Magnetic Resonance in Medicine最新文献

{"title":"Enhancing cardiac MRI reliability at 3 T using motion-adaptive B₀ shimming.","authors":"Yuheng Huang, Archana Vadiraj Malagi, Xinqi Li, Xingmin Guan, Chia-Chi Yang, Li-Ting Huang, Ziyang Long, Jeremy Zepeda, Xinheng Zhang, Ghazal Yoosefian, Xioaming Bi, Chang Gao, Yun Shang, Nader Binesh, Hsu-Lei Lee, Debiao Li, Rohan Dharmakumar, Hui Han, Hsin-Jung R Yang","doi":"10.1002/mrm.70026","DOIUrl":"https://doi.org/10.1002/mrm.70026","url":null,"abstract":"<p><strong>Purpose: </strong>Magnetic susceptibility differences at the heart-lung interface introduce B₀-field inhomogeneities that challenge cardiac MRI at high field strengths (≥ 3 T). Although hardware-based shimming has advanced, conventional approaches often neglect dynamic variations in thoracic anatomy caused by cardiac and respiratory motion, leading to residual off-resonance artifacts. This study aims to characterize motion-induced B₀-field fluctuations in the heart and evaluate a deep learning-enabled motion-adaptive B₀ shimming pipeline to mitigate them.</p><p><strong>Methods: </strong>A motion-resolved B₀ mapping sequence was implemented at 3 T to quantify cardiac and respiratory-induced B₀ variations. A motion-adaptive shimming framework was then developed and validated through numerical simulations and human imaging studies. B₀-field homogeneity and T₂* mapping accuracy were assessed in multiple breath-hold positions using standard and motion-adaptive shimming.</p><p><strong>Results: </strong>Respiratory motion significantly altered myocardial B₀ fields (p < 0.01), whereas cardiac motion had minimal impact (p = 0.49). Compared with conventional scanner shimming, motion-adaptive B₀ shimming yielded significantly improved field uniformity across both inspiratory (post-shim SD_ratio: 0.68 ± 0.10 vs. 0.89 ± 0.11; p < 0.05) and expiratory (0.65 ± 0.16 vs. 0.84 ± 0.20; p < 0.05) breath-hold states. Corresponding improvements in myocardial T₂* map homogeneity were observed, with reduced coefficient of variation (0.44 ± 0.19 vs. 0.39 ± 0.22; 0.59 ± 0.30 vs. 0.46 ± 0.21; both p < 0.01).</p><p><strong>Conclusion: </strong>The proposed motion-adaptive B₀ shimming approach effectively compensates for respiration-induced B₀ fluctuations, enhancing field homogeneity and reducing off-resonance artifacts. This strategy improves the robustness and reproducibility of T₂* mapping, enabling more reliable high-field cardiac MRI.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144855718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Absolute quantification of cerebral metabolites using two-dimensional proton MR spectroscopic imaging with quantitative MRI-based water reference.","authors":"Dennis C Thomas, Seyma Alcicek, Andrei Manzhurtsev, Elke Hattingen, Katharina J Wenger, Ulrich Pilatus","doi":"10.1002/mrm.70027","DOIUrl":"https://doi.org/10.1002/mrm.70027","url":null,"abstract":"<p><strong>Purpose: </strong>Metabolite concentrations are valuable biomarkers in brain tumors (BTs). However, absolute quantification of metabolites using MR spectroscopy requires a correction of water relaxation using time-consuming quantitative MRI (qMRI) sequences in addition to a lengthy two-dimensional spectroscopic water-reference acquisition. The goal of this work was to develop and validate a fast quantification method where a two-dimensional spectroscopic water reference is obtained using qMRI and a single-voxel stimulated-echo acquisition mode (STEAM) sequence.</p><p><strong>Methods: </strong>The semi-adiabatic localization by adiabatic selective refocusing (sLASER) sequence was used for MR spectroscopy imaging (MRSI) acquisition. A single-voxel unsuppressed water signal was acquired using a STEAM sequence. A qMRI protocol was also acquired, and the H₂O map was calibrated based on the STEAM signal to obtain the spectroscopic water reference (proposed method). Five healthy volunteers and one BT patient were scanned at 3 T. Concentrations obtained using the proposed and two reference methods-one where water-relaxation effects were corrected using literature values (reference method) and one where they were corrected using qMRI-derived values (reference method with qMRI)-were compared.