NMR in Biomedicine最新文献

{"title":"Domain-Conditioned and Temporal-Guided Diffusion Modeling for Accelerated Dynamic MRI Reconstruction.","authors":"Liping Zhang, Iris Yuwen Zhou, Sydney B Montesi, Li Feng, Fang Liu","doi":"10.1002/nbm.70256","DOIUrl":"10.1002/nbm.70256","url":null,"abstract":"<p><p>This study introduces a domain-conditioned and temporally guided diffusion framework for accelerated dynamic MRI reconstruction, in which the reverse diffusion process is explicitly guided to model spatiotemporal structure in time-resolved data. The framework integrates temporal information from time-resolved dimensions, allowing for the concurrent capture of intraframe spatial features and interframe temporal dynamics in diffusion modeling. Meanwhile, it employs additional spatiotemporal and self-consistent frequency-temporal priors to guide the diffusion process, ensuring precise temporal alignment and enhancing fine image detail recovery. To facilitate a smooth diffusion process, the nonlinear conjugate gradient algorithm is utilized during the reverse diffusion steps. The proposed model was tested on two types of MRI data: Cartesian-acquired multicoil cardiac MRI and golden-angle-radial-acquired multicoil free-breathing lung MRI, across various undersampling rates. It achieved high-quality reconstructions, demonstrating improved temporal alignment and structural recovery compared with other competitive reconstruction methods, both qualitatively and quantitatively. This diffusion framework exhibited robust performance in handling both Cartesian and non-Cartesian acquisitions, effectively reconstructing dynamic datasets in cardiac and lung MRI under different imaging conditions.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 5","pages":"e70256"},"PeriodicalIF":2.8,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13197192/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147504577","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":"The Impact of Gadolinium on Quantitative Myelin Metrics in Ex Vivo Spinal Cord.","authors":"Hannah E Alderson, Mark D Does, Kevin D Harkins","doi":"10.1002/nbm.70275","DOIUrl":"10.1002/nbm.70275","url":null,"abstract":"<p><p>The goal of this work was to evaluate the impact of gadolinium on quantitative myelin MRI metrics in ex vivo tissue. Ex vivo ferret spinal cords were imaged with and without gadolinium. Mean metrics were calculated across white and gray matter. T₁ of the free proton pool and T₂ of water other than myelin showed the largest differences between gadolinium and without gadolinium samples. Myelin water fraction, bound pool fraction, and myelin water T₂ showed a 2%-12% change between gadolinium and no gadolinium data. The relationships between the myelin water fraction, bound pool fraction, and myelin water T₂ and a recently established axon diameter surrogate were not affected by gadolinium; however, the trends observed between T₁ of the free proton pool and other water T₂ and the axon diameter surrogate without gadolinium were flattened in the samples with gadolinium. Overall, the impacts of gadolinium were primarily observed in the relaxation parameters of the non-myelin proton pools.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 5","pages":"e70275"},"PeriodicalIF":2.8,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13006719/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147499651","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":"3D Plastronics Culture Chambers and Benchtop MRI Setup Toward Tissue Engineering Applications.","authors":"Valernst Martial Gilmus, Yilbert Gimenez, Tony Gerges, Philippe Lombard, Vincent Semet, Christophe Marquette, Emma Petiot, Michel Cabrera, Simon Auguste Lambert","doi":"10.1002/nbm.70272","DOIUrl":"10.1002/nbm.70272","url":null,"abstract":"<p><p>The rise of low-field benchtop MRI offers exciting opportunities for non-invasive, volumetric imaging of large biofabricated tissues in standard tissue engineering labs. Although low-field benchtop MRI scanners provide a cost-effective and accessible option, their performance is often restricted by low signal-to-noise ratio (SNR) and the use of generic, non-optimized hardware. This study introduces a novel, fully integrated benchtop MRI setup for in situ imaging of 3D bioprinted constructs. A custom perfusion culture chamber was designed and fabricated using 3D Plastronics, a method that allows