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Purpose: To develop and validate a noninvasive imaging technique for accurately assessing very slow CSF flow within shunt tubes in pediatric patients with hydrocephalus, aiming to identify obstructions that might impede CSF drainage. Theory and Methods: A simulation of shunt flow enhancement of signal intensity (shunt‐FENSI) signal is used to establish the relationship between signal change and flow rate. The quantification of flow enhancement of signal intensity data involves normalization, curve fitting, and calibration to match simulated data. Additionally, a phase sweep method is introduced to accommodate the impact of magnetic field inhomogeneity on the flow measurement. The method is tested in flow phantoms, healthy adults, intensive care unit patients with external ventricular drains (EVD), and shunt patients. EVDs enable shunt‐flow measurements to be acquired with a ground truth measure of CSF drainage. Results: The flow‐rate‐to‐signal simulation establishes signal–flow relationships and takes into account the T1 of draining fluid. The phase sweep method accurately accounts for phase accumulation due to frequency offsets at the shunt. Results in phantom and healthy human participants reveal reliable quantification of flow rates using controlled flows and agreement with the flow simulation. EVD patients display reliable measures of flow rates. Shunt patient results demonstrate feasibility of the method and consistent flow rates for functional shunts. Conclusion: The results demonstrate the technique's applicability, accuracy, and potential for diagnosing and noninvasively monitoring hydrocephalus. Limitations of the current approach include a high sensitivity to motion and strict requirement of imaging slice prescription. [ABSTRACT FROM AUTHOR]

Nuclear spin singlet is a special quantum state that lasts longer than T1 and can be used to study slow diffusion and motion between molecules. The preparation of singlet states is the key to their successful application. Currently, various methods for preparing singlet states have been reported in the literature, which are mainly applicable to isolated two-spin systems. When the nuclear spin involved in the singlet state is coupled to other spins, the preparation efficiency of the singlet state often decreases. In this paper, taking a three-spin system as an example, we studied the effect of non-singlet spin coupling on the preparation efficiency of singlet states under different coupling configurations. The simulation results show that as the singlet spin changes from weak coupling to strong coupling, the preparation efficiency of the singlet state will maintain a certain stability when the coupling between the singlet spin and the non-singlet spin is symmetrical. This characteristic can provide a reference for selecting appropriate spins to prepare singlet states in complex systems. We experimentally verified this conclusion using a three-spin system in the N-acetyl-L-aspartic acid (NAA) molecule. By adjusting the pH of the NAA molecule, the three-spin system can transfer from weak coupling to strong coupling. The experimental results show that the preparation efficiency of the singlet state is significantly higher when the three spins are in strong coupling than that when the spins are in weak coupling.

Nuclear magnetic resonance (NMR) is an established method to determine self‐diffusion coefficients in liquids with high precision. The development of benchtop NMR spectrometers makes the method accessible to a wider community. In most cases, 1H NMR spectroscopy is used to determine self‐diffusion coefficients due to its high sensitivity. However, especially when using benchtop NMR spectrometers for the investigation of complex mixtures, the signals in 1H NMR spectra can overlap, hindering the precise determination of self‐diffusion coefficients. In 13C NMR spectroscopy, the signals of different compounds are generally well resolved. However, the sensitivity of 13C NMR is significantly lower than that of 1H NMR spectroscopy leading to very long measurement times, which makes diffusion coefficient measurements based on 13C NMR practically infeasible with benchtop NMR spectrometers. To circumvent this problem, we have combined two known pulse sequences, one for polarization transfer from 1H to the 13C nuclei (PENDANT) and one for the measurement of diffusion coefficients (PFG). The new method (PENPFG) was used to measure the self‐diffusion coefficients of three pure solvents (acetonitrile, ethanol and 1‐propanol) as well as in all their binary mixtures and the ternary mixture at various compositions. For comparison, also measurements of the same systems were carried out with a standard PFG‐NMR routine on a high‐field NMR instrument. The results are in good agreement and show that PENPFG is a useful tool for the measurement of the absolute value of the self‐diffusion coefficients in complex liquid mixtures with benchtop NMR spectrometers. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) magnetic resonance elastography (MRE) is more accurate than two-dimensional (2D) MRE; however, it requires long-term acquisition. This study aimed to reduce the acquisition time of abdominal 3D MRE using a new sample interval modulation (short-SLIM) approach that can acquire all three motions faster while reducing the prolongation of echo time and flow compensation. To this end, two types of phantom studies and an in vivo test of the liver in three healthy volunteers were performed to compare the performances of conventional spin-echo echo-planar (SE-EPI) MRE, conventional SLIM and short-SLIM. One phantom study measured the mean amplitude and shear modulus within the overall region of a homogeneous phantom by changing the mechanical vibration power to assess the robustness to the lowered phase-to-noise ratio in short-SLIM. The other measured the mean shear modulus in the stiff and background materials of a phantom with an embedded stiffer rod to assess the performance of short-SLIM for complex wave patterns with wave interference. The Spearman's rank correlation coefficient was used to assess similarity of elastograms in the rod-embedded phantom and liver between methods. The results of the phantom study changing the vibration power indicated that there was little difference between conventional MRE and short-SLIM. Moreover, the elastogram pattern and the mean shear modulus in the rod-embedded phantom in conventional SLIM and short-SLIM did not change for conventional MRE; the liver test also showed a small difference between the acquisition techniques. This study demonstrates that short-SLIM can provide MRE results comparable to those of conventional MRE. Short-SLIM can reduce the total acquisition time by a factor of 2.25 compared to conventional 3D MRE time, leading to an improvement in the accuracy of shear modulus estimation by suppressing the patient movements. • A new approach to MRE acquisition and processing for fast abdominal 3D elastic imaging. • Technique to reduce the acquisition time of 3D abdominal MRE by a factor of 2.25. • Improvement of accuracy of stiffness estimation by suppressing patient movement. [ABSTRACT FROM AUTHOR]

