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Full determination of chemical shift tensor in magnetically oriented microcrystals with modulated rotation and temporal tilt 具有调制旋转和时间倾斜的磁取向微晶体中化学位移张量的完全测定
IF 2 3区 化学 Q3 BIOCHEMICAL RESEARCH METHODS Pub Date : 2025-02-19 DOI: 10.1016/j.jmr.2025.107853
Ryosuke Kusumi , Hayate Yasui , Hiroshi Kadoma , Masahisa Wada , Kazuyuki Takeda
Complete characterization of 13C chemical shift tensor in magnetically oriented microcrystal suspension (MOMS) is demonstrated with an inhouse 1H-13C double resonance probe capable of rotating microcrystals and of tilting the sample temporarily during the period of NMR signal acquisition. The 13C chemical shift tensor in three-dimensional MOMS of l-alanine is determined from 13C rotation patterns around a tilted axis. The present results prove that even for micrometer-sized microcrystals the chemical shift tensor can be fully determined like in the case of a single piece of bulky crystal but without elaborate sample mounting. Two-dimensional experiments correlating chemical shifts for different sample orientations are also demonstrated.
利用内部的h -13C双共振探针,可以旋转微晶体,并在核磁共振信号采集期间暂时倾斜样品,完整地表征了磁取向微晶悬浮液(mom)中13C化学位移张量。l-丙氨酸三维mom中的13C化学位移张量是由13C围绕倾斜轴的旋转模式确定的。目前的结果证明,即使对于微米大小的微晶体,化学位移张量也可以完全确定,就像在单个大块晶体的情况下一样,而无需精心安装样品。二维实验还证明了不同样品取向的化学位移。
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引用次数: 0
Implementation of the X-centric pulse sequence at low field for MRI of water penetration in clay 低场x心脉冲序列在粘土中水渗透核磁共振成像中的实现
IF 2 3区 化学 Q3 BIOCHEMICAL RESEARCH METHODS Pub Date : 2025-02-18 DOI: 10.1016/j.jmr.2025.107852
Samuel Perron , Claire S. Tully , Shivam Gupta , Matthew S. Fox , Dmitrij Zagidulin , James J. Noël , Alexei Ouriadov
Although the relaxation time constants of free water are relatively long, the relaxation of water in concrete and other sedimentary materials is significantly shorter. Dissolved ions and porous environments can cause increased magnetic susceptibility effects, leading to the apparent transverse relaxation time T2 of this water to decrease drastically, from seconds to less than a millisecond. The longer T2 of the low field regime (less than 0.5 T) should allow for 2D and even 3D imaging of water content in these types of materials; developing a suitable technique for imaging of short-T2 samples would permit imaging of porous rocks and concrete.
A 12 mL wet bentonite clay sample was placed within a syringe and allowed to absorb increasing volumes of standing water. This progressing absorption was imaged on a 73.5 mT magnetic resonance imaging (MRI) system using the X-Centric pulse sequence. This pulse sequence is a modified version of the common gradient echo (GE) pulse sequence, in which each half of k-space is acquired separately, from the centre outwards in the readout direction, ensuring minimal T2-weighting of the resulting image and allowing for 2D imaging within the short time frame of the shorter T2 of water in the clay. Bulk relaxation measurements of T2 and the longitudinal relaxation time T1 were performed for increasing water content, with a mean T1 of 12.0 ± 1.1 ms and mean T2 of 4.5 ± 0.7 ms; 2D imaging of the clay sample was performed with both GE and X-Centric. In addition, a 2D T2 map was generated from eight X-Centric images taken at different echo times.
The X-Centric pulse sequence was demonstrated to be an effective imaging method for short signal-lifetime samples, such as water trapped in bentonite clay. The ease of implementation, minimal diffusion-weighting and T2 weighting of the k-space centre, and considerable gains in signal-to-noise ratio and imaging efficiency position this pulse sequence as a viable alternative or complement to conventional GE acquisitions. Additionally, the short echo-time of the X-Centric pulse sequence allows it to be used effectively with non-proton MRI, including 23Na and fluorinated gases (e.g., 19F) where the T2-decay is a potentially significant source of signal decay.