</p><p><strong>Results: </strong>In healthy subjects, white-matter metabolite concentrations obtained using water relaxation using literature values (reference method) significantly differed from those using individual-specific corrections (reference method with qMRI and proposed method). Bland-Altman analyses revealed a very low bias and standard deviation of the differences between the reference method with qMRI and the proposed method (bias < 0.5% and standard deviation < 10%). The BT regions showed an approximate 35% underestimation of metabolite concentrations using the reference method.</p><p><strong>Conclusion: </strong>For metabolite quantification, accurate water referencing with individual-specific corrections for water relaxation times was obtained in 8 min using the proposed method.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144847270","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamic contrast enhanced-magnetic resonance fingerprinting (DCE-MRF): A new quantitative MRI method to reliably assess tumor vascular perfusion","authors":"Christina J. MacAskill,&nbsp;Yuran Zhu,&nbsp;Guanhua Wang,&nbsp;Bernadette O. Erokwu,&nbsp;Chetan B. Dhakan,&nbsp;Andrew Dupuis,&nbsp;Barbara J. Schiemann,&nbsp;Michael Kavran,&nbsp;Chunying Wu,&nbsp;William P. Schiemann,&nbsp;Mark A. Griswold,&nbsp;Xin Yu,&nbsp;Mark D. Pagel,&nbsp;Chris A. Flask","doi":"10.1002/mrm.70019","DOIUrl":"10.1002/mrm.70019","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>The clinical utility of conventional DCE-MRI methods is limited by the use of conventional qualitative dynamic T₁-weighted images, resulting in poor reproducibility. This study presents the initial implementation of a new DCE-magnetic resonance fingerprinting (DCE-MRF) methodology to provide reproducible, quantitative assessments of tumor vascular perfusion.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>The DCE-MRF acquisition combines multiple T₁ preparations, highly undersampled spiral trajectories (<i>R</i> = 48), a low-rank reconstruction method, and low tip angles on a 9.4 T preclinical MRI scanner to rapidly generate dynamic T₁ maps (23-s temporal resolution). In vitro validation experiments were conducted across a range of Gadovist concentrations to assess accuracy and temporal precision in comparison to conventional methods. The DCE-MRF method was also evaluated in vivo in an orthotopic 4T1 mouse model of breast cancer (<i>n</i> = 25). Pharmacokinetic modeling of the in vivo data was performed using a linear reference region model (LRRM).</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>In vitro DCE-MRF studies demonstrated good agreement with conventional MRI methods for T₁ measurements (<i>R</i>² <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>≥</mo>\u0000 </mrow>\u0000 <annotation>$$ ge $$</annotation>\u0000 </semantics></math> 0.99). The iterative low-rank reconstruction method also reduced artifacts compared to conventional reconstruction methods. DCE-MRF demonstrated a 2- to 3-fold reduction in temporal variability compared to conventional DCE-MRI, and enabled effective in vivo pharmacokinetic modeling using the LRRM by generating voxelwise maps of <i>RK</i>^trans and <i>k</i>_ep,T as measures of tumor vascular perfusion.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>DCE-MRF represents a new inherently quantitative approach to measuring tumor vascular perfusion that can be used in animal models and eventually in patients.</p>\u0000 </section>\u0000 </div>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":"94 6","pages":"2578-2592"},"PeriodicalIF":3.0,"publicationDate":"2025-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/mrm.70019","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144847272","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Automatic detection of arterial input function for brain DCE-MRI in multi-site cohorts","authors":"Lucas Saca,&nbsp;Raghav Gaggar,&nbsp;Ioannis Pappas,&nbsp;Tammie Benzinger,&nbsp;Eric M. Reiman,&nbsp;Mark S. Shiroishi,&nbsp;Elizabeth B. Joe,&nbsp;John M. Ringman,&nbsp;Hussein N. Yassine,&nbsp;Lon S. Schneider,&nbsp;Helena C. Chui,&nbsp;Daniel A. Nation,&nbsp;Berislav V. Zlokovic,&nbsp;Arthur W. Toga,&nbsp;Ararat Chakhoyan,&nbsp;Samuel Barnes","doi":"10.1002/mrm.70020","DOIUrl":"10.1002/mrm.70020","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>Arterial input function (AIF) extraction is a crucial step in quantitative pharmacokinetic modeling of DCE-MRI. This work proposes a robust deep learning model that can precisely extract an AIF from DCE-MRI images.