Journal of magnetic resonance最新文献

{"title":"Homonuclear decoupled INADEQUATE NMR methods with improved sensitivity and resolution in solid-state NMR","authors":"Yury G. Kolyagin ,&nbsp;Julien Trébosc ,&nbsp;Koffi Jean Baptiste Alloko ,&nbsp;Olivier Lafon ,&nbsp;Jean-Paul Amoureux","doi":"10.1016/j.jmr.2024.107822","DOIUrl":"10.1016/j.jmr.2024.107822","url":null,"abstract":"<div><div>The two-dimensional (2D) refocused INADEQUATE NMR experiment, which correlates double-quantum (DQ) and single-quantum (SQ) coherences, is widely used to probe the chemical connectivities in solids. Nevertheless, the multiplets along the <em>F</em>₂ dimension reduce the resolution and sensitivity of this experiment. The Composite-Refocusing (CR) technique with two excitation pulses has been proposed to suppress these multiplets in 2D INADEQUATE spectra of liquids. Recently (Kolyagin et al., <em>J. Phys. Chem. Lett</em>., 13 (<strong>2022</strong>) 10793), we showed that this technique can also be applied to suppress doublets in 2D ²⁹Si INADEQUATE spectra of ²⁹Si-enriched zeolites, which resulted in improved sensitivity and resolution. We investigate here how this INADEQUATE-CR scheme can also be applied for two other spin-1/2 isotopes: ¹³C and ³¹P. We also demonstrate the possibility to accelerate the acquisition of these 2D INADEQUATE-CR spectra with a very simple bi-exponential non-uniform sampling (NUS). For instance, in the case of ³¹P nuclei in SnP₂O₇, the use of the INADEQUATE-CR method with NUS yields a 7.5-fold reduction in experimental time with a simultaneous 1.4–1.5 gain in resolution with respect to a conventional INADEQUATE acquisition. Furthermore, we analyze the origins of the possible artifacts in these 2D spectra, including mismatching between <em>J</em>-coupling constants and refocusing delays, differences in relaxation times, coupling with a proton bath, and spin systems containing multiple identical nuclei. Based on this analysis, we introduce a new z-filtered INADEQUATE-CR version, which produces artifact-free 2D spectra, even in the presence of several distinct <em>J</em>-couplings and relaxation times or for multi-spin systems, and notably samples with high proton density.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"370 ","pages":"Article 107822"},"PeriodicalIF":2.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142901471","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":"Physics-guided multi-dimensional scan optimization and quasi-steady-state reconstruction to enhance CEST MRI sensitivity efficiency and quantification accuracy","authors":"Phillip Zhe Sun","doi":"10.1016/j.jmr.2024.107821","DOIUrl":"10.1016/j.jmr.2024.107821","url":null,"abstract":"<div><div>Chemical exchange saturation transfer (CEST) MRI has become increasingly utilized for detecting dilute labile protons and characterizing microenvironment properties. However, the CEST MRI effect is only a few percent, and there is a need for a systematic approach to optimize scan parameters for sensitive and accurate CEST quantification. We propose multi-dimensional adjustments of key parameters such as the repetition time (TR) and RF duty cycle to optimize CEST MRI sensitivity per unit of time and utilization of quasi-steady-state (QUASS) reconstruction to recover the full CEST effect during postprocessing. Our work herein derived the CEST effect based on the generalized spin-lock CEST model and determined the interdependency of the optimal RF duty cycle and TR, showing the optimal TR decreases with the RF duty cycle but plateaus beyond 60–80 %. The accuracy of the solution was validated with both numerical simulations and CEST MRI experiments on a dual pH creatine gel phantom. The desired equilibrium CEST effect was further reconstructed with the QUASS algorithm from the optimized CEST MRI scan. In summary, our study establishes a workflow for CEST MRI scan optimization and postprocessing analysis, providing a framework to boost both the sensitivity of CEST MRI scans and the accuracy of CEST quantification. This approach holds promise for future in vivo validation and translation.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"370 ","pages":"Article 107821"},"PeriodicalIF":2.