Journal of magnetic resonance最新文献

{"title":"Significant acceleration of solid-state NMR simulations via three-angle powder averaging","authors":"Elijah Burlinson ,&nbsp;Frédéric A. Perras","doi":"10.1016/j.jmr.2025.107966","DOIUrl":"10.1016/j.jmr.2025.107966","url":null,"abstract":"<div><div>The anisotropic frequency shifts imparted onto the NMR resonance frequency depend on the spherical angular coordinates that describe the orientations of the NMR interaction tensors with respect to the applied magnetic field direction. Experiments performed using magic-angle spinning, however, gain a dependence on a third angle: the rotor phase <em>γ</em>. Traditionally, a carousel average is performed to integrate over <em>γ</em>, which leads to a slow convergence of intensities without contributing to the underlying powder patterns. Herein, we show an order of magnitude acceleration in computation time may be obtained by including the <em>γ</em>-averaging into the main powder average to eliminate redundant calculation of resonance frequencies.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107966"},"PeriodicalIF":1.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145048240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sample-accessible multi-resonance X-band EPR triple ring resonator","authors":"Chun Him Lee ,&nbsp;Meltem Elitaş ,&nbsp;Jan G. Korvink ,&nbsp;Mazin Jouda","doi":"10.1016/j.jmr.2025.107988","DOIUrl":"10.1016/j.jmr.2025.107988","url":null,"abstract":"<div><div>Micro-resonators downsize their resonating structures, reaching frequencies required for electron paramagnetic resonance (EPR) spectroscopy, thus allowing sensitive detection of mass-limited samples. Planar resonators provide accessibility of the sample space, allowing <em>in situ</em> and <em>operando</em> experiments for convenient characterization with access to environmental parameters such as UV radiation, gas and liquid flow, and better temperature gradient control. We report a novel triple-ring resonating structure that exploits the benefits of sample accessibility and its miniaturized structure. It offers three simultaneously operating X-band channels (8<!--> <!-->GHz to 11<!--> <!-->GHz) with a real-time accessible 50<!--> <!-->nL sample volume for each channel, with a maximum spin sensitivity of <span><math><mrow><mn>1</mn><mo>.</mo><mn>18</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>8</mn></mrow></msup></mrow></math></span> Spin/Hz^1/2. By cascading the ring resonators, we improve the quality factor of each resonance by reflecting and confining the electromagnetic energy by the neighboring rings. The Q-factor of the center resonance at 9.45<!--> <!-->GHz with the enhancement of 2 passive reflectors reaches 73. Three relative translations allow a wide range of tuning, matching, suppressing, and isolating the resonances. While the introduced resonator exhibits three resonances only, it can be readily upscaled to feature more resonances, thus opening the door to high-throughput parallel EPR spectroscopy.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107988"},"PeriodicalIF":1.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145314445","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rapid MRI profiling of two-phase flow in porous media","authors":"Quirine Krol ,&nbsp;Matthew E. Skuntz ,&nbsp;Sarah L. Codd ,&nbsp;Joseph D. Seymour","doi":"10.1016/j.jmr.2025.107971","DOIUrl":"10.1016/j.jmr.2025.107971","url":null,"abstract":"<div><div>Two-phase flow in porous media underpins a wide range of natural and industrial processes, but its transient dynamics remain challenging to capture at the spatiotemporal resolution required to resolve pore-scale phenomena. We present a method for rapid one-dimensional (1D) magnetic resonance imaging (MRI) profiling that simultaneously acquires spin-echo signal intensity and phase angle profiles with <span><math><mrow><mn>98</mn><mspace></mspace><mi>μm</mi></mrow></math></span> spatial and <span><math><mrow><mn>20</mn><mspace></mspace><mi>ms</mi></mrow></math></span> temporal resolution. The technique enables real-time observation of both fluid saturation and velocity fluctuations across a porous medium. We demonstrate its capabilities through three benchmark experiments: (1) controlled drainage and filling of a cylindrical tank, (2) buoyancy-driven rise of oil droplets in water, and (3) drainage and imbibition of a model porous medium. The results reveal dynamic interfacial behavior, velocity fluctuations linked to Haines jumps, and flow-dependent signal attenuation effects. We further analyze the relationship between flow velocity and signal attenuation in porous media using stop-motion dual-echo experiments. Our findings show that rapid magnetic resonance imaging provides a sensitive tool for probing two-phase flow dynamics, with implications for understanding complex fluid behavior in porous materials.