虽然自由水的弛豫时间常数相对较长,但水在混凝土和其他沉积材料中的弛豫时间明显较短。溶解的离子和多孔环境会引起磁化率效应的增加,导致该水的表观横向弛豫时间T2急剧减少,从几秒到不到一毫秒。低场较长的T2(小于0.5 T)应该允许对这些类型的材料中的含水量进行二维甚至三维成像;开发一种合适的短t2样品成像技术将允许对多孔岩石和混凝土进行成像。将12ml湿的膨润土粘土样品放入注射器中,让其吸收越来越多的静水。在73.5 mT磁共振成像(MRI)系统上使用x中心脉冲序列对这种渐进吸收进行成像。该脉冲序列是通用梯度回波(GE)脉冲序列的改进版本,其中k空间的每一半分别从读取方向的中心向外获取,确保所得到的图像具有最小的T2,并允许在粘土中较短的T2的短时间框架内进行2D成像。为了增加水含量,进行了T2的体积弛豫测量和纵向弛豫时间T1,平均T1为12.0±1.1 ms,平均T2为4.5±0.7 ms;使用GE和X-Centric对粘土样品进行二维成像。此外,从不同回波时间拍摄的8张以x为中心的图像生成2D T2图。x中心脉冲序列被证明是一种有效的成像方法,用于短信号寿命的样品,如被困在膨润土粘土中的水。该脉冲序列易于实现,最小的扩散加权和k空间中心的T2加权,以及在信噪比和成像效率方面的显著提高,使其成为传统GE采集的可行替代或补充。此外,x中心脉冲序列的短回波时间使其能够有效地用于非质子MRI,包括23Na和氟化气体(例如19F),其中T2 β衰变是信号衰减的潜在重要来源。
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引用次数: 0
A deep learning framework for multiplet splitting classification in 1H NMR 一种用于1H NMR多组分裂分类的深度学习框架
IF 2 3区 化学 Q3 BIOCHEMICAL RESEARCH METHODS Pub Date : 2025-02-16 DOI: 10.1016/j.jmr.2025.107851
Giulia Fischetti , Nicolas Schmid , Simon Bruderer , Björn Heitmann , Andreas Henrici , Alessandro Scarso , Guido Caldarelli , Dirk Wilhelm
One-dimensional 1H Nuclear Magnetic Resonance (NMR) stands out as the quickest and simplest among various NMR experimental setups. Unfortunately, it suffers from lengthy annotation times and does not always have a clear and unique interpretation. From NMR discovery, efforts have been dedicated to introducing an automated approach to streamline the characterization of chemical compounds while ensuring consistency of the results across the scientific community. Nonetheless, this remains an ongoing challenge that has garnered renewed interest with the emergence of deep learning techniques. Here, we present MuSe Net, a novel supervised probabilistic deep learning framework that can emulate the tasks performed by an expert spectroscopist in annotating one-dimensional NMR spectra generated by small molecules. Considering only the spectrum, MuSe Net detects and classifies multiplets with up to four coupling constants for their splitting phenotype, providing a segmentation of the spectral range. We exploit uncertainty quantification to produce a confidence score to both assess classification reliability and to detect signals that do not fit into any other phenotype class. The results of the evaluation against 48 experimental 1H NMR spectra of small molecules annotated by experts demonstrate that MuSe Net can deal with anomalies and unclear signals while correctly classifying multiplets and detecting overlapping peaks.