Background: The societal burden of chronic pain and the contribution-in-part to the opioid crisis, is a strong motivation to improve and expand nonaddictive treatments, including spinal cord stimulation (SCS). For several decades standard SCS has consisted in delivery of tonic pulses with static parameter settings in frequency, pulse width, and amplitude. These static parameters have limited ability to personalize the quality of paresthesia, the dermatomal coverage, and thus may affect SCS efficacy. Further, static settings may contribute to the build-up of tolerance or loss of efficacy of the therapy over time in some patients. Methods: We conducted an acute exploratory study to evaluate the effects of SCS using time-dynamic pulses as compared to time-static (conventional tonic) stimulation pulses, with the hypotheses that dynamic pulse SCS may enable beneficial tailoring of the sensation and the patient's expectation for better pain relief with SCS. During a single clinic visit, consented subjects undergoing a standard SCS trial had their implanted leads temporarily connected to an investigational external stimulator capable of delivering timestatic and six categories of time-dynamic pulse sequences, each characterized by continuously varying a stimulation parameter. Study subjects provided several assessments while blinded to the stimulation pattern, including: drawing of paresthesia maps, descriptions of sensation, and ratings for comfort and helpfulness to pain relief. Results: Even without optimization of the field location, a majority of subjects rated sensations from dynamic stimulation as better or equal to that of static stimulation for comfortableness and for helpfulness to pain relief. The initial data showed a gender and/or pain dermatomal location related preference to a stimulation pattern. In particular, female subjects and subjects with pain at higher dermatomes tended to rank the sensation from dynamic stimulation better. Dynamic stimulation produced greater pain coverage without optimization; in 70% (9/13) of subjects, maximal pain coverage was achieved with a dynamic stimulation pattern. There was also greater variety in the words used by patients to describe stimulation sensation in the free text and free form verbal descriptions associated with dynamic stimulation. Conclusions: With the same electrode configuration and comparable parameter settings, acute SCS using dynamic pulses produced more positive ratings, expanded paresthesia coverage, and greater variation in sensation as compared to SCS using static pulses, suggesting that dynamic stimulation has the potential to improve capabilities of SCS for the treatment of chronic pain. Further study is warranted. [ABSTRACT FROM AUTHOR]

Purpose: To optimize the choice of the flip angles of magnetization‐prepared gradient‐echo sequences for improved accuracy, precision, and speed of 3D‐T1ρ mapping. Methods: We propose a new optimization approach for finding variable flip‐angle values that improve magnetization‐prepared gradient‐echo sequences used for 3D‐T1ρ mapping. This new approach can improve the accuracy and SNR, while reducing filtering effects. We demonstrate the concept in the three different versions of the magnetization‐prepared gradient‐echo sequences that are typically used for 3D‐T1ρ mapping and evaluate their performance in model agarose phantoms (n = 4) and healthy volunteers (n = 5) for knee joint imaging. We also tested the optimization with sequence parameters targeting faster acquisitions. Results: Our results show that optimized variable flip angle can improve the accuracy and the precision of the sequences, seen as a reduction of the mean of normalized absolute difference from about 5%–6% to 3%–4% in model phantoms and from 15%–16% to 11%–13% in the knee joint, and improving SNR from about 12–28 to 22–32 in agarose phantoms and about 7–14 to 13–17 in healthy volunteers. The optimization can also compensate for the loss in quality caused by making the sequence faster. This results in sequence configurations that acquire more data per unit of time with SNR and mean of normalized absolute difference measurements close to its slower versions. Conclusion: The optimization of the variable flip angle can be used to increase accuracy and precision, and to improve the speed of the typical imaging sequences used for quantitative 3D‐T1ρ mapping of the knee joint. [ABSTRACT FROM AUTHOR]