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107971"},"PeriodicalIF":1.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145305131","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of the spin-locking B1 radiofrequency field strength on the signal enhancement with Magic Sandwich Echo sequence","authors":"Eloïse Mougel ,&nbsp;Hélène Ratiney ,&nbsp;Eric Van Reeth ,&nbsp;Kevin Tse Ve Koon ,&nbsp;Olivier Beuf ,&nbsp;Denis Grenier","doi":"10.1016/j.jmr.2025.107973","DOIUrl":"10.1016/j.jmr.2025.107973","url":null,"abstract":"<div><div>Contrast methods based on dipolar coupling are of great interest for imaging tissues containing large macromolecules, such as myelin. Most of these conventional methods deal with various “relaxation” phenomena influenced by dipolar coupling such as inhomogeneous magnetization transfer. In this work we propose to investigate the benefit of using another method, called magic sandwich echo (MSE), which allows direct modulation of the dipolar coupling (<em>H</em>_<em>d</em>) as described by the work of Matsui and the Redfield theory. To verify the potential of this method in biological tissue, we first proposed an experimental model for dipolar coupling modulation in an <em>ex vivo</em> tendon (as a highly anisotropic tissue) and used it to prove <em>H</em>_<em>d</em> modulation by varying the amplitude of the spin-lock radiofrequency pulse of this sequence. We then proposed a potential <em>in vivo</em> usable metric, directly related to the residual amount of <em>H</em>_<em>d</em>, which we called MaSteR for Magic sandwich echo to Stimulated echo ratio, as it is based on the ratio of the signal acquired with the MSE sequence and a stimulated echo sequence. First, we show that the higher <em>H</em>_<em>d</em>, the more effective the spin-lock radiofrequency amplitude. We measured with MaSteR that the change in radiofrequency amplitude allowed us to distinguish between different <em>H</em>_<em>d</em> intensities, with a greater MaSteR when <em>H</em>_<em>d</em> is higher.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107973"},"PeriodicalIF":1.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145350838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Identifying intermolecular multiple-quantum coherences in ionic liquids","authors":"Yanan Li ,&nbsp;Florin Teleanu ,&nbsp;Alexej Jerschow","doi":"10.1016/j.jmr.2025.107984","DOIUrl":"10.1016/j.jmr.2025.107984","url":null,"abstract":"<div><div>Intermolecular multiple quantum coherences (iMQCs) may arise in isotropic systems with high spin concentrations, of which ionic liquids are an important example. In examining the ¹H, ¹⁹F, and ¹¹B nuclei of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF<span><math><msub><mrow></mrow><mrow><mn>4</mn></mrow></msub></math></span>]), we identified the existence of homonuclear iMQCs for all these nuclei. In addition, for the ¹¹B quadrupolar nuclei, we investigated the possible excitation of intramolecular triple quantum coherences (TQCs) which could in principle arise from the slow tumbling in ionic liquids. These experiments showed that while iMQCs can be excited for ¹¹B, (intramolecular) triple-quantum coherences were not detectable. These findings may help clarifying the ion dynamics and intermolecular interactions in ionic liquids.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107984"},"PeriodicalIF":1.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145305109","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Computationally efficient 4D spectral-spatial EPR imaging","authors":"Mark Tseytlin ,&nbsp;Oxana Tseytlin","doi":"10.1016/j.jmr.2025.107980","DOIUrl":"10.1016/j.jmr.2025.107980","url":null,"abstract":"<div><div>Four-dimensional spectral–spatial imaging (4D SSI) enables noninvasive mapping of spin probes and their microenvironments. Despite its demonstrated utility, 4D SSI remains constrained by substantial computational demands, including large data volumes, the iterative nature of reconstruction algorithms, and significant requirements for memory and computational resources. These resource demands scale cubically with the size of the imaged object. To address these limitations, a set of computational strategies has been developed to improve reconstruction efficiency without compromising image fidelity. These include the use of filtered back projection (FBP) to generate an initial spin concentration map, which serves both as an initial guess for further iterations and as a mask to exclude non-signal voxels. Eliminating these empty voxels significantly reduces the problem size, thereby lowering memory usage and computation time. Additional acceleration is achieved by transforming the 4D reconstruction into a reduced 2D problem, minimizing redundant computation through precomputed values, and employing a compact look-up table for spectral fitting. The resulting workflow, implemented in MATLAB with performance-critical routines compiled as C-based MEX functions, achieves iteration times as low as one minute. Numerical phantom simulations and experimental data from physical phantoms confirm that convergence is substantially improved by excluding non-signal voxels. Among all evaluated approaches, the FBP-based masking of non-signal voxels and the use of a lookup table proved most effective in accelerating algorithm convergence. These improvements enable scalable and computationally efficient 4D SSI suitable for high-resolution, larger-animal preclinical studies and future clinical imaging applications.