Journal of magnetic resonance最新文献_第4页

Flexible and shape-adjustable coaxial capacitor (COCA) coils for ultrahigh field MRI: a comparative analysis with rigid coils 用于超高场MRI的柔性和可调形状同轴电容器（COCA）线圈：与刚性线圈的比较分析

IF 1.9 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-08-25 DOI: 10.1016/j.jmr.2025.107955

Ming Lu , Caiwan Sun , Xiaoyu Jiang , Jason E. Moore , John C. Gore , Xinqiang Yan

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.

柔性射频线圈提高了患者的舒适度，增加了填充系数，使其对MRI具有吸引力。然而，在7 T下实现大直径柔性线圈的第一模共振仍然是一个挑战。我们提出了一种同轴电容器（COCA）线圈，它的直径可以是10厘米，仍然在298 MHz的第一谐振模式下工作。与依靠自共振的同轴电缆线圈不同，COCA线圈结合了超软利兹线的电感和短同轴结构的电容。台架测试表明，1电容器COCA线圈具有与具有3个分布式集总电容器的传统刚性线圈相当的调谐/匹配鲁棒性、有效失谐和元件间去耦性能。磁共振成像显示了高信噪比，特别是当线圈符合负载的曲率时，与平面配置相比，信噪比提高了20%。线圈在不同形状之间保持调谐和匹配的能力也支持了形状可调阵列的发展。通过使灵活的大直径线圈在超高场的第一共振模式下工作，COCA设计为具有复杂几何形状的解剖成像提供了一个有前途的解决方案，例如肩部，足部和脊柱。

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引用次数: 0

High-speed, high-memory NMR spectrometer and hyperpolarizer 高速，高存储核磁共振光谱仪和超偏振器

IF 1.9 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-08-19 DOI: 10.1016/j.jmr.2025.107952

Leo Joon Il Moon , William Beatrez , Jason Ball , Joan Mercade , Mark Elo , Angad Singh , Emanuel Druga , Ashok Ajoy

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

\sim

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.

我们报告了一种新型核磁共振（NMR）波谱仪的发展，该波谱仪结合了高速，商用任意波形收发器(AWT) - Tabor Proteus P9484M。该光谱仪针对集成电子-核自旋控制和动态核极化（DNP）进行了优化，并利用了AWT的快速采样率（9 g /s）、显著的内存容量（16 GB）和高效的数据传输能力（6 g /s）。这些特点使有效的核磁共振发射-接收操作和电子控制DNP。特别是，高采样率允许在高达2.7 GHz的拉莫尔频率下直接进行核磁共振脉冲合成和信号接收。这可以通过消除信号外差来提高核磁共振信噪比（SNR）。此外，该光谱仪具有机载相敏检测功能，由数控振荡器（NCO）启用；窗口采集可以在较长的时间内进行，跨越数百万个脉冲，从而可以直接在旋转框架中询问核自旋动力学。该设备的架构为核磁共振脉冲控制和DNP开辟了新的途径，包括闭环反馈控制、电子解耦、3D自旋跟踪以及量子传感中的潜在应用。

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引用次数: 0

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] 心脏中葡萄糖产生乳酸的速率不受葡萄糖氘化的影响[J]。粉剂。理性，284(2017)86-93]。

IF 1.9 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-08-18 DOI: 10.1016/j.jmr.2025.107942

Alexander M. Funk , Brian L. Anderson , Xiaodong Wen , Thomas Hever , Chalermchai Khemtong , Zoltan Kovacs , A. Dean Sherry , Craig R. Malloy

引用次数: 0

Recurrence formula-based automatic gradient eddy current compensation method for a 0.255 T MRI system 基于递推公式的0.255 T MRI自动梯度涡流补偿方法

IF 1.9 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-08-18 DOI: 10.1016/j.jmr.2025.107951

Jinhao Liu , Miutian Wang , Wenchen Wang , Yaohui Wang , Wenhui Yang , Weimin Wang , Feng Liu

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

B_{0}

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

μT / m

, for a test gradient of 20 mT/m. Furthermore, the

B_{0}

eddy field is suppressed to below 0.1

μT

when a

B_{0}

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.