Accelerating the release of the antenna residual energy to weaken the antenna ringing signal is beneficial to shorten the echo time (TE) of low-field nuclear magnetic resonance (NMR) instruments, thus improving the measurement resolution and signal-to-noise ratio (SNR) of fast relaxation components. The antenna Q value has an opposite effect on the energy emission efficiency and discharge speed. For this reason, we first designed a new Q-switch circuit, which can greatly shorten the energy discharge time while ensuring the transmission efficiency. On this basis, an optimized pulse sequence was applied to overcome the defect that traditional phase alternated pair stacking (PAPs) cannot eliminate 90° pulse ringing, and the SNR was further improved by the method of phase cycling. Finally, the new Q-switch circuit was tested on a 2 MHz core analyzer, the Q value of the antenna was reduced to about 1/5 of the transmit period, and the antenna recovery time was reduced from 280.0 μs to 18.2 μs. Moreover, with the new Q-switch circuit and optimized pulse sequence, the T2 signal of the fast relaxation component can be effectively obtained when TE=60 μs.

Hyperpolarized 13 C MRI takes advantage of the unprecedented 50 000-fold signal-to-noise ratio enhancement to interrogate cancer metabolism in patients and animals. It can measure the pyruvate-to-lactate conversion rate, kPL , a metabolic biomarker of cancer aggressiveness and progression. Therefore, it is crucial to evaluate kPL reliably. In this study, three sequence components and parameters that modulate kPL estimation were identified and investigated in model simulations and through in vivo animal studies using several specifically designed pulse sequences. These factors included a magnetization spoiling effect due to RF pulses, a crusher gradient-induced flow suppression, and intrinsic image weightings due to relaxation. Simulation showed that the RF-induced magnetization spoiling can be substantially improved using an inputless kPL fitting. In vivo studies found a significantly higher apparent kPL with an additional gradient that leads to flow suppression (kPL,FID-Delay,Crush /kPL,FID-Delay  = 1.37 ± 0.33, P

• Development of widely used solvent suppression techniques. • First 1H-detected methods for relaxation measurement of low-γ nuclei. • Used NMR to study the first structure of a DNA triplex formed by a single strand. • Developed heteronuclear triple resonance schemes for assigning nucleic acids. [ABSTRACT FROM AUTHOR]

Objective: The bifurcation of neuronal firing is one of important nonlinear phenomena in the nervous system and is characterized by a significant change in the rate or temporal pattern of neuronal firing on responding to a small disturbance from external inputs. Previous studies have reported firing bifurcations for individual neurons, not for a population of neurons. We hypothesized that the integrated firing of a neuronal population could also show a bifurcation behavior that should be important in certain situations such as deep brain stimulations. The hypothesis was verified by experiments of rat hippocampus in vivo. Methods: Stimulation sequences of paired-pulses with two different inter-pulse-intervals (IPIs) or with two different pulse intensities were applied on the alveus of hippocampal CA1 region in anaesthetized rats. The amplitude and area of antidromic population spike (APS) were used as indices to evaluate the differences in the responses of neuronal population to the different pulses in stimulations. Results: During sustained paired-pulse stimulations with a high mean pulse frequency such as ∼130 Hz, a small difference of only a few percent in the two IPIs or in the two intensities was able to generate a sequence of evoked APSs with a substantial bifurcation in their amplitudes and areas. Conclusion: Small differences in the excitatory inputs can cause nonlinearly enlarged differences in the induced firing of neuronal populations. Significance: The novel dynamics and bifurcation of neuronal responses to electrical stimulations provide important clues for developing new paradigms to extend neural stimulations to treat more diseases. [ABSTRACT FROM AUTHOR]

In this work, we studied the threshold voltage ${V} _{\text {th}}$ for an ovonic threshold switch (OTS) device in a high-frequency continuous operation. By applying a pulse sequence with small pulse intervals, the dependence of ${V} _{\text {th}}$ on the falling edge of the prior pulse has been investigated in the Te-based OTS device. The results indicate that the ${V} _{\text {th}}$ presents a Weibull distribution in the pulse sequence, and the ${V} _{\text {th}}$ distribution drifts nonmonotonically with the pulse falling edge. Meanwhile, the drift tendency of the ${V} _{\text {th}}$ distribution was found depending on the device area. Furthermore, the recovery process and the time-resolved current profiles in the device operation have been investigated to further study the ${V} _{\text {th}}$ drift. The results indicate that the ${V} _{\text {th}}$ drift in continuous device operation is controllable and results from a combination of the effects of heat accumulation and the recovery process. The ${V} _{\text {th}}$ drift at high-frequency operating can be reduced by optimizing the device lateral dimension according to the mapping results of the ${V} _{\text {th}}$. Our results can guide the design and operation of the OTS device with a low ${V} _{\text {th}}$ drift requirement. [ABSTRACT FROM AUTHOR]

The preparation and detection of the nuclear singlet state are valuable and prospective for many applications related with compound molecular analysis. In this work, a proton spin coupled system containing two H nuclei in tripeptide (Ala-Gly-Gly, AGG) was selected as research object, and singlets were prepared with three sets of different pulse sequences based on different principles. The lifetime of those singlets were measured, and the singlet preparation efficiencies of different sequences were compared. The results indicated that for the same spin coupling system of the same molecule, there is no significant difference in the lifetime of the singlet state prepared by different pulse sequences, while their preparation efficiencies could be relatively different.

