Low-field, mobile NMR systems are increasingly used across diverse fields, including medical diagnostics, food quality control, and forensics. The throughput and functionality of these systems, however, are limited due to their conventional single-channel detection: one NMR probe exclusively uses an NMR console at any given time. Under this design, multi-channel detection could only be accomplished by either serially accessing individual probes or stacking up multiple copies of NMR electronics; this approach still retains limitations such as long assay times and increased system complexity. Here we present a new scalable architecture, HERMES (hetero-nuclear resonance multichannel electronic system), for versatile, high-throughput NMR analyses. HERMES exploits the concept of software-defined radio by virtualizing NMR electronics in the digital domain. This strategy i) creates multiple NMR consoles without adding extra hardware; ii) acquires signals from multiple NMR channels in parallel; and iii) operates in wide frequency ranges. All of these functions could be realized on-demand in a single compact device. We interfaced HERMES with an array of NMR probes; the combined system simultaneously measured NMR relaxation from multiple samples and resolved spectra of hetero-nuclear spins (1H, 19F, 13C). For potential diagnostic uses, we applied the system to detect dengue fever and molecularly profile cancer cells through multi-channel protein assays. HERMES holds promise as a powerful analytical tool that enables rapid, reconfigurable, and parallel detection.
A bridged loop gap resonator (BLGR) was developed as a transmit and receive coil for a mobile insert to be used for small animal proton imaging by 1.5 T MRI devices. The insert system has its own gradient system, radio frequency (RF) transmit and receive coil, and control and signal processing unit. The reflection S11 and transmission S21 parameters, quality factor (Q), sensitivity, signal to noise ratio (SNR), and maps of the static (B0) and RF (B1) magnetic flux densities were measured. The RF coil was developed starting from a loop gap resonator (LGR) for a balanced LGR and a shielded balanced LGR for a shielded bridged balanced LGR. The purpose of developing this device is to minimize the influence of the sample and surroundings on the RF coil parameters. The final design of the BLGR does not require retuning after a sample change. A 3D image of a mouse in formalin was acquired with a fast low angle shot (FLASH) MRI sequence. The SNR was calculated from one FLASH image. The signal for SNR calculation was acquired from a gadolinium-doped water sample and the noise from the air outside of the sample. This article verifies that the BLGR is viable for small animal nuclear magnetic resonance imaging at 1.5 T and is independent of sample size and material.
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