NMR in Biomedicine最新文献

{"title":"Fine-Tuning Deep Learning Model for Quantitative Knee Joint Mapping With MR Fingerprinting and Its Comparison to Dictionary Matching Method: Fine-Tuning Deep Learning Model for Quantitative MRF.","authors":"Xiaoxia Zhang, Hector L de Moura, Anmol Monga, Marcelo V W Zibetti, Ravinder R Regatte","doi":"10.1002/nbm.70045","DOIUrl":"10.1002/nbm.70045","url":null,"abstract":"<p><p>Magnetic resonance fingerprinting (MRF), as an emerging versatile and noninvasive imaging technique, provides simultaneous quantification of multiple quantitative MRI parameters, which have been used to detect changes in cartilage composition and structure in osteoarthritis. Deep learning (DL)-based methods for quantification mapping in MRF overcome the memory constraints and offer faster processing compared to the conventional dictionary matching (DM) method. However, limited attention has been given to the fine-tuning of neural networks (NNs) in DL and fair comparison with DM. In this study, we investigate the impact of training parameter choices on NN performance and compare the fine-tuned NN with DM for multiparametric mapping in MRF. Our approach includes optimizing NN hyperparameters, analyzing the singular value decomposition (SVD) components of MRF data, and optimization of the DM method. We conducted experiments on synthetic data, the NIST/ISMRM MRI system phantom with ground truth, and in vivo knee data from 14 healthy volunteers. The results demonstrate the critical importance of selecting appropriate training parameters, as these significantly affect NN performance. The findings also show that NNs improve the accuracy and robustness of T₁, T₂, and T_1ρ mappings compared to DM in synthetic datasets. For in vivo knee data, the NN achieved comparable results for T₁, with slightly lower T₂ and slightly higher T_1ρ measurements compared to DM. In conclusion, the fine-tuned NN can be used to increase accuracy and robustness for multiparametric quantitative mapping from MRF of the knee joint.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"38 6","pages":"e70045"},"PeriodicalIF":2.7,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12129367/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143983412","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":"Diffusion Tensor Imaging of Rat Rotator Cuff Muscle With Histopathological Correlation: An Exploratory Study.","authors":"James Lo, David B Berry, Qingbo Tang, Xin Cheng, Marco Toto-Brocchi, Jiang Du, Samuel R Ward, Yajun Ma, Eric Y Chang","doi":"10.1002/nbm.70058","DOIUrl":"10.1002/nbm.70058","url":null,"abstract":"<p><p>The purpose of this exploratory study was to quantify the relationship between scalar-based measures of diffusion tensor imaging (DTI) and histologically derived microstructural measurements in precisely colocalized rat rotator cuff muscle tissue and to compare the results when imaged at 0.25- and 0.5-mm isotropic resolutions. Four Lewis rats subject to a unilateral chronic massive rotator cuff tear model were evaluated on a 3-T preclinical MRI scanner using spin echo DTI sequences at 0.25- and 0.5-mm isotropic resolutions, and histology was subsequently performed. Fractional anisotropy (FA), mean diffusivity (MD), and radial diffusivity (RD) were calculated. Whole muscle myofiber boundary segmentation was performed, and muscle fiber diameter and cross-sectional area were calculated on slides that passed rigorous histologic quality control. Scatter plots were generated on a pixel-by-pixel basis from meticulously colocalized DTI and histology data. Pearson's correlations were performed. Twenty-two distinct supraspinatus and infraspinatus muscle locations from two rats were included. Negligible correlations were found between DTI metrics, including FA, MD, and RD, and histological measurements, including muscle fiber diameters and cross-sectional areas. Using the most commonly employed spin echo DTI sequences with intermediate diffusion times, there may be negligible sensitivity to direct measures of muscle tissue microstructure. Our findings underscore the need for further research with optimized imaging parameters to enhance our knowledge regarding the capability of DTI to determine important features of muscle microstructure.