Low-Field NMR/MRI Systems Using LabVIEW and Advanced Data-Acquisition Techniques

Asfour, Aktham

doi:10.5772/19751

Cited by 6 publications

(15 citation statements)

References 13 publications

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“…Raw data was digitized at a sample rate of 5 MS/s with 512 000 points collected to obtain a spectral resolution of 10 Hz and spectral width of 2.5 MHz. In path 1, the offset at zero voltage is removed from the raw data, and then the data is multiplied by the sine and cosine of the working frequency to generate digital quadrature I and Q data . The real and imaginary components of the FID are Fast‐Fourier‐Transformed (FFT), digitally filtered (notch filter, 10 kHz) and then displayed as either FFT‐Magnitude (Figure A) or phase adjustable data (Figure B).…”

Section: Resultsmentioning

confidence: 99%

“…In path 2, digital down‐sampling and decimation (DDC), as described in has been employed. The raw data is digitally filtered (bandpass 1.5 kHz, 8th order) before generation of digital quadrature as was done in path 1.…”

Section: Resultsmentioning

confidence: 99%

“…The main goal for the authors in was monitoring of the absolute polarization of laser‐polarized 129 Xe, so the FFT‐Magnitude display was sufficient, and the down‐sampling and decimation works very well to focus on a narrow window around the sample. Since temperature changes at the sample can manifest as phase changes in the spectrum, we added the phased display to provide more information about our system.…”

Section: Resultsmentioning

confidence: 99%

“…Control of the instrument was performed using the Delphi software in a Windows environment. A LabVIEW system was reported in a series of papers and conference proceedings from 2006‐2011 . This spectrometer still used a standalone PC, but the system shed many external analog components, and relied on a single AWG (NI 5411) and digitizer card (NI 5911).…”

Section: Discussionmentioning

confidence: 99%

“…For our digital NMR PXI system, we removed the need for TTL signaling and shifted control of pulse formation to the AWG. Shifting the pulse control to the AWG was not trivial, but allowed us to push down to useable pulse widths in the 25‐50 μs ranges, as demonstrated by the tip angle experiments, compared with longer pulse sequences used from 800 μs‐1 ms in . The majority of the instrument components are available commercially.…”

Section: Discussionmentioning

confidence: 99%

See 4 more Smart Citations

Characterization of a PXIe based low‐field digital NMR spectrometer

Biller

Stupic

Kos

et al. 2017

Concepts Magn Reson

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A low‐field nuclear magnetic resonance (NMR) instrument is an important tool for investigating a wide variety of samples under different conditions. In this paper, we describe a system constructed primarily with commercially available hardware and control software, capable of single‐pulse NMR experiments. Details of the construction of the main B0 magnet are also included. The operating frequency for demonstration is 460 kHz (10 mT), however, the range of the hardware spans 700 Hz (16 μT) to 25 MHz (0.6 T). Tip angle optimizations are used to find the most narrow usable pulse width for this configuration, and the T1 of water is measured by single‐pulse‐saturation‐recovery (SPSR) to demonstrate the potential for this system as a relaxometer. Discussions of resonator construction and efficiency, power requirements and programming strategies that would increase the utility of this system are also included. Construction of any low‐field NMR system will depend on experimental interests, budget and engineering resources. A survey of other low‐field NMR systems from the literature is included to aid the novice or experienced magnetic resonance scientist in consideration of how a low‐field spectrometer could be constructed and used in the lab.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Characterization of a PXIe based low‐field digital NMR spectrometer

Biller

Stupic

Kos

et al. 2017

Concepts Magn Reson

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Digital filters for low‐field NMR

Valori

Mitchell

Fordham

2016

Concepts Magn Reson

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We review the theory and operation of digital filters in modern nuclear magnetic resonance (NMR) spectrometers with fully digital receivers. Custom digital filters tailored for particular experimental requirements offer substantial improvements in signal‐to‐noise ratio (SNR), sensitivity, pulse sequence timing, and rejection of heteronuclear contamination. Pass‐band filters are designed and applied in the frequency domain. In high‐field imaging and spectroscopy, the impact of the filter is straight forward to visualize. However, low‐field NMR data acquired on bench‐top magnets are typically analyzed in the time‐domain where the influence of a frequency‐domain filter is not obvious and largely overlooked by end‐users. We provide practical guidance on the design and implementation of digital filters for bench‐top NMR applications, with examples of data acquired at 2.4 and 12.9 MHz. We discuss the compromise between speed (filter settling time) and noise rejection, and consider the special case of 19F signal contamination in 1H measurements. We suggest filter designs for narrow‐line liquid samples, broad‐line samples, and imaging.

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A table‐top PXI based low‐field spectrometer for solution dynamic nuclear polarization

Biller

Stupic

Moreland

2017

Magnetic Reson in Chemistry

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We present the development of a portable dynamic nuclear polarization (DNP) instrument based on the PCI eXtensions for Instrumentation platform. The main purpose of the instrument is for study of H polarization enhancements in solution through the Overhauser mechanism at low magnetic fields. A DNP probe set was constructed for use at 6.7 mT, using a modified Alderman-Grant resonator at 241 MHz for saturation of the electron transition. The solenoid for detection of the enhanced H signal at 288 kHz was constructed with Litz wire. The largest observed H enhancements (ε) at 6.7 mT for N-CTPO radical in air saturated aqueous solution was ε~65. A concentration dependence of the enhancement is observed, with maximum ε at 5.5 mM. A low resonator efficiency for saturation of the electron paramagnetic resonance transition results in a decrease in ε for the 10.3 mM sample. At high incident powers (42 W) and long pump times, capacitor heating effects can also decrease the enhancement. The core unit and program described here could be easily adopted for multi-frequency DNP work, depending on available main magnets and selection of the "plug and play" arbitrary waveform generator, digitizer, and radiofrequency synthesizer PCI eXtensions for Instrumentatione cards.

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Low-Field NMR/MRI Systems Using LabVIEW and Advanced Data-Acquisition Techniques

Cited by 6 publications

References 13 publications

Characterization of a PXIe based low‐field digital NMR spectrometer

Characterization of a PXIe based low‐field digital NMR spectrometer

Digital filters for low‐field NMR

A table‐top PXI based low‐field spectrometer for solution dynamic nuclear polarization

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