梯度线圈通过产生快速开关磁场实现空间编码，在磁共振成像（MRI）系统中起着至关重要的作用。然而，这些时变场会在周围的导电结构中产生涡流，导致梯度场畸变和成像伪影。在这项研究中，我们提出了一种在现场可编程门阵列（FPGA）平台上实现的自动涡流补偿方法。该方法采用线性梯度和B0涡旋场的迭代校正公式，实现实时补偿。为了提高计算效率，本文还介绍了一种新的预强调单元布局。与传统的补偿技术相比，所提出的基于fpga的补偿方案在实现简单性和系统稳定性方面有显著改进。实验结果表明，当测试梯度为20 mT/m时，直接项和交叉项涡流场的残余量降至0.02%以下，相当于4 μT/m。此外，采用B0补偿线圈将B0涡流场抑制到0.1 μT以下。这些改进有效地降低了多层梯度回波（GRE）伪影图像中的重影伪影。在各种成像序列中，包括t1加权（T1w）和t2加权（T2w）协议，进一步验证了该方法的鲁棒性。

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引用次数: 0

A wireless bilateral transceiver coil based on volume decoupled resonators for a clinical MR mammography 一种基于体积解耦谐振器的双侧无线收发线圈，用于临床磁共振乳房x光检查

IF 1.9 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-08-14 DOI: 10.1016/j.jmr.2025.107941

Pavel Tikhonov , Aleksandr Fedotov , Georgiy Solomakha , Anna Hurshkainen

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

B_{1}^{+}

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 in vivo study on healthy volunteers. Additionally in vivo 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. In vivo 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%.

无线射频线圈为各种磁共振应用提供了有价值的低成本解决方案，因为它有几个优点，例如无电缆连接和与不同供应商的磁共振平台兼容。即，用于临床高场人体乳房成像的无线收发器线圈有几种，它们的工作原理都是基于与人体线圈的电感耦合。这些线圈通常由几个体积谐振器组成，用于双侧乳房成像。由于体积谐振器的电邻近位置，观察到强的电感耦合，导致混合模式的发生。原则上，由于B1+分布的均匀性，使用其中一种混合模式的MR成像是可能的。然而，体积谐振腔耦合对无线线圈发射效率和接收灵敏度的影响问题，以往没有研究过。通过这项工作，我们对这一问题进行了研究。开发了第一个具有解耦谐振器的无线线圈，并对其进行了数值和实验评估，包括对健康志愿者的体内研究。此外，通过传统的接收阵列获得体内图像，与开发的无线线圈进行比较。结果表明，采用该结构的一对解耦亥姆霍兹谐振器的发射效率和接收灵敏度比一对相同耦合谐振器的发射效率和接收灵敏度至少提高24%。使用六通道接收阵列也获得了体内图像，以与开发的无线线圈进行比较。与多通道接收阵列相比，所设计的无线线圈的信噪比降低了10%，扫描时间提高了68%。

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引用次数: 0

Specificity and reactivity of bromoacrylaldehyde spin labels 溴丙醛自旋标记的特异性和反应性

IF 1.9 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-08-12 DOI: 10.1016/j.jmr.2025.107953

Dominik Gendreizig , Christina Elsner , Svetlana Kucher , Gunnar Jeschke , Alistair J. Fielding , Enrica Bordignon

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.

电子顺磁共振（EPR）光谱结合定点自旋标记提供了生物分子的结构和动力学信息。增加具有不同性质的自旋标签的可用性是促进与所调查的生物学问题相关的EPR数据更准确分析的一种优雅方法。在本研究中，我们对基于氮的溴丙醛自旋标签（BASL）与两种商业自旋标签MTSL（甲乙硫磺酸自旋标签）和MAP（马来酰丙基）在两种蛋白质上获得的标记效率、表面可及性、位点特异性和距离分布宽度进行了比较研究。基于旋转体库方法的预测距离和实验距离分布，与其他氮氧化物标签相比，BASL提供的距离分布通常更窄。BASL相对于MAP的精致的表面特异性可以成功地用于选择性地标记含有大量天然半胱氨酸的蛋白质的表面半胱氨酸。此外，利用BASL和MAP对两种表面暴露的半胱氨酸的不同位点反应性，利用氮氧化物和钆标签的正交标记策略。

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引用次数: 0

Cryogenic magic-angle spinning continuous wave EPR and DNP spectroscopy at 7 T with a gyrotron 7 T低温魔角旋转连续波EPR和DNP光谱学

IF 1.9 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-08-08 DOI: 10.1016/j.jmr.2025.107938

Marthe Millen , Nicholas Alaniva , Snædís Björgvinsdóttir , Alexander Däpp , Ioannis Gr. Pagonakis , Wolfgang Harneit , Alexander B. Barnes

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

\times

10¹³ spins/(G

\sqrt{H z}

). 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.

