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Nuclear hyperpolarization in electron-transfer proteins: Revealing unexpected light-induced 15N signals with field-cycling magic-angle spinning NMR 电子传递蛋白中的核超极化:用场循环魔角旋转 NMR 揭示意想不到的光诱导 15N 信号
IF 2.624 Pub Date : 2024-10-05 DOI: 10.1016/j.jmro.2024.100168
Patrick Kurle-Tucholski , Luca Gerhards , Yonghong Ding , Yunmi Kim , Irina S. Anisimova , A. Alia , Ilia A. Solov'yov , Jörg Matysik
The solid-state photo-CIDNP (photo-chemically induced dynamic nuclear polarization) effect allows for nuclear hyperpolarization, i.e., non-Boltzmann nuclear spin population. The effect relies on the light-induced formation of a spin-correlated radical pair (SCRP) and has been observed in various photosynthetic reaction center (RC) proteins and flavin-containing light, oxygen, voltage (LOV) proteins. Both systems exhibit strongly enhanced NMR signals originating from the electron transfer partners. Here, we present experimental data on the magnetic field dependence of the 15N solid-state photo-CIDNP effect in both phototropin LOV1 C57S from Chlamydomonas reinhardtii and the bacterial photosynthetic RC from Rhodobacter sphaeroides. Using a pneumatic field-cycling system, samples containing a frozen solution of the proteins are explored between 0.25 T and 9.4 T. Both systems yield hyperpolarized 15N NMR signals across the entire magnetic field range originating from the electron transfer moieties. Also, in both systems, hyperpolarized signals from unexpected positions are detected between 1.0 T and 2.0 T: position N-1 of the flavin in the LOV1 protein and the τ-N of the axial magnesium-coordinating histidine of the donor. A first attempt to explain the occurrence of these unexpected signals based on quantum chemical calculations is presented.
固态光-CIDNP(光化学诱导动态核极化)效应允许核超极化,即非玻尔兹曼核自旋群。这种效应依赖于光诱导形成的自旋相关自由基对(SCRP),并已在各种光合反应中心(RC)蛋白质和含黄素的光、氧、电压(LOV)蛋白质中观察到。这两个系统都显示出源自电子转移伴侣的强烈增强 NMR 信号。在这里,我们展示了有关 15N 固态光-CIDNP 效应在莱茵衣藻的趋光蛋白 LOV1 C57S 和孢氏红杆菌的细菌光合 RC 中的磁场依赖性的实验数据。利用气动磁场循环系统,在 0.25 T 和 9.4 T 之间对含有冷冻蛋白质溶液的样品进行了探究。在整个磁场范围内,两个系统都产生了源于电子传递分子的超极化 15N NMR 信号。此外,在这两个系统中,在 1.0 T 和 2.0 T 之间都检测到了来自意外位置的超极化信号:LOV1 蛋白中黄素的 N-1 位置和供体的轴向镁配位组氨酸的 τ-N 位置。本文首次尝试根据量子化学计算来解释这些意外信号的出现。
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引用次数: 0
Measurement and modeling of xenon gas transfer in the human brain with 1H and hyperpolarized 129Xe MRI 利用 1H 和超极化 129Xe MRI 测量人脑中的氙气转移并建立模型
IF 2.624 Pub Date : 2024-09-23 DOI: 10.1016/j.jmro.2024.100166
Graham Norquay , Madhwesha R Rao , Jim M Wild

Background

The feasibility of imaging hyperpolarized 129Xe dissolved in brain tissue following inhalation of xenon gas in the lungs has recently been demonstrated in humans. The image contrast in 129Xe brain MRI represents a combination of factors, including regional perfusion, polarization decay and gas transfer rate across the blood-brain barrier.

Purpose

To investigate the repeatability of hyperpolarized 129Xe brain MRI in healthy normal individuals and to identify the dominant mechanisms of image contrast by assessing voxel-wise correlation between HP 129Xe brain MRI and models of 129Xe brain uptake derived from 1H arterial spin labeling (ASL) perfusion mapping.

