NMR in Biomedicine最新文献

{"title":"VesMamba: Vessel Morphology-Enhanced State Space Model for Cerebrovascular Delineation.","authors":"Lei Xie, Jiangxu Zhang, Jiawei Zhang, Qingrun Zeng, Yuanjing Feng","doi":"10.1002/nbm.70339","DOIUrl":"10.1002/nbm.70339","url":null,"abstract":"<p><p>Accurate delineation of cerebrovascular structures from Time-Of-Flight Magnetic Resonance Angiography (TOF-MRA) and Computed Tomography Angiography (CTA) is essential for the clinical diagnosis and treatment of cerebrovascular diseases. However, the intricate topology and fine-scale nature of cerebral vessels pose significant challenges for deep learning methods, which often struggle to capture long-range dependencies and precise morphological details. In this work, we propose VesMamba, a deep learning framework that integrates explicit vascular morphological priors into a state-space model. Unlike generic SSM-based methods that rely on fixed scanning patterns, we introduce a Tri-oriented Vessel-aware Mamba (ToVM) module, which dynamically reorders input 1D sequences using cerebrovascular edge features to better model complex vascular structures. Complementarily, we present the 3D Large-Small Gated Convolution (LSGC) module after the ToVM module to preserve critical spatial information. We conducted extensive experiments on two TOF-MRA and one CTA dataset, comparing our method with eight state-of-the-art approaches. Our results show that VesMamba achieves superior performance on the majority of evaluation metrics relative to all competing methods.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 9","pages":"e70339"},"PeriodicalIF":2.8,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13379598/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148472125","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\">Feasibility of Concurrent <ns0:math> <ns0:mrow><ns0:msup><ns0:mrow /> <ns0:mrow><ns0:mn>1</ns0:mn></ns0:mrow> </ns0:msup> </ns0:mrow> </ns0:math> H MRS and <ns0:math> <ns0:mrow><ns0:msup><ns0:mrow /> <ns0:mrow><ns0:mn>31</ns0:mn></ns0:mrow> </ns0:msup> </ns0:mrow> </ns0:math> P MRSI at 7 T: Brain Energy Metabolism Responses to Hyperglycemia.","authors":"Mark Widmaier, Brooke C Matson, Uzay Emir, Janice J Hwang","doi":"10.1002/nbm.70369","DOIUrl":"10.1002/nbm.70369","url":null,"abstract":"<p><p>How the human brain adjusts fuel handling and its bioenergetic state during changing glucose levels remains difficult to assess noninvasively. In this study, we established an interleaved multinuclear 7 T MR spectroscopy protocol to track a glucose-related <math> <mrow><msup><mrow></mrow> <mrow><mn>1</mn></mrow> </msup> </mrow> </math> H signal alongside <math> <mrow><msup><mrow></mrow> <mrow><mn>31</mn></mrow> </msup> </mrow> </math> P measures of high-energy phosphate metabolism during a hyperglycemic clamp. Five healthy adults completed a morning, fasted infusion experiment consisting of baseline, ramp-up, and hyperglycemic stages over <math><mrow><mo>∼</mo></mrow> </math> 120 min. Short-block, short-TE <math> <mrow><msup><mrow></mrow> <mrow><mn>1</mn></mrow> </msup> </mrow> </math> H single-voxel spectroscopy (STEAM, TE = 11 ms; mean block duration <math><mrow><mn>5</mn> <mo>.</mo> <mn>71</mn> <mo>±</mo> <mn>0</mn> <mo>.</mo> <mn>62</mn></mrow> </math>  min) was acquired in frontal cortex and quantified using the composite glucose <math><mrow><mo>+</mo></mrow> </math> taurine (Glc <math><mrow><mo>+</mo></mrow> </math> Tau) measure. <math> <mrow><msup><mrow></mrow> <mrow><mn>31</mn></mrow> </msup> </mrow> </math> P was acquired with rapid 3D PETALUTE MRSI using an ultrashort echo time (UTE; TE = 65  <math><mrow><mi>μ</mi></mrow> </math> s; 381 s per block), and high-energy phosphate ratios were derived from a posterior cortical region of interest. Across participants, <math> <mrow><msup><mrow></mrow> <mrow><mn>1</mn></mrow> </msup> </mrow> </math> H Glc <math><mrow><mo>+</mo></mrow> </math> Tau increased with blood glucose and showed significant elevations from baseline into hyperglycemia. In parallel, <math> <mrow><msup><mrow></mrow> <mrow><mn>31</mn></mrow> </msup> </mrow> </math> P ratios exhibited smaller but significant glycemia-linked responses: both PCr/Pi and <math><mrow><mi>γ</mi></mrow> </math> ATP/Pi increased with blood glucose and differed across glucose clamp stages. These findings show that <math> <mrow><msup><mrow></mrow> <mrow><mn>1</mn></mrow> </msup> </mrow> </math> H and <math> <mrow><msup><mrow></mrow> <mrow><mn>31</mn></mrow> </msup> </mrow> </math> P MRS(I) can be interleaved at 7 T to measure energy metabolism within a single session.