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"38 6","pages":"e70058"},"PeriodicalIF":2.7,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12143938/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144012654","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":"Reproducibility of the Determination of ¹³C-Labeling of Glutamate and Glutamine in the Human Brain Using selPOCE-MRS at 7 T Upon [U-¹³C]-Labeled Glucose Infusion.","authors":"Narjes Ahmadian, Sarah M Jacobs, Mark Gosselink, Wybe J M van der Kemp, Hans Hoogduin, Anastasia Coppoli, Graeme F Mason, Robin A de Graaf, Helia Norouzizadeh, Chantal Mahon, Pieter van Eijsden, Renger Tiessen, Dirk Cerneus, Corin O Miller, Inge De Lepeleire, Anthony S Basile, Dennis W J Klomp, Jeanine J Prompers, Evita C Wiegers","doi":"10.1002/nbm.70026","DOIUrl":"https://doi.org/10.1002/nbm.70026","url":null,"abstract":"<p><p>Glutamate (Glu) is the major excitatory neurotransmitter in the central nervous system. The measurement of Glu/glutamine (Gln) neurotransmitters in the brain provides valuable insights into the dynamic aspects of neuroenergetics and neurotransmitter cycles and can be accomplished through the detection of ¹³C-labeling of Glu and Gln during the administration of ¹³C-labeled glucose. Our goal is to evaluate the reproducibility of selective proton-observed, carbon-edited (selPOCE) MRS at 7 T for the detection of ¹³C-labeled Glu and Gln in the human brain. Data of three healthy participants, who were scanned twice at 7 T while undergoing [U-¹³C]-glucose infusion for 120 min, were used to detect ¹³C-labeled Glu and Gln in the brain, using selPOCE-STEAM-MRS. There was a rapid increase of plasma glucose ¹³C fractional enrichment (FE) during the first 20 min of infusion, followed by a steady state of plasma glucose ¹³C FE until the end of the [U-¹³C]-glucose infusion. The time courses of ¹³C-labeling of Glu and Gln were similar for test/retest. The test/retest variability was 15.8% for ¹³C-Glu and 33.3% for ¹³C-Gln. Knowing the variability of these readings using selPOCE-STEAM-MRS can inform the application to future studies on disease-specific alterations in Glu/Gln cycling.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"38 5","pages":"e70026"},"PeriodicalIF":2.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11981885/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144020598","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":"Machine Learning Analysis of Single-Voxel Proton MR Spectroscopy for Differentiating Solitary Fibrous Tumors and Meningiomas.","authors":"Lili Fanni Toth, Carles Majós, Albert Pons-Escoda, Carles Arús, Margarida Julià-Sapé","doi":"10.1002/nbm.70032","DOIUrl":"10.1002/nbm.70032","url":null,"abstract":"<p><p>Solitary fibrous tumor (SFT), formerly known as hemangiopericytoma, is an uncommon brain tumor often confused with meningioma on MRI. Unlike meningiomas, SFTs exhibit a myoinositol peak on magnetic resonance spectroscopy (MRS). This study aimed to develop automated classifiers to distinguish SFT from meningioma grades using MRS data from a 26-year patient cohort. Four classification tasks were performed on short echo (SE), long echo (LE) time, and concatenated SE + LE spectra, with datasets split into 80% training and 20% testing sets. Sequential forward feature selection and linear discriminant analysis identified features to distinguish between meningioma Grade 1 (Men-1), meningioma grade 2 (Men-2), meningioma grade 3 (Men-3), and SFT (the 4-class classifier); Men-1 from Men-2 + 3 + SFT; meningioma (all) from SFT; and Men-1 from Men-2 + 3 and SFT. The best classifier was defined by the smallest balanced error rate (BER) in the testing phase. A total of 136 SE cases and 149 LE cases were analyzed. The best features in the 4-class classifier were myoinositol and alanine at SE, and myoinositol, glutamate, and glutamine at LE. Myoinositol alone distinguished SFT from meningiomas. Differentiating Men-1 from Men-2 was not possible with MRS, and combining higher meningioma grades did not improve distinction from Men-1. Notably, combining short and long echo times (TE) enhances classification performance, particularly in challenging outlier cases. Furthermore, the robust classifier demonstrates efficacy even when dealing with spectra of suboptimal quality. The resulting classifier is available as Supporting Information of the publication. Extensive documentation is provided, and the software is free and open to all users without a login requirement.