Materials and Methods

To assess repeatability, 3 sets of hyperpolarized 129Xe brain images were acquired from 5 healthy volunteers. Quantitative maps of the human brain, including cerebral blood flow, volume and predicted xenon uptake, were derived from 1H arterial spin labeling and T2-weighted MRI. These maps were then spatially cross-correlated with hyperpolarized 129Xe brain MRI.

Results

Signal to noise ratios of 8.7–17.7 were observed across volunteers for a voxel size of 8 × 8 × 50 mm3 with intra-subject repeatability of between 6 and 29 %. Hyperpolarized 129Xe brain images showed voxel-wise correlations with cerebral blood flow (R = 0.32 to 0.62), volume (R = 0.33 to 0.63) and predicted xenon uptake (R = 0.34 to 0.63), but did not correlate with arterial transit time (R = 0.05 to 0.26).

Conclusion

Voxel-wise cross correlation between 129Xe and 1H ASL suggests that the regional quantity of dissolved xenon delivered by cerebral blood flow is the dominant mechanism of image contrast in HP 129Xe brain MRI, assuming normal blood-brain barrier function. Combining 1H and 129Xe brain MRI provides new opportunities to quantitatively investigate brain pathophysiology and function.
背景最近在人体中证实了对肺部吸入氙气后溶解在脑组织中的超极化 129Xe 进行成像的可行性。129Xe 脑磁共振成像的图像对比度由多种因素共同决定,包括区域灌注、偏振衰减和气体通过血脑屏障的传输速率。目的通过评估 HP 129Xe 脑磁共振成像与 1H 动脉自旋标记(ASL)灌注图得出的 129Xe 脑摄取模型之间的体素相关性,研究健康正常人的超极化 129Xe 脑磁共振成像的可重复性,并确定图像对比度的主要机制。通过 1H 动脉自旋标记和 T2 加权磁共振成像得出人脑的定量图,包括脑血流量、体积和预测的氙摄取量。结果在体素大小为 8 × 8 × 50 mm3 的情况下,不同志愿者的信噪比为 8.7-17.7,受试者内的重复性为 6%-29%。超极化 129Xe 脑图像与脑血流量(R = 0.32 至 0.62)、体积(R = 0.33 至 0.63)和预测氙摄取量(R = 0.34 至 0.63)呈体素相关性,但与动脉通过时间(R = 0.05 至 0.26)不相关。结论 129Xe 和 1H ASL 的象素交叉相关性表明,假设血脑屏障功能正常,脑血流输送的区域溶解氙数量是 HP 129Xe 脑磁共振成像图像对比的主要机制。结合 1H 和 129Xe 脑磁共振成像为定量研究大脑病理生理学和功能提供了新的机会。
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引用次数: 0
13C-Formate as an indirect low-temperature 1H lineshape polarimeter 作为间接低温 1H 线形偏振计的 13C 甲酸酯
IF 2.624 Pub Date : 2024-09-23 DOI: 10.1016/j.jmro.2024.100162
Stuart J. Elliott , Quentin Stern, Sami Jannin
1H polarization quantification is important for dissolution-dynamic nuclear polarization (dDNP) but can be cumbersome due to the requirement of acquiring thermal equilibrium signals and measurements that are complicated by large background signals. 1H nuclear magnetic resonance (NMR) spectra can also be deleteriously influenced by line distortions linked with radiation damping from 1H DNP and cannot be used for accurate calculation of 1H polarization. Determining 1H polarization via immediate 13C lineshape analysis of a simple molecule removes such complications. We present 13C-sodium formate as a straightforward system for indirect 1H polarimetry. The 13C NMR spectra acquired under dDNP conditions have distinct features that are readily reproduced with 13C lineshape simulations. 1H polarizations built-up during 1H DNP were indirectly inferred by fitting simulations to 13C lineshapes. We provide the MATLAB scripts used for 13C lineshape analysis in order that the method can be readily implemented in other laboratories.