一维1H核磁共振(NMR)是各种核磁共振实验装置中最快、最简单的。不幸的是,它的注释时间很长,而且并不总是有清晰和独特的解释。从核磁共振发现开始,人们一直致力于引入一种自动化的方法来简化化合物的表征,同时确保整个科学界结果的一致性。尽管如此,这仍然是一个持续的挑战,随着深度学习技术的出现,它重新引起了人们的兴趣。在这里,我们提出了MuSe Net,这是一个新的监督概率深度学习框架,可以模拟光谱专家在注释由小分子生成的一维核磁共振光谱时所执行的任务。仅考虑光谱,MuSe Net检测和分类具有多达四个耦合常数的多胞胎,用于其分裂表型,提供光谱范围的分割。我们利用不确定性量化来产生一个置信度评分,以评估分类可靠性并检测不适合任何其他表型类别的信号。对48个经专家注释的小分子1H NMR实验谱的评价结果表明,MuSe Net在处理异常和不清晰信号的同时,能够正确分类多联体并检测重叠峰。
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引用次数: 0
400 MHz/263 GHz ultra-low temperature MAS-DNP using a closed-cycle helium gas cooling system and a solid-state microwave source 400 MHz/263 GHz超低温MAS-DNP采用闭式循环氦气冷却系统和固态微波源
IF 2 3区 化学 Q3 BIOCHEMICAL RESEARCH METHODS Pub Date : 2025-02-06 DOI: 10.1016/j.jmr.2025.107842
Fumio Hobo , Yusuke Tanimoto , Yuki Endo , Yoh Matsuki , Hiroki Takahashi
Dynamic nuclear polarization (DNP) is widely used in a wide range of applications in solid-state NMR nowadays due to recent advancements of magic-angle spinning (MAS) DNP. Conventionally, an MAS-DNP system employs a gyrotron as a microwave source and operates at 100 K using nitrogen gas. As an alternative, we present a 400 MHz/263 GHz MAS-DNP system utilizing a compact solid-state microwave source and an ultra-low temperature (ULT) helium MAS probe equipped with a cryogenic preamplifier. Compared to gyrotrons, solid-state microwave sources are compact, cost-effective, and frequency agile. The ULT compensates for the decreased DNP efficiency resulting from the lower microwave power of the solid-state source. Additionally, the large Boltzmann polarization at ULT and the improved signal-to-noise ratio provided by the cryogenic preamplifier enhance the sensitivity of the MAS-DNP system. The system is tested using a DNP standard sample of proline in a mixture of deuterated glycerol and partially deuterated water doped with AMUPol, achieving a DNP enhancement of 85 using a 2 mm-diameter rotor at a sample temperature of 30 K and microwave power of 160 mW. Experimental data show that the Boltzmann polarization and the cryogenic preamplifier contribute an additional sensitivity gain of 11× at 30 K compared to 100 K. Overall, the ULT-DNP related sensitivity gain of this system is estimated to be roughly twice that of a 100 K gyrotron system, although the DNP enhancement factor alone is smaller using a solid-state microwave source.
由于魔角自旋(MAS)动态核极化(DNP)技术的发展,动态核极化(DNP)技术在固体核磁共振中得到了广泛的应用。传统上,MAS-DNP系统采用回旋管作为微波源,使用氮气在~ 100 K下工作。作为替代方案,我们提出了一种400 MHz/263 GHz MAS- dnp系统,该系统利用紧凑型固态微波源和配备低温前置放大器的超低温(ULT)氦MAS探头。与回旋管相比,固态微波源结构紧凑,成本效益高,频率灵活。ULT补偿了由于固体源的微波功率较低而导致的DNP效率下降。此外,低温前置放大器提供的大玻尔兹曼偏振和改进的信噪比提高了MAS-DNP系统的灵敏度。该系统使用脯氨酸DNP标准样品在掺有AMUPol的氘化甘油和部分氘化水的混合物中进行测试,在样品温度为30 K,微波功率为160 mW的条件下,使用直径为2 mm的转子实现DNP增强85。实验数据表明,与100 K相比,玻尔兹曼偏振和低温前置放大器在30 K下的灵敏度增益增加了11倍。总体而言,该系统的ULT-DNP相关灵敏度增益估计大约是100 K回旋管系统的两倍,尽管使用固态微波源的DNP增强因子较小。
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引用次数: 0
Diffusion coefficient measurements for moving samples under strong magnetic field gradients 强磁场梯度下移动样品的扩散系数测量。
IF 2 3区 化学 Q3 BIOCHEMICAL RESEARCH METHODS Pub Date : 2025-02-01 DOI: 10.1016/j.jmr.2025.107830
Agide Gimenez Marassi , Arthur Gustavo de Araújo-Ferreira , Everton Lucas-Oliveira , Aparecido Donizeti Fernandes de Amorim , Edson Luiz Géa Vidoto , Willian Andrighetto Trevizan , Tito José Bonagamba
Among the numerous measurements carried out during a well-logging procedure, the Nuclear Magnetic Resonance (NMR) assessment is one of the fundamental analyses in determining the economic viability of a well for the oil industry. Nowadays, two reliable approaches, Wireline Logging (WL) and Logging While Drilling (LWD), stand out. WL comprises the acquisition of NMR data under static conditions. On the other hand, in LWD, the NMR measurements happen simultaneously with the drilling process, while the NMR tool experiences translation, rotation, and vibration motions relative to the rock formation. In order to comprehend better the NMR response acquired under LWD conditions, a setup emulating an LWD tool was developed, consisting of a single-sided magnet, rf probes, and a mechanical device that emulates a relative sinusoidal movement between the sample and the applied magnetic field. A bulk sample and three representative rocks, Fontainebleau Sandstone, Berea Sandstone, and Indiana Limestone, were investigated. Even though the diffusion coefficient measurements remain neglected for their intrinsic characteristics of data acquisition, the findings demonstrate that the diffusion coefficient parameter of a fluid in a bulk sample or confined in a porous rock can be precise and accurately predicted. In strong magnetic field gradients, the Hahn spin echo is predominantly weighted by the diffusion process, an effect used to measure diffusion coefficients. Under LWD conditions, the diffusion coefficient measurement is considerably affected by signal phase modulation due to sample movement in the presence of strong magnetic field gradients, making this measurement difficult. This article present solutions for correct diffusion coefficient measurements, synchronizing Hahn spin echo experiments with sample movement.