for the direct integration of a bridged loop-gap resonator (BLGR) onto the chamber's surface. The performance of this integrated setup was quantitatively compared to a conventional setup using a commercial, all-purpose coil. The evaluation included measurements of the quality factor (Q), noise factor (F), SNR, and B₁ ⁺ field mapping. The practical application was demonstrated by high-resolution imaging of a 3D bioprinted hydrogel scaffold under perfusion. The 3D Plastronics setup demonstrated superior performance over the commercial coil setup, achieving a 60% increase in measured SNR, which was consistent with theoretical predictions. This improvement was attributed mainly to a higher filling factor due to the coil's proximity to the sample, enabled by the 3D Plastronics approach. B₁ ⁺ field maps also indicated higher mean field strength and improved homogeneity for the integrated coil due to its optimized design. High-resolution (234 <math> <semantics><mrow><mi>μ</mi></mrow> <annotation>$$ upmu $$</annotation></semantics> </math> m³) images of the bioprinted scaffold clearly displayed its internal macroporous structure, in 20 min. Integrating radio frequency (RF) coils directly onto a culture chamber with 3D Plastronics greatly enhances imaging performance in low-field MRI for tissue engineering. This method offers a scalable, customizable platform for nondestructive, long-term monitoring of 3D tissue constructs and opens new possibilities for in situ studies of tissue development.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 5","pages":"e70272"},"PeriodicalIF":2.8,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147575026","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":"Correction of Respiratory Motion in Free-Breathing DCE-MRI Using a Pilot-Tone Coil.","authors":"Ruoxun Zi, Mario Bacher, Peter Speier, Hersh Chandarana, Riccardo Lattanzi, Kai Tobias Block","doi":"10.1002/nbm.70278","DOIUrl":"10.1002/nbm.70278","url":null,"abstract":"<p><p>Respiratory motion poses a major challenge in abdominopelvic MRI and often leads to strong artifacts. Self-navigation techniques have been proposed for motion correction, allowing free-breathing examination. However, self-navigation methods typically fail to track respiratory motion for dynamic contrast-enhanced (DCE) scans due to concurrent signal changes caused by the contrast injection. In this study, we investigated the use of a pilot-tone (PT) transmitter integrated into the receive coil as an alternative approach for obtaining respiratory curves. The amplitude of the received PT signal gets modulated by respiratory motion due to changes in the coil load. A pipeline for extracting respiratory curves from the PT signal was developed and applied for motion-corrected free-breathing abdominal DCE-MRI. Validation experiments included real-time cine imaging and comparison with self-navigation for five late-phase liver scans. Dynamic experiments were performed for a liver DCE scan of one healthy volunteer and kidney DCE scans of 24 patients. A motion-weighted GRASP algorithm was used for reconstructing dynamic images. Quantitative metrics, including gradient entropy for individual images and the L2 norm of the temporal differences for each dynamic frame set, were calculated. Motion-weighted DCE GRASP reconstructions using PT-derived respiratory curves showed improved image sharpness, especially in regions such as the diaphragm, kidney boundaries, and vessels, as well as better temporal consistency compared to conventional GRASP reconstructions. These improvements were observed both qualitatively and quantitatively. This work demonstrates that the PT technique can accurately detect respiration during contrast injections, reducing motion blurring in free-breathing dynamic DCE-MRI. The proposed technique can be easily implemented in the clinical workflow by using a coil with an integrated PT transmitter and requires no external belts or sensors.