1H 极化定量对于溶解-动态核极化(dDNP)非常重要,但由于需要获取热平衡信号,且测量工作因大量背景信号而变得复杂,因此可能非常麻烦。1H 核磁共振 (NMR) 图谱也会受到与 1H DNP 辐射阻尼有关的线畸变的有害影响,无法用于精确计算 1H 极化。通过对简单分子进行直接 13C 线形分析来确定 1H 极化,可以消除这些复杂问题。我们将 13C 甲酸钠作为间接 1H 极化测量的一个直接系统。在 dDNP 条件下获得的 13C NMR 光谱具有明显的特征,这些特征很容易通过 13C 线形模拟再现。通过模拟拟合 13C 线型,可间接推断出 1H DNP 期间建立的 1H 极化。我们提供了用于 13C 线形分析的 MATLAB 脚本,以便其他实验室也能方便地使用这种方法。
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引用次数: 0
Investigation of biomolecular dynamics by sensitivity-enhanced 1H–2H CPMAS NMR using matrix-free dynamic nuclear polarization 利用无基质动态核偏振的灵敏度增强型 1H-2H CPMAS NMR 研究生物分子动力学
IF 2.624 Pub Date : 2024-09-18 DOI: 10.1016/j.jmro.2024.100161
Thomas Biedenbänder , Aryana Rodgers , Mirjam Schröder , Liliya Vugmeyster , Björn Corzilius
Molecular dynamics of functional groups contain valuable information about structural properties and functional activities in biomolecules. NMR spectroscopy is a sensitive tool for the investigation of molecular dynamics over a wide range of timescales and thus may deepen the understanding of the biomolecules of interest. Here, we present an approach to use DNP-enhanced 2H NMR to study dynamics of selectively deuterated methyl groups in insoluble proteins such as amyloid beta (Aβ) fibrils. We adopted and optimized the matrix-free DNP approach by varying the amount of added polarizing agent as well as the rehydration level of model proteins. We show that the DNP enhancement obtained in 1H–2H cross-polarization (CP) MAS spectra may increase the sensitivity for selectively deuterated Aβ fibril samples by more than one order of magnitude, accelerating the collection of spin-lattice relaxation data in the DNP-accessible temperature range between 100 and 150 K by up to 400-fold. However, below the coalescence temperature, which describes the transition from the fast to the slow exchange regime, the experimentally obtained relaxation time constants suffer from a paramagnetic relaxation enhancement effect due to the presence of the polarizing agent. This seems to be a general effect for biomolecules as it is also confirmed for two other protein model systems. Our demonstration opens the possibility to extend the scope of 2H NMR for dynamics measurements to effective concentrations and/or temperatures below what is currently accessible; however, the observed interplay between paramagnetic relaxation and molecular dynamics also emphasizes the necessity for a better understanding of relaxation effects in DNP-enhanced NMR.
功能基团的分子动力学包含有关生物分子结构特性和功能活动的宝贵信息。核磁共振光谱是一种灵敏的工具,可用于研究各种时间尺度的分子动力学,从而加深对相关生物大分子的了解。在此,我们介绍一种利用 DNP 增强 2H NMR 研究淀粉样 beta (Aβ) 纤维等不溶性蛋白质中选择性氚化甲基的动力学的方法。我们采用了无基质 DNP 方法,并通过改变极化剂的添加量和模型蛋白质的复水水平对该方法进行了优化。我们的研究表明,在 1H-2H 交叉偏振 (CP) MAS 图谱中获得的 DNP 增强可将选择性氚化 Aβ 纤维样品的灵敏度提高一个数量级以上,从而将 100 至 150 K DNP 可及温度范围内的自旋晶格弛豫数据的收集速度提高 400 倍。然而,在描述从快速交换体系向慢速交换体系过渡的凝聚温度以下,由于极化剂的存在,实验获得的弛豫时间常数受到顺磁弛豫增强效应的影响。这似乎是生物大分子的一种普遍效应,因为它在另外两个蛋白质模型系统中也得到了证实。我们的演示为将 2H NMR 的动态测量范围扩展到目前可获得的有效浓度和/或温度以下提供了可能;然而,观察到的顺磁弛豫与分子动力学之间的相互作用也强调了更好地理解 DNP 增强 NMR 中弛豫效应的必要性。