Purpose: The performance of pulse sequences in vivo can be limited by fast relaxation rates, magnetic field inhomogeneity, and nonuniform spin excitation. We describe here a method for pulse sequence optimization that uses a stochastic numerical solver that in principle is capable of finding a global optimum. The method provides a simple framework for incorporating any constraint and implementing arbitrarily complex cost functions. Efficient methods for simulating spin dynamics and incorporating frequency selectivity are also described. Methods: Optimized pulse sequences for polarization transfer between protons and X‐nuclei and excitation pulses that eliminate J‐coupling modulation were evaluated experimentally using a surface coil on phantoms, and also the detection of hyperpolarized [2‐13C]lactate in vivo in the case of J‐coupling modulation‐free excitation. Results: The optimized polarization transfer pulses improved the SNR by ~50% with a more than twofold reduction in the B1 field, and J‐coupling modulation‐free excitation was achieved with a more than threefold reduction in pulse length. Conclusion: This process could be used to optimize any pulse when there is a need to improve the uniformity and frequency selectivity of excitation as well as to design new pulses to steer the spin system to any desired achievable state. [ABSTRACT FROM AUTHOR]

We have studied the laser pulse shape dependence of the conversion efficiency of λ = 1.03 μm laser pulse energy into 13.5 nm extreme ultraviolet (EUV) emission from a Sn laser-produced plasma. Laser pulses of arbitrary temporal shape ranging from hundreds of picoseconds to several nanoseconds were generated using a programmable pulse synthesizer based on a diode-pumped chirped pulse amplification Yb: YAG laser. Measurements show that the conversion efficiency favors the use of nearly square pulses of duration longer than 2 ns, in agreement with hydrodynamic/atomic physics simulations. A 35% increase in conversion efficiency was obtained when Q-switched pulses were substituted by square pulses of a similar duration. Experiments conducted irradiating a Sn target with a sequence of two time-delayed 250 ps pulses showed a 30 percent increase in the EUV yield respect to a single pulse of the same total energy when the pulse separation was optimum at 2.1 ns. This suggests that re-heating of the plasma with delayed laser pulses could be used to improve the EUV yield. The spectroscopic characterization of EUV emission and in-band EUV images that characterize the source size are also presented.

Surveillance radar is confronted with serious two-dimensional ambiguity (i.e., range dimension and velocity dimension) and low signal-to-noise ratio (SNR) problems in the time sensitive (TS) target detection process, which may result in the deterioration of target detection performance. Combining the advantages of the intra-frame detection and the inter-frame detection, a novel two-step thresholds track before detect (TBD) algorithm based on the integration techniques, i.e., two-dimensional ambiguity resolution and multi-frame joint detection, is proposed in this paper. Firstly, the fusion design strategy, including the pulse repetition frequency, the carrier frequency and the orthogonal waveform, is adopted in the transmitting pulse sequence. As a result, not only the range ambiguity number and the spatial filling time are reduced synchronously, but the decoupling of range-velocity ambiguity is realized, which is conductive to multi-target detection in low SNR environment. Then, the first level adaptive threshold is obtained by employing the judgment criterion based on cumulative value function (CVF), and thus the false trajectory number is effectively eliminated from the perspective of cumulative amplitude. Finally, through analyzing the inherent relation between the local trajectory characteristics and the global trajectory characteristics comprehensively, different types of false alarm trajectories are further reduced by means of the polynomial coefficient variance statistics. Experimental results verify the effectiveness of the proposed algorithm.

Nb-doped SnO 2 (NTO) thin films were synthesized by atomic layer deposition technique at low temperature (100 °C). For an efficient incorporation of the Nb atoms, i.e. fine control of their amount and distribution, various supercycle ratios and precursor pulse sequences were explored. The thin film growth process studied by in-situ QCM revealed that the Nb incorporation is highly impacted by the surface nature as well as the amount of species available at the surface. This was confirmed by the actual concentration of the Nb atom incorporated inside the thin film as determined by XPS. Highly transparent thin films which transmit more than 95% of the AM1.5 global solar irradiance over a wide spectral range (300-1000 nm) were obtained. In addition, the Nb atoms influenced the optical band gap, conduction band, and valence band levels. While SnO 2 thin film were too resistive, films tuned to conductive nature upon Nb incorporation with controlled concentration. Optimal incorporation level was found to be ⩽1 at.% of Nb, and carrier concentration reached up 2.5 × 10 18 cm -3 for the as-deposited thin films. As a result, the high optical transparency accompanied with tuned electrical property of NTO thin films fabricated by ALD at low temperature paves the way for their integration into temperature-sensitive, nanostructured optoelectrical devices., (© 2024 IOP Publishing Ltd.)