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>A diverse dataset of human brain DCE-MRI images from 289 participants, totaling 384 scans, from five different institutions with extracted gadolinium-based contrast agent curves from large penetrating arteries, and with most data collected for blood–brain barrier (BBB) permeability measurement, was retrospectively analyzed. A 3D UNet model was implemented and trained on manually drawn AIF regions. The testing cohort was compared using proposed AIF quality metric AIFitness and K^trans values from a standard DCE pipeline. This UNet was then applied to a separate dataset of 326 participants with a total of 421 DCE-MRI images with analyzed AIF quality and K^trans values.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>The resulting 3D UNet model achieved an average AIFitness score of 93.9 compared to 99.7 for manually selected AIFs, and white matter K^trans values were 0.45/min × 10⁻³ and 0.45/min × 10⁻³, respectively. The intraclass correlation between automated and manual K^trans values was 0.89. The separate replication dataset yielded an AIFitness score of 97.0 and white matter K^trans of 0.44/min × 10⁻³.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusion</h3>\u0000 \u0000 <p>Findings suggest a 3D UNet model with additional convolutional neural network kernels and a modified Huber loss function achieves superior performance for identifying AIF curves from DCE-MRI in a diverse multi-center cohort. AIFitness scores and DCE-MRI-derived metrics, such as K^trans maps, showed no significant differences in gray and white matter between manually drawn and automated AIFs.</p>\u0000 </section>\u0000 </div>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":"94 6","pages":"2732-2744"},"PeriodicalIF":3.0,"publicationDate":"2025-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/mrm.70020","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144847271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"DBFF-Net: A Dual-Branch Feature Fusion Network for low angular resolution fiber orientation distribution reconstruction","authors":"Yingying Yao,&nbsp;Lingmei Ai,&nbsp;Ruoxia Yao","doi":"10.1002/mrm.70025","DOIUrl":"10.1002/mrm.70025","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>Estimation of Fiber Orientation Distribution (FOD) is an essential step in tractography. However, traditional reconstruction methods such as Multi-shell Multi-Tissue Constrained Spherical Deconvolution (MSMT-CSD) are demanding in terms of data quality and hardware equipment, limiting their application to low-angle resolution data. Deep learning has demonstrated significant potential for fiber orientation distribution reconstruction in recent years. Nevertheless, there is still room for improvement in the models, particularly in terms of reconstruction accuracy and the retention of fine details. This study aims to develop an efficient and reliable deep- learning framework to improve the accuracy of fiber orientation distribution reconstruction, namely, the Dual-Branch Feature Fusion Network (DBFF-Net).</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>DBFF-Net learns the key features of high angular resolution FOD through a multi-branch network architecture, which incorporates high-quality MSMT-CSD data as the target during the training process, and by fusing multi-scale feature information, significantly improves the FOD reconstruction performance of Low Angular Resolution Diffusion Imaging (LARDI) data.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>The experimental results show that DBFF-Net surpasses existing traditional and deep-learning methods across multiple metrics, particularly in the fiber crossing regions and under LARDI data conditions.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusion</h3>\u0000 \u0000 <p>DBFF-Net provides an efficient and reliable FOD reconstruction scheme and offers a new white matter fiber imaging tool in clinical and scientific research.