FID Signal Research Articles

Higher-Order Singular Value Tensor Decomposition-Based Tuning Frequency Estimation for FID Signals Under Low SNR

Higher-Order Singular Value Tensor Decomposition-Based Tuning Frequency Estimation for FID Signals Under Low SNR

Estimation and Utilization of the Geomagnetic Field Inhomogeneities Using the Relaxation Characteristics of the FID Signal in an Overhauser Magnetometer

Estimation and Utilization of the Geomagnetic Field Inhomogeneities Using the Relaxation Characteristics of the FID Signal in an Overhauser Magnetometer

Early FID Signal Detection Technique With a Gradient Coil for Magnetic Resonance Sounding

Early FID Signal Detection Technique With a Gradient Coil for Magnetic Resonance Sounding

Real-time 14N NQR-based sodium nitrite analysis in a noisy field

Noise and Radio-frequency interference or RFI causes a significant restriction on the Free induction Decay or FID signal detection of the Nuclear Quadrupole Resonance procedure. Therefore, using this method in non-isolated environments such as industry and ports requires extraordinary measures. For this purpose, noise reduction algorithms and increasing signal-to-noise-and-interference ratio or SNIR have been used. In this research, sodium nitrite has been used as a sample and algorithms have been tested in a non-isolated environment. The resonant frequencies for the 150 g of test sample were measured at 303 K at about 1 MHz and 3.4 MHz. The main novelty in this study was, (1) using two types of antennas in the receiver to improve adaptive noise and interference cancellation, (2) using a separate helical antenna in the transmitter to eliminate the duplexer, (3) estimating the noise before sending the pulse to calculate the weighting factors and reduce the noise by adaptive noise cancellation, (3) reject the interference by blanking algorithm, (4) pulse integration in the frequency domain to increase the SNR, and (5) increasing the detection speed by new pulse integration technique. By interference rejection and noise cancellation, the SNIR is improved to 9.24 dB at 1 MHz and to 7.28 dB at 3.4 MHz, and by pulse integration 44.8 dB FID signal amplification is achieved, and the FID signals are detected at 1.057 MHz and 3.402 MHz at room temperature.

Algorithms for Direct and Inverse Parametric Fast Fourier Transform

Русский Main page New issue Archive of articles Editorial board For the authors Publishing house ABSTRACTS OF ARTICLES OF THE JOURNAL "INFORMATION TECHNOLOGIES". No. 1. Vol. 28. 2022 DOI: 10.17587/it.28.9-19 O. V. Ponomareva, Dr. Sc., Tech., Professor, A. V. Ponomarev, PhD, Econ., Associate Professor, Kalashnikov Izhevsk State Technical University, Izhevsk, 426069, Russian Federation, N. V. Smirnova, PhD, Tech., Associate Professor, Sevastopol State University, Sevastopol, 299053, Russian Federation Algorithms for Direct and Inverse Parametric Fast Fourier Transform Classical Fourier processing of finite information discrete signals (FID signals) is the most important method of digital analysis, modeling, optimization, improvement of control and decision making. The theoretical basis of classical Fourier processing of FID signals is the discrete Fourier transform (DFT). The practical basis of classical Fourier processing of FID signals is the Fast Fourier Transform (FFT). The practice of using classical Fourier processing of FID signals, having confirmed its effectiveness, revealed a number of negative effects inherent in this type of digital signal processing (DSP). The aliasing effect, scalloping effect, picket fence effect, significantly affect the effectiveness of analysis, modeling, optimization, improvement of management and decision making. To increase the efficiency of Fourier processing of FID signals, the authors of the paper have developed a generalization of DFT in the form of a parametric DFT (DFT-P). Since the direct application of parametric Fourier processing of FID signals (as well as the use of classical Fourier processing of FID signals) requires complex multiplications, fast procedures are required for the practical implementation of this type of FID signals. Purpose of the research is to develop algorithms for the fast parametric discrete Fourier transform (FFT-P). The work developed fast procedures for the implementation of DFT-P by time decimation. Parametric FFT-P with substitution (in place) and without substitution (no place) are proposed. The estimation of the efficiency of the FFT-P algorithms is given. The practical significance of the work is in the fact that developing algorithms for the parametric fast Fourier transform can reduce the computational costs of performing parametric discrete transformations by three or more orders of magnitude.

