: Strafi-masmentioning

confidence: 99%

Magnetic resonance imaging of DNP enhancements in a rotor spinning at the magic angle

Perras

Kobayashi

Pruski

2016

Journal of Magnetic Resonance

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Simulations performed on model, static, samples have shown that the microwave power is non-uniformly distributed in the magic angle spinning (MAS) rotor when using conventional dynamic nuclear polarization (DNP) instrumentation. Here, we applied the stray-field magic angle spinning imaging (STRAFI-MAS) experiment to generate a spatial map of the DNP enhancements in a full rotor, which is spun at a low rate in a commercial DNP-MAS NMR system. Notably, we observed that the enhancement factors produced in the center of the rotor can be twice as large as those produced at the top of the rotor. Surprisingly, we observed that the largest enhancement factors are observed along the axis of the rotor as opposed to against its walls, which are most directly irradiated by the microwave beam. We lastly observed that the distribution of enhancement factors can be moderately improved by degassing the sample and increasing the microwave power. The inclusion of dielectric particles greatly amplifies the enhancement factors throughout the rotor. The STRAFI-MAS approach can provide useful guidance for optimizing the access of microwave power to the sample, and thereby lead to further increases in sensitivity of DNP-MAS NMR.

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