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 9","pages":"e70369"},"PeriodicalIF":2.8,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13485382/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148796115","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":"Automated Surface-Based Segmentation of Deep Gray Matter Regions Based on Diffusion Tensor Images Reveals Unique Age Trajectories Over the Healthy Lifespan.","authors":"Graham Little, J Alejandro Acosta-Franco, Christian Beaulieu","doi":"10.1002/nbm.70353","DOIUrl":"10.1002/nbm.70353","url":null,"abstract":"<p><p>Many studies have demonstrated unique trajectories of deep gray matter (GM) volumes over development and aging, suggesting but not measuring microstructural alterations. Only a few studies have measured diffusion tensor imaging (DTI) parameters in deep GM or reported these values across a wide age range in a large cohort. Because many clinical protocols do not acquire T1-weighted images and registration between T1-weighted and diffusion images is error-prone, an automated segmentation technique is proposed that works solely on parametric maps calculated from DTI, enabling efficient DTI studies of deep GM in large cohorts without the need for additional structural imaging. The algorithm segments five subcortical GM structures by deforming 3D models to their boundaries visible on diffusion-weighted images and DTI maps. This DTI-only method is compared against standard T1-weighted segmentation using a 1.5-mm isotropic test-retest diffusion data (n = 24). Inter-method Dice coefficients were high (> 0.7) for 5 of 10 structures but were low for the left/right globus pallidus, left/right amygdala, and right hippocampus. The proposed DTI-only segmentation qualitatively appeared more accurate and yielded smaller volumes than T1w for all 10 structures. The segmentation method was then applied to a \"lifespan\" cohort (n = 357, 5-90 years, 203 females) to assess age changes in volume, fractional anisotropy (FA), and mean diffusivity (MD). For all five structures, MD trajectories were quadratic, decreasing and then increasing after ~30-35 years. For the globus pallidus and hippocampus, FA trajectories remained flat from 5 to ~25 years and then started to decrease over 5-90 years; FA decreased linearly for amygdala, increased linearly for striatum, and remained constant for the thalamus. Notably, the trajectories for DTI were distinct from those of the deep GM volumes. The proposed automated deep GM segmentation method on DTI-only will facilitate the analysis of deep GM DTI (not typically measured in most studies) and will be advantageous for studies without a T1-weighted scan, as in many clinical populations.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 8","pages":"e70353"},"PeriodicalIF":2.8,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13348013/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148412468","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":"Multicenter Assessment of Combined Brain and Cervical Spinal cord 3T MP2RAGE T1 Measurements for Reliable Tissue Microstructure Quantification.","authors":"Malo Gaubert, Benoit Combès, Henitsoa Rasoanandrianina, Jean-Christophe Ferré, Alice Dufey, Raphaël Chouteau, Bertrand Audoin, Jean Pelletier, Sarah Demortière, Anne Kerbrat, Elise Bannier, Virginie Callot","doi":"10.1002/nbm.70350","DOIUrl":"10.1002/nbm.70350","url":null,"abstract":"<p><p>Recent developments in quantitative T1 have enabled simultaneous scanning of both the brain and the cervical spinal cord (cSC) using the magnetization-prepared two rapid acquisition gradient echoes (MP2RAGE) sequence. However, the multicentre variability of such an approach has not yet been assessed. In this paper, we aim to evaluate multicentre variability (inter-scanner, between-session, between-participant) of T1 MP2RAGE measurements in the brain and cSC. A total of 52 MP2RAGE scans were acquired at two centres equipped with Siemens 3T MRI systems using an optimized MP2RAGE sequence. A subset of participants underwent scanning at both centres to evaluate inter-site variability. Between-session and inter-participant variability were assessed both globally and within specific regions, including brain white matter, cortical gray matter, deep gray matter, and cervical spinal cord vertebral levels using a linear mixed effect model. Mean intra-site/inter-site/between-participant coefficients of variation (COV) were 0.4/0.9/2.3% for the brain ROIs and 2.0/2.4/1.7% for the cSC. Our findings validate the consistency and reliability of the MP2RAGE brain and cervical spinal cord simultaneous acquisition in a multicentre setting. This approach has the potential to significantly impact the study of central nervous system pathologies, such as multiple sclerosis, by enabling fast, accurate, and reproducible quantitative imaging collection across multiple centres.