Purpose: To determine which sequence for frequently used general contrast-enhanced brain MRI shows the least radiofrequency shielding effect of a titanium mesh in cranioplasty using a phantom. Methods: A 1.5T MRI scanner was used. Frequently used general 2D and 3D spin-echo sequences (SE) and T1 spoiled gradient echo sequences (GRE) used for MRI in clinical settings were adopted in this study. A titanium mesh was placed above a cubic phantom containing manganese chloride tetrahydrate and sodium chloride. The signal attenuation ratio and normalized absolute average deviation (NAAD) were calculated. Moreover, the flip angle (FA) dependency in SE and area of excitation dependency in 3D sequences were analyzed using NAAD. Results: The signal attenuation ratio at the position nearest to the titanium mesh for 2D SE was 71.8% larger than that at the position nearest to the titanium mesh for 3D GRE. With regard to NAAD, 3D GRE showed the highest values among the sequences. When FA was increased, radiofrequency shielding effect was improved. There were no significant differences between the narrow and wide area of excitation. 3D GRE showed the least radio frequency shielding effect, and it was considered as the optimal sequence for MRI in the presence of a titanium mesh. Conclusion: 3D GRE shows the least radiofrequency shielding effect of a titanium mesh after cranioplasty among frequently used general sequences for contrast-enhanced brain MRI. [ABSTRACT FROM AUTHOR]

Tremendous progress of developing nuclear magnetic resonance (NMR) fluid analyzer has been witnessed in the oil industry for last two decades. This device allows extensive and accurate exploration of fluid properties, such as its hydrogen content, composition, viscosity, hydrogen index (HI), mud filtrate invasion, gas to oil ratio, average velocity, velocity distribution etc., in the situations of in situ downhole or surface Petro-pipelines. In this review article, we focus on the design principle, manufacturing, implementation, methodology and applications of NMR fluid analyzer to oil and gas industry. A detailed description of the state-of-art NMR fluid analyzers was firstly given to exhibit their respective characteristics. With these experiences on hand, we introduced a series of NMR fluid analyzers designed by us at China University of Petroleum-Beijing with continuous optimizations, in terms of magnet construction, antenna layout, circuit design and operating surroundings. These systems discussed in this article have been demonstrated to achieve multiple NMR parameter acquisition when the fluid is in stationary or flowing state. In the end, a prototype was fabricated and validated considering a vast of engineering influences, such as variable temperatures in a large range, high pressure, limited volume, detection efficiency, etc. A particular emphasis of this paper is to expedite the measurement efficiency of the NMR fluid analyzer to reduce the operation costs. This dilemma can be Figured out by upgrading both pulse sequence and observational mode. For different fluid states, two rapid pulse sequences were proposed to sufficiently obtain the multi-dimensional NMR correlation map. Meanwhile, two observational modes were developed to take full advantage of the polarization time, during which the individual antenna was systematically switched. Another domain of interest in this review concerns the applications of this new tool. For stationary fluids case, accurate identification of fluid properties is of great value for scheme building in oil and gas exploration process. Particularly, it can acquire the fluid content by different NMR responses of different components. In addition, with Bloembergen theory and Stokes–Einstein equation, not only molecular dynamics and composition, but also oil viscosity can be readily evaluated. Moreover, HI information of crude oils will be speculated through partial least square regression. As for flowing fluids case, velocity is a significant parameter to understand the in situ fluid exploitation and therefore evaluate the productivity of certain oil wells or pipelines. Regarding to the unique magnet and antenna designs in our NMR fluid analyzer; this review adopts two distinct methods to obtain flow velocity at a wide rating scale. The first one is a time-of-flight method adaptive in a homogeneous magnetic field, which is suitable in the case of fluid at high flow velocity. The other one relies on the adjacent echo phase difference at a magnetic field with constant gradient, which is preferred for relatively low flow velocity. In the near future, this tool will be tested underground to offer individual fluid velocities by combining both the stationary and flowing analysis methods. [ABSTRACT FROM AUTHOR]