Analysis of molecular mobility in corn and quinoa flours through 1H NMR and its relationship with water distribution, glass transition and enthalpy relaxation

Solids-water interactions of corn and quinoa flours were evaluated through 1H NMR, DSC, and water sorption isotherms. Glass transition temperature (Tg), observed by DSC, was better distinguished through FID signals, and correlated to water content through the Gordon and Taylor model. Enthalpy relaxations, identified by thermal analysis at 50–70 °C were studied through transverse relaxation times (T2) measured after Hahn spin-echo sequence, which revealed a rearrangement of the biopolymers structures that cause immobilization of polymer chains and reduced mobility of water molecules with weak interactions with solids (lower T22). The higher lipid content of quinoa flour was manifested after the CPMG sequence (T2 ≈ 100 ms) and caused reduced hygroscopicity and Tg values compared with corn flour systems. 1H NMR resulted efficient for assigning proton populations and understanding the changes in their distribution with temperature, analyzing glass transition and interpreting the implications of enthalpy relaxations processes in corn and quinoa flours.

A retrospective physiological noise correction method for oscillating steady-state imaging.

Oscillating steady-state imaging (OSSI) is an SNR-efficient steady-state sequence with sensitivity suitable for FMRI. Due to the frequency sensitivity of the signal, respiration- and drift-induced field changes can create unwanted signal fluctuations. This study aims to address this issue by developing retrospective signal correction methods that utilize OSSI signal properties to denoise task-based OSSI FMRI experiments. A retrospective denoising approach was developed that leverages the unique signal properties of OSSI to perform denoising without a manually specified noise region of interest and works with both voxel timecourses (oscillating steady-state correction [OSSCOR]) or FID timecourses (F-OSSCOR). Simulations were performed to estimate the number of principal components optimal for denoising. In vivo experiments at 3 T field strength were conducted to compare the performance of proposed methods against a standard principal component analysis-based method, measured using mean t score within an region of interest, number of activations, and mean temporal SNR. Correction using OSSCOR was significantly better than the standard method in all metrics. Correction using F-OSSCOR was not significantly different from the standard method using an equal number of principal components. Increasing the number of OSSCOR principal components decreased activation strength and increased the number of suspected false positives. However, increasing the number of principal components in F-OSSCOR increased activation strength with little to no increase in false activation. Both OSSCOR and F-OSSCOR substantially reduce physiological noise components and increase temporal SNR, improving the functional results of task-based OSSI functional experiments. F-OSSCOR demonstrates a proof of concept utilization of coil-localized FID signal information for physiological noise correction.

Power-optimized, time-reversal pulse sequence for a robust recovery of signals from rigid segments using time domain NMR

Time domain NMR (TD-NMR) has been widely used on the analysis of liquids or liquid components in heterogeneous materials such as food, biological tissues, synthetic and bio polymers, oil-bearing rocks, biomasses and cement-based materials. The use of TD-NMR for studying solid and soft mater has been growing in number and variety of applications, mostly for organic systems where the detection of 1H signals is highly advantageous. However, the strong 1H–1H dipolar interactions in solids make the 1H FID to decay in the same order of the dead time of most commercially available NMR probe heads. Thus, solid echoes are often used for recovering signals from solid components. In this article we reinvestigate the time-reversal solid-echo pulse sequence proposed by Rhim and Kessemeier, seeking for optimal pulse power and timing conditions that maximize its efficiency on recovering 1H signals from rigid segments. We show that under these optimized conditions, which we denote as Rhim and Kessemeier - Radiofrequency Optimized Solid-Echo (RK-ROSE), the experiment can be more efficient than its most popular counterparts Solid-Echo (SE) and mixed-Magic Sandwich Echoes (mixed-MSE). Our results also suggest that, despite the finite pulse power, with current probe technology the RK-ROSE experiment is potentially able to provide an accurate estimation of rigid components, without relying on an external calibration using multiple standard samples, as usually done in SFC analysis of the FID signal. At last, we demonstrate that RK-ROSE can be adapted as a simple filter to supress signals from mobile segments in heterogeneous materials.

