Journal of magnetic resonance最新文献

{"title":"Passive shimming performance in 3 T MRI systems: Influence of shim parameters under varying magnet field distributions","authors":"Jinhao Liu ,&nbsp;Miutian Wang ,&nbsp;Wenchen Wang ,&nbsp;Yaohui Wang ,&nbsp;Wenhui Yang ,&nbsp;Weimin Wang ,&nbsp;Feng Liu","doi":"10.1016/j.jmr.2025.107969","DOIUrl":"10.1016/j.jmr.2025.107969","url":null,"abstract":"<div><div>This study proposes a simple and computationally efficient method to optimize the structural design parameters of passive shimming slots, aiming to improve magnetic field homogeneity in cryogen-free 3 T/200 mm superconducting magnets used across diverse application environments. The proposed method combines Latin Hypercube Sampling (LHS), utilizing over 300 sampled configurations, with a linear programming (LP)-based optimization framework to explore high-dimensional design spaces while adhering to structural constraints. The method was applied to four distinct magnets, each characterized by unique field inhomogeneity patterns resulting from manufacturing and assembly variations. Through harmonic decomposition, system-specific sensitivities were identified and effectively mitigated using customized passive shimming strategies tailored to each magnet. The optimization process achieved substantial improvements in magnetic field homogeneity, with peak-to-peak (PP) values enhanced to 12.16, 10.04, 27.28, and 54.59 parts per million (ppm) for Magnets 1 to 4, respectively. Correspondingly, the root-mean-square error (RMSE) homogeneity improved to 2.28, 1.98, 5.07, and 9.68 ppm. Furthermore, the magnitudes of all harmonic terms were reduced by 1-2 orders of magnitude, with suppression levels exceeding 90%, while minimizing the use of ferromagnetic materials. The practical feasibility of the proposed strategy was validated on-site: Magnet 1 successfully delivered high-quality animal MRI imaging with excellent signal-to-noise ratios (SNRs), and the remaining magnets are currently undergoing final calibration and delivery. This work presents a robust and scalable optimization framework for precise and resource-efficient passive shimming, offering valuable guidance for future magnet design, customization, and deployment in biomedical and industrial applications.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107969"},"PeriodicalIF":1.9,"publicationDate":"2025-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145202542","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":"NMR of chemical exchange: Revisited","authors":"Janez Stepišnik ,&nbsp;Aleš Mohorič","doi":"10.1016/j.jmr.2025.107968","DOIUrl":"10.1016/j.jmr.2025.107968","url":null,"abstract":"<div><div>Nuclear magnetic resonance is a powerful technique for examining chemical exchange in liquids by observing how molecular structures evolve. The Carr-Purcell-Meiboom-Gill technique, one of key NMR methods, enables the detection of molecular conformation fluctuations and their influence on observed chemical shifts. This study proposes how NMR measurements of chemical exchange processes can be interpreted using a molecular conformation fluctuation spectrum framework together with chemical Langevin equations. Experimental results obtained for sucrose solutions support the proposed approach, revealing insights into chemical exchange dynamics and spectral line behavior.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107968"},"PeriodicalIF":1.9,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145156202","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":"2025-09-22","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":"A simple algorithm to suppress diagonal peaks in high-resolution homonuclear chemical shift correlation NMR spectra","authors":"Shengyu Zhang ,&nbsp;Jhinuk Saha ,&nbsp;Yuchen Li ,&nbsp;Xinhua Peng ,&nbsp;Ryan P. McGlinchey ,&nbsp;Ayyalusamy Ramamoorthy ,&nbsp;Riqiang Fu","doi":"10.1016/j.jmr.2025.107967","DOIUrl":"10.1016/j.jmr.2025.107967","url":null,"abstract":"<div><div>Previous experimental strategies aimed at completely suppressing diagonal peaks in NMR homonuclear correlation spectra often resulted in reduced sensitivity for cross peaks. In this work, we report a spectral shearing approach that transforms diagonal peaks along the diagonal axis of a homonuclear correlation spectrum into a zero-frequency line in the indirect dimension. This allows for effective extraction and substantial suppression of diagonal peaks using a recently proposed data processing algorithm based on quadrature-detected spin-echo diagonal peak suppression. Since the shearing process only rearranges the positions of cross peaks without affecting their intensities, the sensitivity of cross peaks is fully preserved while diagonal peaks are significantly reduced. The effectiveness of this method is demonstrated using uniformly ¹³C,¹⁵N labeled α-synuclein amyloid fibrils and aquaporin Z membrane protein samples.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"381 ","pages":"Article 107967"},"PeriodicalIF":1.9,"publicationDate":"2025-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145093324","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":"2025-09-04","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":"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":"2025-08-30","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":"Revealing the sensitivity of methyl tunneling towards local environment changes with quantum-rotor EPR spectroscopy","authors":"Andrea Eggeling,&nbsp;Janne Soetbeer,&nbsp;Gunnar Jeschke","doi":"10.1016/j.jmr.2025.107943","DOIUrl":"10.1016/j.jmr.2025.107943","url":null,"abstract":"<div><div>Methyl rotors have potential as local environment probes because their rotation barrier is sensitive to hindering interactions with the nearby surrounding. Quantum-rotor electron paramagnetic resonance (EPR) measurements allow access to this local environment information of the methyl rotor if it is