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 5","pages":"e70278"},"PeriodicalIF":2.8,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147531246","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":"DEEP-DISORDER: Motion Correction in 3D MRI via Segment Reconstruction and Registration.","authors":"Laurens Beljaards, Martijn Nagtegaal, Chinmay Rao, Yiming Dong, Matthias J P van Osch, Nicola Pezzotti, Mariya Doneva, Marius Staring","doi":"10.1002/nbm.70286","DOIUrl":"10.1002/nbm.70286","url":null,"abstract":"<p><p>3D MR image acquisition is inherently time intensive, rendering it susceptible to patient motion during scanning. This may introduce significant blurring and artifacts, potentially necessitating reacquisition. We propose a modular framework to retrospectively correct for intrascan motion in 3D brain MRI, without active motion tracking. Serving as the backbone of our approach is an existing distributed and incoherent sampling scheme (DISORDER), combined with a fast network trained for highly undersampled reconstruction. This enables approximate reconstructions of anatomy after every few seconds, using only a tiny fraction of k-space data (< 2%). While these reconstructions are only approximate, we postulate they are sufficient to estimate motion patterns at said temporal resolution. Groupwise registration, notable for its elimination of registration bias, is utilized for estimating rigid motion parameters, which are leveraged to reconstruct the measured data with reduced motion artifacts. The approach was evaluated on 94 retrospectively and 3 prospectively motion-corrupted in vivo 3D T1-weighted brain MRI acquisitions. The estimated motion parameters matched the known retrospective motion with 0.06 mm and 0.13° accuracy, resulting in an improvement in reconstruction quality from <math> <semantics><mrow><mn>0</mn> <mo>.</mo> <mn>942</mn> <mo>±</mo> <mn>0</mn> <mo>.</mo> <mn>026</mn></mrow> <annotation>$$ 0.942pm 0.026 $$</annotation></semantics> </math> to <math> <semantics><mrow><mn>0</mn> <mo>.</mo> <mn>992</mn> <mo>±</mo> <mn>0</mn> <mo>.</mo> <mn>003</mn></mrow> <annotation>$$ 0.992pm 0.003 $$</annotation></semantics> </math> SSIM for the retrospective scans. The prospective scans improved from <math> <semantics><mrow><mn>0</mn> <mo>.</mo> <mn>915</mn> <mo>±</mo> <mn>0</mn> <mo>.</mo> <mn>024</mn></mrow> <annotation>$$ 0.915pm 0.024 $$</annotation></semantics> </math> to <math> <semantics><mrow><mn>0</mn> <mo>.</mo> <mn>936</mn> <mo>±</mo> <mn>0</mn> <mo>.</mo> <mn>014</mn></mrow> <annotation>$$ 0.936pm 0.014 $$</annotation></semantics> </math> SSIM after correction in the case of gradual motion and from <math> <semantics><mrow><mn>0</mn> <mo>.</mo> <mn>764</mn> <mo>±</mo> <mn>0</mn> <mo>.</mo> <mn>008</mn></mrow> <annotation>$$ 0.764pm 0.008 $$</annotation></semantics> </math> to <math> <semantics><mrow><mn>0</mn> <mo>.</mo> <mn>923</mn> <mo>±</mo> <mn>0</mn> <mo>.</mo> <mn>011</mn></mrow> <annotation>$$ 0.923pm 0.011 $$</annotation></semantics> </math> SSIM for extreme motion. In conclusion, the proposed approach, that is free of external tracking devices or navigators, successfully estimated and corrected 3D motion between small subportions of a scan. This resulted in vastly improved image quality, making volumetric MRI substantially more tolerant to motion.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 5","pages":"e70286"},"PeriodicalIF":2.8,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13066780/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147645946","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":"Monte Carlo Assessment of Accuracy for Mean Kärger Model Water Exchange Rate Estimates From Diffusional Kurtosis Time Dependence.","authors":"Jens H Jensen, Ricardo Coronado-Leija, Els Fieremans","doi":"10.1002/nbm.70281","DOIUrl":"10.1002/nbm.70281","url":null,"abstract":"<p><p>Intercompartmental water exchange in brain and other biological tissue can be probed in vivo with diffusion MRI (dMRI). We assess the accuracy of a recently proposed method for estimating a mean exchange rate by performing Monte Carlo simulations of random walkers through a packing of permeable, randomly placed, parallel cylinders to model water exchange within axonal fiber bundles. The diffusivity and kurtosis of the full system are calculated for a broad range of diffusion times and model parameters. The mean exchange rate is estimated from the logarithmic derivative of the kurtosis with respect to the diffusion time and compared with the exchange rate predicted by the Kärger model (KM), which is exact in certain limits. The mean exchange rate is also compared with the reciprocal exchange time obtained by conventional fitting of the kurtosis time dependence to a two-compartment KM, with a high correlation being found between the two quantities. The estimates from the logarithmic derivative are in good agreement with the KM predictions when the exchange time is long in comparison to the compartment traversal times, which corresponds to barrier-limited exchange. Compared to the standard procedure of fitting the kurtosis to the KM over a broad range of diffusion times, using the logarithmic derivative reduces the data acquisition burden by only requiring a narrow range of times and increases generality in that number of compartments need not be specified. This method may be useful for estimating the mean exchange rate from the kurtosis time dependence measured with dMRI.