在测井过程中进行的众多测量中,核磁共振(NMR)评估是确定石油工业油井经济可行性的基本分析之一。目前,有两种可靠的方法,即电缆测井(WL)和随钻测井(LWD),脱颖而出。WL包括静态条件下核磁共振数据的采集。另一方面,在随钻测井中,核磁共振测量与钻井过程同时进行,而核磁共振工具相对于岩层经历平移、旋转和振动运动。为了更好地理解随钻条件下获得的核磁共振响应,开发了一个模拟随钻工具的装置,该装置由单面磁铁、射频探头和一个模拟样品与外加磁场之间相对正弦运动的机械装置组成。研究了大量样品和三种代表性岩石,枫丹白露砂岩、伯里亚砂岩和印第安纳石灰岩。尽管扩散系数测量由于其数据采集的固有特性而被忽略,但研究结果表明,在散装样品中或在多孔岩石中限制的流体的扩散系数参数可以精确和准确地预测。在强磁场梯度中,哈恩自旋回波主要由扩散过程加权,这是一种用于测量扩散系数的效应。在随钻条件下,在强磁场梯度存在的情况下,试样移动引起的信号相位调制对扩散系数的测量有很大影响,使测量变得困难。本文提出了正确测量扩散系数、同步哈恩自旋回波实验和样品运动的解决方案。
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引用次数: 0
Double-quantum filtered 23Na NMR and MRI: Selective detection of ordered sodium in an inhomogeneous B0 field 双量子过滤23Na核磁共振和核磁共振:非均匀B0场中有序钠的选择性检测。
IF 2 3区 化学 Q3 BIOCHEMICAL RESEARCH METHODS Pub Date : 2025-02-01 DOI: 10.1016/j.jmr.2024.107810
Stephen Wimperis , Galina E. Pavlovskaya
Double-quantum filtered 23Na NMR experiments with one or two “magic angle” (54.7°) pulses in the filter step are widely used for selective observation of sodium ions that are interacting with ordered biological structures (“ordered sodium”) and hence exhibit a distribution of quadrupolar splittings in their NMR spectrum. This approach has recently been extended to 23Na MRI where the conventional experiment has been modified, omitting the 180° pulse to reduce the absorption of radiofrequency energy during human studies. Here, the “magic angle” double-quantum filtered 23Na NMR experiment (without a 180° pulse) is analysed in terms of coherence pathways that lead to refocusing in an inhomogeneous B0 field (“echoes”) and those that do not (“antiechoes”). It is shown that the echo and antiecho pathways can be separated by phase cycling and that the antiecho pathway contributes very little to the overall signal in an inhomogeneous B0 field. Hence, a double-quantum filtered 23Na NMR experiment that utilises just the echo pathway and so achieves complete refocusing of the effects of B0 inhomogeneity without making use of a 180° pulse is proposed. The new method is demonstrated both in 23Na NMR spectroscopy in an inhomogeneous B0 field and in 23Na MRI of a three-component phantom.