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142848664","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":"Denoising low-field MR images with a deep learning algorithm based on simulated data from easily accessible open-source software","authors":"Aram Salehi ,&nbsp;Mathieu Mach ,&nbsp;Chloe Najac ,&nbsp;Beatrice Lena ,&nbsp;Thomas O’Reilly ,&nbsp;Yiming Dong ,&nbsp;Peter Börnert ,&nbsp;Hieab Adams ,&nbsp;Tavia Evans ,&nbsp;Andrew Webb","doi":"10.1016/j.jmr.2024.107812","DOIUrl":"10.1016/j.jmr.2024.107812","url":null,"abstract":"<div><div>In this study, we introduce a denoising method aimed at improving the contrast ratio in low-field MRI (LFMRI) using an advanced 3D deep convolutional residual network model. Our approach employs synthetic brain imaging datasets that closely mimic the contrast and noise characteristics of LFMRI scans, addressing the limitation of available in-vivo LFMRI datasets for training deep learning models. In the simulation data, the Relative Contrast Ratio (RCR) increased, and similar improvements were observed in the in-vivo data across different imaging conditions. Comparative evaluations demonstrate that our model performs better than the widely used non-deep learning method, BM4D, in enhancing RCR and maintaining high spatial frequency components in in-vivo data.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"370 ","pages":"Article 107812"},"PeriodicalIF":2.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142796632","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Using machine learning to improve the hard modeling of NMR time series","authors":"Jan Hellwig ,&nbsp;Tobias Strauß ,&nbsp;Erik von Harbou ,&nbsp;Klaus Neymeyr","doi":"10.1016/j.jmr.2024.107813","DOIUrl":"10.1016/j.jmr.2024.107813","url":null,"abstract":"<div><div>Modeling time series of NMR spectra is a useful method to accurately extract information such as temporal concentration profiles from complex processes, e.g. reactions. Modeling these time series by using nonlinear optimization often suffers from high runtimes. On the other hand, using deep learning solves the modeling problem quickly, especially for single spectra with separated peaks. However, the accuracy decreases significantly when peaks overlap or cross. We propose a hybrid approach combining the strengths of both methods while mitigating their drawbacks. This hybrid methods improves on a previous work (Meinhardt et al., 2022) and employs neural networks to predict initial parameters for the optimization algorithm, which only needs to fine-tune the parameters afterwards. We present results for both constructed and experimental data sets and achieve improvements in both runtime and accuracy.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"370 ","pages":"Article 107813"},"PeriodicalIF":2.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142866467","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Complete solution for rotating frame relaxation functions during adiabatic pulses","authors":"Shalom Michaeli","doi":"10.1016/j.jmr.2024.107809","DOIUrl":"10.1016/j.jmr.2024.107809","url":null,"abstract":"<div><div>During adiabatic full passage (AFP) radiofrequency (RF) pulses the relaxation functions are conventionally treated in the Tilting Doubly Rotating Frame (TDRF), or the second rotating frame (SRF) of reference. Such a description is adequate when during the adiabatic passage the magnetization <strong>M</strong> is perfectly aligned with the time dependent effective magnetic field, <strong><em>B⁽¹⁾_eff</em></strong><em>(t)</em>, leading to <em>T_1ρ(t)</em> relaxation, or evolves on a plane perpendicular to <strong><em>B⁽¹⁾_eff</em></strong><em>(t)</em>, leading to <em>T_2ρ(t)</em> relaxation. Time evolution of <strong><em>B⁽¹⁾_eff</em></strong><em>(t)</em> results in formation of a fictitious magnetic field, which is typically neglected during the AFP pulses operating in adiabatic regime, i.e., given that the adiabatic condition <em>|γ⁻¹dα⁽¹⁾(t)/dt|</em> ≪ <em>B⁽¹⁾_eff(t)</em> is well satisfied. Here <em>α⁽¹⁾(t)</em> is the angle between <strong><em>B⁽¹⁾_eff</em></strong><em>(t)</em> and the axis of quantization of the first rotating frame (FRF) <em>z′</em>, and <em>dα⁽¹⁾(t)/dt</em> is the angular velocity. When the fictitious field component cannot be neglected, for the adequate