</p>\u0000 </section>\u0000 </div>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":"94 6","pages":"2758-2770"},"PeriodicalIF":3.0,"publicationDate":"2025-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144816992","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Myocardial Arterial Spin Labeling with Double Inversion Recovery for reduced physiological noise","authors":"Maša Božić-Iven,&nbsp;Stanislas Rapacchi,&nbsp;Yi Zhang,&nbsp;Qian Tao,&nbsp;Lothar Rudi Schad,&nbsp;Sebastian Weingärtner","doi":"10.1002/mrm.70018","DOIUrl":"10.1002/mrm.70018","url":null,"abstract":"&lt;div&gt;\u0000 \u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Purpose&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;To introduce Double Inversion Recovery (DIR) preparations for myocardial Arterial Spin Labeling (myoASL) for mitigation of heart rate (HR) variability induced physiological noise (PN).&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Methods&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;DIR-labeling was implemented for double ECG-gated myoASL-sequences and compared with conventional Flow-sensitive Alternating Inversion Recovery (FAIR) labeling using single inversions. In DIR-preparations, the FAIR-inversion pulses were immediately followed by an identical reinversion pulse, applied either slice-selectively or nonselectively. Bloch-equation-based simulation and phantom experiments were performed to evaluate the PN and SNR across a range of HR variabilities. Data from six healthy subjects were acquired to evaluate myocardial blood flow (MBF), PN, and SNR in vivo.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Results&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;Simulation experiments showed that the average MBF values remained nearly constant across the range of HR variabilities and were comparable across all three sequences. However, DIR-labeling allowed for greater recovery of the myocardial background signal, which mitigates the sensitivity to HR-dependent changes in the inversion time. Consequently, PN in the presence of HR variability was substantially reduced with DIR-labeling. For HR variabilities corresponding to the mean value observed in vivo, this resulted in a simulated SNR gain of 1.79 &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;±&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$$ pm $$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; 0.90 for selective and 1.55 &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;±&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$$ pm $$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; 0.77 for nonselective DIR-labeling. In vivo, DIR-labeling showed reduced PN, with 53% (&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;p&lt;/mi&gt;\u0000 &lt;mo&gt;&lt;&lt;/mo&gt;\u0000 &lt;mn&gt;0&lt;/mn&gt;\u0000 &lt;mo&gt;.&lt;/mo&gt;\u0000 &lt;mn&gt;05&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$$ p&lt;0.05 $$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;)/44% (&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;p&lt;/mi&gt;\u0000 &lt;mo&gt;=&lt;/mo&gt;\u0000 &lt;mn&gt;0&lt;/mn&gt;\u0000 ","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":"94 6","pages":"2460-2474"},"PeriodicalIF":3.0,"publicationDate":"2025-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/mrm.70018","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144816996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Flow-suppressed 2D spin-echo imaging with high tolerance to B₁ inhomogeneity using hyperbolic secant pulses.","authors":"Jae-Youn Keum, Jeong Hee Yoon, Michael Garwood, Jang-Yeon Park","doi":"10.1002/mrm.70032","DOIUrl":"https://doi.org/10.1002/mrm.70032","url":null,"abstract":"<p><strong>Purpose: </strong>To demonstrate flow-suppressed two-dimensional (2D) spin-echo and spin-echo diffusion echo-planar imaging (EPI) sequences using hyperbolic secant (HS) pulses for both π/2 excitation and π refocusing.</p><p><strong>Theory and methods: </strong>A theoretical framework to derive phase dispersion of moving spins under π/2 excitation and π refocusing using HS pulses was described. Numerical simulations were performed to verify the validity of the theoretical analysis. All experiments were performed on a 3T clinical scanner. Phantom and human-brain imaging was performed using 2D spin-echo sequence, and liver imaging was performed using 2D spin-echo diffusion EPI. The signal-to-noise ratio and residual blood flow signal of the proposed sequences were compared with those of conventional spin-echo sequences using sinc pulses.