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 5","pages":"e70281"},"PeriodicalIF":2.8,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13051334/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147623529","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":"Assessing Age-Associated Influences on Paramagnetic and Diamagnetic Susceptibility Maps in Postmortem Human Brains.","authors":"José Henrique Monteiro de Azevedo, Maria Concepción Garcia Otaduy, Andre Avanzine, Roberta Diehl Rodriguez, Fábio Seiji Otsuka, Fernando Barbosa, Chunlei Liu, Carlos Ernesto Garrido Salmon","doi":"10.1002/nbm.70259","DOIUrl":"10.1002/nbm.70259","url":null,"abstract":"<p><p>Maps of paramagnetic and diamagnetic components of magnetic susceptibility can provide insights into the distribution of iron and myelin during brain aging. Postmortem validation is essential to ensure that these maps accurately reflect in vivo biological processes. In this study, we applied the APART-QSM method for susceptibility separation to in situ (intracranial) postmortem MRI data from 47 subjects (ages 31-91) to investigate how age affects magnetic susceptibility components, comparing the results with previously reported in vivo associations. Linear regression was used to assess age-related associations with susceptibility values in 17 deep gray matter (DGM) and white matter (WM) regions. Diamagnetic susceptibility showed a consistent age-related decline in DGM basal ganglia regions, which appeared to result from a shared underlying factor across these areas. Based on the assumption that fractional anisotropy (FA) reflects myelin integrity, we also investigated the correlation between FA and diamagnetic susceptibility in WM regions. A negative correlation was found, suggesting a potential myelin contribution to the diamagnetic component. Consistent with in vivo analyses, the putamen's paramagnetic and total QSM susceptibility values demonstrated a strong age association in our postmortem condition, and it was the only region in which susceptibility values increased linearly with age. Finally, the analysis of ex vivo putamen tissue samples revealed a moderate association between paramagnetic susceptibility and iron concentration, supporting iron's biological contribution to MRI paramagnetic susceptibility maps of the putamen. The results enhance the biological interpretability of MRI data and promote cross-validation between imaging and direct tissue analysis, with implications for both clinical and research applications related to aging and neurodegenerative diseases.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 5","pages":"e70259"},"PeriodicalIF":2.8,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13018726/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147513783","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":"Heterogeneous Myocardial Adaptation to Pressure Overload Reveals a Spared, Vulnerable Segment Identified by Multiparametric Cardiac MRI.","authors":"Vitali Koch, Andreas T Ochs, Simon Martin, Thomas Vogl, Marco M Ochs, David M Leistner, Sebastian M Haberkorn","doi":"10.1002/nbm.70288","DOIUrl":"10.1002/nbm.70288","url":null,"abstract":"<p><p>Cardiac adaptation to chronic pressure overload is traditionally viewed as a uniform concentric hypertrophy; however, growing evidence suggests that the myocardium responds in a spatially heterogeneous manner. This study aimed to systematically map regional and temporal adaptation patterns of the left ventricle (LV) under experimental pressure overload using high-resolution multiparametric cardiac MRI, with the hypothesis that distinct regional adaptation phenotypes contribute to both local functional differences and global ventricular dysfunction. Thirty-seven male 129/SvEv mice underwent transverse aortic constriction (TAC) surgery and were followed longitudinally over 7 weeks. Cine imaging, T1- and T2-mapping were performed at baseline, 3 days, 4 weeks and 7 weeks using a 9.4 T small-animal scanner. A 200-sector LV segmentation enabled quantitative regional analysis of wall thickness, fractional shortening (FS) and relaxation times. Global and regional imaging parameters were correlated with histological and biochemical indices at study termination, and statistical analyses were performed using the Mann-Whitney test and correlation modelling, with p < 0.05 considered significant. All TAC animals developed global LV hypertrophy and an early increase in LV mass (+62% ± 15% at Week 7, p < 0.001). Unexpectedly, in 18 animals (49%), a discrete basolateral LV segment failed to hypertrophy (spared hypertrophy, SH) despite uniform pressure elevation. This region exhibited markedly reduced regional FS (10.2% ± 3.1% vs. 24.9% ± 2.2%, p = 0.01) and was associated with lower global ejection fraction (32.5% ± 1.8% vs. 49.8% ± 4.1%, p < 0.05) and LV dilatation. Parametric MRI revealed distinct tissue signatures: T1 increased in hypertrophied sectors (+22.6% ± 1.1%), whereas it decreased in SH sectors (-5.1% ± 1.7%, p < 0.01) over the 7-week observation period. Sector-wise correlations linked T1 shortening with reduced FS (R² = 0.58, p = 0.002), suggesting maladaptive regional remodeling. In conclusion, pressure overload elicits diverse regional adaptation, and failure to hypertrophy identifies myocardial territories prone to early dysfunction and global decline. Recognizing hypertrophy as an essential adaptive mechanism shifts the paradigm of pressure-overload remodeling. Multiparametric MRI provides a translational platform for detecting regional vulnerability and guiding early intervention.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 5","pages":"e70288"},"PeriodicalIF":2.8,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13066756/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147645911","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":"<ArticleTitle xmlns:ns0=\"http://www.w3.org/1998/Math/MathML\">Cross-Site Generalization of CNN-Based <ns0:math> <ns0:semantics> <ns0:mrow><ns0:msubsup><ns0:mi>B</ns0:mi> <ns0:mn>1</ns0:mn> <ns0:mo>+</ns0:mo></ns0:msubsup> </ns0:mrow> <ns0:annotation>$$ {B}_1^{+} $$</ns0:annotation></ns0:semantics> </ns0:math> Mapping in UHF MRI.","authors":"Kimon Hadjikiriakos, Felix Krüger, Felix Frederik Zimmermann, Johannes A Grimm, Constantin Schorling, Max Lutz, Simon Schmidt, Layla Tabea Riemann, Katja Degenhardt, Tobias Schäffter, Mark E Ladd, Gregory J Metzger, Christoph Stefan Aigner, Sebastian Schmitter","doi":"10.1002/nbm.70263","DOIUrl":"10.1002/nbm.70263","url":null,"abstract":"<p><p>Convolutional neural networks (CNNs) can rapidly predict channel-wise <math> <semantics> <mrow><msubsup><mi>B</mi> <mn>1</mn> <mo>+</mo></msubsup> </mrow> <annotation>$$ {B}_1^{+} $$</annotation></semantics> </math> maps from 7T localizer images, reducing acquisition time to seconds. This paper investigates if a CNN trained on one site's data can generalize to predict <math> <semantics> <mrow><msubsup><mi>B</mi> <mn>1</mn> <mo>+</mo></msubsup> </mrow> <annotation>$$ {B}_1^{+} $$</annotation></semantics> </math> maps for brain imaging at unseen sites supporting the feasibility of a universal network for subject-specific <math> <semantics> <mrow><msubsup><mi>B</mi> <mn>1</mn> <mo>+</mo></msubsup> </mrow> <annotation>$$ {B}_1^{+} $$</annotation></semantics> </math> - mapping. We evaluated a U-Net CNN cross-site generalization by training on datasets from two different 7T sites and testing its performance across three 7T sites (1 additional testing site) to assess robustness, adaptability, and generalization. The study design included both commercially same systems and the identical physical hardware unit transported between two sites, enabling a more insightful attribution of performance differences to either hardware issues or dataset-specific variations. To assess prediction quality, we examined magnitude/phase images, error maps, correlation plots, Pearson coefficients, and residual spread plots. Quantitative evaluation included RMSE and SSIM scores. Finally, we calculated 4 kT-points pulses with both on-site and cross-site CNNs to evaluate the effectiveness of the obtained <math> <semantics> <mrow><msubsup><mi>B</mi> <mn>1</mn> <mo>+</mo></msubsup> </mrow> <annotation>$$ {B}_1^{+} $$</annotation></semantics> </math> maps for parallel-transmission (pTx). While on-site <math> <semantics> <mrow><msubsup><mi>B</mi> <mn>1</mn> <mo>+</mo></msubsup> </mrow> <annotation>$$ {B}_1^{+} $$</annotation></semantics> </math> transversal magnitude RMSE scores were as low as 3.0% and 3.1% for the two CNNs, their respective transfer yielded 3.6% and 4.1%. The dynamic pTx-application showed a CV of 6.5% when using <math> <semantics> <mrow><msubsup><mi>B</mi> <mn>1</mn> <mo>+</mo></msubsup> </mrow> <annotation>$$ {B}_1^{+} $$</annotation></semantics> </math> maps predicted by a network trained on its own site. The transfer case, using a map predicted from a network trained on a different site, yielded an increased CV of 13.7%. Although cross-site applications introduced larger deviations, the predicted maps remained qualitatively plausible and enabled practical use cases, such as calculating dynamic-pTx. These findings support the potential of cross-site training, suggesting CNNs trained at one site may generalize sufficiently to unseen sites without additional adjustments. This strengthens the feasibility of a transferable training approach where a single network could be deployed across different institutions without extensive retraining.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 5","pages":"e70263"},"PeriodicalIF":2.8,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13051333/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147623499","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":"Cerebral Hemodynamic Changes During Cardiac Surgery: A Feasibility MR Study in Piglets.","authors":"Dominik T Schulte, Ruth O'Gorman Tuura, Henning Richter, Michael Hofmann, Francesca Del Chicca, Tobias Aigner, Christoph Loeschmann, Martina Lentini, Manuela Wieser, Frauke Seehusen, Rima Bektas, Melanie Zeilinger, Martin O Schmiady, Marianne Schmid Daners","doi":"10.1002/nbm.70284","DOIUrl":"10.1002/nbm.70284","url":null,"abstract":"<p><p>Congenital heart disease often requires early surgical intervention. Cardiopulmonary bypass (CPB) is a standard procedure, but infants undergoing CPB show an increased risk of postoperative white matter injury. These injuries are associated with adverse neurodevelopmental outcomes, yet the underlying mechanisms remain poorly understood. MR imaging offers unique opportunities to study cerebral perfusion and metabolism in vivo but has not previously been feasible during CPB with a heart-lung machine (HLM) in close proximity to the patient and the MR scanner, respectively, because conventional HLMs interfere with scanner operation. To address this limitation, we developed an MR-conditional HLM and evaluated it in an in vivo piglet model, which closely mimics the neonatal brain and circulation. Unlike conventional systems, our MR-conditional roller pump can be positioned directly inside the scanner bore without compromising imaging quality or pump performance. Four trials were conducted, in which piglets were cannulated and maintained on CPB inside the MR scanner. During CPB, cooling, rewarming, and unilateral carotid clamping were performed while repeatedly acquiring MR data on flow, diffusion, perfusion, and metabolism. Crucial brain structures-including the basal ganglia, hippocampus, and internal capsule-were consistently visualized without artifacts, and no disturbances occurred in pump operation or monitoring signals. The MR scans revealed flow-related changes and a progressive increase in lactate, suggesting the onset of metabolic stress under hypoperfusion. These results demonstrate the technical feasibility of performing CPB within the MR scanner using an MR-conditional HLM. Although not sufficient to identify specific mechanisms of brain injury, this platform provides a unique foundation for mechanistic studies in relevant large-animal models. In the future, such an approach could help identify early markers of cerebral vulnerability, improve the safety of pediatric cardiac surgery, and inform the development of neuroprotective strategies for CPB and extracorporeal membrane oxygenation patients.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 5","pages":"e70284"},"PeriodicalIF":2.8,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13050816/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147623543","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}