Non-targeted analysis of the particulate phase of heated tobacco product aerosol and cigarette mainstream tobacco smoke by thermal desorption comprehensive two-dimensional gas chromatography with dual flame ionisation and mass spectrometric detection

An analytical methodology based on thermal desorption and comprehensive two-dimensional gas chromatography with dual time-of-flight mass spectrometry and flame ionization detection (TD-GC × GC-TOFMS/FID) has been developed for non-target analysis of volatile organic compounds (VOCs). The technique was optimised for the measurement of the VOC content of the particulate phase (PP) fraction of aerosols produced by a tobacco heating product (THP1.0) and 3R4F mainstream tobacco smoke (MTS). The method involves sampling the PP fraction on quartz wool packed in a sorbent tube directly connected to machine-puffing, followed by a dilution through a TD recollection procedure over Tenax/Sulficarb sorbent before TD-GC × GC-TOFMS/FID analysis. The comparison of the VOC content of the PP fraction of aerosols produced by THP1.0 and MTS highlighted the compositional difference between tobacco combustion (592 peaks) and tobacco heating process (160 peaks). Mass spectrometric signals were used for qualitative analyses based on linear retention indices, mass spectral matches, and GC × GC structured chromatograms, which collectively identified up to 90% of analytes detected in PP samples. FID signals were used for semi-quantitative analyses based on a chemical class external calibration method. The global chemical composition of PP samples showed that hydrocarbons, oxygenated, and nitrogen-containing compounds were fewer in number and much less abundant in THP1.0 PP. Overall, 93 compounds were common to the two sample types. Excepted for a few highly volatile compounds (mainly furan family) as well as glycerine and its acetate, analyte concentrations were higher in MTS PP.

Whole-brain B1 -mapping using three-dimensional DREAM.

Demonstration of a 3D version of the DREAM sequence (3DREAM) for rapid 3D flip angle and mapping of the human brain. A rectangular non-selective STE preparation is followed by a 3D readout with a Cartesian center-out spiral phase encoding order. This enables parallel imaging acceleration in both phase encoding dimensions as well as early capture of the prepared magnetization. mapping of the whole human head is demonstrated on a 7T system at a nominal resolution of 5 mm with and without parallel imaging acceleration. Artifacts caused by the different signal decay of the FID and STE signal during the long imaging train is suppressed by appropriate filtering of the FID image. Remaining blurring can be controlled by adjusting the echo train length and readout flip angle. 3DREAM provides a whole-brain flip angle map in a few seconds or individual maps for an 8-channel array in about a minute.

Cardiorespiratory motion-tracking via self-refocused rosette navigators.

To develop a flexible method for tracking respiratory and cardiac motions throughout MR and PET-MR body examinations that requires no additional hardware and minimal sequence modification. The incorporation of a contrast-neutral rosette navigator module following the RF excitation allows for robust cardiorespiratory motion tracking with minimal impact on the host sequence. Spatial encoding gradients are applied to the FID signal and the desired motion signals are extracted with a blind source separation technique. This approach is validated with an anthropomorphic, PET-MR-compatible motion phantom as well as in 13 human subjects. Both respiratory and cardiac motions were reliably extracted from the proposed rosette navigator in phantom and patient studies. In the phantom study, the MR-derived motion signals were additionally validated against the ground truth measurement of diaphragm displacement and left ventricle model triggering pulse. The proposed method yields accurate respiratory and cardiac motion-state tracking, requiring only a short (1.76ms) additional navigator module, which is self-refocusing and imposes minimal constraints on sequence design.

A multicontrast imaging method using steady-state free precession with alternating RF flip angles.

To obtain multicontrast images including fat-suppressed contrast image, a novel multicontrast imaging method using an SSFP sequence with alternating RF flip angles is proposed. The proposed method uses the balanced SSFP sequence with 2 flip angles. In general, the conventional balanced SSFP sequence has its own unique contrast, which combines both FID signal and echo signal under a steady-state condition. By using alternating RF flip angles and RF phase cycling, various image contrasts weighted by proton density, T1 , and T2 can be obtained. The proposed method offers multicontrast images with fat suppression by using the combination of 2 images obtained just after alternating RF pulses, respectively. As demonstrated by simulations, phantom and in vivo experiments, the proposed method provides multicontrast knee images including fat-suppressed contrast images. The proposed method can be a useful tool for clinical diagnosis, such as the cartilage segmentation and the fast screening of lesions.

Multi-step phase-cycling in a free-electron laser-powered pulsed electron paramagnetic resonance spectrometer.

