Journal of magnetic resonance最新文献

{"title":"Recurrence formula-based automatic gradient eddy current compensation method for a 0.255 T MRI system","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.2025.107951","DOIUrl":"10.1016/j.jmr.2025.107951","url":null,"abstract":"<div><div>Gradient coils play a critical role in magnetic resonance imaging (MRI) systems by enabling spatial encoding through generating rapidly switching magnetic fields. However, these time-varying fields induce eddy currents in surrounding conductive structures, leading to gradient field distortions and imaging artifacts. In this study, we propose an automatic eddy current compensation method implemented on a field-programmable gate array (FPGA) platform. The approach employs iterative correction formulas for both linear gradient and <span><math><msub><mrow><mi>B</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> eddy fields, enabling real-time compensation. To enhance computational efficiency, a novel layout for the pre-emphasis (PE) unit is also introduced. Compared to conventional compensation techniques, the proposed FPGA-based solution offers significant improvements in implementation simplicity and system stability. Experimental results demonstrate that the residual direct- and cross-term eddy current fields are reduced to below 0.02%, equivalent to 4 <span><math><mrow><mi>μT</mi><mo>/</mo><mi>m</mi></mrow></math></span>, for a test gradient of 20 mT/m. Furthermore, the <span><math><msub><mrow><mi>B</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> eddy field is suppressed to below 0.1 <span><math><mi>μT</mi></math></span> when a <span><math><msub><mrow><mi>B</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span> compensation coil is employed. These improvements effectively reduce ghosting artifacts in multi-slice gradient-echo (GRE) phantom images. The robustness of the method is further validated across various imaging sequences, including T1-weighted (T1w) and T2-weighted (T2w) protocols.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"380 ","pages":"Article 107951"},"PeriodicalIF":1.9,"publicationDate":"2025-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144922377","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 wireless bilateral transceiver coil based on volume decoupled resonators for a clinical MR mammography","authors":"Pavel Tikhonov ,&nbsp;Aleksandr Fedotov ,&nbsp;Georgiy Solomakha ,&nbsp;Anna Hurshkainen","doi":"10.1016/j.jmr.2025.107941","DOIUrl":"10.1016/j.jmr.2025.107941","url":null,"abstract":"<div><div>Wireless radiofrequency coils offer a valuable low cost solution for various MR applications due to several benefits, such as cable-free connection and compatibility with MR platforms of different vendors. Namely, for the purpose of clinical high-field human breast imaging several wireless transceiver coils are known to the date, those operational principle is based on inductive coupling with a body coil. These coils are commonly consist of a several volume resonators to perform bilateral breast imaging. Due to the electrically close location of volume resonators, strong inductive coupling is observed, resulting in the occurrence of hybrid modes. In principle, MR imaging using one of the hybrid modes is possible provided by the homogeneity of a <span><math><msubsup><mrow><mi>B</mi></mrow><mrow><mn>1</mn></mrow><mrow><mo>+</mo></mrow></msubsup></math></span> distribution. However, the question of influence of volume resonators coupling on wireless coil transmit efficiency and receive sensitivity was not previously studied. By this work, we performed study to understand this issue. The first wireless coil with decoupled resonators is developed, evaluated numerically and experimentally including <em>in vivo</em> study on healthy volunteers. Additionally <em>in vivo</em> images were obtained by a conventional receive array to compare with developed wireless coil. According to the obtained results, transmit efficiency and receive sensitivity of a pair of decoupled Helmholtz resonators of the configuration under study is at least 24% higher than for a pair of the same coupled resonators. <em>In vivo</em> images were also obtained using a six-channel receive array to compare with a developed wireless coil. Comparison with a multi-channel receive array have shown that SNR of the developed wireless coil is 10% lower, while time scanning was increased by 68%.