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引用次数: 0
DNP enhanced solid-state NMR – A powerful tool to address the surface functionalization of cellulose/paper derived materials DNP 增强固态 NMR - 解决纤维素/纸张衍生材料表面功能化问题的有力工具
IF 2.624 Pub Date : 2024-09-14 DOI: 10.1016/j.jmro.2024.100163
Mark V. Höfler , Jonas Lins , David Seelinger , Lukas Pachernegg , Timmy Schäfer , Stefan Spirk , Markus Biesalski , Torsten Gutmann
This concept summarizes recent advances in development and application of DNP enhanced multinuclear solid-state NMR to study the molecular structure and surface functionalization of cellulose and paper-based materials. Moreover, a novel application is presented where DNP enhanced 13C and 15N solid-state NMR is used to identify structure moieties formed by cross-linking of hydroxypropyl cellulose. Given these two aspects of this concept-type of article, we thus combine both, a review on recent findings already published and unpublished recent data that complement the existing knowledge in the field of characterization of functional lignocellulosic materials by DNP enhanced solid-state NMR.
这一概念总结了在开发和应用 DNP 增强型多核固态 NMR 研究纤维素和纸基材料的分子结构和表面功能化方面的最新进展。此外,还介绍了一种新颖的应用,即利用 DNP 增强 13C 和 15N 固态 NMR 来识别羟丙基纤维素交联形成的结构分子。鉴于这篇文章概念类型的这两个方面,我们将这两方面结合起来,综述了已发表的最新研究成果和未发表的最新数据,这些数据补充了利用 DNP 增强固态 NMR 表征功能性木质纤维素材料领域的现有知识。
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引用次数: 0
Dual hyperpolarized [1-13C]pyruvate and [13C]urea magnetic resonance imaging of prostate cancer 前列腺癌的双重超极化[1-13C]丙酮酸和[13C]尿素磁共振成像
IF 2.624 Pub Date : 2024-09-11 DOI: 10.1016/j.jmro.2024.100165
Ivan de Kouchkovsky , Hao Nguyen , Hsin-Yu Chen , Xiaoxi Liu , Hecong Qin , Bradley A. Stohr , Romelyn Delos Santos , Michael A. Ohliger , Zhen Jane Wang , Robert A. Bok , Jeremy W. Gordon , Peder E.Z. Larson , Mary Frost , Kimberly Okamoto , Daniel Gebrezgiabhier , Matthew Cooperberg , Daniel B. Vigneron , John Kurhanewicz , Rahul Aggarwal
<div><h3>Background</h3><p>Although multiparametric (mp) <sup>1</sup>H magnetic resonance imaging (MRI) is increasingly used to detect and localize prostate cancer (PC), its correlation with tumor grade is limited. Hyperpolarized (HP) carbon-13 (<sup>13</sup>C) MR is an emerging imaging technique, which can be used to interrogate key biologic processes through in vivo detection of various HP probes. A distinct attribute of HP <sup>13</sup>C MRI is the ability to detect multiple HP probes within a single acquisition. Here we report on the first simultaneous dual HP [1-<sup>13</sup>C]pyruvate and [<sup>13</sup>C]urea MRI with correlations to histopathologic findings in a patient with localized PC scheduled for radical prostatectomy.