双量子过滤23Na核磁共振实验在过滤步骤中具有一个或两个“魔角”(54.7°)脉冲,广泛用于选择性观察与有序生物结构(“有序钠”)相互作用的钠离子,因此在其核磁共振光谱中表现出四极分裂的分布。这种方法最近被扩展到23Na MRI,其中传统的实验已经被修改,省略了180°脉冲,以减少人体研究期间射频能量的吸收。在这里,“魔角”双量子滤波23Na核磁共振实验(没有180°脉冲)分析了导致在非均匀B0场(“回波”)和那些不(“反回波”)重新聚焦的相干路径。结果表明,在非均匀B0场中,回波路径和反回波路径可以通过相位循环分离,并且反回波路径对整个信号的贡献很小。因此,提出了一种双量子滤波23Na核磁共振实验,该实验仅利用回波路径,从而在不使用180°脉冲的情况下实现B0不均匀性效应的完全重新聚焦。该方法在非均匀B0场的23Na核磁共振波谱和三组分模体的23Na核磁共振中得到了验证。
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引用次数: 0
1H–19F cross-polarization magic angle spinning dynamic nuclear polarization NMR investigation of advanced pharmaceutical formulations h - 19f交叉极化魔角自旋动态核极化核磁共振研究先进药物配方。
IF 2 3区 化学 Q3 BIOCHEMICAL RESEARCH METHODS Pub Date : 2025-02-01 DOI: 10.1016/j.jmr.2024.107827
Mária Šoltésová , Arthur C. Pinon , Fabien Aussenac , Judith Schlagnitweit , Christian Reiter , Armin Purea , Roberto Melzi , Frank Engelke , Dave Martin , Stefanie Krambeck , Annabelle Biscans , Emma Kay , Lyndon Emsley , Staffan Schantz
A new 3.2 mm 1H–19F–X magic angle spinning dynamic nuclear polarization NMR (MAS DNP-NMR) probe was developed with a unique coil design with separate radiofrequency channels for 1H excitation and 13C or 19F detection to enable acquisition of 1H–19F cross-polarization (CP) MAS experiments, direct-detected 19F spectra with proton decoupling, and acquisition on 13C with simultaneous double decoupling on the 1H and 19F channels as well as 1H–19F–13C double-CP experiments under low temperature MAS DNP conditions. We use these sequences to study AZD2811, which is an active pharmaceutical ingredient (API), in its pure dry state as well as in its corresponding drug delivery formulation consisting of drug-loaded polymeric nanoparticles (PNPs). Included in this study are also small interfering RNAs (siRNAs) for therapeutic targeting of peptidyl-prolyl cis–trans isomerase B (Ppib) mRNA. We demonstrate that 1H–19F CP MAS experiments performed on the new HFX probe represent a notable advantage over usually acquired direct-detected 19F experiments. The indirect 19F DNP enhancement εon/off(19F) = 26 was obtained via 1H–19F CP for the pure API impregnated with DNP solution, with an overall 30-fold sensitivity gain compared to the direct-detected 19F experiment under similar conditions. DNP enhancement value of εon/off(19F) = 42 was obtained via 1H–19F CP for the polymeric nanoparticle suspension and εon/off(19F) ≈ 150 were obtained for two different siRNAs in frozen DNP solution.
研制了一种新型3.2 mm 1H-19F- x魔角自旋动态核极化NMR (MAS DNP-NMR)探针,该探针具有独特的线圈设计,具有用于1H激励和13C或19F检测的独立射频通道,能够采集1H-19F交叉极化(CP) MAS实验,直接检测质子去耦的19F光谱。在1H和19F通道同时双去耦的13C采集以及低温MAS DNP条件下1H-19F-13C双cp实验。我们使用这些序列来研究AZD2811,它是一种活性药物成分(API),在其纯干燥状态下,以及由载药聚合物纳米颗粒(PNPs)组成的相应的给药配方。本研究还包括用于治疗肽酰脯氨酸顺式反式异构酶B (Ppib) mRNA的小干扰rna (sirna)。我们证明,在新的HFX探针上进行的1H-19F CP MAS实验比通常获得的直接检测19F实验具有显着优势。用1H-19F CP对浸有DNP溶液的纯API进行间接19F DNP增强,得到了间接19F DNP增强εon/off(19F) = 26,与在相同条件下直接检测19F实验相比,总体灵敏度提高了30倍。聚合物纳米颗粒悬浮液通过1H-19F CP得到DNP增强值εon/off(19F) = 42,两种sirna在DNP冷冻溶液中得到εon/off(19F)≈150。
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引用次数: 0
A thermally polarized, dissolved-phase 129Xe phantom for quality-control and multisite comparisons of gas-exchange imaging 用于气体交换成像质量控制和多位点比较的热极化、溶解相129Xe模体。
IF 2 3区 化学 Q3 BIOCHEMICAL RESEARCH METHODS Pub Date : 2025-02-01 DOI: 10.1016/j.jmr.2025.107829
Matthew M. Willmering , Brice J. Albert , Joseph W. Plummer , Josh Greer , Laura L. Walkup , Diana M. Lindquist , Zackary I. Cleveland