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107980"},"PeriodicalIF":1.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145314455","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Residual motion artifact removal enables dynamic μMRI of a behaving Pachnoda marginata","authors":"Ajmal Chenakkara ,&nbsp;Mazin Jouda ,&nbsp;Ulrike Wallrabe ,&nbsp;Jan G. Korvink","doi":"10.1016/j.jmr.2025.107954","DOIUrl":"10.1016/j.jmr.2025.107954","url":null,"abstract":"<div><div>Microscopic magnetic resonance imaging, also referred to as <span><math><mi>μ</mi></math></span>MRI, is a non-invasive imaging modality ideal for studying small live model organisms. However, <span><math><mi>μ</mi></math></span>MRI raw data acquisition is inherently sequential and slow in comparison to the biomechanics timescale of the behaving organism, leading to motion artifacts upon image reconstruction. Recently, we have developed an integrated spherical treadmill with a prospectively triggered k-space acquisition technique to provide position consistency for studying live, behaving insect using <span><math><mi>μ</mi></math></span>MRI. Despite this advancement, behaving insects on the treadmill still exhibited motion artifacts due to tethered locomotion being coupled with internal organ dynamics. Here, we are addressing the large-scale non-rigid nature of the abdominal motion of the behaving insect by developing a fully retrospective gating strategy using the motion information obtained from an in-situ computer vision system. Residual motion artifacts persisting after gating are effectively managed through a deep learning technique. We trained a U-Net-based deep convolutional neural network using pairs of simulated motion-corrupted and motion-free images as a supervised image-to-image translation problem. Our results demonstrate that combining retrospective gated <span><math><mi>μ</mi></math></span>MRI reconstruction with a deep learning residual motion compensation technique can significantly reduce the motional artifacts, thereby paving the way for the non-invasive dynamic imaging studies of behaving organisms with 117 <span><math><mi>μ</mi></math></span>m in-plane resolution.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107954"},"PeriodicalIF":1.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145048178","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Separate and detailed characterization of signal and noise at low resonance frequencies","authors":"A. Guinness ,&nbsp;Alec A. Beaton ,&nbsp;John M. Franck","doi":"10.1016/j.jmr.2025.107956","DOIUrl":"10.1016/j.jmr.2025.107956","url":null,"abstract":"<div><div>When developing or deploying a Nuclear Magnetic Resonance (NMR) spectrometer, especially for Overhauser Dynamic Nuclear Polarization (ODNP) or other experiments that require low-volume low-field measurements, the ability to mitigate noise and to quantitatively predict signal amplitude prove crucial. A quantitative treatment allows separate analysis of signal and noise and independent optimization of each. In particular, the results here emphasize that clarity and insight come from (1) characterizing the spectral distribution of the noise, and (2) integrating elements of theory and notation originally developed for Electron Spin Resonance (ESR) spectroscopy. Specifically, the spectral noise density “fingerprint spectrum” identifies sources of electromagnetic interference (EMI) and definitively confirms which actions do and do not mitigate the EMI, while the quantitative ratio (<span><math><mi>Λ</mi></math></span>) of <span><math><msub><mrow><mi>B</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> to the square root of the power on the transmission line provides a useful focal point that simplifies the prediction of signal intensity and that decomposes into a few simple but exact factors. Thus, this article provides a relatively comprehensive overview of signal and noise in low-field NMR instruments. The protocol/toolkit introduced here should apply to a wide range of instruments, and give most spectroscopists the freedom to systematically design sensitive NMR hardware even in cases where it must be integrated with multiple other hardware modules (<em>e.g.