description of relaxation during AFP pulses the solutions for the relaxation functions in a multi-fold rotating frame are necessary. Such a general treatment is currently unavailable for adiabatic RF pulses. Here, we obtain the solution for the relaxation functions in the Tilting Triply Rotating Frame (TTRF) during the Hyperbolic Secant (HS) pulses of the HSn family, HS1 and HS4, where <em>n</em> is the stretching factor. We show that the contribution to the relaxations originating from the non-negligible magnitude of the fictitious field depends on the pulse modulation functions of the AFP pulses and the parameters of the pulses. The corrections to describe the relaxations are given, which may be relevant in specific experimental setups especially for high-resolution NMR.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"370 ","pages":"Article 107809"},"PeriodicalIF":2.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142792919","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":"Changing the resonant nucleus by altering the static field, compensation of γ and B0 effects in T2 and T2* measurements of porous media","authors":"Rheya Rajeev ,&nbsp;Naser Ansaribaranghar ,&nbsp;Andrés Ramírez Aguilera ,&nbsp;Florea Marica ,&nbsp;Laura Romero de Zerón ,&nbsp;Bruce J. Balcom","doi":"10.1016/j.jmr.2024.107811","DOIUrl":"10.1016/j.jmr.2024.107811","url":null,"abstract":"<div><div>Multinuclear ¹H, ¹³C, and ²³Na magnetic resonance (MR) has many advantages for studying porous media systems containing hydrocarbons and brine. In recent work, we have explored changing the nucleus measured, keeping the Larmor frequency constant, by changing the static magnetic field B₀. Increasing the static B₀ field distorts the field in the pore space due to susceptibility mismatch between the matrix and pore fluid. Distortion of the magnetic field in the pore space scales with the applied static field. The gradients that result from the spatial variation of the distorted field will also scale with B₀. The equations that describe the inhomogeneous broadening in T₂* show that the MR result depends on <span><math><mrow><mi>γ</mi></mrow></math></span>B₀. The diffusion through internal field gradients effect on T₂ depends on the product of <span><math><mrow><mi>γ</mi></mrow></math></span> and G, with G depending on B₀.</div><div>Increasing the static field to bring a nucleus with lower <span><math><mrow><mi>γ</mi></mrow></math></span> into resonance at the same frequency will result in the products <span><math><mrow><mi>γ</mi></mrow></math></span>B₀ and <span><math><mrow><mi>γ</mi></mrow></math></span>G being constant, and therefore, inhomogeneous broadening and diffusion attenuation effects in porous media are predicted to be constant. We explore the T₂* hypothesis with ²³Na and ¹H measurements of brine in porous reservoir core plugs. We explore the diffusion through internal field gradients effect hypothesis with ¹H and ¹³C measurements of decane saturated glass beads.</div><div>The nuclei chosen for study: ¹H, ¹³C, and ²³Na are the three most important nuclei for studies of fluids (brine and hydrocarbons) in reservoir core plugs. These three nuclei have a common resonance frequency of 33.7 MHz at static fields of 0.79 T, 3.19 T, and 2.99 T, respectively. All three fields are readily achieved with our variable field superconducting magnet.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"369 ","pages":"Article 107811"},"PeriodicalIF":2.0,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142759481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Tribute to a Friend, a Mentor, a Spin Master, and a Mensch – Eriks Kupce","authors":"Lewis E. Kay","doi":"10.1016/j.jmr.2024.107794","DOIUrl":"10.1016/j.jmr.2024.107794","url":null,"abstract":"","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"369 ","pages":"Article 107794"},"PeriodicalIF":2.0,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142684031","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 compact and mobile stray-field NMR sensor","authors":"Belal M.K. Alnajjar ,&nbsp;Jürgen Frick ,&nbsp;Bernhard Blümich ,&nbsp;Jens Anders","doi":"10.1016/j.jmr.2024.107798","DOIUrl":"10.1016/j.jmr.2024.107798","url":null,"abstract":"<div><div>In this paper, we introduce a compact, single-sided stray field sensor for NMR relaxometry applications. The sensor consists of four main components: the magnet, the RF coil, the spectrometer, and the translation stage. Our proposed magnet, an improved design of the Profile NMR<span><math><mo>−</mo></math></span>MOUSE, is designed for low weight, compactness, and magnetic field homogeneity, achieved through various shim strategies using a mixed genetic algorithm. The magnet comprises eight NdFeB blocks, generating a magnetic field of 0.424<!