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 8","pages":"e70350"},"PeriodicalIF":2.8,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13344110/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148405238","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":"Basal Energetics and Phosphocreatine Recovery Kinetics in Ambulatory Boys With Duchenne Muscular Dystrophy.","authors":"Pratiksha P Awale, Christophor Lopez, Tanja Taivassalo, Krista Vandenborne, Glenn A Walter, Sean C Forbes","doi":"10.1002/nbm.70336","DOIUrl":"10.1002/nbm.70336","url":null,"abstract":"<p><p>Duchenne muscular dystrophy (DMD) is an X-linked recessive condition that is characterized by muscle deterioration, loss of functional abilities, and shortened lifespan. There is growing evidence of skeletal muscle mitochondrial impairments in DMD, and ³¹phosphorous magnetic resonance spectroscopy (³¹P-MRS) provides a noninvasive marker of functional oxidative capacity of muscle. Therefore, the purpose of this study was to examine ³¹P-MRS indices of energetic status and oxidative capacity in DMD and correlate with clinical functional measures. In this study, we evaluated ambulatory participants with DMD (n = 21, 8.7 ± 1.9 years) and unaffected age-matched controls (n = 20, 9.0 ± 2.8 years) using a 3T MR system. ³¹P-MRS was used to measure relative changes in high-energy phosphates and muscle pH of the anterior compartment of the lower leg during and following isometric dorsiflexion muscle contractions (120 s rest, 60 s of contractions at 0.5 Hz, and 420 s recovery). Data were analyzed with jMRUI (v7.0), and a mono-exponential model was used to estimate the time constant (tau) of PCr recovery (PCrτ). We observed that relative concentrations of inorganic phosphate to phosphocreatine (Pi/PCr) and phosphodiesters to ATP (PDE/ATP) were elevated (p < 0.05) in DMD compared to controls, and the PCrτ recovery was slower (p < 0.01) in DMD than controls. PCrτ recovery was correlated with the distance covered in the 6-min walk test (6MWT) (ρ = -0.61, p < 0.01) and other timed functional measures (ρ = 0.54-0.67, p < 0.05). The findings from this study demonstrated that energetic status is altered and PCr recovery time is impaired in ambulatory boys with DMD indicating reduced oxidative capacity compared to unaffected controls. Overall, these findings support the use of ³¹P-MRS as a valuable noninvasive tool to evaluate skeletal muscle energetics and mitochondrial function in individuals with DMD.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 8","pages":"e70336"},"PeriodicalIF":2.8,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13284526/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148295778","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":"Skeletal Motor Unit Recruitment During Periodic Auditory Cueing: A Simultaneous Behavioral and Motor Unit Magnetic Resonance Imaging (MUMRI) Study.","authors":"Ao Wang, Ian Schofield, Matthew G Birkbeck, Daniel Baxter-Beard, Andrew M Blamire, Roger G Whittaker","doi":"10.1002/nbm.70347","DOIUrl":"10.1002/nbm.70347","url":null,"abstract":"<p><p>Rhythmic motor paradigms are widely used to study sensorimotor timing, yet magnetic resonance imaging (MRI) research has largely focused on central processes, with limited insight into peripheral neuromuscular mechanisms. Motor unit MRI (MUMRI), a motion-sensitive technique in which muscle contraction induces intravoxel water redistribution and transient signal attenuation, enables in vivo visualization of muscle activity. In this study, we developed and validated a combined behavioral-MUMRI paradigm to characterize muscle recruitment during rhythmic foot tapping. Healthy participants performed an auditory-paced tapping task inside an MRI scanner while timing was recorded via an MRI-compatible force transducer and muscle activity was measured using single-slice MUMRI. A variable-latency cueing design systematically sampled the temporal relationship between auditory cues, motor execution, and image acquisition, allowing identification of the optimal latency window for detecting contraction-related signal changes. Fixed-latency acquisitions were then used to assess reproducibility. Behavioral results showed stable performance across conditions, with low variability in tapping accuracy (mean coefficient of variation [CoV] ≈0.078). Transient, localized signal reductions consistent with muscle contraction were observed in anterior lower leg muscles during dorsiflexion. Voxel-wise analyses demonstrated high within-condition reproducibility and latency-dependent spatial patterns, with the greatest average consistency when tapping aligned with scanner rhythm (r ≈0.68). These findings establish a robust framework for integrating rhythmic motor tasks with MUMRI, highlighting the importance of precise temporal alignment for reliable measurement of muscle activity. This approach provides a reproducible method for linking motor behavior to peripheral neuromuscular dynamics and offers potential for advancing both basic and clinical MRI research.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 8","pages":"e70347"},"PeriodicalIF":2.8,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13333902/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148391571","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 System for Retrofitting Conventional MRI Systems for Simultaneous Multinuclear MRI/MRS.","authors":"Jue Hou, Courtney Bauer, Edith Touchet-Valle, Mary P McDougall, Steven M Wright","doi":"10.1002/nbm.70326","DOIUrl":"10.1002/nbm.70326","url":null,"abstract":"<p><p>Proton magnetic resonance imaging (MRI) and spectroscopy (MRS) are widely used in clinical and research applications. Recent interest in X-nuclei studies highlights their ability to provide additional biochemical information, but the intrinsically low X-nuclear signal-to-noise ratio (SNR) significantly increases scan time. Simultaneous (rather than serial) acquisition of multiple nuclei can significantly reduce experiment time, but most conventional MR systems lack this capability without modifications. We present a cost-effective system that enables simultaneous multinuclear imaging and spectroscopy on conventional MR spectrometers. Our approach offers enhanced flexibility for multinuclear experiments, supports multinuclear array receive capability, and maintains phase stability in the radio frequency (RF) chain. The proposed system comprised multiple transmit and receive mixing channels and a four-channel flexible local oscillator (LO) source. By interfacing with the spectrometer, simultaneous transmit and receive at different frequencies were achieved. The performance of the system was evaluated through bench measurement and phantom multinuclear MRI and MRS experiments. Transmit and receive channel isolation of better than 30 dB was measured on the bench. Simultaneous excitation and reception of ²H and ²³Na gradient echo images were acquired, as well as interleaved excitation with simultaneous reception of ¹H, ²H, and ²³Na FIDs. Water-suppressed ¹H and ³¹P MRS were performed simultaneously on phantoms mimicking muscle metabolites. Results across all experiments showed no signal-to-noise ratio (SNR) loss compared to single-frequency operation. The proposed system supports multiple variations of simultaneous experiments on conventional MRI systems, demonstrating its flexibility in configuring experiments with varying numbers of nuclei (2-4), different transmit modes (simultaneous or interleaved), and supporting receive array coils of up to 16 channels, while maintaining phase stability in the RF chain without the need for retrospective correction.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 8","pages":"e70326"},"PeriodicalIF":2.8,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13278807/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148278216","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":"Standard Model Imaging in the Brain and Spinal Cord of MS Patients: Initial Assessment and Comparison to Diffusion Tensor Imaging.","authors":"Atlee Witt, Alicia E Cronin, Bailey Busher, Isabella Stuart, Grace Sweeney, Kristin P O'Grady, Seth A Smith, Samantha By, Kurt Schilling","doi":"10.1002/nbm.70354","DOIUrl":"10.1002/nbm.70354","url":null,"abstract":"<p><p>Multiple sclerosis (MS) pathology manifests across the central nervous system (CNS), yet magnetic resonance imaging (MRI) studies frequently assess the brain and spinal cord (SC) in isolation. It remains unclear whether microstructural injury in normal-appearing white matter (NAWM) and lesions manifests identically across these distinct anatomical environments or if advanced biophysical models offer diagnostic advantages over standard diffusion techniques. We performed a comprehensive 3T MRI protocol with same-session brain and cervical SC imaging on 34 persons with relapsing-remitting MS (pwRRMS) and 36 healthy controls (HCs). We focused on diffusion