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"38 5","pages":"e70032"},"PeriodicalIF":2.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143788548","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":"Dynamics of Ionic and Cytotoxic Edema During Acute and Subacute Stages of Patients With Ischemic Stroke: Complementarity of ²³Na MRI and Diffusion MRI.","authors":"Maëva Cotinat, Noëlle Messaoudi, Emmanuelle Robinet, Laurent Suissa, Emilie Doche, Maxime Guye, Bertrand Audoin, Laurent Bensoussan, Jean-Philippe Ranjeva, Wafaa Zaaraoui","doi":"10.1002/nbm.70028","DOIUrl":"10.1002/nbm.70028","url":null,"abstract":"<p><p>Cerebral imaging is crucial in the diagnosis and treatment algorithm of acute stroke to determine salvageable brain tissue. While diffusion MRI is commonly used to define the ischemic core, it cannot reliably distinguish irreversibly damaged from salvageable tissue. We investigated the added value of ²³Na MRI to define irreversible necrotic tissue after a stroke. Fifteen patients with acute stroke involving medial cerebral artery occlusion were longitudinally explored with conventional and ²³Na MRI within 24 h, 70 h following stroke and at 3 months to characterize the necrotic area. Time-courses of sodium accumulations were observed within regions presenting with or spared by cytotoxic/ionic edema and converting or not to necrosis. Dynamics of sodium accumulations were very different across subjects. At the group level, time-courses of sodium signal in cytotoxic edema showed a non-linear increase with an upper asymptote of 59 ± 6%% relative to the contralateral hemisphere. Regions with a larger early increase in ²³Na signal (ionic edema) showed a non-linear accumulation during the first 70 h and were associated with subsequent necrosis at month 3. Some of the regions with no ionic edema during the first 70 h became necrotic at month 3, showing that pejorative pathophysiological processes could worsen after 70 h following attack. Final necrotic volume was well predicted by the cytotoxic volume (ADC decrease) during the first 24 h, and by the volume of ionic edema during the subacute period (25-70 h) following attack. The regions showing ionic edema showed a non-linear increase of ²³Na signal during the first 70 h, with larger sodium accumulations in regions converting to necrosis at month 3. It may be of interest to consider the role of ionic edema imaging in the 70 h after stroke and reperfusion, with a view to better understand stroke pathophysiology. Sodium MRI could add complementary information about the fate of cell necrosis within low ADC signal regions.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"38 5","pages":"e70028"},"PeriodicalIF":2.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11964797/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143772824","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":"In Vivo Brain B₁ ⁺ Inhomogeneity Correction and NOE Image Enhancement at 7 T via Flexible Metasurfaces.","authors":"Paul S Jacobs, Anshuman Swain, Neil E Wilson, Wyger M Brink, Abeer Mathur, Ravi Prakash Reddy Nanga, Mark A Elliott, John A Detre, Ravinder Reddy","doi":"10.1002/nbm.70027","DOIUrl":"10.1002/nbm.70027","url":null,"abstract":"<p><p>Nuclear Overhauser effect (NOE) MRI has been used for in vivo brain imaging to assess lipid and protein composition and benefits from 7 T field strengths due to the larger chemical shift dispersion. However, a continuing challenge is signal drop off observed in regions such as the medial temporal lobes due to \"standing wave\" effects from shorter radiofrequency (RF) wavelengths at ultra-high fields. 