</em>, an existing ESR system), or where other requirements constrain the design of the NMR hardware. It enables a systematic approach to instrument design and optimization. For the specific X-band ODNP design demonstrated here (and utilized in other laboratories), it facilitates a reduction of the noise power by more than an order of magnitude, and accurately predicts the signal amplitude from measurements of the nutation frequency. Finally, it introduces reasoning to exactly determine the field distribution factor (<span><math><msup><mrow><mi>η</mi></mrow><mrow><mo>′</mo></mrow></msup></math></span>, essentially, a more specific definition of the filling factor) experimentally from <span><math><mi>Λ</mi></math></span> and thus identifies the inefficient distribution of fields in the hairpin loop probe as the main remaining bottleneck for the improvement of low-field, low-volume ODNP signal-to-noise ratio (SNR).</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107956"},"PeriodicalIF":1.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145120051","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Shim coil design by Fourier synthesis","authors":"D.I. Hoult","doi":"10.1016/j.jmr.2025.107934","DOIUrl":"10.1016/j.jmr.2025.107934","url":null,"abstract":"<div><div>A new method of creating “shims”, i.e. spherically harmonic fields, is proposed. The technique relies on a direct correspondence between the spatial frequency of sinusoidal azimuthal currents on the surface of an axially aligned cylinder and the degree of the spherically harmonic, axial magnetic fields they create. The sinusoidal current waveform is sampled at at least twice the maximum desired degree/frequency, and the current samples are then applied to the same number of identical conducting arcs, at the same axial position, evenly distributed in a ring. Repetition of this building block at differing axial positions and with appropriate sinusoidal current amplitudes is then used to allow a mix of harmonics of any degree less than or equal to the maximum; the maximum order is determined by the number of axial positions. Calculations are analytical, apart from numerical minimisation of power consumption or mean square current, and correction of minor end effects. Access to the author's <em>Mathematica</em> Notebooks that may help with concepts and calculations is provided. The design holds the promise of more accurate generation of higher orders and degrees than is currently normal, and of easy fabrication with either foil or ribbon cable; the complexity usually associated with construction is essentially transferred to exterior electronics. A novel, conceptual current driver with high efficiency and compliance is also mentioned.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107934"},"PeriodicalIF":1.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145093311","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A steady-state approach for analysis of high-resolution relaxometry","authors":"Shibani Bhattacharya ,&nbsp;Michael Goger ,&nbsp;Tassadite Dahmane ,&nbsp;Arthur G. Palmer III","doi":"10.1016/j.jmr.2025.107989","DOIUrl":"10.1016/j.jmr.2025.107989","url":null,"abstract":"<div><div>High-resolution relaxometry measures nuclear spin longitudinal relaxation rate constants at low static magnetic field, either in the fringe field of a high-field NMR magnet or in an external electromagnetic coil, while polarizing and detecting nuclear magnetization at high field to optimize resolution and sensitivity for biological macromolecules. Detected magnetization depends on relaxation in the low magnetic field and on relaxation during transfer to and from the high magnetic field. Relaxation for backbone amide ¹⁵N magnetization in proteins is inherently multiexponential because of dipole–dipole and chemical shift anisotropy interactions with the amide ¹H spin and dipole–dipole interactions between the amide ¹H spin and ¹H remote spins. Nevertheless, relaxation decay profiles for backbone amide ¹⁵N spins in proteins are empirically observed to be essentially monoexponential with a single effective relaxation rate constant at magnetic fields as low as 1 T. The present work derives an expression for the effective relaxation rate constant under that assumption that relaxation in the network of dipole–dipole coupled ¹H spins is sufficiently rapid. This result enables efficient analysis of relaxometry data without explicit integration of the stochastic Liouville equation for relaxation of the amide N-H moiety and remote amide ¹H spins. The approach is validated by relaxometry measurements for ¹⁵N-labeled human ubiquitin and <em>E. coli</em> ribonuclease HI. The results obtained with the proposed approach agree well with results obtained using the MINOTAUR program (N. Bolik-Coulon et al., 2023), which integrates the full stochastic Liouville equation.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107989"},"PeriodicalIF":1.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145423657","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}