Two‐ and three‐dimensional multinuclear stray‐field imaging of rotating samples with magic‐angle spinning (STRAFI‐MAS): From bio to inorganic materials

Abstract

Purpose: To revisit and illustrate the potential of a simple and effective multidimensional stray-field imaging technique with magic-angle spinning, known as STRAFI-MAS.Materials and Methods: STRAFI-MAS images are acquired with a standard NMR magnet and a traditional magic-angle sample spinning (MAS) probe. The stray-field gradients are achieved by placing the MAS probe, along the z-direction, at a distance from the center of the magnet. No pulsed-field gradients are applied. The multidimensional spatial encoding is carried out by synchronizing the radiofrequency pulses with the sample MAS rotation.Results: Two-dimensional (2D) and 3D multinuclear images of various phantoms, including a tibia bone and silicon carbide, are recorded. Images of inorganic solids containing quadrupolar nuclei, 23 Na and 27 Al, are also explored for the first time by STRAFI-MAS. Conclusion:We have demonstrated that STRAFI-MAS is a simple and user-friendly technique for multidimensional imaging without the need of imaging equipment. With the current advancements in NMR and MRI methodologies, STRAFI-MAS is expected to be further developed and improved. We anticipate that STRAFI-MAS can spark a wide spectrum of interest, from material to bio science, where can benefit from high-resolution images.

NMR signal detection using inductive coupling: Applications to rotating microcoils

“…Even though extremely promising recent developments in the areas of microdetection come from nano-sized solid-state detectors (such as diamond NV centers (60) and cantilevers (61)), the versatility and user friendliness of microcoils together with the possibility to use traditional NMR sequences makes them a gold standard for the detection of microscopic size samples or objects. In combination with extremely strong field gradients coming either from pulsed B 0 coils (62,63), static stray B 0 fields (64)(65)(66) or even pulsed radio-frequency B 1 gradients (67), they can also offer ultra high spatial resolution 3D microscopic imaging and open the way for new types of investigations.…”

Contrast STRAFI–MAS imaging

“…As mentioned in the previous studies [8,10], the image distortion arising from STRAFI-MAS is mainly attributed by the constant sample MAS rotation. This induces the imperfection of the effective gradient orientations (i.e.…”

“…All images were acquired with Fig. 1A with a short TE of 5 ls to minimize image distortion [10]. The dashed contour line represents the same intensity level allowing for visual comparison.…”

“…Due to the simplicity of the experiment, and its ability of accessing large field gradient (up to 100 T/m) from the stray-field, this STRAFI-MAS imaging technique could be an important application to material science. After STRAFI-MAS was first demonstrated with 1 H 2D projection spin density images [8], we further extended toward to 2D and 3D imaging of biological and inorganic solid materials with various observable nuclei: 29 Si, 23 Na and 27 Al [10]. In this communication, we explore the possibility of contrast STRAFI-MAS -T 1 -and T 2 -weighted, and triple-quantum filtered imaging -on various phantoms.…”

Solid-state STRAFI NMR probe for material imaging of quadrupolar nuclei

“…Stray field imaging (STRAFI) has been used to study thin films [12][13][14][15][16][17][18][19][20][21][22], paramagnetic samples [23][24][25], water content of soil samples [26][27][28][29][30][31], various dental materials [32][33][34][35][36][37][38][39][40][41][42][43], and for diffusion experiments [44][45][46][47][48]. Thus far, 1 H STRAFI experiments are employed most often and only a few low-gamma nuclei STRAFI studies have been published [24,[49][50][51][52][53][54].…”