Harmonizing and validating 129Xe gas exchange imaging across multiple sites is hampered by a lack of a quantitative standard that 1) displays the unique spectral properties of 129Xe observed from human subjects in vivo and 2) has short enough T1 times to enable practical imaging. This work describes and demonstrates the development of two dissolved-phase, thermally polarized phantoms that mimic the in-vivo, red blood cell and membrane resonances of 129Xe dissolved in human lungs. Following optimization, combinations of two common organic solvents, acetone and dimethyl sulfoxide, resulted in two in-vivo-like dissolved-phase 129Xe phantoms yielding chemical shifts of 212.4 ppm and 193.9 ppm. By doping the solutions with iron(iii) acetylacetonate, the longitudinal relaxation time was reduced T1 = 1.2 s for both phantoms at 3 T and 7 T. There was minimal change in chemical shift (+1.58 ppm) and T1 (+1.2 %) over 1 year. In a 2D Dixon-type acquisition with 3 mm2 in-plane resolution, 129Xe dissolved-phase images yielded signal-to-noise ratios 6 and 12 for the RBC and membrane phantoms, respectively. A simple scaling of these phantoms to clinically relevant volumes of several liters would result in an SNR of 7 for the RBC phantom acquired in less than one minute. These findings demonstrate the ability to fabricate robust, quantitative, thermally polarized dissolved-phase phantoms, which will be needed to validate and harmonize gas exchange imaging in multi-site clinical trials.
协调和验证跨多个位点的129Xe气体交换成像受到缺乏定量标准的阻碍:1)显示从人体受试者体内观察到的129Xe的独特光谱特性;2)具有足够短的T1时间以实现实际成像。这项工作描述并展示了两种溶解相、热极化幻象的发展,这些幻象模拟了溶解在人肺中的129Xe的体内、红细胞和膜共振。优化后,两种常见的有机溶剂丙酮和二甲亚砜的组合产生了两种体内样的溶解相129Xe幻象,化学位移为212.4 ppm和193.9 ppm。通过在溶液中掺入乙酰丙酮铁(iii),在3 T和7 T时,两种模态的纵向弛豫时间都缩短了T1 = 1.2 s。在1年内,化学位移(+1.58 ppm)和T1(+ 1.2%)的变化最小。在平面内分辨率为3mm2的二维dixon型采集中,129Xe溶解相图像的RBC和膜影的信噪比分别为6和12。将这些幻影简单地缩放到临床相关的几升体积,将导致在不到一分钟内获得的RBC幻影的信噪比为7。这些发现证明了制造稳健的、定量的、热极化的溶解相幻象的能力,这将需要在多地点临床试验中验证和协调气体交换成像。
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引用次数: 0
Pseudo-3D HSQC0, a method to create a true 2D HSQC0-plane. Application to softwood extract analysis 伪3d HSQC0,一个创建一个真正的二维HSQC0平面的方法。在软木提取物分析中的应用。
IF 2 3区 化学 Q3 BIOCHEMICAL RESEARCH METHODS Pub Date : 2025-02-01 DOI: 10.1016/j.jmr.2024.107825
Maarit H. Lahtinen , Tuomas Niemi-Aro , Danila Morais de Carvalho , Kirsi S. Mikkonen , Ilkka Kilpeläinen , Sami Heikkinen
Pseudo-3D HSQC0 provides an alternative and easy way to record and analyze quantitative HSQC0-data. In the original time-zero extrapolated 1H–13C HSQC (HSQC0), three separate 2D constant-time (CT) HSQC-experiments (HSQCi, i = 1–3) are acquired, where either 1,2 or 3 consecutive CT-HSQC-propagators are repeated in each pulse sequence, and the 2D integral data from the three 2D experiments is analyzed via linear regression. In the presented pseudo-3D HSQC0, HSQCi is one of the dimensions and all data is contained within one dataset, which is recorded in interleaved manner by acquiring the same t1-value for each HSQCi-point before t1-incrementation. The 3D-nature of the data allows the utilization of backward linear prediction to calculate an actual time-zero 2D HSQC0 spectrum, which can be analyzed using normal 2D integration procedures for quantitative results. In all, the pseudo-3D enables straightforward, intuitive and easy analysis of the quantitative 2D HSQC0 spectrum/plane. As the recorded pseudo 3D data contains the normal HSQCi planes, also the classic linear regression analysis can be applied.