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"380 ","pages":"Article 107941"},"PeriodicalIF":1.9,"publicationDate":"2025-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144866961","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":"Specificity and reactivity of bromoacrylaldehyde spin labels","authors":"Dominik Gendreizig ,&nbsp;Christina Elsner ,&nbsp;Svetlana Kucher ,&nbsp;Gunnar Jeschke ,&nbsp;Alistair J. Fielding ,&nbsp;Enrica Bordignon","doi":"10.1016/j.jmr.2025.107953","DOIUrl":"10.1016/j.jmr.2025.107953","url":null,"abstract":"<div><div>Electron paramagnetic resonance (EPR) spectroscopy in combination with site-directed spin labelling provides information on structure and dynamics of biomolecules. Increasing the availability of spin labels with different properties is an elegant way to foster a more accurate analysis of the EPR data in relation to the biological problem investigated. In this study, we present a comparative investigation of labelling efficiency, surface accessibility, site specificity and width of the distance distributions obtained on two proteins with the nitroxide-based bromoacrylaldehyde spin label (BASL) versus the two commercial spin labels MTSL (methanethiosulfonate spin label) and MAP (maleimido proxyl). Based on the predicted distances from a rotamer library approach and on the experimental distance distributions, BASL is shown to provide generally narrower distance distributions compared to the other nitroxide labels. The exquisite surface specificity of BASL with respect to MAP could be successfully exploited to selectively label surface cysteines in proteins containing a high number of native cysteines. In addition, the distinct site-reactivity of BASL and MAP towards two surface-exposed cysteines was leveraged for orthogonal labelling strategies with nitroxide and gadolinium labels.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"380 ","pages":"Article 107953"},"PeriodicalIF":1.9,"publicationDate":"2025-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144860268","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":"Cryogenic magic-angle spinning continuous wave EPR and DNP spectroscopy at 7 T with a gyrotron","authors":"Marthe Millen ,&nbsp;Nicholas Alaniva ,&nbsp;Snædís Björgvinsdóttir ,&nbsp;Alexander Däpp ,&nbsp;Ioannis Gr. Pagonakis ,&nbsp;Wolfgang Harneit ,&nbsp;Alexander B. Barnes","doi":"10.1016/j.jmr.2025.107938","DOIUrl":"10.1016/j.jmr.2025.107938","url":null,"abstract":"<div><div>Dynamic nuclear polarization (DNP) relies on the transfer of electron polarization to nuclei through microwave irradiation and is typically performed under cryogenic magic-angle spinning (MAS) at high magnetic fields. Gyrotrons are commonly used microwave sources in DNP because of their ability to produce high-power microwaves over a broad frequency range. An important step towards a more in-depth understanding of DNP mechanisms and rational optimization of DNP performance is the access to instrumentation, which can provide information about the DNP process. Continuous wave (CW) electron paramagnetic resonance (EPR) can reveal important information on the electron spin system during DNP experiments. Here, we present a dual CW EPR/DNP spectrometer operated under MAS at 100 K and 7 T using a frequency-agile 198 GHz gyrotron. The measured sensitivity for CW EPR at 198 GHz using an MAS stator is 4 <span><math><mo>×</mo></math></span> 10¹³ spins/(G<span><math><msqrt><mrow><mi>H</mi><mi>z</mi></mrow></msqrt></math></span>). To illustrate the electron and nuclear detection capabilities of our setup, DNP profiles and CW EPR spectra of a diamond powder and a trityl sample were recorded under the same conditions, specifically at 100 K and under MAS.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"380 ","pages":"Article 107938"},"PeriodicalIF":1.9,"publicationDate":"2025-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144866960","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":"Optimisation and impact of gradient waveform modulation on Non-uniform Oscillating Gradient Spin-Echo sequences for microstructural characterisation","authors":"Melisa L. Gimenez ,&nbsp;Pablo Jimenez ,&nbsp;Leonardo A. Pedraza Pérez ,&nbsp;Diana Betancourth ,&nbsp;Analia Zwick ,&nbsp;Gonzalo A. Álvarez","doi":"10.1016/j.jmr.2025.107940","DOIUrl":"10.1016/j.jmr.2025.107940","url":null,"abstract":"<div><div>Neurological diseases often result in changes at microscopic scales in the nervous system, emphasising the need for non-invasive imaging techniques that can quantify these alterations as potential biomarkers for diagnosis. Diffusion-weighted magnetic resonance imaging (DWI), particularly using modulated gradient spin-echo (MGSE) sequences, has significantly advanced in revealing tissue microstructure by probing molecular diffusion. Among the MGSE sequences, the Non-uniform Oscillating Gradient Spin-Echo (NOGSE) sequence generates a contrast based on selective microstructure sizes through a signal decay-shift, rather than probing conventional decay rates. In this study, we evaluate the performance of NOGSE in estimating microstructure sizes using a preclinical MRI scanner. Our results show that while sharp, instantaneous gradient modulations maximise the decay-shift, smooth gradient modulations still provide meaningful contrast. Through a combination of phantom experiments, numerical simulations and information-theoretic analysis, we optimise NOGSE parameters for accurate microstructural size estimation under both sharp and smooth gradient modulations. We identify optimal NOGSE parameters that are compatible with preclinical hardware constraints, providing reliable microstructure size characterisation. Especially smooth gradient modulations expand the range of compatible MRI scanners and are almost suitable for <em>in-vivo</em> applications. These findings represent a step toward developing quantitative imaging tools for probing microstructural features in diffusion-weighted magnetic resonance imaging.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"380 ","pages":"Article 107940"},"PeriodicalIF":1.9,"publicationDate":"2025-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144842914","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":"2025-08-05","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":"Removing magnetic field noise from NMR spectra: Reference deconvolution revisited","authors":"Alexander Karabanov ,&nbsp;Eugeny Kryukov ,&nbsp;Gareth Morris ,&nbsp;Jeremy Good","doi":"10.1016/j.jmr.2025.107937","DOIUrl":"10.1016/j.jmr.2025.107937","url":null,"abstract":"<div><div>Reference deconvolution, a powerful mathematical tool for removing the effects of imperfections of the main magnetic field on NMR spectra, is revisited in the context of strong static and dynamic field perturbations. The theoretical basis and experimental evidence for the high efficiency of reference deconvolution for strong magnetic field distortions in basic liquid-state one- and two-dimensional NMR are given.</div><div>In particular, in 2D NMR, we utilise our observation that a strong static inhomogeneity of the main magnetic field suppresses anti-echo coherence transfer contributions, enabling reference deconvolution to be applied to the remaining echo contributions, in each indirect increment separately, in a manner similar to 1D NMR. We show that, in both 1D and 2D NMR, reference deconvolution enables one to remove the vibrational artefacts of cold head operation in cryogen-free magnets.</div><div>This extends the applicability of reference deconvolution in multi-dimensional NMR and advances cryogen-free technology in liquid-state NMR.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"379 ","pages":"Article 107937"},"PeriodicalIF":1.9,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144723392","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":"Gradient coil design for a 0.23 T NICU MRI system using an improved two-step Target-Field Method with enhanced linearity and compact design","authors":"Jinhao Liu ,&nbsp;Miutian Wang ,&nbsp;Wenchen Wang ,&nbsp;Yaohui Wang ,&nbsp;Weimin Wang ,&nbsp;Feng Liu","doi":"10.1016/j.jmr.2025.107936","DOIUrl":"10.1016/j.jmr.2025.107936","url":null,"abstract":"<div><div>This study presents an optimized gradient coil design for a miniature 0.23 T MRI system, aimed at improving absolute and relative magnetic field linearity while accommodating various gradient thicknesses. The design uses a two-step optimization approach: the first step uses Tikhonov regularization to solve a linear problem, providing a stable solution, and the second step refines the solution through nonlinear constrained optimization to further enhance field linearity. An explicit objective function for the inductance matrix of biplanar gradient coils is simplified to enhance computational efficiency. Validation through MATLAB and COMSOL finite element analysis showed excellent performance. Imaging experiments were conducted on small animals (cats and dogs, whose sizes are similar to neonates) while awaiting ethical approval for human neonatal studies. Results demonstrated that all gradient coils achieved absolute and relative linearity errors below 5%. Cubic phantom scans showed slight displacement at the edges, but the structured phantom