Journal of magnetic resonance最新文献_第2页

An array of paired folded-end dipoles for whole-brain imaging at 9.4 T 用于 9.4 T 全脑成像的成对折叠端偶极子阵列

IF 2 3区化学

Journal of magnetic resonance Pub Date : 2024-10-19 DOI: 10.1016/j.jmr.2024.107791

K.I. Popova , F. Glang , D. Bosch , K. Scheffler , N.I. Avdievich , S.B. Glybovski , G.A. Solomakha

{"title":"An array of paired folded-end dipoles for whole-brain imaging at 9.4 T","authors":"K.I. Popova , F. Glang , D. Bosch , K. Scheffler , N.I. Avdievich , S.B. Glybovski , G.A. Solomakha","doi":"10.1016/j.jmr.2024.107791","DOIUrl":"10.1016/j.jmr.2024.107791","url":null,"abstract":"<div><h3>Purpose</h3><div>To improve transmit B<sub>1</sub><sup>+</sup> field homogeneity and longitudinal coverage of a human head RF array, we developed a novel eight-element transceiver (TxRx) array using composite elements based on paired folded-end dipoles.</div></div><div><h3>Methods</h3><div>The developed array consisted of eight pairs of coupled folded-end dipoles. Only one dipole in each pair was driven during transmission, while the other was passively coupled with the active one. The distribution of the transmit B<sub>1</sub><sup>+</sup> field was numerically optimized by changing the overlap between the dipoles and the value of the reactive lumped element placed in the middle of the passive dipole.</div></div><div><h3>Results</h3><div>The proposed array of paired folded-end dipoles substantially improved the B<sub>1</sub><sup>+</sup> homogeneity and longitudinal coverage over the entire brain including the brain stem compared to a single-row folded-end dipole array. The improved whole brain coverage was demonstrated both numerically and experimentally.</div></div><div><h3>Conclusion</h3><div>As a proof of concept, we developed and characterized both numerically and experimentally a prototype of a single-row eight-element 9.4 T array for human brain imaging consisting of composite array elements based on paired passively-coupled folded-end dipoles. The array improved the transmit magnetic field distribution due to the laterally elongated field pattern created by one active and one passive dipole per channel. As a result, the provided coverage was substantially better than that of an 8-element dipole array consisting of long folded-end dipoles. For the first time, an image of the entire human brain at 9.4 T, covering the brain stem up to the fourth vertebra, was obtained using a simple single row eight-element array.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"368 ","pages":"Article 107791"},"PeriodicalIF":2.0,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142526880","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}

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“Nutation” of electron spins in biradicals 双拉子中电子自旋的 "突变"。

IF 2 3区化学

Journal of magnetic resonance Pub Date : 2024-10-18 DOI: 10.1016/j.jmr.2024.107790

Ruslan Zaripov, Ravil Galeev, Kev Salikhov

引用次数: 0

Rationalising spin relaxation during slice-selective refocusing pulses 合理解释切片选择性再聚焦脉冲期间的自旋弛豫。

IF 2 3区化学

Journal of magnetic resonance Pub Date : 2024-10-16 DOI: 10.1016/j.jmr.2024.107789

Howard M. Foster , Runchao Li , Yushi Wang , Laura Castañar , Mathias Nilsson , Ralph W. Adams , Gareth A. Morris

{"title":"Rationalising spin relaxation during slice-selective refocusing pulses","authors":"Howard M. Foster , Runchao Li , Yushi Wang , Laura Castañar , Mathias Nilsson , Ralph W. Adams , Gareth A. Morris","doi":"10.1016/j.jmr.2024.107789","DOIUrl":"10.1016/j.jmr.2024.107789","url":null,"abstract":"<div><div>Slice-selective refocusing pulses are powerful building blocks in contemporary magnetic resonance experiments, but their use in quantitative applications is complicated by the site-dependent signal loss they introduce. One source of this attenuation is the spin relaxation that occurs during such pulses, which causes losses that depend on the specific longitudinal and transverse relaxation time constants for a given resonance. This dependence is complicated both by any amplitude shaping of the radiofrequency pulse, and by the presence of the spatial encoding pulsed field gradient. The latter causes the net signal measured to be the weighted sum of signal contributions from a continuous range of offsets from resonance. In general, each offset will make a different contribution to the overall signal, and will be attenuated by a different mixture of longitudinal and transverse relaxation that is dictated by the different trajectories that the nuclear magnetisations take during experiments. Despite this complex behaviour, we present evidence from experiments and numerical simulations showing that in practical experimental applications a relatively simple empirical function can be used to accurately predict relaxational attenuation during slice-selective refocusing pulses. This approach may be of practical use in correcting for relaxational losses in quantitative applications of slice-selective pulse methods such as Zangger–Sterk pure shift NMR.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"368 ","pages":"Article 107789"},"PeriodicalIF":2.0,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142515402","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}