</p></div><div><h3>Material and methods</h3><p>Paired HP <sup>13</sup>C and standard mp <sup>1</sup>H MRI were performed in a patient with biopsy-proven Gleason score 4 + 3 = 7 adenocarcinoma of the prostate scheduled for radical prostatectomy through a first-in-human pilot study of dual-agent HP MRI (NCT02526368). HP <sup>13</sup>C MRI was performed using a clinical 3T scanner with <sup>13</sup>C transmit-and-receive capabilities. Dynamic series of HP <sup>13</sup>C pyruvate, lactate and urea imaging were acquired following intravenous (IV) injection of co-hyperpolarized [<sup>13</sup>C]urea (25 mM) and [1–<sup>13</sup>C]pyruvate (125 mM). The [1-<sup>13</sup>C]pyruvate-to-[1-<sup>13</sup>C]lactate conversion rate (k<sub>PL</sub>) was calculated using an inputless two-site exchange model; AUC<sub>urea</sub> was the [<sup>13</sup>C]urea signal summed over time. Following radical prostatectomy, whole-mount prostate histopathological slides were prepared and reviewed by an experienced genitourinary pathologist.</p></div><div><h3>Results</h3><p>Following informed consent, the patient underwent paired mp <sup>1</sup>H MRI and dual-agent HP MRI. mp <sup>1</sup>H MRI revealed a 1.2 cm lesion in the left apical posterior zone. Dual-agent HP MRI identified a focus of increased [1-<sup>13</sup>C]pyruvate-to-[1-<sup>13</sup>C]lactate conversion rate (k<sub>PL</sub>) extending from the left apical posterior peripheral zone to the right gland. A corresponding area of abnormal tissue perfusion (AUC<sub>urea</sub>) was seen in the left gland. Metabolism-perfusion mismatch (with several foci of increased <em>k<sub>PL</sub></em>/AUC<sub>urea</sub>) was observed throughout the tumor. Tumor extension to the right midgland was confirmed at the time of radical prostatectomy and staining for lactate dehydrogenase-A was increased throughout the tumor relative to surrounding benign prostatic tissue.</p></div><div><h3>Conclusion</h3><p>This first-in-human radiopathologic study demonstrates the feasibility of dual-agent HP MRI in PC patients. Simultaneous assessment of tumor metabolism and perfusion was able to detect occult disease as well as to show a significant mismatch between intra-tumoral metabolism and tissue perfusion in high-grade PC.
背景虽然多参数(mp)1H 磁共振成像(MRI)越来越多地用于检测和定位前列腺癌(PC),但其与肿瘤分级的相关性有限。超极化(HP)碳-13(13C)磁共振成像是一种新兴的成像技术,可通过在体内检测各种 HP 探针来探查关键的生物过程。HP 13C MRI 的一个显著特点是能在一次采集中检测多个 HP 探针。在此,我们报告了首次同时进行的双 HP [1-13C] 丙酮酸和 [13C] 尿素 MRI 与组织病理学检查结果的相关性,该患者患有局部 PC,计划进行根治性前列腺切除术。材料和方法通过首次在人体中进行的双试剂 HP MRI 试验研究(NCT02526368),对一名经活检证实 Gleason 评分为 4 + 3 = 7 的前列腺腺癌患者进行了成对 HP 13C 和标准 mp 1H MRI。HP 13C MRI 是使用具有 13C 发射和接收功能的临床 3T 扫描仪进行的。在静脉注射共超极化[13C]尿素(25 mM)和[1-13C]丙酮酸(125 mM)后,采集了一系列动态的 HP 13C 丙酮酸、乳酸和尿素成像。[1-13C]丙酮酸到[1-13C]乳酸的转化率(kPL)是通过无输入的双位点交换模型计算得出的;AUCurea是[13C]尿素信号在一段时间内的总和。根治性前列腺切除术后,由经验丰富的泌尿生殖系统病理学家制备并审查整张前列腺组织病理切片。结果在知情同意后,患者接受了成对的 mp 1H MRI 和双试剂 HP MRI 检查。双剂 HP MRI 发现一个[1-13C]丙酮酸-[1-13C]乳酸转化率(kPL)升高的病灶,从左侧心尖后外周区延伸至右侧腺体。左侧腺体出现了相应的组织灌注异常区域(AUCurea)。整个肿瘤都出现了代谢-灌注不匹配现象(有几个 kPL/AUCurea 增高的病灶)。根治性前列腺切除术时证实肿瘤扩展到了右侧腺体中部,与周围良性前列腺组织相比,整个肿瘤的乳酸脱氢酶-A染色增加。同时评估肿瘤的代谢和灌注能够检测出隐匿性疾病,并显示高级别 PC 中肿瘤内代谢和组织灌注之间存在明显的不匹配。有必要对这些发现进行前瞻性验证。
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引用次数: 0
Discontinuous hyperpolarization schemes in liquid-state overhauser dynamic nuclear polarization experiments 液态超豪斯动态核极化实验中的非连续超极化方案
IF 2.624 Pub Date : 2024-09-02 DOI: 10.1016/j.jmro.2024.100160
Alex van der Ham