2D periodic unit cell metasurfaces have been a promising approach for providing improvements in anatomical imaging but have not yet been evaluated in chemical exchange saturation transfer (CEST)-based sequences. Here, we report the use of metasurfaces for enhancement of NOE imaging as well as for improvement of Lorentzian line fitting of full Z-spectrum data. 3D NOE image data, B₁ ⁺ maps, and B₀ maps were acquired on five healthy volunteers using a 7 T MRI system with and without metasurfaces positioned near the temporal lobes. A frequency offset range of -5 to +5 ppm with additional separate acquisitions of ±20 and ±100 ppm offset images. A five-pool Lorentzian line fitting model was employed to fit and quantitatively compared magnetization transfer (MT), amide proton transfer (APT), amine, and relayed NOE (rNOE) metabolite pools. NOE_MTR-weighted contrast maps were also calculated via Z-spectrum asymmetry analysis. The metasurfaces globally enhanced the transmit efficiency within the imaging slab by approximately 9.6% and reduced B₁ ⁺ inhomogeneity by approximately 16.6% and increased transmit efficiency by 55.8% in the temporal lobes. Amplitude fit maps showed decreases in contrast magnitude ranging from 1 to 16% and changes in image uniformity ranging from a 4.3 decrease to a 34.7% increase, while NOE_MTR-weighted contrast maps demonstrated similar changes. The results presented here demonstrate that metasurfaces can enhance CEST-based techniques complementing previously reported benefits in anatomical imaging.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"38 5","pages":"e70027"},"PeriodicalIF":2.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11964795/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143772830","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":"³¹P-MRS-Measured Phosphocreatine Recovery Kinetics in Human Muscles in Health and Disease-A Systematic Review and Meta-Analysis.","authors":"Maninder Singh, Aditya Jhajharia, Rajat Pruthi, Owen T Carmichael","doi":"10.1002/nbm.70023","DOIUrl":"10.1002/nbm.70023","url":null,"abstract":"<p><p>The noninvasive, in vivo measurement of postexercise phosphocreatine (PCr) recovery kinetics using 31-phosphorus magnetic resonance spectroscopy (³¹P-MRS) is a highly prevalent method for assessing skeletal muscle energetics. However, ³¹P-MRS methodology is notoriously laboratory-specific, leading to uncertainty about the normal range of PCr recovery kinetics among healthy individuals, as well as relationships with disease and demographic factors. This systematic review and meta-analysis characterized the normal range of PCr recovery kinetics from ³¹P-MRS in human skeletal muscles across the lifespan, differences between healthy and those with muscle-related diseases, and relationships between intermuscular PCr recovery measurements and demographic factors. PubMed, Web of Science, Cochrane, and Google Scholar databases were searched for PCr recovery studies, which resulted in a final set of 128 studies eligible for meta-analysis. Studies were categorized into three muscle groups (forearm, upper leg, and lower leg) and further subdivided into three groups: diseased, control (the comparator group in studies of disease), and healthy (those recruited into studies that lacked a disease group). Only English-language studies were included. All statistical analysis was performed using Stata 17 software. Forest plots showed significant heterogeneity across PCr recovery time estimates and outlier study removal significantly reduced this heterogeneity. Greater age was associated with longer PCr recovery in upper leg muscles among both healthy (ρ = 0.387, p < 0.05) and diseased (ρ = 0.733, p < 0.05) individuals. Additionally, longer PCr recovery time was correlated with more acidic end-of-exercise pH in all three muscle groups among healthy individuals. In conclusion, skeletal muscle energetics as indexed by ³¹P-MRS-based PCr recovery time is similar across three different skeletal muscle groups among healthy people. Common diseases significantly prolong PCr recovery times. Methodological heterogeneity has a significant impact on PCr recovery time measurements in this literature. Greater age and more acidic pH increase PCr recovery time among healthy people.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"38 5","pages":"e70023"},"PeriodicalIF":2.