动态核极化（DNP）依赖于微波辐照下电子极化向原子核的转移，通常在高磁场下低温魔角旋转（MAS）下进行。回旋管是DNP中常用的微波源，因为它们能够在宽频率范围内产生高功率微波。深入了解DNP机制和合理优化DNP性能的重要一步是使用仪器，它可以提供有关DNP过程的信息。连续波（CW）电子顺磁共振（EPR）可以在DNP实验中揭示电子自旋系统的重要信息。在这里，我们提出了一个双连续波EPR/DNP光谱仪，在100 K和7 T的MAS下工作，使用频率灵活的198 GHz回旋管。使用MAS定子测量的198 GHz连续波EPR灵敏度为4 × 1013个自旋/(GHz)。为了说明我们的装置的电子和核探测能力，在相同的条件下，特别是在100 K和MAS下，记录了金刚石粉末和三烷基样品的DNP谱和连续波EPR谱。

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引用次数: 0

Optimisation and impact of gradient waveform modulation on Non-uniform Oscillating Gradient Spin-Echo sequences for microstructural characterisation 梯度波形调制对非均匀振荡梯度自旋回波序列微结构表征的优化及影响

IF 1.9 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-08-08 DOI: 10.1016/j.jmr.2025.107940

Melisa L. Gimenez , Pablo Jimenez , Leonardo A. Pedraza Pérez , Diana Betancourth , Analia Zwick , Gonzalo A. Álvarez

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 in-vivo applications. These findings represent a step toward developing quantitative imaging tools for probing microstructural features in diffusion-weighted magnetic resonance imaging.

神经系统疾病通常导致神经系统在微观尺度上的变化，强调了对非侵入性成像技术的需求，这种技术可以量化这些变化，作为诊断的潜在生物标志物。扩散加权磁共振成像（DWI），特别是使用调制梯度自旋回波（MGSE）序列，在通过探测分子扩散来揭示组织微观结构方面取得了显著进展。在MGSE序列中，非均匀振荡梯度自旋回波（NOGSE）序列通过信号衰减移位产生基于选择性微观结构尺寸的对比度，而不是探测传统的衰减率。在这项研究中，我们使用临床前MRI扫描仪评估了NOGSE在估计微观结构尺寸方面的性能。我们的研究结果表明，虽然尖锐的瞬时梯度调制使衰减位移最大化，但平滑的梯度调制仍然提供有意义的对比度。通过模拟实验、数值模拟和信息论分析相结合，我们优化了NOGSE参数，以准确估计尖锐和光滑梯度调制下的微结构尺寸。我们确定了与临床前硬件限制兼容的最佳NOGSE参数，提供了可靠的微观结构尺寸表征。特别是平滑的梯度调制扩展了兼容MRI扫描仪的范围，几乎适用于体内应用。这些发现代表了开发定量成像工具的一步，用于探测扩散加权磁共振成像中的微观结构特征。

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引用次数: 0

Shim coil design by Fourier synthesis 用傅立叶合成法设计垫片线圈。

IF 1.9 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-08-05 DOI: 10.1016/j.jmr.2025.107934

D.I. Hoult

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 Mathematica 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.

提出了一种产生“垫片”的新方法，即球谐场。这项技术依赖于一个轴向排列的圆柱体表面上正弦方位电流的空间频率与它们产生的球谐轴向磁场的程度之间的直接对应关系。正弦电流波形至少以最大所需度/频率的两倍采样，然后将电流采样施加到相同数量的相同导电电弧上，在相同的轴向位置，均匀分布在一个环中。然后，在不同的轴向位置和适当的正弦电流幅值处重复使用该构件，以允许小于或等于最大值的任何程度的谐波混合；最大顺序由轴向位置的数量决定。计算是分析性的，除了功率消耗或均方电流的数值最小化，以及轻微末端效应的校正。访问作者的Mathematica笔记本，可以帮助概念和计算提供。该设计拥有比目前正常的更高阶和度的更准确的生成的承诺，并且易于与箔或带状电缆制造；通常与结构相关的复杂性基本上转移到外部电子设备上。本文还介绍了一种新型的、概念性的、具有高效率和顺应性的电流驱动器。

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引用次数: 0

Removing magnetic field noise from NMR spectra: Reference deconvolution revisited 从核磁共振波谱中去除磁场噪声：参考反褶积

IF 1.9 3区化学 Q3 BIOCHEMICAL RESEARCH METHODS

Journal of magnetic resonance

Pub Date : 2025-07-28 DOI: 10.1016/j.jmr.2025.107937

Alexander Karabanov , Eugeny Kryukov , Gareth Morris , Jeremy Good

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.

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.

This extends the applicability of reference deconvolution in multi-dimensional NMR and advances cryogen-free technology in liquid-state NMR.

参考反褶积是一种强大的数学工具，用于消除主磁场缺陷对核磁共振波谱的影响，在强静态和动态场扰动的背景下重新审视。给出了对强磁场畸变进行高效参考反褶积的理论基础和实验证据。特别是，在二维核磁共振中，我们利用我们的观察，即主磁场的强静态不均匀性抑制了反回波相干转移贡献，使得参考反卷积能够以类似于一维核磁共振的方式，在每个间接增量中分别应用于剩余的回波贡献。我们表明，在一维和二维核磁共振中，参考反褶积使人们能够消除无低温磁体中冷头操作的振动伪影。这扩大了参考反褶积在多维核磁共振中的适用性，并推进了液态核磁共振的无低温技术。

引用次数: 0