NMR in Biomedicine最新文献

{"title":"Structural Characterization of Cardiac Free-Running Purkinje Fibers Using Inhomogeneous Magnetization Transfer (ihMT): A Proof of Concept MRI-Histology Approach.","authors":"Arash Forodighasemabadi, Evgenios N Kornaropoulos, Marion Constantin, Lucas Soustelle, Fanny Vaillant, Jude Leury, Richard Walton, Olivier Bernus, Bruno Quesson, Olivier M Girard, Guillaume Duhamel, Julie Magat","doi":"10.1002/nbm.70289","DOIUrl":"10.1002/nbm.70289","url":null,"abstract":"<p><p>The cardiac Purkinje network plays a critical role in maintaining synchronized ventricular activation but remains difficult to image due to its fine and complex structure. Conventional MRI techniques lack sufficient contrast to distinguish the structural composition of Purkinje fibers (PFs). This study investigates the potential of inhomogeneous magnetization transfer (ihMT) as a novel contrast mechanism for visualizing and differentiating subregions of the Purkinje network. Five fixed ex vivo sheep hearts containing free-running PFs were scanned using a 9.4 T MRI system with a 2D ihMT RARE sequence. ihMTR maps were analyzed using manually defined regions of interest (ROIs) corresponding to free-running fibers, the Purkinje-myocardial junction (PMJ), and the surrounding myocardium. Histological analysis was performed on matched tissue sections to quantify collagen types I and III, adipocytes, Purkinje cells, and cardiomyocytes. Three ihMT protocols that produced high ihMTR values in free-running fibers (9.25-10.83%) and strong contrast relative to myocardium (2.00-2.17%) and the PMJ (2.99-3.40%) in 1 sample were selected and applied to all samples. Across all hearts, mean ihMTR values were consistently higher in free-running fibers compared to the PMJ (11.5 ± 1.5% vs 9.0 ± 2.9%). Histological analysis revealed significantly greater collagen content in free-running regions compared with the PMJ (72.4 ± 15.9% vs 31.1 ± 13.1%; p = 0.001), along with higher adipocyte content at the PMJ compared to free-running regions (12.3 ± 6.1% vs 3.8 ± 2.7%, not significant). Collagen type III was more prominent at the PMJ but remained a minor component overall. These findings demonstrate that ihMT imaging can distinguish PF subregions based on underlying microstructural differences, particularly collagen and adipocyte distribution. This study lays the groundwork for developing biophysical models to interpret ihMT signals in terms of tissue composition and microstructure, providing a foundation for future studies.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 6","pages":"e70289"},"PeriodicalIF":2.8,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13092648/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147723366","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Open-Source Multinuclear Low-Field Preclinical MRI Scanner.","authors":"Gonzalo G Rodriguez, Sergey Korchak, Charlotte von Petersdorff-Campen, Oscar Sucre, Jan Felger, Ruhuai Mei, Stefan Glöggler","doi":"10.1002/nbm.70291","DOIUrl":"10.1002/nbm.70291","url":null,"abstract":"<p><p>Low-field MRI (B₀ ≤ 0.2 T) is emerging as a technology with the potential to revolutionize clinical diagnostics and patient monitoring. The reduction in magnetic field strength comes along with a decrease in the cost of the scanners and the infrastructure required for their operation. This, in turn, enables the development of compact, portable systems that extend imaging capabilities to locations and scenarios that were previously inaccessible. This democratization has empowered research groups worldwide to design and build their own scanners, resulting in a surge of new devices. However, the majority of low-field scanners are optimized for human studies, which limits their application in preclinical research and constrains the testing and development of contrast agents tailored for low-field regimes. In particular, hyperpolarized agents hold considerable promise for low-field MRI due to their capacity to enhance signal and provide metabolic imaging of living systems. This signal enhancement counteracts the inherently low signal-to-noise ratio of thermally polarized studies, which is the main limitation of low-field MRI. To exploit this potential, hyperpolarization studies frequently require the detection of X-nuclei, such as ¹³C and ¹⁵N, thereby emphasizing the need for versatile, multinuclear preclinical scanners. In this study, we present an open-source multinuclear low-field MRI scanner that has been specifically designed for hyperpolarized preclinical research. The device operates at 66 mT and allows the detection of ¹H, ²³Na, ¹³C, and ¹⁵N nuclei. Comprehensive documentation and complete CAD designs are provided to facilitate replication and adaptation by the research community. To illustrate the performance of the system, the results of the acquisition of NMR spectra from each nucleus are presented, as well as the first images obtained with the scanner. This platform aims to bridge the gap in preclinical low-field MRI, enabling rigorous in vivo testing of novel contrast agents and supporting broader innovation in the field.