--> <!-->T within the sensitive region, positioned 12 mm above the magnet surface. For high spatial resolution measurements, we optimized the sensor performance by using a custom-designed rf coil, providing maximum sensitivity, lateral selectivity, and a dead time of less than 20<!--> <!-->µs. Moreover, we utilized 3D-printed structures to precisely align the sensitive slice within the object, using an experimental approach based on CPMG measurements. The presented setup achieved a spatial resolution of 50<!--> <!-->µm, with resolution changes proportional to acquisition time. We demonstrate the sensor’s versatility and high resolution with measurements on materials such as cosmetics, elastomers, glue, and wood, verifying the good performance of our design, our alignment strategy, and the measuring scheme.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"369 ","pages":"Article 107798"},"PeriodicalIF":2.0,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142702166","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Optimizing EPR pulses for broadband excitation and refocusing","authors":"Eric R. Lowe ,&nbsp;Stefan Stoll ,&nbsp;J.P. Kestner","doi":"10.1016/j.jmr.2024.107807","DOIUrl":"10.1016/j.jmr.2024.107807","url":null,"abstract":"<div><div>In this paper, we numerically optimize broadband pulse shapes that maximize Hahn echo amplitudes. Pulses are parameterized as neural networks (NN), nonlinear amplitude limited Fourier series (FS), and discrete time series (DT). These are compared to an optimized choice of the conventional hyperbolic secant (HS) pulse shape. A power constraint is included, as are realistic shape distortions due to power amplifier nonlinearity and the transfer function of the microwave resonator. We find that the NN, FS, and DT parameterizations perform equivalently, offer improvements over the best HS pulses, and contain a large number of equivalent optimal maxima, implying the flexibility to include further constraints or optimization goals in future designs.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"369 ","pages":"Article 107807"},"PeriodicalIF":2.0,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142702165","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":"Eliminating electromagnetic interference for RF shielding-free MRI via k-space convolution: Insights from MR parallel imaging advances","authors":"Yilong Liu ,&nbsp;Linfang Xiao ,&nbsp;Mengye Lyu ,&nbsp;Ruixing Zhu","doi":"10.1016/j.jmr.2024.107808","DOIUrl":"10.1016/j.jmr.2024.107808","url":null,"abstract":"<div><div>Recent advances in ultra-low field MRI have attracted attention from both academic and industrial MR communities for its potential in democratizing MRI applications. One of the most striking features on those advances is shielding-free imaging by actively sensing and eliminating the electromagnetic interference (EMI). In this study, we review the analytical approaches for EMI estimation/elimination, and investigate their theoretical basis and relations with parallel imaging reconstruction. We provide further understanding of the existing approaches, formulating EMI estimation as convolution in k-space or multiplication in spectrum-space. We further propose to use tailored convolutional kernel to adaptively fit the varying EMI coupling across the acquisition window. These methods were evaluated with both simulation study and human brain imaging. The results show that using tailored convolutional kernel can achieve more robust performance against system and acquisition imperfections.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"369 ","pages":"Article 107808"},"PeriodicalIF":2.0,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142693981","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}