</p><p><strong>Results: </strong>Results from human brain and liver images demonstrated that the proposed method substantially reduced blood flow artifacts. In the brain, venous blood flow was suppressed more effectively with the proposed method than with conventional spin-echo sequence using presaturation. In the liver, as compared with spin-echo sequence using sinc pulses, the proposed method showed noticeable attenuation of bright blood signals at low b-values, whereas the overall tissue signal in peripheral regions was higher. The signal-to-noise ratio was enhanced by 10% to 30%, indicating improved B₁ tolerance due to the adiabatic π refocusing HS pulse.</p><p><strong>Conclusion: </strong>Flow suppression and partial B₁ insensitivity were achieved by replacing sinc pulses with HS pulses in conventional 2D spin-echo imaging and spin-echo diffusion EPI sequences. This approach may be particularly useful in various applications requiring reduced vascular signal contamination, such as liver and brain imaging.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144816994","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The choroid plexus water density.","authors":"Abigail R Dubois, Maeve Curtin, Kilian Hett, Melanie Leguizamon, Alexander K Song, Maria Garza, Colin D McKnight, Ciaran M Considine, Manus J Donahue","doi":"10.1002/mrm.70028","DOIUrl":"https://doi.org/10.1002/mrm.70028","url":null,"abstract":"<p><strong>Purpose: </strong>To quantify normative ranges and circadian variability of the choroid plexus (ChP) water density in healthy adults.</p><p><strong>Methods: </strong>Actigraphy assessments of circadian activity were performed for 5 days in healthy participants (n = 15; age = 28.5 ± 6.5 years) and subsequently participants underwent repeated, high spatial resolution proton density-weighted imaging (spatial resolution = 0.25 × 0.25 × 1.50 mm) with a driven equilibrium (DRIVE) module at 3 T across four time epochs during wakefulness: 7:00 to 9:00, 11:00 to 13:00, 16:00 to 18:00, and 19:00 to 21:00. ChP water density (unitless ratio of mL water/mL ChP) was calculated as the product of white matter water density and the ratio of the ChP and white matter signal intensity at the level of the atria of the lateral ventricles. Descriptive statistics (mean ± SD; range; median) of water density values at each time were recorded. Spearman and Kendall rank coefficients were used to assess relationships between time, circadian variability, and ChP water density (significance criterion: p < 0.05).</p><p><strong>Results: </strong>Across all participants and scans (n = 60), mean ChP water density was 0.895 ± 0.047 (range = 0.806-0.983; median = 0.892). Across time periods, water density was 0.891 ± 0.038 (time = 7:44), 0.891 ± 0.050 (time = 12:17), 0.896 ± 0.045 (time = 16:03), and 0.901 ± 0.058 (time = 19:31), and no relationships between ChP water density and time of day or circadian activity were observed.</p><p><strong>Conclusions: </strong>The ChP water density at the level of the atria of the lateral ventricles is approximately 0.895 ± 0.047 in healthy adults and does not change significantly with time of day during wakefulness. This value should provide a useful reference for the growing number of neuroimaging protocols that aim to derive quantitative contrast and functional metrics from ChP MRI.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144816998","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multiband Fast Spin Echo on portable low-field systems.","authors":"Philip K Lee, Yueqi Qiu, Changyue Wang, Zhiyong Zhang","doi":"10.1002/mrm.70036","DOIUrl":"https://doi.org/10.1002/mrm.70036","url":null,"abstract":"<p><strong>Purpose: </strong>To improve the SNR efficiency of Fast Spin Echo (FSE) using RF-encoded multiband imaging and to develop techniques that correct artifacts from non-Carr-Purcell-Meiboom-Gill (CPMG) magnetization arising from system imperfections.</p><p><strong>Methods: </strong>Optimal refocusing pulse <math> <semantics><mrow><mn>0</mn> <mo>-</mo> <mi>π</mi></mrow> <annotation>$$ 0-pi $$</annotation></semantics> </math> band phase modulations that satisfy the CPMG condition were calculated for different multiband factors. Fast recovery was used to enhance T2 contrast. Quadratic phase refocusing pulses, phase encode and slice select gradient reshaping, and zeroth-order phase calibrations were tested to reduce residual non-CPMG magnetization. Image contrast of T2-weighted and T1-weighted imaging and SNR improvements were evaluated in phantom and in vivo experiments on an in-house portable 110 mT system.