MRI lines align precisely with the physical markers, indicating negligible geometric distortion. The shield design maintained Z-leakage fields below 5 Gauss, with eddy current compensation achieving a 90% reduction (residual X/Y-gradient <span><math><mo>&lt;</mo></math></span> 0.05%, Z-gradient <span><math><mo>&lt;</mo></math></span> 0.20%). T1 and T2-weighted images depicted clear brain structures, while FLAIR and STIR sequences effectively highlighted tissue changes. The proposed gradient coil design method significantly improves absolute and relative linearity while accommodating various gradient thicknesses, demonstrating strong resistance to interference and broad applicability. The comprehensive design-to-manufacturing process ensures optimal parameter selection, resulting in high-quality imaging across multiple MRI sequences. This design demonstrates strong potential for precise <em>in-vivo</em> brain imaging in further NICU applications.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"379 ","pages":"Article 107936"},"PeriodicalIF":2.0,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144704306","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 flow characterization measurements using a modified CPMG measurement with incremented echo times, phase cycling and filtering","authors":"Sebastian J. Richard,&nbsp;Benedict Newling,&nbsp;Bruce J. Balcom","doi":"10.1016/j.jmr.2025.107923","DOIUrl":"10.1016/j.jmr.2025.107923","url":null,"abstract":"<div><div>We recently demonstrated a magnetic resonance methodology for measuring and characterizing various pipe flows, using a series of individually-acquired spin echoes at different <span><math><mi>τ</mi></math></span>. The key advantage of our approach lies in the simplicity of the experiment, MR hardware, and data processing. However, acquiring each spin echo separately results in prolonged measurement times. To address this, we employ an echo-train approach to acquire the series of variable <span><math><mi>τ</mi></math></span> spin echoes. By incrementing CPMG echo pulse spacings within the echo train and implementing a four-step phase cycling scheme to suppress coherence pathway effects, we obtain the same echo phase and magnitude response to flow as a function of <span><math><msup><mrow><mi>τ</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> as in our original method, without requiring individual echo acquisitions. This new approach significantly reduces the number of required experiments, shortening measurement time by a factor of <span><math><mrow><mn>1</mn><mo>/</mo><mi>N</mi></mrow></math></span>, where <span><math><mi>N</mi></math></span> is the number of utilized echoes per echo train. Our phase cycling strategy, combined with incremented pulse spacings, enables <span><math><mrow><mi>N</mi><mo>=</mo><mn>3</mn></mrow></math></span> in our benchtop flow measurement. Validation experiments with Newtonian and shear-thinning fluids confirm that the new echo-train technique yields results consistent with the original approach of acquiring each spin echo separately.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"379 ","pages":"Article 107923"},"PeriodicalIF":2.0,"publicationDate":"2025-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144655402","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":"Broadband excitation of nuclei spin by refocused feedback","authors":"Vishesh Kaushik,&nbsp;Navin Khaneja","doi":"10.1016/j.jmr.2025.107927","DOIUrl":"10.1016/j.jmr.2025.107927","url":null,"abstract":"<div><div>The ability to precisely control the spin states of nuclei in an ensemble is critical for advancing NMR spectroscopy. In this paper, we present a technique referred to as <em>Refocused Feedback</em> to construct RF pulses that enable uniform transitions of spin states across the continuous spectrum of chemical shifts. It is used to achieve uniform broadband excitation of nuclei ensemble. The RF pulses are designed based on strategically selected hypothetical initial and final conditions, with the pulse phase iteratively updated according to the feedback control law. The control sequence is then transformed for applications in real systems. This approach ensures uniform excitation across the continuous range of chemical shifts while digitally constructing the pulse sequence from discrete samples.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"379 ","pages":"Article 107927"},"PeriodicalIF":2.0,"publicationDate":"2025-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144695090","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}