Journal of magnetic resonance最新文献

{"title":"Full determination of chemical shift tensor in magnetically oriented microcrystals with modulated rotation and temporal tilt","authors":"Ryosuke Kusumi ,&nbsp;Hayate Yasui ,&nbsp;Hiroshi Kadoma ,&nbsp;Masahisa Wada ,&nbsp;Kazuyuki Takeda","doi":"10.1016/j.jmr.2025.107853","DOIUrl":"10.1016/j.jmr.2025.107853","url":null,"abstract":"<div><div>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 <span>l</span>-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.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"373 ","pages":"Article 107853"},"PeriodicalIF":2.0,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143519875","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":"Implementation of the X-centric pulse sequence at low field for MRI of water penetration in clay","authors":"Samuel Perron ,&nbsp;Claire S. Tully ,&nbsp;Shivam Gupta ,&nbsp;Matthew S. Fox ,&nbsp;Dmitrij Zagidulin ,&nbsp;James J. Noël ,&nbsp;Alexei Ouriadov","doi":"10.1016/j.jmr.2025.107852","DOIUrl":"10.1016/j.jmr.2025.107852","url":null,"abstract":"<div><div>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 <em>T</em>_<em>2</em>^<em>⁎</em> of this water to decrease drastically, from seconds to less than a millisecond. The longer <em>T</em>_<em>2</em>^<em>⁎</em> 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-<em>T</em>_<em>2</em>^<em>⁎</em> samples would permit imaging of porous rocks and concrete.</div><div>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 <em>k</em>-space is acquired separately, from the centre outwards in the readout direction, ensuring minimal <em>T</em>_<em>2</em>^<em>⁎</em>-weighting of the resulting image and allowing for 2D imaging within the short time frame of the shorter <em>T</em>_<em>2</em>^<em>⁎</em> of water in the clay. Bulk relaxation measurements of <em>T</em>_<em>2</em>^<em>⁎</em> and the longitudinal relaxation time <em>T</em>_<em>1</em> were performed for increasing water content, with a mean <em>T</em>_<em>1</em> of 12.0 ± 1.1 ms and mean <em>T</em>_<em>2</em>^<em>⁎</em> of 4.5 ± 0.7 ms; 2D imaging of the clay sample was performed with both GE and X-Centric. In addition, a 2D <em>T</em>_<em>2</em>^<em>⁎</em> map was generated from eight X-Centric images taken at different echo times.</div><div>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 <em>T</em>_<em>2</em>^<em>⁎</em> weighting of the <em>k</em>-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 <em>T</em>_<em>2</em>^<em>⁎</em>-decay is a potentially significant source of signal decay.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"373 ","pages":"Article 107852"},"PeriodicalIF":2.0,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143437930","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 deep learning framework for multiplet splitting classification in 1H NMR","authors":"Giulia Fischetti ,&nbsp;Nicolas Schmid ,&nbsp;Simon Bruderer ,&nbsp;Björn Heitmann ,&nbsp;Andreas Henrici ,&nbsp;Alessandro Scarso ,&nbsp;Guido Caldarelli ,&nbsp;Dirk Wilhelm","doi":"10.1016/j.jmr.2025.107851","DOIUrl":"10.1016/j.jmr.2025.107851","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"373 ","pages":"Article 107851"},"PeriodicalIF":2.0,"publicationDate":"2025-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143444601","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":"400 MHz/263 GHz ultra-low temperature MAS-DNP using a closed-cycle helium gas cooling system and a solid-state microwave source","authors":"Fumio Hobo ,&nbsp;Yusuke Tanimoto ,&nbsp;Yuki Endo ,&nbsp;Yoh Matsuki ,&nbsp;Hiroki Takahashi","doi":"10.1016/j.jmr.2025.107842","DOIUrl":"10.1016/j.jmr.2025.107842","url":null,"abstract":"<div><div>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 <span><math><mo>∼</mo></math></span>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<span><math><mo>×</mo></math></span> 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.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"373 ","pages":"Article 107842"},"PeriodicalIF":2.0,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143387540","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":"Diffusion coefficient measurements for moving samples under strong magnetic field gradients","authors":"Agide Gimenez Marassi ,&nbsp;Arthur Gustavo de Araújo-Ferreira ,&nbsp;Everton Lucas-Oliveira ,&nbsp;Aparecido Donizeti Fernandes de Amorim ,&nbsp;Edson Luiz Géa Vidoto ,&nbsp;Willian Andrighetto Trevizan ,&nbsp;Tito José Bonagamba","doi":"10.1016/j.jmr.2025.107830","DOIUrl":"10.1016/j.jmr.2025.107830","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"371 ","pages":"Article 107830"},"PeriodicalIF":2.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142981057","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":"Double-quantum filtered 23Na NMR and MRI: Selective detection of ordered sodium in an inhomogeneous B0 field","authors":"Stephen Wimperis ,&nbsp;Galina E. Pavlovskaya","doi":"10.1016/j.jmr.2024.107810","DOIUrl":"10.1016/j.jmr.2024.107810","url":null,"abstract":"<div><div>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.