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 6","pages":"e70291"},"PeriodicalIF":2.8,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13112055/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147777445","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Breaking the Limits of Low-Field MRI: Deep Learning Approaches to Image Enhancement.","authors":"Xuanyu Zhu, Yun Shang, Hsin-Jung Yang, Lei Yang, Ziyang Long, Hongfu Sun, Fuchun Lin, Xin Zhou, Hui Han","doi":"10.1002/nbm.70285","DOIUrl":"10.1002/nbm.70285","url":null,"abstract":"<p><p>Low-field magnetic resonance imaging (LF-MRI) has emerged as a transformative technology, offering portable and cost-effective solutions for medical imaging in resource-limited settings. However, LF-MRI systems face inherent challenges, including low signal-to-noise ratio (SNR) and reduced spatial resolution, which can compromise diagnostic accuracy. To systematically address these fundamental limitations, which involve complex, nonlinear image transformations, deep learning (DL) presents a powerful solution due to its proven capability in learning such mappings from data. This review explores the pivotal role of DL techniques in overcoming these limitations, focusing on two critical applications: denoising and super-resolution. Recent advancements in DL architectures-such as U-Net, generative adversarial networks (GANs), and diffusion models (DMs)-have demonstrated remarkable success in enhancing LF-MRI image quality. For denoising, supervised models like U-Net and denoising auto-encoders (DAEs) effectively suppress noise while preserving anatomical details, while unsupervised approaches (e.g., Cycle-GANs) leverage unpaired datasets to bridge the gap between low-field (LF) and high-field (HF) MRI. In super-resolution, DL models like 3D U-Net and residual channel attention networks (RCANs) reconstruct high-resolution images from LF inputs, enabling finer detail visualization for clinical diagnostics. Key findings highlight the superiority of DL over conventional iterative methods in adaptability, robustness, and real-time performance. However, challenges persist, including data dependency, computational costs, and limited interpretability. Innovations such as diffusion-driven neural representations and dual-acquisition 3D super-resolution further push the boundaries of LF-MRI quality. This review underscores DL's potential to democratize MRI access, particularly in low-resource regions, while outlining future directions: improving generalization, reducing training data requirements, and integrating postprocessing pipelines. By directly tackling the key barriers of image quality, DL-enhanced LF-MRI is poised to make a significant impact in clinical scenarios where accessibility and speed are paramount, such as point-of-care diagnostics and emergency clinic, thereby helping bridge global healthcare disparities.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 6","pages":"e70285"},"PeriodicalIF":2.8,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147777396","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"In Vivo Imaging With a Low-Cost MRI Scanner and Cloud Data Processing in Low-Resource Settings.","authors":"Teresa Guallart-Naval, Robert Asiimwe, Patricia Tusiime, Mary A Nassejje, Leo Kinyera, Lemi Robin, Maureen Nayebare, Luiz G C Santos, Marina Fernández-García, Lucas Swistunow, José M Algarín, John Stairs, Michael Hansen, Ronald Amodoi, Andrew Webb, Joshua Harper, Steven J Schiff, Johnes Obungoloch, Joseba Alonso","doi":"10.1002/nbm.70293","DOIUrl":"10.1002/nbm.70293","url":null,"abstract":"<p><p>The goal of this work is to demonstrate in vivo imaging with a low-cost, low-field MRI scanner built and operated in Africa and to show how systematic hardware and software improvements can mitigate the main operational limitations encountered in low-resource environments. To this end, a 46-mT Halbach scanner located at the Mbarara University of Science and Technology (Uganda) was upgraded through a complete reorganization of grounding and shielding, installation of new control electronics, and open-source user-interface software. Noise performance was quantified using a standardized protocol and in vivo brain images were acquired with three-dimensional RARE sequences. Distortion correction was implemented using cloud-based reconstructions incorporating magnetic field maps. The revamped system reached noise levels routinely below three times the thermal limit and demonstrated stable operation over multi-day measurements. Three-dimensional T <math> <semantics> <mrow><msub><mrow></mrow> <mrow><mn>1</mn></mrow> </msub> </mrow> <annotation>$$ {}_1 $$</annotation></semantics> </math> - and T <math> <semantics> <mrow><msub><mrow></mrow> <mrow><mn>2</mn></mrow> </msub> </mrow> <annotation>$$ {}_2 $$</annotation></semantics> </math> -weighted brain images were successfully acquired and distortion-corrected with remote GPU-based reconstructions and near real-time visualization through the user interface. The results show that low-cost MRI systems can achieve clinically relevant image quality when electromagnetic noise and power-grid instabilities are properly addressed. This work highlights the feasibility of sustainable MRI development in low-resource settings and identifies stable power delivery and local capacity building as the key next steps toward clinical translation.