NMR Probeheads for Biophysical and Biomedical Experiments

Mispelter, Joël; Lupu, Mihaela; Briguet, A.

doi:10.1142/p759

Cited by 92 publications

(100 citation statements)

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“…We have designed a NQR prototype sensor with a sample volume of 0.78 L. A loop-gap coil or an Alderman-Grant resonator (AGR) [Mispelter et al, 2009] can be used as transceiver coil (RF coil in Figure 4). A symmetric tuning-matching circuit has been applied to balance the coil [Mispelter et al, 2009] and match the system to 50 Ω for optimal power transfer. The resonator was driven by a 2 kW class AB power amplifier (Tomco Technologies).…”

Section: The Nqr Sensormentioning

confidence: 99%

Rapid detection of arsenic minerals using portable broadband NQR

Lehmann-Horn

Miljak

O’Dell

et al. 2014

Geophysical Research Letters

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The remote real-time detection of specific arsenic species would significantly benefit in minerals processing to mitigate the release of arsenic into aquatic environments and aid in selective mining. At present, there are no technologies available to detect arsenic minerals in bulk volumes outside of laboratories. Here we report on the first room-temperature broadband 75 As nuclear quadrupole resonance (NQR) detection of common and abundant arsenic ores in the Earth crust using a large sample (0.78 L) volume prototype sensor. Broadband excitation aids in detection of natural minerals with low crystallinity. We briefly discuss how the proposed NQR detector could be employed in mining operations.

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Section: The Nqr Sensormentioning

confidence: 99%

Rapid detection of arsenic minerals using portable broadband NQR

Lehmann-Horn

Miljak

O’Dell

et al. 2014

Geophysical Research Letters

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“…Of course, many research groups with extensive probe-building experience have written their own programs to assist in their probe building efforts, and at least one group has made their programs freely available with supportive documentation. 22 There appears to be a need within the NMR community for a tutorial-type treatment of applying linear circuit simulators to complex probe design problems. That was the purpose of an effort started by the author in the December 2015 issue of an on-line company newsletter, but it was interrupted by a combination of events that changed priorities.…”

Section: Introductionmentioning

confidence: 99%

Guide to simulating complex NMR probe circuits

Doty

2018

Concepts Magnetic Resonance

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S‐parameter‐based circuit simulators are well suited to obtaining accurate solutions of even the most complex rf probe circuits. The basic theory necessary for determining the relative S/N of the probe circuit, based on B1/P0.5, from the voltage, current, impedance, and S‐parameter data that come from circuit simulators, is presented. Examples of simulator applications to circuits of increasing complexity are presented. A key requirement for effective utilization of circuit simulators in probe circuit optimizations is constructing an approximate analytical solution of the circuit, or an inverse simulation program, to accompany the direct circuit simulation, that calculates all the needed circuit component values based on minimal input data, such as B0, desired nuclides, sample coil description, and hardware options and details such as characteristics of various leads. A method of developing the needed inverse simulation program is presented for a simplified single‐coil HXY probe circuit. The inverse program is validated by the direct simulation itself. The methods are then applied to a detailed circuit that includes all significant leads, stray capacitances, couplings, and losses for a NB 28.2‐T 1‐mm HXYZ MAS probe. Similar HXY circuit models were validated by NMR experiments with rotor sizes from 0.75 mm to 3.2 mm at fields from 11.7 T to 21 T. Detailed HXYZ circuit model results at 11.7 T, including pulse widths, component values, voltages, and port isolations, agreed with experimental results within a few per cent. The 1200‐MHz HXYZ simulation predicted a 1H π/2 pulse of 1.3 μs at 25 W.

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“…3 He and 129 Xe images provide signal only from the inhaled or dissolved gas, whereas 1 H imaging provides signals from lung parenchyma, muscle, fat, and other tissues (8). In conventional MRI, the energy difference between the nuclear-spin energy levels is small (e.g., 4.23e 219 J for protons at 1.5 T), and thus, the maximum longitudinal spin polarization as described by the Boltzmann distribution (9) is relatively weak. At 1.5 T, the population difference between the excited and ground states is only a few spins per million.…”

Section: Introductionmentioning

confidence: 99%

A novel switched frequency ³He/¹H high‐pass birdcage coil for imaging at 1.5 tesla

Pratt¹,

Giaquinto²,

Ireland³

et al. 2015

Concepts Magn Reson

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The ability to produce hyperpolarized noble gases 3He and 129Xe has opened up exciting possibilities for pulmonary magnetic resonance imaging (MRI). We have recently built a hyperpolarizer with the goal of using hyperpolarized 3He gas for MRI in neonatal lungs in a dedicated small foot‐print 1.5 T MR scanner developed at our institution and sited in our Neonatal Intensive Care Unit. Although hyperpolarized gas imaging can provide unique insights into lung ventilation, acinar microstructure, and gas‐exchange dynamics, there is an undiminished need for 1H MRI of the lung to provide anatomic references, B1 and B0 maps, and 1H images of lung parenchyma. To address this need, we designed, built and tested a novel radiofrequency body coil that provides a high‐pass birdcage coil that can be used for both 3He and 1H frequencies (48.65 and 63.86 MHz, respectively, at 1.5 T). To switch between frequencies, the birdcage coil has a large mechanical actuator that simultaneously changes the capacitance between every rung of the birdcage. Advantages of this coil design include: 1) quadrature excitation and reception at the 3He and 1H frequencies, 2) identical B1 field maps for 3He and 1H imaging, 3) excellent signal‐to‐noise ratio and B1 homogeneity at both frequencies, and 4) rapid (10–20 s) switching times between 3He and 1H operation. This report provides details of the coil's design and fabrication. Images of hyperpolarized 3He and 1H in phantoms and ex vivo rabbit lungs demonstrate the image quality obtained with the coil. © 2015 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 45B: 174–182, 2015

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NMR Probeheads for Biophysical and Biomedical Experiments

Cited by 92 publications

References 0 publications

Rapid detection of arsenic minerals using portable broadband NQR

Rapid detection of arsenic minerals using portable broadband NQR

Guide to simulating complex NMR probe circuits

A novel switched frequency ³He/¹H high‐pass birdcage coil for imaging at 1.5 tesla

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NMR Probeheads for Biophysical and Biomedical Experiments

Cited by 92 publications

References 0 publications

Rapid detection of arsenic minerals using portable broadband NQR

Rapid detection of arsenic minerals using portable broadband NQR

Guide to simulating complex NMR probe circuits

A novel switched frequency 3He/1H high‐pass birdcage coil for imaging at 1.5 tesla

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A novel switched frequency ³He/¹H high‐pass birdcage coil for imaging at 1.5 tesla