frameworks (diffusion tensor imaging [DTI], standard model imaging with free water [SMIfw]) to quantify and compare microstructural integrity between the brain and cervical SC for the first time. Specifically, we assessed the feasibility of SMI for clinical implementation in terms of sensitivity (contrast between lesions and NAWM in pwRRMS) and reliability (HC reproducibility). Our findings indicate that both simple (DTI) and advanced (SMI) models are sensitive to MS-related microstructural changes, but the utility varied by region: notably, SMI-derived neurite density fraction (f) emerged as a robust marker of MS pathology in both the brain and SC, while DTI metrics like fractional anisotropy (FA) and radial diffusivity (RD) showed comparable sensitivity exclusively in the brain. Though axonal loss appears to be a global feature detectable even in early-stage disease, the inflammatory or edematous environment of lesions differs fundamentally between the brain and SC. Taken together, these findings demonstrate the utility of SMI for comprehensive CNS assessment and support its potential for future usage in clinical trials and improved disease monitoring.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 8","pages":"e70354"},"PeriodicalIF":2.8,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13346334/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148412472","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":"Restriction-Weighted Q-Space Trajectory Imaging (ResQ): Toward Mapping Diffusion-Time Effects With Tensor-Valued Diffusion Encoding in Human Prostate Cancer Xenografts.","authors":"Filip Szczepankiewicz, Malwina Molendowska, Samo Lasič, Marcella E Safi, Michael Gottschalk, Evangelia Sereti, Anders Bjartell, Linda Knutsson, Oskar Vilhelmsson Timmermand, Crister Ceberg, Joanna Strand","doi":"10.1002/nbm.70344","DOIUrl":"10.1002/nbm.70344","url":null,"abstract":"<p><p>Tensor-valued diffusion encoding employs gradient waveforms that enable unique sensitivity to microstructural features of tissue, but the interpretation of signal and parameters may be confounded by diffusion-time dependence. We introduce a framework for restriction-weighted q-space trajectory imaging (ResQ) that incorporates diffusion-time effects via the restriction-weighting tensor, and we evaluate it in a longitudinal study of prostate cancer xenografts treated by external radiotherapy. We proposed a novel gradient waveform design for tensor-valued encoding with controlled restriction weighting and applied a set of four waveforms at a 9.4 T preclinical MRI system. Mice were inoculated with human prostate cancer cells (LNCaP) and assigned to groups that were untreated controls or treated by external beam irradiation. ResQ produced parameters that describe the diffusion process in terms of the mean diffusivity (D), isotropic diffusional variance (V_Di), and microscopic diffusion anisotropy (V_Da) as well as their diffusion-time dependence (ΔD, ΔV_Di, ΔV_Da). Analyses were performed to characterize parameters longitudinally and across groups. To highlight the consequences of ignoring restriction effects, we compared ResQ to analogous parameters estimated by q-space trajectory imaging (QTI). ResQ revealed clear diffusion-time dependence across all tumors, with significant longitudinal differences between treated and untreated groups, most prominent in D, ΔD, and V_Di. The ResQ signal representation captured the signal dynamics, whereas QTI did not. Neglecting diffusion-time dependence in QTI led to substantial parameter bias, most notably a pronounced overestimation of microscopic diffusion anisotropy. Diffusion-time effects are non-negligible in prostate cancer and must be considered when using tensor-valued diffusion encoding. The ResQ framework enables controlled restriction weighting and improved interpretability of diffusion MRI parameters compared with approaches that ignore the effects of restriction. This provides a more principled approach for tensor-valued diffusion encoding and may enable novel imaging biomarkers that disentangle diffusivity, isotropic diffusional variance, microscopic anisotropy, and their diffusion-time dependence.