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 6","pages":"e70293"},"PeriodicalIF":2.8,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13093243/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147723395","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Z-Score Template Method for Person-Specific Augmentation of Clinical Brain MRI: An Investigation in Multiple Sclerosis.","authors":"Olayinka Oladosu, Rehman Tariq, Shayan Shahrokhi, Yunyan Zhang","doi":"10.1002/nbm.70313","DOIUrl":"10.1002/nbm.70313","url":null,"abstract":"<p><p>Clinical MRI is essential for managing neurological disorders such as multiple sclerosis (MS) but often inconsistent, limiting secondary analyses for enhanced information characterization. Our goal was to establish a new Z-score template method for person-specific image augmentation, as compared to a common deep learning approach termed cycle generative adversarial network (CycleGAN), and test their utility using a treatment response predicting example in MS. We examined 148 MS participants (102 females) from two cohorts, 104 and 44, respectively, with equivalent sex ratio and age, and each included T1-weighted, T2-weighted, and fluid attenuated inversion recovery (FLAIR) brain MRI. The 104/148 participants were used for method development and 44/148 for held-out testing. Z-score templates were constructed using different sample sizes to compare. Z scores from the best template were used to create person- and sequence-specific images. Similar experiments were done using CycleGAN along with tests using the same cohort. Image quality was assessed using peak signal-to-noise ratio, structural similarity index, and root mean square error. Utility testing applied ResNet50-based deep learning models with cycling of the typically unavailable T1-weighted MRI. We found that Z-score template constructed with 75 individuals was the best. Using existing images, potentially unavailable MRI could be created using either method investigated. At an individual level, Z-score template synthesis was equivalent to CycleGAN results. Further, models trained with synthetic or source T1-weighted images achieved similar accuracies (0.82-0.84 ± 0.04 vs. 0.84 ± 0.02) in tests of treatment response prediction. Without using T1-weighted MRI, the model accuracy decreased to 0.72, and AUC decreased below chance. Overall, Z-score template appeared to be a competitive method for person-specific brain MRI augmentation, and synthesized images such as T1-weighted brain MRI have the potential to support downstream applications as seen in prediction of treatment response in MS.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 6","pages":"e70313"},"PeriodicalIF":2.8,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147974067","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Optimal Control-Based Generic Framework for Radiofrequency Pulse Design in MRI.","authors":"Emilio Molina, Hélène Ratiney, Eric Van Reeth","doi":"10.1002/nbm.70307","DOIUrl":"10.1002/nbm.70307","url":null,"abstract":"<p><p>This work proposes a general framework for the optimal design of radiofrequency pulses in MRI. Based on optimal control theory, it proposes a Python-based numerical implementation using state-of-the-art nonlinear optimization solver (IPOPT). This study proposes three main contributions. It allows the incorporation of hard constraints to the problem and their consistent integration into the optimization process. It proposes to express the pulse as wavelet coefficients which proves to be highly effective in an applicative context. Finally, an innovative approach to minimize the pulse peak amplitude is presented by taking advantage of the efficient constraint management. The proposed framework is made available through a Python package, along with Jupyter Notebooks to reproduce the paper results. It also allows external users to solve their own design problem, benefiting from the generality and flexibility of the proposed implementation. The efficacy of the proposed method is validated in the context of short- <math> <semantics> <mrow> <msub><mrow><mi>T</mi></mrow> <mrow><mn>2</mn></mrow> </msub> </mrow> <annotation>$$ {T}_2 $$</annotation></semantics> </math> selective excitation and <math> <semantics> <mrow> <msub><mrow><mi>B</mi></mrow> <mrow><mn>1</mn></mrow> </msub> </mrow> <annotation>$$ {B}_1 $$</annotation></semantics> </math> -robust problems, with a primary focus on power and energy minimization. The optimized pulses provide a substantial enhancement regarding the compromise between energy/peak power and overall pulse performances, when compared to state-of-the-art solutions.