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143796048","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":"Measurement of Twitch Dynamics in Response to Exercise Induced Changes in Mitochondrial Disease Using Motor Unit Magnetic Resonance Imaging (MUMRI): A Proof-of-Concept Study.","authors":"Matthew G Birkbeck, Mathew Elameer, Linda Heskamp, Jane Newman, Renae J Stefanetti, Isabel Barrow, Oksana Pogoryelova, Gráinne S Gorman, Julie Hall, Ian S Schofield, Andrew M Blamire, Roger G Whittaker","doi":"10.1002/nbm.70021","DOIUrl":"https://doi.org/10.1002/nbm.70021","url":null,"abstract":"<p><p>Muscle twitch dynamics and fatigability change in response to muscle disease. In this study, we developed an imaging paradigm to measure muscle twitch dynamics, and the response of the muscle to voluntary fatiguing contractions. We used a novel imaging technique called motor unit magnetic resonance imaging (MUMRI). MUMRI allows visualisation of muscle and motor unit activity by combining in-scanner electrical stimulation with dynamic pulsed gradient spin echo (twitch dynamics, PGSE-MUMRI) and phase contrast (fatigue, PC-MUMRI) imaging. In Part I of this study, we scanned 10 healthy controls, we measured the muscle rise (T_rise), contraction (T_contract) and half-relaxation time (T_half-relax) of the tibialis anterior (TA) muscle on a voxel-wise basis using PGSE-MUMRI. Five controls were scanned twice to assess reproducibility; PGSE-MUMRI demonstrated reproducible results, with low variation between scans 3.4% for T_rise, 6.4% for T_contract and 7.1% for T_half-relax. We then developed a PC-MUMRI paradigm to measure the recovery of the TA in response to a fatiguing voluntary exercise. In Part II of the study, we applied these two novel imaging paradigms in a cohort study of nine patients with single large-scale mtDNA deletion primary mitochondrial myopathy (PMM). Patients underwent a 12-week resistance exercise programme and baseline, and follow-up MRI was performed. PGSE-MUMRI detected a significantly longer muscle contraction time between baseline and follow-up in PMM patients 108.7 ± 7.9 vs. post-119.3 ± 10.4 ms; p = 0.018. There was no statistical difference in the recovery half maximum measured using PC-MUMRI in PMM patients between baseline and follow-up 254 ± 109 vs. 137 ± 41 s; p = 0.074. In conclusion, PGSE-MUMRI has detected differences in muscle twitch dynamics between controls and PMM following an exercise programme, and we can visualise differences in twitch dynamics subregions of muscle using this technique. The PC-MUMRI technique has shown promise as a novel measure of muscle fatigue.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"38 5","pages":"e70021"},"PeriodicalIF":2.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11981886/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143974926","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":"Advancing Myocardial T1 Mapping: A Comparative Study of the Frequency-Independent MFA Sequence and Standard MOLLI.","authors":"Vitali Koch, Mukaram Rana, Christina Seppi, Simon Martin, Thomas Vogl, David M Leistner, Marco M Ochs, Sebastian M Haberkorn","doi":"10.1002/nbm.70031","DOIUrl":"10.1002/nbm.70031","url":null,"abstract":"<p><p>T1 mapping is essential for detecting myocardial changes, but standard methods like the MOLLI sequence are limited by heart rate dependency and sensitivity to motion artifacts. This study introduces the multiflip angle (MFA) sequence as a novel alternative, aiming to provide frequency-independent and robust T1 mapping, particularly in challenging cardiac conditions. The novel MFA sequence was validated using nickel (II) chloride phantoms and systematically compared with the standard MOLLI sequence in 20 healthy volunteers using a 1.5 Tesla Philips Achieva MRI system. T1 values were assessed at rest and under mild physical exertion to evaluate frequency dependency, measurement precision, and robustness to motion artifacts. The MFA sequence demonstrated robust frequency independence, with T1 values remaining stable across varying heart rates, unlike MOLLI, which exhibited a significant correlation between T1 values and heart rate (R = 0.52, p < 0.001), and sex (3% higher values in females; p = 0.044). Although both sequences showed no statistically significant age-related differences, MOLLI yielded more precise T1 measurements with lower variability compared to MFA. Additionally, MFA exhibited reduced susceptibility to motion artifacts, maintaining consistent values across myocardial regions and physiological conditions, particularly in basal segments where MOLLI showed greater variability. The MFA sequence offers a frequency-independent and motion-robust alternative to the MOLLI sequence for myocardial T1 mapping. Although the MOLLI sequence provides higher precision, MFA's stability across varying heart rates and resistance to motion artifacts positions it as a promising option, particularly for patients with arrhythmias or during stress testing. Further investigation is warranted to refine its clinical applications.