We have studied the laser pulse shape dependence of the conversion efficiency of λ = 1.03 μm laser pulse energy into 13.5 nm extreme ultraviolet (EUV) emission from a Sn laser-produced plasma. Laser pulses of arbitrary temporal shape ranging from hundreds of picoseconds to several nanoseconds were generated using a programmable pulse synthesizer based on a diode-pumped chirped pulse amplification Yb: YAG laser. Measurements show that the conversion efficiency favors the use of nearly square pulses of duration longer than 2 ns, in agreement with hydrodynamic/atomic physics simulations. A 35% increase in conversion efficiency was obtained when Q-switched pulses were substituted by square pulses of a similar duration. Experiments conducted irradiating a Sn target with a sequence of two time-delayed 250 ps pulses showed a 30 percent increase in the EUV yield respect to a single pulse of the same total energy when the pulse separation was optimum at 2.1 ns. This suggests that re-heating of the plasma with delayed laser pulses could be used to improve the EUV yield. The spectroscopic characterization of EUV emission and in-band EUV images that characterize the source size are also presented. [ABSTRACT FROM AUTHOR]

Nuclear magnetic resonance (NMR) is an established method to determine self-diffusion coefficients in liquids with high precision. The development of benchtop NMR spectrometers makes the method accessible to a wider community. In most cases, 1 H NMR spectroscopy is used to determine self-diffusion coefficients due to its high sensitivity. However, especially when using benchtop NMR spectrometers for the investigation of complex mixtures, the signals in 1 H NMR spectra can overlap, hindering the precise determination of self-diffusion coefficients. In 13 C NMR spectroscopy, the signals of different compounds are generally well resolved. However, the sensitivity of 13 C NMR is significantly lower than that of 1 H NMR spectroscopy leading to very long measurement times, which makes diffusion coefficient measurements based on 13 C NMR practically infeasible with benchtop NMR spectrometers. To circumvent this problem, we have combined two known pulse sequences, one for polarization transfer from 1 H to the 13 C nuclei (PENDANT) and one for the measurement of diffusion coefficients (PFG). The new method (PENPFG) was used to measure the self-diffusion coefficients of three pure solvents (acetonitrile, ethanol and 1-propanol) as well as in all their binary mixtures and the ternary mixture at various compositions. For comparison, also measurements of the same systems were carried out with a standard PFG-NMR routine on a high-field NMR instrument. The results are in good agreement and show that PENPFG is a useful tool for the measurement of the absolute value of the self-diffusion coefficients in complex liquid mixtures with benchtop NMR spectrometers., (© 2023 The Authors. Magnetic Resonance in Chemistry published by John Wiley & Sons Ltd.)

Research on the effect of pulsed electric field in cell electroporation attracts more attention, especially tumor ablation. This puts forward higher requirements for pulsed electric field parameters. The shape of the pulse waveform was also required in different electroporation applications. Based on this, a multilevel pulse generator with series capacitor structure was proposed in this article. Besides, it can also obtain the different shapes of the pulse waveforms by controlling the timing of semiconductor switches. The voltage amplitude, the number of pulses, and the pulsewidth are all adjustable. A ten-level test prototype with 11 switches was built. The structure was simple and was more compact. It can work stably under the simulated small resistance load. Finally, when the dc charging voltage was 1 kV, the system can achieve a maximum output voltage of ±500 V. The number of pulse in one pulse sequence was 1–500. The pulsewidth was adjustable from 1 to $10~\mu \text{s}$. By controlling the switch’s timing, it can also obtain the multilevel voltage output, exponential waveform voltage output, and composite waveform output combined narrow pulse with wide pulse. [ABSTRACT FROM AUTHOR]

Background: Magnetic resonance imaging (MRI) is widely used to diagnose acute abdominal pain; however, it remains unclear which pulse sequence has priority in acute abdominal pain. Purpose: To investigate the diagnostic accuracy of MRI and to assess the conspicuity of each pulse sequence for the diagnosis of acute abdominal pain due to gastrointestinal diseases Material and Methods: We retrospectively enrolled 60 patients with acute abdominal pain who underwent MRI for axial and coronal T2-weighted (T2W) imaging, fat-suppressed (FS)-T2W imaging, and true-fast imaging with steady-state precession (True-FISP) and axial T1-weighted (T1W) imaging and investigated the diagnosis with endoscopy, surgery, histopathology, computed tomography, and clinical follow-up as standard references. Two radiologists determined the diagnosis with MRI and rated scores of the respective sequences in assessing intraluminal, intramural, and extramural abnormality using a 5-point scale after one month. Diagnostic accuracy was calculated and scores were compared by Wilcoxon-signed rank test with Bonferroni correction. Results: Diagnostic accuracy was 90.0% and 93.3% for readers 1 and 2, respectively. Regarding intraluminal abnormality, T2W, FS-T2W, and True-FISP imaging were superior to T1W imaging in both readers. FS-T2W imaging was superior to True-FISP in reader 2 (P < 0.0083). For intramural findings, there was no significant difference in reader 1, whereas T2W, FS-T2W, and True-FISP imaging were superior to T1W imaging in reader 2 (P < 0.0083). For extramural findings, FS-T2W imaging was superior to T2W, T1W, and True-FISP imaging in both readers (P < 0.0083). Conclusion: T2W and FS-T2W imaging are pivotal pulse sequences and should be obtained before T1W and True-FISP imaging. [ABSTRACT FROM AUTHOR]