Electron paramagnetic resonance (EPR) is a powerful tool for research in chemistry, biology, physics and materials science, which can benefit significantly from moving to frequencies above 100 GHz. In pulsed EPR spectrometers driven by powerful sub-THz oscillators, such as the free electron laser (FEL)-powered EPR spectrometer at UCSB, control of the duration, power and relative phases of the pulses in a sequence must be performed at the frequency and power level of the oscillator. Here we report on the implementation of an all-quasioptical four-step phase cycling procedure carried out directly at the kW power level of the 240 GHz pulses used in the FEL-powered EPR spectrometer. Phase shifts are introduced by modifying the optical path length of a 240 GHz pulse with precision-machined dielectric plates in a procedure we call phase cycling with optomechanical phase shifters (POPS), while numerical receiver phase cycling is implemented in post-processing. The POPS scheme was successfully used to reduce experimental dead times, enabling pulsed EPR of fast-relaxing spin systems such as gadolinium complexes at temperatures above 190 K. Coherence transfer pathway selection with POPS was used to perform spin echo relaxation experiments to measure the phase memory time of P1 centers in diamond in the presence of a strong unwanted FID signal in the background. The large excitation bandwidth of FEL-EPR, together with phase cycling, enabled the quantitative measurement of instantaneous electron spectral diffusion, from which the P1 center concentration was estimated to within 10%. Finally, phase cycling enabled saturation-recovery measurements of T1 in a trityl-water solution at room temperature - the first FEL-EPR measurement of electron T1.

Development of Stepwise-Field-Swept Solid-State NMR of Half-Integer Quadrupoles towards High Digital-Resolution NMR Spectra

Abstract Stepwise-field-swept solid-state nuclear magnetic resonance (NMR) experiments, which potentially make it possible to achieve high digital-resolution NMR spectra, are presented using 79/81Br NMR of strontium bromide hydrate. In contrast to the conventional field-swept NMR in which magnetic fields are continuously varied while FID signals are accumulated, FID signals can be observed with a static magnetic field, and the magnetic fields are stepwise changed after each accumulation. Spectral simulations for the field-swept NMR spectra, calculated by a direct diagonalization method in which the Zeeman and quadrupolar Hamiltonians were numerically diagonalized to obtain transition probabilities, are also described. Improvements necessary to achieve high digital-resolution NMR spectra, including the stability of superconducting magnets and DC power supply sources that control the superconducting magnets in non-persistent mode, are briefly discussed.

Dynamic of NAA and BOLD after single short stimulus in motor cortex of Schizophrenia patients

IntroductionThe aim of this study was the analysis of dynamics of motor cortex metabolite in the norm and in early stage of schizophrenia in period of BOLD response to event related single stimulus.ObjectivesThe patients group consisted of 9 mails of 16–28 years old in initial stage of schizophrenia and in remission. The group of 9 age matched healthy mails was used as a control.MethodsPhillips Achieva 3.0 T scanner was used for the study. Volume of interest in motor cortex was localized on the base of fMRI. 1Н МR spectra were run using synchronization of FID signals acquisition (PRESS, TE = 30 ms TR = 3000 ms) with dynamics of BOLD response at the same paradigm.ResultsThe BOLD signal in both groups demonstrated maximum at the 6th s after target stimulus, however its value was reliably lover in schizophrenia in comparison with the control. The only [NAA] in normal motor cortex was changed after stimulation. The stable values of [NAA], [Cr] and [Cho] were observed in dynamic of resting state as well. [NAA] in normal cortex statistically significantly decreased at the 12th s after stimulus presentation and returned to initial value at the 15th s.ConclusionDifferent behavior of [NAA] in the norm and schizophrenia might be related with a difference in location (or activity) of aspartoacylaze (ASPA). Decreased expression of glutamate transporters in schizophrenia could also reduce consumption of NAA as a source of acetate in synthesis of AcCoA which is used for restoration of ATP.Disclosure of interestThe authors have not supplied their declaration of competing interest.

Alternative data processing techniques for serial NMR experiments

AbstractNMR measurements are often performed in a serial manner, that is, the acquisition of an FID signal is repeated under various conditions, either controlled (as temperature or pH changes) or uncontrolled (as reaction progress). The traditional approach to process “serial” data is to perform the Fourier transform of each FID in a series. However, it suffers from several problems, in particular, from the need to sample full Nyquist grid and reach a sufficient signal‐to‐noise ratio in each separate spectrum. The problems become particularly cumbersome in the case of multidimensional signals, where sampling is costly and sensitivity is an issue. Over the years, several methods of alternative, “joint” processing of FID series have been proposed. In this paper, we discuss the principles of some of them: Accordion Spectroscopy, Multidimensional Decomposition, Radon transform, a combination of Compressed Sensing and the Laplace transform. According to our knowledge, this is the first review on serial NMR data processing approaches. The reader is provided with MATLAB scripts allowing to perform simulations and processing using these algorithms.