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"38 5","pages":"e70031"},"PeriodicalIF":2.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11964786/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143772786","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":"Towards Large Diameter Transmit Coils for 7-T Head Imaging: A Detailed Comparison of a Set of Transmit Element Design Concepts.","authors":"Max Joris Hubmann, Stephan Orzada, Robert Kowal, Johannes Anton Grimm, Oliver Speck, Holger Maune","doi":"10.1002/nbm.70030","DOIUrl":"10.1002/nbm.70030","url":null,"abstract":"<p><p>Many different transmit (Tx) coil concepts and designs for 7-T magnetic resonance imaging of the head have been proposed. Most of them are placed close to the head and in combination with the receive coils creating a helmet-like structure. This limits the space for additional equipment for external stimuli. A large diameter transmit coil can increase the ease using supplementary measurement devices. Therefore, this study systematically evaluated nine different Tx elements regarding their performance within a large diameter transmit coil with a diameter <math> <semantics><mrow><mo>></mo></mrow> <annotation>$$ > $$</annotation></semantics> </math>  350 mm. Each Tx element was examined regarding its power and specific absorption rate (SAR) efficiencies, its loading dependence, intrinsic decoupling, and its radio frequency (RF) shimming capability. Additionally, an experimental validation of <math> <semantics><mrow><mo>|</mo> <msubsup><mrow><mi>B</mi></mrow> <mrow><mtext>1</mtext></mrow> <mrow><mtext>+</mtext></mrow> </msubsup> <mo>|</mo></mrow> <annotation>$$ mid {B}_1^{+}mid $$</annotation></semantics> </math> -maps was performed. The loop-based Tx elements (circular and rectangular loop) provided the highest power and SAR efficiency with at least 15.5% and 21.2% higher efficiencies for a single channel and 22.1% and 18.0% for the eight-channel array, respectively. In terms of voxel-wise power efficiency, the circular loop was the superior Tx element type within most of the head. Looking at the voxel-wise SAR efficiency, the loop-based elements manifest themselves as the most efficient type within most of the central brain. The mutual coupling was lowest for the passively fed dipole ( <math> <semantics><mrow><mo>-</mo></mrow> <annotation>$$ - $$</annotation></semantics> </math> 31.23 dB). The highest RF shimming capability in terms of sum of normalized singular values was calculated for the rectangular (4.21) and the circular loop (4.36), whereby the L-curve results showed that the arrays have only minor <math> <semantics><mrow><mo>|</mo> <msubsup><mrow><mi>B</mi></mrow> <mrow><mtext>1</mtext></mrow> <mrow><mtext>+</mtext></mrow> </msubsup> <mo>|</mo></mrow> <annotation>$$ mid {B}_1^{+}mid $$</annotation></semantics> </math> shimming performance differences for the transversal slice. For the hippocampus, the meander element provided the highest overall homogeneity with a minimal coefficient of variation (CoV) of 5.1%. This work provides extensive and unique data for single and eight-channel Tx elements applying common performance benchmarks and enables further discourse on multi-channel evaluations towards large diameter Tx coils at 7-T head imaging. On the bases of the provided results, the preferable Tx element type for this specific application is loop-based.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"38 5","pages":"e70030"},"PeriodicalIF":2.7,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11971727/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143788561","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}