引用次数: 0

A high-volume resonator for L-band DNP-NMR 用于 L 波段 DNP-NMR 的大容量谐振器。

IF 2 3区化学

Journal of magnetic resonance Pub Date : 2024-10-15 DOI: 10.1016/j.jmr.2024.107788

Adam R. Altenhof , Qing Yang , Michal Kern , Shaun G. Newman , Jens Anders , Michael W. Malone

{"title":"A high-volume resonator for L-band DNP-NMR","authors":"Adam R. Altenhof , Qing Yang , Michal Kern , Shaun G. Newman , Jens Anders , Michael W. Malone","doi":"10.1016/j.jmr.2024.107788","DOIUrl":"10.1016/j.jmr.2024.107788","url":null,"abstract":"<div><div>DNP-NMR and EPR experiments that operate at or greater than L-band (<em>i.e.,</em> ν<sub>0</sub>(e<sup>−</sup>) = 1–2 GHz) are typically limited to maximum sample volumes of several hundred µL. These experiments rely on well-known resonator designs for DNP/EPR irradiation such as the loop-gap resonator and Alderman-Grant coil, where their maximum volumes limit further application to imaging experiments and high-throughput screening beyond L-band. Herein, we demonstrate a birdcage (BC) resonator design that can accommodate several mL of sample while operating around 1.5 GHz. The sample volume is maximized by using two identical BC resonators in a stacked configuration. Simulations are used to optimize the BC design and the performance is validated experimentally with liquid-state Overhauser-DNP-NMR experiments. This BC design exploits just the parasitic capacitance of conductive rings and features no fixed tuning capacitors. An enhancement of −77 is achieved on a 10 mM 4-Amino-TEMPO in H<sub>2</sub>O sample for a 5 mL sample volume. The associated sample heating is minimal due to the low-<em>E</em>-fields generated and the large sample mass with +3.4 K when driving 100 W for several seconds.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"368 ","pages":"Article 107788"},"PeriodicalIF":2.0,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142515400","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}

引用次数: 0

Frequency-independent dual-tuned cable traps for multi-nuclear MRI and MRS 用于多核 MRI 和 MRS 的频率无关双调谐电缆陷阱

IF 2 3区化学

Journal of magnetic resonance Pub Date : 2024-10-10 DOI: 10.1016/j.jmr.2024.107786

Yijin Yang , Ming Lu , Xinqiang Yan

{"title":"Frequency-independent dual-tuned cable traps for multi-nuclear MRI and MRS","authors":"Yijin Yang , Ming Lu , Xinqiang Yan","doi":"10.1016/j.jmr.2024.107786","DOIUrl":"10.1016/j.jmr.2024.107786","url":null,"abstract":"<div><div>Magnetic Resonance Imaging (MRI) and Magnetic Resonance Spectroscopy (MRS) of non-proton nuclei (X-nuclei) typically require additional proton imaging for anatomical reference and B<sub>0</sub> shimming. Therefore, two RF systems exist, necessitating cable traps to block the unwanted common-mode current at both Larmor frequencies of <sup>1</sup>H and X-nuclei. This study introduces a frequency-independent dual-tuned cable trap that combines a standard solenoid cable trap with a float solenoid trap to independently tune high and low frequencies without compromising performance. The methods involved theoretical analysis, electromagnetic simulations, and bench tests. Two design approaches were evaluated: a float cable trap for <sup>1</sup>H, a non-float cable trap for X-nuclei, and vice versa. Results showed that the design with the float trap for X-nuclei and non-float for <sup>1</sup>H had superior performance, with high common-mode current suppression ability at both frequencies. Bench tests confirmed these findings, demonstrating effectiveness across various static fields and X-nuclei. The proposed frequency-independent dual-tuned cable trap provides a compact and efficient solution for multinuclear MRI and MRS, enhancing safety, image quality, and flexibility.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"368 ","pages":"Article 107786"},"PeriodicalIF":2.0,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142432878","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}

引用次数: 0

Homonuclear J-couplings and heteronuclear structural constraints 同核 J耦合和异核结构约束。

IF 2 3区化学

Journal of magnetic resonance Pub Date : 2024-10-09 DOI: 10.1016/j.jmr.2024.107785