</p>","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 8","pages":"e70344"},"PeriodicalIF":2.8,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13311205/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148345362","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":"Improved Radiofrequency Safety Modelling in MRI Using In Vivo Measurements of Brain Conductivity.","authors":"Guillaume Paillart, Zhongzheng He, Grecia Romero, Pauline Ferry, Khalid Ambarki, Paul Soullié, Jacques Felblinger, Freddy Odille","doi":"10.1002/nbm.70335","DOIUrl":"10.1002/nbm.70335","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Tissue electrical properties are required by electromagnetic simulation software to conduct radiofrequency (RF) safety studies. Values are commonly taken from existing databases of tissue properties, where brain conductivity was measured ex vivo. We hypothesize that using in vivo brain conductivity values, as reported in the recent literature on in vivo MRI measurements, can improve the accuracy of such simulations. Sixteen subjects were scanned at 3T to obtain experimental maps of the transmit RF field, &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msubsup&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt; &lt;mo&gt;+&lt;/mo&gt;&lt;/msubsup&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {B}_1^{+} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; , of the head. Electromagnetic simulations were performed using biomodels with varying morphologies, using both a conventional ( &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;σ&lt;/mi&gt; &lt;mrow&gt;&lt;mi&gt;ex&lt;/mi&gt; &lt;mspace&gt;&lt;/mspace&gt; &lt;mtext&gt;vivo&lt;/mtext&gt;&lt;/mrow&gt; &lt;/msub&gt; &lt;mo&gt;=&lt;/mo&gt; &lt;mn&gt;0.46&lt;/mn&gt; &lt;mspace&gt;&lt;/mspace&gt; &lt;mi&gt;S&lt;/mi&gt; &lt;mo&gt;/&lt;/mo&gt; &lt;mi&gt;m&lt;/mi&gt;&lt;/mrow&gt; &lt;annotation&gt;$$ {sigma}_{mathrm{ex} mathrm{vivo}}=0.46 mathrm{S}/mathrm{m} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; ) and a modified brain conductivity ( &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;σ&lt;/mi&gt; &lt;mtext&gt;in vivo&lt;/mtext&gt;&lt;/msub&gt; &lt;mo&gt;=&lt;/mo&gt; &lt;mn&gt;0.70&lt;/mn&gt; &lt;mspace&gt;&lt;/mspace&gt; &lt;mi&gt;S&lt;/mi&gt; &lt;mo&gt;/&lt;/mo&gt; &lt;mi&gt;m&lt;/mi&gt;&lt;/mrow&gt; &lt;annotation&gt;$$ {sigma}_{mathrm{in} mathrm{vivo}}=0.70 mathrm{S}/mathrm{m} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; ). A framework was developed to process the simulated &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msubsup&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt; &lt;mo&gt;+&lt;/mo&gt;&lt;/msubsup&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {B}_1^{+} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; fields, including a systematic method to combine the two excitation ports of the transmit coil model (accounting for different load impedances between simulation and experiment), geometric alignment, and scaling of the simulated fields, allowing a quantitative comparison of complex &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msubsup&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt; &lt;mo&gt;+&lt;/mo&gt;&lt;/msubsup&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {B}_1^{+} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; maps of the brain with experimental maps. Specific absorption rate (SAR) maps were also estimated by different methods, including a novel &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msubsup&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt; &lt;mo&gt;+&lt;/mo&gt;&lt;/msubsup&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {B}_1^{+} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; -derived formula. Normalized root-mean-squared errors between simulation and experiment, in the brain, were approximately 6% for &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msubsup&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt; &lt;mo&gt;+&lt;/mo&gt;&lt;/msubsup&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {B}_1^{+} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; magnitude. While head geometry mainly impacted the accuracy of &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msubsup&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt; &lt;mo&gt;+&lt;/mo&gt;&lt;/msubsup&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {B}_1^{+} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; magnitude, with errors up to 11% (p = 0.007) between the best fitting human model and the worst one, brain electrical conductivity mainly impacted &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msubsup&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt; ","PeriodicalId":19309,"journal":{"name":"NMR in Biomedicine","volume":"39 8","pages":"e70335"},"PeriodicalIF":2.8,"publicationDate":"2026-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13291641/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148308864","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}