Liquid-state Overhauser Dynamic Nuclear Polarization (ODNP) is an emerging technique, aimed at shortening NMR experiment times. It achieves this by increasing the otherwise poor nuclear polarization at room temperature, by polarization transfer from excited electron spins. The present work explores two ideas, aimed at achieving the optimal signal-to-noise per time unit for a given system, and quantitation of spectra showing a large disparity in ODNP enhancements at high magnetic fields (≥ 9.4 T). Both of these ideas are predicated on, perhaps counterintuitively, not allowing full dynamic nuclear polarization to build up, either by rapid rf pulsing, or gating of the microwave irradiation.

液态奥弗豪斯动态核极化(ODNP)是一项新兴技术,旨在缩短核磁共振实验时间。它通过激发电子自旋的极化转移,提高室温下原本较差的核极化,从而实现这一目标。本研究探讨了两个想法,旨在实现特定系统单位时间内的最佳信噪比,以及对高磁场(≥ 9.4 T)下 ODNP 增强差异较大的光谱进行量化。这两个想法的前提都是,通过快速的射频脉冲或微波辐照的门控,不允许建立完全的动态核极化,这可能与直觉相反。
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引用次数: 0
Creating high, portable proton polarization with photo-excited triplet DNP 利用光激发三重 DNP 创建高便携质子极化
IF 2.624 Pub Date : 2024-08-22 DOI: 10.1016/j.jmro.2024.100159
P. Hautle, W.Th. Wenckebach

Dynamic nuclear polarization (DNP) is a powerful tool to polarize nuclear spins and enhance the intensity of their magnetic resonance signal. For DNP a sample is doped with an agent providing unpaired electron spins. Then the sample is cooled in a strong magnetic field to polarize these electron spins and a microwave field is applied to transfer this polarization to the nuclear spins. While DNP is very efficient, it has two inherent issues: the electron spins needed to polarize the nuclear spins are also the main source of polarization decay. Furthermore, polarizing the electron spins requires strong magnets and powerful cryogenics, that may obstruct further use of the polarized nuclear spins.

These issues can be addressed by using the electron spin of photo-excited triplet states for DNP. After DNP the light creating the electron spins can be shut off, thus eliminating the main source of decay of the nuclear polarization. Moreover, for some well-chosen molecules the photo-excitation process creates the triplet state in a highly polarized state, so magnets and cryogenics can be significantly simplified.

The present article presents the state of the art of producing a high proton polarization – up to 0.80 – with a long lifetime – typically 50 h at liquid nitrogen temperature and in a field of 0.75 T – using the photo-excited triplet state of pentacene in a naphthalene host. It describes sample preparation, experimental equipment and procedures required to obtain this result, as well the theoretical background required to maximize the polarization transfer from the triplet spins to the proton spins and to optimize the photo-excitation process. It finishes with methods for long-distance transport and final application of polarized samples.

动态核极化(DNP)是使核自旋极化并增强其磁共振信号强度的有力工具。为了实现 DNP,需要在样品中掺入一种能提供非配对电子自旋的物质。然后将样品在强磁场中冷却,使这些电子自旋极化,并应用微波场将这种极化转移到核自旋上。虽然 DNP 非常有效,但它有两个固有问题:极化核自旋所需的电子自旋也是极化衰变的主要来源。此外,极化电子自旋需要强力磁铁和强大的低温设备,这可能会阻碍对极化核自旋的进一步利用。在 DNP 之后,产生电子自旋的光可以被关闭,从而消除了核极化衰变的主要来源。本文介绍了在液氮温度和 0.75 T 的磁场中利用光激发萘宿主中的五碳烯三重态产生高质子极化(高达 0.80)和长寿命(通常为 50 小时)的最新技术。报告介绍了获得这一结果所需的样品制备、实验设备和程序,以及最大限度地将极化从三重自旋转移到质子自旋和优化光激发过程所需的理论背景。最后还介绍了偏振样品的长距离传输和最终应用方法。
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引用次数: 0
Understanding magnetic fields, for NMR/MRI 了解磁场,用于核磁共振/MRI
IF 2.624 Pub Date : 2024-07-29 DOI: 10.1016/j.jmro.2024.100158
Mark S. Conradi

The basic physics of magnetic fields is presented for a target audience of NMR workers. This group often does not have formal training in electromagnetism, but could benefit from an understanding of a selected subset of topics. The focus here is on a relatively non-mathematical view, intended to deliver an intuitive understanding of the topic. The covered topics start with the fields arising from simple idealized currents, including long straight wires, short flat coils, infinite current sheets, long solenoids, and magnetic dipole moments. The generation of field gradients and shim fields is discussed. All of these can be unified by considering the divergence and curl of the magnetic field. Magnetic materials are treated, both linear magnetizable materials (including the sample itself) and permanently magnetized materials; the approaches of equivalent currents and Ampere's theorem for magnetic circuits are presented.