coupled to an electron spin. This is the case for commonly used nitroxide-based spin-labels, where electron spin echo envelope modulation (ESEEM) signals exhibit two contributions on different time scales at low temperatures. The slower decaying contribution is related to matrix-driven nuclear pair ESEEM while the faster contribution originates from methyl tunneling of the electron spin-coupled methyl rotors. The tunneling ESEEM contribution contains local environment information in terms of a distribution of the rotation barrier, which can be quantified using the methyl quantum rotor model. Here, we study the sensitivity of the tunneling behavior towards changes in the rotors’ surrounding by systematically investigating the two-pulse ESEEM signal of nitroxide spin probes containing two pairs of geminal methyl groups in different biologically-relevant matrix compositions. We find that the nitroxide ring structure of these probes strongly impacts the rotation barrier of the observed methyl rotors whereas the matrix surrounding does not affect the underlying rotation barrier distribution. These insights are crucial for designing nitroxide-based spin-labels as local environments probes in combination with site-directed spin-labeling for protein structure elucidation.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"380 ","pages":"Article 107943"},"PeriodicalIF":1.9,"publicationDate":"2025-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144908820","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":"Flexible and shape-adjustable coaxial capacitor (COCA) coils for ultrahigh field MRI: a comparative analysis with rigid coils","authors":"Ming Lu ,&nbsp;Caiwan Sun ,&nbsp;Xiaoyu Jiang ,&nbsp;Jason E. Moore ,&nbsp;John C. Gore ,&nbsp;Xinqiang Yan","doi":"10.1016/j.jmr.2025.107955","DOIUrl":"10.1016/j.jmr.2025.107955","url":null,"abstract":"<div><div>Flexible RF coils enhance patient comfort and increase filling factors, making them attractive for MRI. However, achieving first-mode resonance at 7 T for large-diameter, flexible coils remains a challenge. We present a coaxial capacitor (COCA) coil, which can be 10 cm in diameter and still operates in the first resonant mode at 298 MHz. Unlike coaxial cable coils that rely on self-resonance, the COCA coil combines ultrasoft Litz wire for inductance with a short coaxial structure for capacitance. Bench tests showed that a 1-capacitor COCA coil provides comparable tuning/matching robustness, effective detuning, and inter-element decoupling performance to conventional rigid coils with three distributed lumped capacitors. MRI acquisitions demonstrated high SNR, especially when the coil conformed to the curvature of the load, with up to 20 % SNR improvement over flat configurations. The coil's ability to retain tuning and matching across different shapes also supports the development of shape-adjustable arrays. By enabling flexible, large-diameter coils to operate in the first resonant mode at ultrahigh fields, the COCA design offers a promising solution for imaging anatomies with complex geometries, such as the shoulder, foot, and spine.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"380 ","pages":"Article 107955"},"PeriodicalIF":1.9,"publicationDate":"2025-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144912347","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":"High-speed, high-memory NMR spectrometer and hyperpolarizer","authors":"Leo Joon Il Moon ,&nbsp;William Beatrez ,&nbsp;Jason Ball ,&nbsp;Joan Mercade ,&nbsp;Mark Elo ,&nbsp;Angad Singh ,&nbsp;Emanuel Druga ,&nbsp;Ashok Ajoy","doi":"10.1016/j.jmr.2025.107952","DOIUrl":"10.1016/j.jmr.2025.107952","url":null,"abstract":"<div><div>We report on the development of a novel nuclear magnetic resonance (NMR) spectrometer, incorporating a high-speed, commercially available arbitrary waveform transceiver (AWT) – Tabor Proteus P9484M. The spectrometer is optimized for integrated electron-nuclear spin control and dynamic nuclear polarization (DNP) and leverages the AWT’s rapid sampling rate (9 Gs/s), significant memory capacity (16 GB), and efficient data transfer capabilities (6 Gs/s). These features enable effective NMR transmit–receive operations and electron control for DNP. In particular, the high sampling rates permit NMR pulse synthesis and signal reception directly at the Larmor frequency up to <span><math><mo>∼</mo></math></span>2.7 GHz. This can yield NMR signal-to-noise ratio (SNR) improvements by obviating the need for signal heterodyning. Additionally, the spectrometer features on-board, phase-sensitive detection, enabled by numerically controlled oscillators (NCO); and windowed acquisition can be carried out over extended periods and across millions of pulses, enabling the interrogation of nuclear spin dynamics directly in the rotating frame. The device’s architecture opens up new avenues for NMR pulse control and DNP, including closed-loop feedback control, electron decoupling, 3D spin tracking, and potential applications in quantum sensing.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"380 ","pages":"Article 107952"},"PeriodicalIF":1.9,"publicationDate":"2025-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144890855","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":"Corrigendum to “The rate of lactate production from glucose in hearts is not altered by per-deuteration of glucose” [J. Magn. Reson. 284 (2017) 86–93]","authors":"Alexander M. Funk ,&nbsp;Brian L. Anderson ,&nbsp;Xiaodong Wen ,&nbsp;Thomas Hever ,&nbsp;Chalermchai Khemtong ,&nbsp;Zoltan Kovacs ,&nbsp;A. Dean Sherry ,&nbsp;Craig R. Malloy","doi":"10.1016/j.jmr.2025.107942","DOIUrl":"10.1016/j.jmr.2025.107942","url":null,"abstract":"","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"379 ","pages":"Article 107942"},"PeriodicalIF":1.9,"publicationDate":"2025-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144884681","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}