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 6","pages":"e70307"},"PeriodicalIF":2.8,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13156480/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147856784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Preclinical Quantitative In Vivo MRI Assessment of Exogenous Surfactant Pulmonary Distribution After Clinically Relevant Intratracheal Delivery.","authors":"Oumaima Marfouk, Rémy Gérard, Ghalia Kaouane, Lara Leclerc, Noël Pinaud, Michael Fayon, Sophie Périnel-Ragey, Jérémie Pourchez, Eric Dumas De La Roque, Yannick Crémillieux","doi":"10.1002/nbm.70300","DOIUrl":"10.1002/nbm.70300","url":null,"abstract":"<p><p>Optimizing pulmonary exogenous surfactant delivery remains a critical challenge in neonatal care, particularly for achieving uniform distal lung deposition while minimizing airway obstruction. This study aimed to establish a preclinical imaging framework for quantitative assessment of exogenous surfactant lung distribution in vivo using contrast-enhanced ultrashort echo time (UTE) MRI and to evaluate the impact of physiological processes on surfactant retention and localization. Six juvenile rabbits received intratracheal instillation of a gadolinium-enhanced surfactant solution under clinically relevant conditions. High-resolution, motion-robust 3D UTE MRI datasets were acquired, enabling voxel-wise quantification of signal enhancement, gadolinium concentration, and spatial surfactant lung distribution. Peripheral volume fraction, laterality index, and distality index were computed to characterize deposition homogeneity and distal penetration. In vivo measurements were compared with previously reported ex vivo data from isolated rabbit thoraces. Quantitative MRI enabled precise mapping of surfactant within peripheral alveolar regions. Forty-two percent of the instilled dose was retained in vivo, compared with 93.5% ex vivo. Laterality indices confirmed balanced right-left distribution, while distality indices demonstrated consistent peripheral deposition. The radial UTE sequence minimized motion artifacts and enabled robust voxel-wise quantification under physiological breathing conditions. Quantitative in vivo MRI provides a sensitive and reliable method for assessing pulmonary surfactant delivery, spatial distribution, distal penetration, and homogeneity of deposition. Comparison with ex vivo data underscores the role of physiological processes in surfactant retention. This framework supports optimization of administration strategies in preclinical models and may be extended to other intrapulmonary therapies, establishing a versatile imaging platform for translational research.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 6","pages":"e70300"},"PeriodicalIF":2.8,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13107092/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147777372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Lactate Changes Quantified by fMRS: A Meta-Analysis.","authors":"Luca Cairone, Maria Guidi, Matteo Mancini, Federico Giove","doi":"10.1002/nbm.70295","DOIUrl":"10.1002/nbm.70295","url":null,"abstract":"<p><p>Over the past 15 years, the number of studies employing functional magnetic resonance spectroscopy (fMRS) has tripled, driven in part by improvements in scanner performance and a growing interest in the investigation of metabolic dynamics associated with the modulation of brain activity. Higher static magnetic fields, enhancements in gradient strength and stability, more sensitive RF coil designs, and refinements in quantification approaches have considerably increased spectral quality and temporal resolution. Together, these developments have further strengthened the unique ability of fMRS to monitor in vivo metabolic changes. Given its role in oxidative metabolism and its relevance in brain energetics, lactate (Lac) is one of the most studied metabolites, following the most important excitatory (glutamate [Glu]) and inhibitory (GABA) neurotransmitters. This meta-analysis aims to obtain an estimate of mean Lac changes in the healthy human brain during a task, by grouping together the papers published to date according to magnetic field strength, spectroscopic sequence echo time, and task design. Across all included studies, an increase in Lac concentration during stimulation is reported by all the papers included in this meta-analysis, with a statistically significant increase between the stimulation and rest periods of 22%. Studies using visual stimuli reported a significantly higher increase of Lac compared to studies employing motor or cognitive tasks. No significant differences emerged between studies at different magnetic field strengths or echo times. This meta-analysis, however, revealed a substantial methodological heterogeneity, highlighting the need for greater standardization in fMRS methodologies.