Hydrothermal changes in wheat starch monitored by two-dimensional NMR

The temperature-dependent changes in wheat starch powder and wheat starch-water mixtures were monitored in real-time throughout the heating/cooling program using a classical one-dimensional T1 method and a novel bi-dimensional approach to correlate spin-lattice and spin-spin relaxation times (T1-T2) including acquisition of the FID signal. The influence of two controlling factors (i.e. water content (11%, 35–50%, wet basis) and temperature (20–90°C and back to 20°C)) on water distribution and starch transformation was investigated. Quantitative analysis of 2D T1-T2 maps greatly facilitated the interpretation of T1 relaxation times, which have been interpreted rather narrowly in the literature when classically measured in one-dimension. Application of the new IR-FID-CPMG sequence allowed distinction between different proton pools with different T1 relaxation times, particularly when the starch gelatinization occurred. The quantification of each T1 component permitted to assign the short T1 to slow cross relaxation phenomena, highlighting proton chemical and/or diffusional exchanges between water and starch.

SVD-Based Technique for Interference Cancellation and Noise Reduction in NMR Measurement of Time-Dependent Magnetic Fields.

A nuclear magnetic resonance (NMR) experiment for measurement of time-dependent magnetic fields was introduced. To improve the signal-to-interference-plus-noise ratio (SINR) of NMR data, a new method for interference cancellation and noise reduction (ICNR) based on singular value decomposition (SVD) was proposed. The singular values corresponding to the radio frequency interference (RFI) signal were identified in terms of the correlation between the FID data and the reference data, and then the RFI and noise were suppressed by setting the corresponding singular values to zero. The validity of the algorithm was verified by processing the measured NMR data. The results indicated that, this method has a significantly suppression of RFI and random noise, and can well preserve the FID signal. At present, the major limitation of the proposed SVD-based ICNR technique is that the threshold value for interference cancellation needs to be manually selected. Finally, the inversion waveform of the applied alternating magnetic field was given by fitting the processed experimental data.

Two dimensional IR-FID-CPMG acquisition and adaptation of a maximum entropy reconstruction

By acquiring the FID signal in two-dimensional TD-NMR spectroscopy, it is possible to characterize mixtures or complex samples composed of solid and liquid phases. We have developed a new sequence for this purpose, called IR-FID-CPMG, making it possible to correlate spin–lattice T1 and spin–spin T2 relaxation times, including both liquid and solid phases in samples. We demonstrate here the potential of a new algorithm for the 2D inverse Laplace transformation of IR-FID-CPMG data based on an adapted reconstruction of the maximum entropy method, combining the standard decreasing exponential decay function with an additional term drawn from Abragam’s FID function. The results show that the proposed IR-FID-CPMG sequence and its related inversion model allow accurate characterization and quantification of both solid and liquid phases in multiphasic and compartmentalized systems. Moreover, it permits to distinguish between solid phases having different T1 relaxation times or to highlight cross-relaxation phenomena.

Application of ICA to realistically simulated (1)H-MRS data.

Introduction1H-MRS signals from brain tissues capture information on in vivo brain metabolism and neuronal biomarkers. This study aims to advance the use of independent component analysis (ICA) for spectroscopy data by objectively comparing the performance of ICA and LCModel in analyzing realistic data that mimics many of the known properties of in vivo data.MethodsThis work identifies key features of in vivo 1H-MRS signals and presents methods to simulate realistic data, using a basis set of 12 metabolites typically found in the human brain. The realistic simulations provide a much needed ground truth to evaluate performances of various MRS analysis methods. ICA is applied to collectively analyze multiple realistic spectra and independent components identified with our generative model to obtain ICA estimates. These same data are also analyzed using LCModel and the comparisons between the ground-truth and the analysis estimates are presented. The study also investigates the potential impact of modeling inaccuracies by incorporating two sets of model resonances in simulations.ResultsThe simulated fid signals incorporating line broadening, noise, and residual water signal closely resemble the in vivo signals. Simulation analyses show that the resolution performances of both LCModel and ICA are not consistent across metabolites and that while ICA resolution can be improved for certain resonances, ICA is as effective as, or better than, LCModel in resolving most model resonances.ConclusionThe results show that ICA can be an effective tool in comparing multiple spectra and complements existing approaches for providing quantified estimates.