本书为核磁共振工作者的目标读者介绍了磁场的基本物理原理。这群人通常没有接受过正规的电磁学培训,但可以从对一些主题的理解中受益。本书的重点是相对非数学的视角,旨在提供对该主题的直观理解。所涵盖的主题从简单的理想化电流(包括长直线、短扁线圈、无限电流片、长螺线管和磁偶极矩)产生的场开始。还讨论了场梯度和垫片场的产生。所有这些都可以通过考虑磁场的发散和卷曲而统一起来。还讨论了磁性材料,包括线性可磁化材料(包括样品本身)和永久磁化材料;介绍了磁路的等效电流方法和安培定理。
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引用次数: 0
Fast quantitative MRI: Spiral Acquisition Matching-Based Algorithm (SAMBA) for Robust T1 and T2 Mapping 快速定量磁共振成像:基于螺旋采集匹配算法 (SAMBA) 的稳健 T1 和 T2 映射
IF 2.624 Pub Date : 2024-07-29 DOI: 10.1016/j.jmro.2024.100157
Mireia Perera-Gonzalez , Christina J. MacAskill , Heather A. Clark , Chris A. Flask

Conventional diagnostic images from Magnetic Resonance Imaging (MRI) are typically qualitative and require subjective interpretation. Alternatively, quantitative MRI (qMRI) methods have become more prevalent in recent years with multiple clinical and preclinical imaging applications. Quantitative MRI studies on preclinical MRI scanners are being used to objectively assess tissues and pathologies in animal models and to evaluate new molecular MRI contrast agents. Low-field preclinical MRI scanners (3.0T) are particularly important in terms of evaluating these new MRI contrast agents at human MRI field strengths. Unfortunately, these low-field preclinical qMRI methods are challenged by long acquisition times, intrinsically low MRI signal levels, and susceptibility to motion artifacts. In this study, we present a new rapid qMRI method for a preclinical 3.0T MRI scanner that combines a Spiral Acquisition with a Matching-Based Algorithm (SAMBA) to rapidly and quantitatively evaluate MRI contrast agents. In this initial development, we compared SAMBA with gold-standard Spin Echo MRI methods using Least Squares Fitting (SELSF) in vitro phantoms and demonstrated shorter scan times without compromising measurement accuracy or repeatability. These initial results will pave the way for future in vivo qMRI studies using state-of-the-art chemical probes.

传统的磁共振成像(MRI)诊断图像通常是定性的,需要主观判读。而近年来,定量磁共振成像(qMRI)方法在临床和临床前成像的多种应用中变得越来越普遍。临床前磁共振成像扫描仪上的定量磁共振成像研究正被用于客观评估动物模型中的组织和病理,以及评估新的分子磁共振成像对比剂。低磁场临床前 MRI 扫描仪(≤3.0T)对于在人体 MRI 磁场强度下评估这些新型 MRI 造影剂尤为重要。遗憾的是,这些低磁场临床前 qMRI 方法面临着采集时间长、磁共振成像信号水平低以及易受运动伪影影响等挑战。在本研究中,我们为临床前 3.0T MRI 扫描仪提出了一种新的快速 qMRI 方法,该方法结合了螺旋采集和基于匹配的算法(SAMBA),可快速定量评估 MRI 造影剂。在这项初步开发中,我们使用最小二乘拟合(SELSF)体外模型对 SAMBA 与黄金标准自旋回波 MRI 方法进行了比较,结果表明,在不影响测量准确性或可重复性的情况下,扫描时间更短。这些初步结果将为未来使用最先进的化学探针进行体内 qMRI 研究铺平道路。
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Journal of Magnetic Resonance Open
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