NMR microscopy with isotropic resolution of 3.0 μm using dedicated hardware and optimized methods

Abstract

Nuclear magnetic resonance microscopy at an isotropic resolution of 3.0 lm was realized by using dedicated hardware such as RF surface microcoils, a planar triple-axis gradient with 6,500 G/cm, and a static magnetic field of 18.8 T. Purely phaseencoded constant time imaging was used to allow increasing the gradient strength for the suppression of diffusion effects without reducing the signal-to-noise ratio. For this method the relationship between gradient strength and true spatial resolution was investigated, and an empirical formula is provided that is useful for practical applications. The characteristics of the different hardware components were investigated experimentally. Furthermore, microscopic phantom images were acquired and evaluated for their true resolution. It is demonstrated that the use of sufficiently large gradients enables suppressing diffusion-related loss of spatial resolution.

Silicon cylinder spiral coil for nuclear magnetic resonance spectroscopy of nanoliter samples

“…As shown in some references, e.g. (28), the preferred approach includes an external coil for locking. However, obtaining a good shim for both coils is not trivial.…”

MRI of human hair

“…Due to the constant delay between signal generation and acquisition, CTI images are free of susceptibility-related displacement artefacts, and image blurring associated with T 2 filtering in k-space is avoided [16,17]. Moreover, by using sufficiently short and strong encoding gradients, the blurring effects caused by molecular diffusion for MRI at very high spatial resolution can be virtually suppressed [9]. The SNR efficiency of CTI is equal or, in case of diffusion, superior to that of the common frequency encoded techniques [9].…”

“…As a general rule, in terms of signal-to-noise-ratio (SNR) and gradient efficiency, it is advantageous to adapt the dimensions and geometry of the NMR probe to the object to be imaged. Here, a probe setup similar to that described in [9] was used, with a triple axis gradient with a maximum strength of 65 T/m per channel in a linearity range of approximately 1 mm. However, no 2 H lock was used and the radio frequency (RF) coil was replaced.…”

Imaging and Characterization of Magnetic Micro- and Nanostructures Using Force Microscopy

“…Due to dissipative effects, the tilted moment will evolve back to its initial alignment (typically on the ms timescale). All commercially available MRI implementations use an inductive detection method involving a coil to manipulate and measure the state of the magnetic moments within the sample, leading to spatial resolutions (so-called voxel volumes) down to 40 mm 3 corresponding to lateral resolutions on the mm length scale [217,218].…”