Background: The societal burden of chronic pain and the contribution-in-part to the opioid crisis, is a strong motivation to improve and expand non-addictive treatments, including spinal cord stimulation (SCS). For several decades standard SCS has consisted in delivery of tonic pulses with static parameter settings in frequency, pulse width, and amplitude. These static parameters have limited ability to personalize the quality of paresthesia, the dermatomal coverage, and thus may affect SCS efficacy. Further, static settings may contribute to the build-up of tolerance or loss of efficacy of the therapy over time in some patients., Methods: We conducted an acute exploratory study to evaluate the effects of SCS using time-dynamic pulses as compared to time-static (conventional tonic) stimulation pulses, with the hypotheses that dynamic pulse SCS may enable beneficial tailoring of the sensation and the patient's expectation for better pain relief with SCS. During a single clinic visit, consented subjects undergoing a standard SCS trial had their implanted leads temporarily connected to an investigational external stimulator capable of delivering time-static and six categories of time-dynamic pulse sequences, each characterized by continuously varying a stimulation parameter. Study subjects provided several assessments while blinded to the stimulation pattern, including: drawing of paresthesia maps, descriptions of sensation, and ratings for comfort and helpfulness to pain relief., Results: Even without optimization of the field location, a majority of subjects rated sensations from dynamic stimulation as better or equal to that of static stimulation for comfortableness and for helpfulness to pain relief. The initial data showed a gender and/or pain dermatomal location related preference to a stimulation pattern. In particular, female subjects and subjects with pain at higher dermatomes tended to rank the sensation from dynamic stimulation better. Dynamic stimulation produced greater pain coverage without optimization; in 70% (9/13) of subjects, maximal pain coverage was achieved with a dynamic stimulation pattern. There was also greater variety in the words used by patients to describe stimulation sensation in the free text and free form verbal descriptions associated with dynamic stimulation., Conclusions: With the same electrode configuration and comparable parameter settings, acute SCS using dynamic pulses produced more positive ratings, expanded paresthesia coverage, and greater variation in sensation as compared to SCS using static pulses, suggesting that dynamic stimulation has the potential to improve capabilities of SCS for the treatment of chronic pain. Further study is warranted., Trial Registration: This study was registered at ClinicalTrials.gov under ID NCT02988713, November 2016 (URL: https://clinicaltrials.gov/ct2/show/NCT02988713)., Competing Interests: CZ, RE, JB and MM were employed by Boston Scientific Neuromodulation. KL was a former employee with Boston Scientific Neuromodulation. The remaining author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2024 Zhu, Esteller, Block, Lechleiter, Frey and Moffitt.)

Background: Multiple sclerosis (MS) is a demyelinating disease, involving almost 2.5 million people around the world. There are different MR pulse sequences, which are used to detect MS plaques. Objectives: This study aimed to compare, T2 weighted, short-tau inversion recovery (STIR) and phase-sensitive inversion recovery (PSIR) pulse sequences, for detecting cervical spinal cord lesions in MS patients. Patients and Methods: Sixty patients with definite MS diagnoses, participated in this study from June to December 2016. 1.5 T Siemens (Avanto, Erlangen, Germany) MR scanner and three pulse sequences (T2 weighted, STIR and PSIR sequences) were used for cervical cord MR imaging. To assess the effectiveness of these pulse sequences, the lesion to cord ratio (LCR) and lesion to noise ratio (LNR) were calculated. Results: The LCR and LNR of the T2 and PSIR were the same (LCR of 0.04, -0.03 and LNR of 2.74, -2.09 respectively), just the intensities were reverse. STIR had a significantly different LCR and LNR [0.23 (P < 0.001) and 22.7(P < 0.001) respectively], hence it was better in diagnosing cervical cord MS plaques. Conclusion: According to the results, using 1.5 T MRI machine, it implies that the STIR pulse sequence was the best pulse sequence in comparison to T2 and PSIR in detecting cervical cord MS plaques. [ABSTRACT FROM AUTHOR]

