Remotely detected high-field MRI of porous samples

Abstract

Remote detection of NMR is a novel technique in which an NMR-active sensor surveys an environment of interest and retains memory of that environment to be recovered at a later time in a different location. The NMR or MRI information about the sensor nucleus is encoded and stored as spin polarization at the first location and subsequently moved to a different physical location for optimized detection. A dedicated probe incorporating two separate radio frequency (RF) -circuits was built for this purpose. The encoding solenoid coil was large enough to fit around the bulky sample matrix, while the smaller detection solenoid coil had not only a higher quality factor but also an enhanced filling factor since the coil volume comprised purely the sensor nuclei. We obtained two-dimensional (2D) void space images of two model porous samples with resolution less than 1.4 mm 2 . The remotely-reconstructed images demonstrate the ability to determine fine structure with image quality superior to their directly detected counterparts and show the great potential of NMR remote detection for imaging applications that suffer from low sensitivity due to low concentrations and filling factor.

Development of a Functionalized Xenon Biosensor

“…Furthermore, xenon NMR and MRI can take advantage of "remote" detection of signals that can be used to reconstruct substantially amplified spectra 22 and images. 23 NMR of 129 Xe has been used to investigate the structure and dynamics of materials, [24][25][26][27] molecular cages, [28][29][30][31][32][33][34] biological systems, and for biomedical applications. [35][36][37] Recently, extensive reviews regarding the history and development of hyperpolarized xenon NMR have been published.…”

Magnetic resonance imaging with an optical atomic magnetometer

“…When the nuclear spins are spread out over a large volume, detection becomes less sensitive. For fluidic analytes, the spins can be concentrated in a detection region and the problem can be circumvented by remote detection (15)(16)(17): a sample is first prepolarized; then it enters an encoding region where large radio frequency coils that cover the whole sample area store spectroscopic or spatial information as nuclear magnetization along the longitudinal axis; downstream the sample is concentrated and its magnetization is measured with improved filling factor.…”

NMR detection using laser-polarized xenon as a dipolar sensor

“…Information about an analyte is encoded onto the spin magnetization of a mobile carrier, which then is moved to a detector that can read out this magnetization with high sensitivity. Remote detection has been applied successfully to measure the chemical shift of 129 Xe on the surface of a porous material, and for imaging at low and at high magnetic fields [14]. However, so far there is no experiment to encode the NMR spectrum of a heteronucleus onto the sensor, especially not if the sensor and the analyte are not in direct contact with each other.…”