Edward P. Saliba , Ravi Shankar Palani, Robert G. Griffin

{"title":"Homonuclear J-couplings and heteronuclear structural constraints","authors":"Edward P. Saliba , Ravi Shankar Palani, Robert G. Griffin","doi":"10.1016/j.jmr.2024.107785","DOIUrl":"10.1016/j.jmr.2024.107785","url":null,"abstract":"<div><div>In magic angle spinning (MAS) experiments involving uniformly <sup>13</sup>C/<sup>15</sup>N labeled proteins, <sup>13</sup>C–<sup>13</sup>C and <sup>13</sup>C–<sup>15</sup>N dipolar recoupling experiments are now routinely used to measure direct dipole–dipole couplings that constrain distances and torsion angles and determine molecular structures. When the distances are short (<4 Å), the direct couplings dominate the evolution of the spin system, and the <sup>13</sup>C–<sup>13</sup>C and <sup>13</sup>C–<sup>15</sup>N J-couplings (scalar couplings) are ignored. However, for structurally interesting >4 Å distances, the dipolar and J-couplings are generally of comparable magnitude, and the variation in J must be included in order to optimize the precision of the experiment. This problem is circumvented in cases with well resolved spectra by using frequency-selective dipolar recoupling methods where the effects of J-couplings are refocused. However, for larger molecules with more spectral crowding, the requisite pulse length to achieve selectivity becomes long and leads to unacceptable sensitivity losses during the pulse or the spectral overlap precludes selective excitation. In this paper, we address this problem with two approaches aimed at facilitating higher precision internuclear distance measurements in systems that are not fully resolved. Namely, (1) we describe an approach for high precision measurements of specific J-couplings using the in-phase anti-phase (IPAP) sequence which is integrated into a non-selective dipolar recoupling technique and (2) we utilize the measured J-couplings to implement a double quantum filter experiment capable of providing the resolution necessary for frequency selective dipolar recoupling techniques without resorting to multidimensional spectroscopy. We illustrate these methods using a 7-peptide segment from the amyloidogenic Sup-35p protein, U-<sup>13</sup>C/<sup>15</sup>N-GNNQQNY, where we have measured 25 of the 27 possible one bond <sup>13</sup>C–<sup>13</sup>C J-couplings.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"368 ","pages":"Article 107785"},"PeriodicalIF":2.0,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142515401","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}

引用次数: 0

Simultaneous multinuclear MRI via a single RF channel 通过单个射频通道同时进行多核磁共振成像

IF 2 3区化学

Journal of magnetic resonance Pub Date : 2024-10-09 DOI: 10.1016/j.jmr.2024.107782

Mohammad Rasool Vaezi K., Jan G. Korvink, Mazin Jouda

{"title":"Simultaneous multinuclear MRI via a single RF channel","authors":"Mohammad Rasool Vaezi K., Jan G. Korvink, Mazin Jouda","doi":"10.1016/j.jmr.2024.107782","DOIUrl":"10.1016/j.jmr.2024.107782","url":null,"abstract":"<div><div>Magnetic resonance imaging (MRI) stands as one of the most powerful noninvasive and non-destructive imaging techniques, finding extensive utility in medical and industrial applications. Its ability to acquire signals from multiple nuclei grants it additional levels of strength by providing multi-dimensional datasets of the object under test. However, this typically requires dedicated hardware to detect each nucleus. In this paper, we report on the use of a digital lock-in amplifier to perform simultaneous multi-nuclear MRI with a single physical radio frequency (RF) channel. While we showcase this concept by demonstrating the results of fully parallel (TX and RX) <sup>1</sup>H and <sup>19</sup>F MRI images, we emphasize that it is not limited to two nuclei but can accommodate more nuclei with no extra cost on the hardware or scan time. The scalability is virtually unlimited, constrained only by the processing speed of the digital unit. Furthermore, we demonstrate that the quality of parallel imaging with SNR of 54 is comparable to the commercial single channel with SNR of 43. Thus with no reduction in imaging quality, the proposed concept promises a tremendous reduction in scan time, system complexity, and hardware costs.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"368 ","pages":"Article 107782"},"PeriodicalIF":2.0,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142442903","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}

引用次数: 0

Optimization of 15N–13C double-resonance NMR experiments under low temperature magic angle spinning dynamic nuclear polarization conditions 低温魔角旋转动态核极化条件下 15N-13C 双共振核磁共振实验的优化。

IF 2 3区化学

Journal of magnetic resonance Pub Date : 2024-10-02 DOI: 10.1016/j.jmr.2024.107783

C. Blake Wilson, Robert Tycko

引用次数: 0

In Memoriam: Professor Vladimír Sklenář (April 16, 1951 – April 13, 2024) 悼念弗拉迪米尔-斯克雷纳日教授（1951 年 4 月 16 日 - 2024 年 4 月 13 日）。

IF 2 3区化学

Journal of magnetic resonance Pub Date : 2024-10-02 DOI: 10.1016/j.jmr.2024.107784

Ad Bax , Juli Feigon

引用次数: 0

Peculiarities in Rabi oscillations for fast-relaxing electron spins 快速松弛电子自旋拉比振荡的特殊性

IF 2 3区化学

Journal of magnetic resonance Pub Date : 2024-09-26 DOI: 10.1016/j.jmr.2024.107781

Antonio Barbon , Grigory A. Rusetsky , Sveva Linarello , Roman Strzelczyk , Ryhor Fedaruk

引用次数: 0