Schematic diagram of new 3D pulse sequence and the simulated echo trains. • A tri-window pulse sequence to collect the full decaying information of porous media is proposed. • A joint inversion algorithm named 'composite-data-processing' to obtain the 3D correlation map is proposed. • A tight oil shale model containing four types of fluid is established and validated the proposed method. Compared with two-dimensional (2D) nuclear magnetic resonance (NMR) technique like correlations among the transversal relaxation time (T 2), the longitudinal relaxation time (T 1), and the diffusion coefficient correlation (D), three-dimensional (3D) NMR technique is superior with the complete measurement of T 2 , T 1 , and D simultaneously. It can solve the problem of overlaps in 2D correlation map and is helpful to characterize relaxation components in unconventional resources such as tight gas and oil shale. However, the existed 3D NMR technique is restricted due to the loss of short relaxation information and the inversion inaccuracy that caused by the incomplete measurement of the diffusion editing window. We developed a tri-window pulse sequence to collect the full decaying information of porous media. In the first window, the inversion-recovery pulse sequence is applied for T 1 encoding. In the second window, D and T 2 are encoded by an adjustable continuous pulse field gradient and echo spacing (TE). In the last window, CPMG with the shortest TE is used to acquire diffusion-free relaxation information. We then proposed a joint inversion algorithm named "composite-data-processing" to obtain the 3D correlation map. The algorithm adopts the dimension reduction technique and the truncated singular value decomposition (TSVD) to speed up the inversion process and enhance the inversion stability. Numerical simulations show that good estimations of the inversion results are obtained at different signal to noise ratios (SNRs). Our results suggest that the novel pulse sequence and inversion algorithm of 3D NMR can be effectively applied to the exploration of unconventional resources. [ABSTRACT FROM AUTHOR]

We present NMRlib, a suite of jython-based tools designed for Bruker spectrometers (TopSpin versions 3.2–4.0) that allow easy setup, management, and exchange of NMR experiments. A NMR experiment can be set up and executed in a few clicks by navigating through the NMRlib GUI tree structure, without any further parameter adjustment. NMRlib is magnetic-field independent, and thus particularly helpful for laboratories operating multiple NMR spectrometers. NMRlib is easily personalized by adding, deleting, or reorganizing experiments. Additional tools are provided for data processing, visualization, and analysis. In particular, NMRlib contains all the polarization-enhanced fast-pulsing NMR experiments (SOFAST, BEST, HADAMAC,...) developed in our laboratory over the last decade. We also discuss some specific features that have been implemented to make these experiments most efficient and user friendly. [ABSTRACT FROM AUTHOR]

Hyperpolarized 13C MRI takes advantage of the unprecedented 50 000‐fold signal‐to‐noise ratio enhancement to interrogate cancer metabolism in patients and animals. It can measure the pyruvate‐to‐lactate conversion rate, kPL, a metabolic biomarker of cancer aggressiveness and progression. Therefore, it is crucial to evaluate kPL reliably. In this study, three sequence components and parameters that modulate kPL estimation were identified and investigated in model simulations and through in vivo animal studies using several specifically designed pulse sequences. These factors included a magnetization spoiling effect due to RF pulses, a crusher gradient‐induced flow suppression, and intrinsic image weightings due to relaxation. Simulation showed that the RF‐induced magnetization spoiling can be substantially improved using an inputless kPL fitting. In vivo studies found a significantly higher apparent kPL with an additional gradient that leads to flow suppression (kPL,FID‐Delay,Crush/kPL,FID‐Delay = 1.37 ± 0.33, P < 0.01, N = 6), which agrees with simulation outcomes (12.5% kPL error with Δv = 40 cm/s), indicating that the gradients predominantly suppressed flowing pyruvate spins. Significantly lower kPL was found using a delayed free induction decay (FID) acquisition versus a minimum‐TE version (kPL,FID‐Delay/kPL,FID = 0.67 ± 0.09, P < 0.01, N = 5), and the lactate peak had broader linewidth than pyruvate (Δωlactate/Δωpyruvate = 1.32 ± 0.07, P < 0.000 01, N = 13). This illustrated that lactate's T2*, shorter than that of pyruvate, can affect calculated kPL values. We also found that an FID sequence yielded significantly lower kPL versus a double spin‐echo sequence that includes spin‐echo spoiling, flow suppression from crusher gradients, and more T2 weighting (kPL,DSE/kPL,FID = 2.40 ± 0.98, P < 0.0001, N = 7). In summary, the pulse sequence, as well as its interaction with pharmacokinetics and the tissue microenvironment, can impact and be optimized for the measurement of kPL. The data acquisition and analysis pipelines can work synergistically to provide more robust and reproducible kPL measures for future preclinical and clinical studies. This study investigated three pulse sequence components and parameters that can affect estimates of kPL in HP‐13C MRI. In vivo animal tumor studies showed significant impact on kPL with crusher‐gradient induced flow suppression, and intrinsic image weighting due to relaxation, corroborated by signal‐model simulations. RF‐induced magnetization spoiling can be substantially improved using an inputless kPL fitting. These outcomes suggested that the pulse sequence, as well as its interaction with pharmacokinetics and tissue microenvironment, can impact the measurement of kPL. [ABSTRACT FROM AUTHOR]

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