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"371 ","pages":"Article 107810"},"PeriodicalIF":2.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142911313","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":"1H–19F cross-polarization magic angle spinning dynamic nuclear polarization NMR investigation of advanced pharmaceutical formulations","authors":"Mária Šoltésová ,&nbsp;Arthur C. Pinon ,&nbsp;Fabien Aussenac ,&nbsp;Judith Schlagnitweit ,&nbsp;Christian Reiter ,&nbsp;Armin Purea ,&nbsp;Roberto Melzi ,&nbsp;Frank Engelke ,&nbsp;Dave Martin ,&nbsp;Stefanie Krambeck ,&nbsp;Annabelle Biscans ,&nbsp;Emma Kay ,&nbsp;Lyndon Emsley ,&nbsp;Staffan Schantz","doi":"10.1016/j.jmr.2024.107827","DOIUrl":"10.1016/j.jmr.2024.107827","url":null,"abstract":"<div><div>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 <em>cis–trans</em> isomerase B (<em>Ppib</em>) 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 ε_on/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 ε_on/off(¹⁹F) = 42 was obtained via ¹H–¹⁹F CP for the polymeric nanoparticle suspension and ε_on/off(¹⁹F) ≈ 150 were obtained for two different siRNAs in frozen DNP solution.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"371 ","pages":"Article 107827"},"PeriodicalIF":2.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142967669","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 thermally polarized, dissolved-phase 129Xe phantom for quality-control and multisite comparisons of gas-exchange imaging","authors":"Matthew M. Willmering ,&nbsp;Brice J. Albert ,&nbsp;Joseph W. Plummer ,&nbsp;Josh Greer ,&nbsp;Laura L. Walkup ,&nbsp;Diana M. Lindquist ,&nbsp;Zackary I. Cleveland","doi":"10.1016/j.jmr.2025.107829","DOIUrl":"10.1016/j.jmr.2025.107829","url":null,"abstract":"<div><div>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 <em>in vivo</em> and 2) has short enough <span><math><msub><mi>T</mi><mn>1</mn></msub></math></span> times to enable practical imaging. This work describes and demonstrates the development of two dissolved-phase, thermally polarized phantoms that mimic the <em>in-vivo</em>, 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 <em>in-vivo</em>-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 <span><math><msub><mi>T</mi><mn>1</mn></msub></math></span> = 1.2 s for both phantoms at 3 T and 7 T. There was minimal change in chemical shift (+1.58 ppm) and <span><math><msub><mi>T</mi><mn>1</mn></msub></math></span> (+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.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"371 ","pages":"Article 107829"},"PeriodicalIF":2.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142985694","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":"Pseudo-3D HSQC0, a method to create a true 2D HSQC0-plane. Application to softwood extract analysis","authors":"Maarit H. Lahtinen ,&nbsp;Tuomas Niemi-Aro ,&nbsp;Danila Morais de Carvalho ,&nbsp;Kirsi S. Mikkonen ,&nbsp;Ilkka Kilpeläinen ,&nbsp;Sami Heikkinen","doi":"10.1016/j.jmr.2024.107825","DOIUrl":"10.1016/j.jmr.2024.107825","url":null,"abstract":"<div><div>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 (HSQC_i, <em>i</em> = 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, HSQC_i 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 HSQC_i-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 HSQC_i planes, also the classic linear regression analysis can be applied.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"371 ","pages":"Article 107825"},"PeriodicalIF":2.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142904576","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":"Spatially constrained hyperpolarized 13C MRI pharmacokinetic rate constant map estimation using a digital brain phantom and a U-Net","authors":"Sule Sahin ,&nbsp;Anna Bennett Haller ,&nbsp;Jeremy Gordon ,&nbsp;Yaewon Kim ,&nbsp;Jasmine Hu ,&nbsp;Tanner Nickles ,&nbsp;Qing Dai ,&nbsp;Andrew P. Leynes ,&nbsp;Daniel B. Vigneron ,&nbsp;Zhen Jane Wang ,&nbsp;Peder E.Z. Larson","doi":"10.1016/j.jmr.2025.107832","DOIUrl":"10.1016/j.jmr.2025.107832","url":null,"abstract":"<div><div>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.</div><div>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, k_PL, 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.</div><div>In simulation where ground-truth k_PL 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 k_PL maps appear oversmoothed. After further training with in vivo data, the resulting k_PL maps appear more realistic.</div><div>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.</div></div>","PeriodicalId":16267,"journal":{"name":"Journal of magnetic resonance","volume":"371 ","pages":"Article 107832"},"PeriodicalIF":2.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143019058","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}