伪3d HSQC0提供了一种记录和分析定量HSQC0数据的简便方法。在原始的时间零外推1H-13C HSQC (HSQC0)中,获得3个独立的二维恒定时间(CT) HSQC实验(HSQCi, i = 1-3),在每个脉冲序列中重复1、2或3个连续的CT-HSQC传播子,并对3个二维实验的二维积分数据进行线性回归分析。在本文提出的伪三维HSQC0中,HSQCi是其中一个维度,所有数据都包含在一个数据集中,通过在t1递增之前对每个HSQCi点获取相同的t1值,以交错方式记录。数据的3d性质允许利用反向线性预测来计算实际的时间零二维HSQC0光谱,可以使用正常的二维积分程序进行分析以获得定量结果。总之,伪3d可以直接,直观和轻松地分析定量二维HSQC0光谱/平面。由于记录的伪三维数据包含正常的HSQCi平面,因此也可以应用经典的线性回归分析。
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引用次数: 0
Spatially constrained hyperpolarized 13C MRI pharmacokinetic rate constant map estimation using a digital brain phantom and a U-Net 利用数字脑幻影和U-Net估算空间受限超极化13C MRI药代动力学速率常数图。
IF 2 3区 化学 Q3 BIOCHEMICAL RESEARCH METHODS Pub Date : 2025-02-01 DOI: 10.1016/j.jmr.2025.107832
Sule Sahin , Anna Bennett Haller , Jeremy Gordon , Yaewon Kim , Jasmine Hu , Tanner Nickles , Qing Dai , Andrew P. Leynes , Daniel B. Vigneron , Zhen Jane Wang , Peder E.Z. Larson
Fitting rate constants to Hyperpolarized [1-13C]Pyruvate (HP C13) MRI data is a promising approach for quantifying metabolism in vivo. Current methods typically fit each voxel of the dataset using a least-squares objective. With these methods, each voxel is considered independently, and the spatial relationships are not considered during fitting.
In this work, we use a convolutional neural network, a U-Net, with convolutions across the 2D spatial dimensions to estimate pyruvate-to-lactate conversion rate, kPL, maps from dynamic HP C13 datasets. We designed a framework for creating simulated anatomically accurate brain data that matches typical HP C13 characteristics to provide large amounts of data for training with ground truth results. The U-Net is initially trained with the digital phantom data and then further trained with in vivo datasets for regularization.
In simulation where ground-truth kPL maps are available, the U-Net outperforms voxel-wise fitting with and without spatiotemporal denoising, particularly for low SNR data. In vivo data was evaluated qualitatively, as no ground truth is available, and before regularization the U-Net predicted kPL maps appear oversmoothed. After further training with in vivo data, the resulting kPL maps appear more realistic.
This study demonstrates how to use a U-Net to estimate rate constant maps for HP C13 data, including a comprehensive framework for generating a large amount of anatomically realistic simulated data and an approach for regularization. This simulation and architecture provide a foundation that can be built upon in the future for improved performance.
将速率常数拟合到超极化[1-13C]丙酮酸(HP C13) MRI数据中是一种很有前景的体内代谢量化方法。目前的方法通常使用最小二乘目标来拟合数据集的每个体素。在这些方法中,每个体素都是独立考虑的,在拟合过程中不考虑空间关系。在这项工作中,我们使用卷积神经网络,即U-Net,在二维空间维度上进行卷积,以估计动态HP C13数据集的丙酮酸-乳酸转化率(kPL)图。我们设计了一个框架,用于创建模拟解剖学上准确的大脑数据,该数据与典型的HP C13特征相匹配,为训练提供大量具有真实结果的数据。U-Net最初使用数字幻影数据进行训练,然后使用体内数据集进行进一步训练以进行正则化。在地面真实kPL地图可用的模拟中,U-Net在有无时空去噪的情况下都优于体素拟合,特别是对于低信噪比数据。体内数据进行了定性评估,因为没有真实的基础,并且在正则化之前,U-Net预测的kPL地图显得过于平滑。经过体内数据的进一步训练,得到的kPL图看起来更加真实。本研究演示了如何使用U-Net来估计HP C13数据的速率常数图,包括一个用于生成大量解剖学逼真模拟数据的综合框架和一种正则化方法。这种模拟和体系结构为将来改进性能提供了基础。
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引用次数: 0
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Journal of magnetic resonance
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