Sensitivity quantification of remote detection NMR and MRI

Abstract

A sensitivity analysis of the remote detection NMR technique is presented. With remote detection, information about a sample is encoded onto a mobile sensor fluid, which facilitates a spatial separation of encoding and detection of spin magnetization. This approach can be interpreted as a two-dimensional NMR experiment, therefore the same general formalism can be used for a sensitivity analysis. Even though remote detection is a point-by-point experiment, the sensitivity does not scale unfavorably with the number of detected points compared to transient detection. It is proportional to the relative sensitivity between the remote detector and the circuit that is used for encoding. The influence of the different signal decay times is analyzed, and the distinction between spectroscopy and imaging experiments is made.Key words: NMR, MRI, Remote detection, Sensitivity, Indirect detection, Flow NMR remote detection, a novel technique to spatially and temporally separate encoding and detection of nuclear spin magnetization, has the potential to enhance the sensitivity of NMR spectroscopy and imaging experiments. It employs a flowing sensor medium that samples a stationary analyte of interest, which can be a liquid, a surface, a porous medium, or void space [1,2]. In these experiments the sensor medium, thus far hyperpolarized 129 Xe [3], is first introduced to a sample of interest, is encoded with information regarding that sample, and is then transferred to a different location for sensitive detection. This separation of the encoding and detection steps allows optimizing them independently. The encoding region may be configured in the most convenient way to accommodate the sample, while different conditions optimized for sensitivity are used in the detection region. This communication aims to provide a more quantitative discussion of the sensitivity achievable with this technique.The longitudinal magnetization of the sensor medium is the property that is altered by the encoding step. An arbitrary pulse sequence can be used that is able to transfer the desired information about the stationary analyte onto longitudinal magnetization of the sensor medium.

Spectrally resolved flow imaging of fluids inside a microfluidic chip with ultrahigh time resolution

“…The details of the remote detection methodology including a discussion of the sensitivity gains are described elsewhere ( [13]). A remote detection experiment is like any other magnetic resonance experiment with a few notable exceptions.…”

Sensitivity enhancement by exchange mediated magnetization transfer of the xenon biosensor signal

“…Thus, a simple model was constructed to predict relative signal-to-noise for direct and indirect detection to predict the sensitivity of each experiment. The method of indirect detection is analogous to that of remote detection; therefore the sensitivity comparison introduced by Granwehr and Seeley [16] was implemented.…”

“…To make a signal-to-noise-per-time comparison between our indirect detection and ESA, we calculated how many ESA experiments can be performed in the same time it takes to run an indirect experiment. The sensitivity comparison of the first point of both FIDs using one approach of Granwher and Seeley [16] is calculated according to equations 3, 4, and 5…”

Multiplicative or t 1 Noise in NMR Spectroscopy

“…During encoding the spin magnetization was inverted with a hard on-resonant π pulse, and detection was done with a series of 40 π/2 pulses, spaced by 15 ms [37]. The FID after each of these pulses was multiplied with an exponentially decaying apodization function with a time constant of 0.5 ms.…”