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 6","pages":"e70295"},"PeriodicalIF":2.8,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13137767/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147818293","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Data-Driven Characterization of Knee Structures Using Non-Negative Matrix Factorization of 3D Multi-Echo UTE MRI.","authors":"Céline Smekens, Pieter Van Dyck, Patrick S Fuchs, Jan Sijbers, Thomas Janssens, Ben Jeurissen","doi":"10.1002/nbm.70299","DOIUrl":"10.1002/nbm.70299","url":null,"abstract":"<p><p>T₂* quantification based on multi-echo ultrashort echo time (UTE) MRI has been widely proposed for knee tissue characterization, yet accurate model-based parameter estimation remains challenging due to ill-conditioning of the corresponding inverse problems. Alternatively, data-driven methods such as non-negative matrix factorization (NMF) can derive tissue features without relying on biophysical model assumptions. This study aimed to investigate the use of an NMF-based framework informed by 3D multi-echo UTE MRI for multi-compartmental analysis of healthy and impaired knee structures. To this end, six asymptomatic adults and 13 patients underwent 3-T MRI, including routine anatomical sequences, and a 3D UTE spiral research sequence with six echo times. Convexity-constrained NMF was used to identify characteristic signal components from UTE T₂*-weighted datasets. Basis functions were determined based on asymptomatic knee data and used to compute subject-specific weight maps. Normalized weight distributions were computed for 13 regions of interest across asymptomatic knees and contrasted with median weights of selected structures in patients. The application of the NMF-based framework yielded four reproducible basis functions associated with fast decay, slow decay, water-fat mixing, and fat-like behavior. Knee structures with known short T₂* showed a dominant fast-decaying component (median weights ≥ 0.68), while structures with long T₂* showed a greater contribution from the slowly-decaying component (median weights ≥ 0.44). The fat-like component was predominant in Hoffa's fat pad, while the water-fat mixture-related component's contribution was overall low. Lesioned menisci and ligaments generally displayed reduced fast-decaying and increased slowly decaying component contributions. These findings suggest that convexity-constrained NMF of 3D multi-echo UTE MRI is feasible for data-driven knee tissue characterization as it extracts biophysically related signal components and describes their relative contribution to the measured signal in various knee tissues. Moreover, the proposed framework shows potential for differentiation between asymptomatic and impaired knee tissues, particularly in the posterior horn of the medial meniscus and the anterior cruciate ligament, and consequently holds promise for more objective diagnosis and monitoring of internal knee derangements.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 6","pages":"e70299"},"PeriodicalIF":2.8,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13150805/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147840716","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tension-Dependent Variability and Repeatability of Achilles Tendon UTE-T₂* Mapping Using Mono- and Bi-Exponential Models.","authors":"Ananya Goyal, Marco Barbieri, Valentina Mazzoli, Feliks Kogan","doi":"10.1002/nbm.70302","DOIUrl":"10.1002/nbm.70302","url":null,"abstract":"<p><p>Quantitative MRI using ultrashort echo time (UTE)-T₂* mapping is sensitive to collagen-bound water and tendon microstructure, enabling noninvasive assessment of tendon integrity and laxity. However, the extent to which UTE-T₂* measures reflect changes in tendon tension, and their repeatability, remain incompletely understood. We evaluated the sensitivity of mono- and bi-exponential UTE-T₂* measures of the Achilles tendon to changes in tendon tension induced by ankle positioning and assessed the test-retest repeatability of these metrics across repeated scan sessions. In this study, healthy adult volunteers underwent UTE-MRI of the Achilles tendon at two scan sessions, spaced 1 week apart, with the ankle positioned in dorsiflexion (higher tendon tension) and plantarflexion (lower tendon tension). Mono-exponential T₂* (T₂*_mono) and bi-exponential parameters (T₂*_short, T₂*_long, and short-component fraction ρ_short) were quantified. We performed a two-way repeated-measures ANOVA to assess the main effects of ankle position and scan session, and their interaction. Repeatability was evaluated using root mean square error (RMSE), coefficient of variation (CV%), and Bland-Altman analysis. We observed that short-component T₂* metrics demonstrated significant sensitivity to tendon tension. A main effect of ankle position was observed for T₂*_mono (p < 0.001) and T₂*_short (p = 0.02), with lower values in dorsiflexion compared with plantarflexion. No significant effect of scan session or ankle position × scan session interactions were observed. T₂*_long and ρ_short showed no significant dependence on position or scan session, suggesting that bulk hydration and relative water-compartment contributions remained stable across loading conditions. Dorsiflexion demonstrated lower RMSE and CV% across metrics than plantar flexion, indicating improved repeatability under passive tendon tension. UTE-T₂* relaxometry of the Achilles tendon is repeatable and sensitive to changes in tendon tension. Short T₂* measures may provide quantitative imaging markers related to tendon mechanical integrity and laxity, while highlighting the importance of standardized tendon tension for longitudinal quantitative tendon MRI.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 6","pages":"e70302"},"PeriodicalIF":2.8,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147856800","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}