</p><p><strong>Results: </strong>The peak <math> <semantics> <mrow> <msub><mrow><mi>B</mi></mrow> <mrow><mn>1</mn></mrow> </msub> </mrow> <annotation>$$ {B}_1 $$</annotation></semantics> </math> of multiband refocusing pulses using the obtained optimal <math> <semantics><mrow><mn>0</mn> <mo>-</mo> <mi>π</mi></mrow> <annotation>$$ 0-pi $$</annotation></semantics> </math> phase modulations varies closely with the expected increase of <math> <semantics> <mrow> <msqrt> <mrow> <msub><mrow><mi>N</mi></mrow> <mrow><mi>b</mi> <mi>a</mi> <mi>n</mi> <mi>d</mi> <mi>s</mi></mrow> </msub> </mrow> </msqrt> </mrow> <annotation>$$ sqrt{N_{bands}} $$</annotation></semantics> </math> . Modulations satisfying the CPMG phase condition provide similar peak <math> <semantics> <mrow> <msub><mrow><mi>B</mi></mrow> <mrow><mn>1</mn></mrow> </msub> </mrow> <annotation>$$ {B}_1 $$</annotation></semantics> </math> reductions to previously proposed subband modulation schemes. Quadratic phase increment reduced shading from residual non-CPMG magnetization, and bipolar phase encoding reduced residual ghosting. Zeroth-order RF phase calibrations on the excitation and tipup, and slice select reshaping that minimized residual phase on 2D maps calculated from even and odd echo images improved contrast with long T2 species. RF-encoded multiband FSE improved SNR by a factor close to the theoretical expected improvement of <math> <semantics> <mrow> <msqrt> <mrow> <msub><mrow><mi>N</mi></mrow> <mrow><mi>b</mi> <mi>a</mi> <mi>n</mi> <mi>d</mi> <mi>s</mi></mrow> </msub> </mrow> </msqrt> </mrow> <annotation>$$ sqrt{N_{bands}} $$</annotation></semantics> </math> .</p><p><strong>Conclusion: </strong>RF-encoded multiband imaging is a viable approach for improving SNR efficiency on low-field portable systems.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144816995","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical and experimental study of RF-induced heating of passive implantable medical devices at 5T MRI","authors":"Mir Khadiza Akter,&nbsp;Ao Shen,&nbsp;Md Zahidul Islam,&nbsp;Lingfei Zhang,&nbsp;Jianfeng Zheng,&nbsp;Ji Chen","doi":"10.1002/mrm.70024","DOIUrl":"10.1002/mrm.70024","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>To assess the RF-induced heating of orthopedic implants in a 5T whole-body MRI system through electromagnetic simulations and experimental validation, with the goal of ensuring patient safety in ultra-high field (UHF) MRI.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>Numerical and experimental studies were conducted to evaluate RF-induced heating in five titanium screws (4–12 cm) inside a 60-cm wide 5T whole-body MRI scanner using the standard ASTM phantom. The temperature rise over 15 min was determined through full-wave electromagnetic simulations and direct measurements. The Finite Difference Time Domain (FDTD) method was used to quantify the 1 g mass-averaged specific absorption rate (pSAR_1g) in 10 clinically relevant plate-and-screw configurations implanted in the Duke and Ella human body models at three anatomical locations: humerus, femur, and tibia.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>In the phantom study, the 6 cm screw exhibited the highest SAR and temperature rise, demonstrating a resonance effect at 5T. However, in human body models, the worst-case implant lengths shifted to 7–11 cm, highlighting the influence of tissue heterogeneity on resonance conditions. SAR values were also affected by the implant's position within the RF coil. The strong agreement between simulations and measurements validates the computational approach.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusion</h3>\u0000 \u0000 <p>This study systematically evaluates RF-induced heating in orthopedic implants within the newly approved 5T whole-body MRI, demonstrating that implant length, positioning, and surrounding media significantly impact heating risks. The findings highlight the necessity for updated MRI safety guidelines at UHF strengths, as implant safety conditions at 5T systems may differ from those at 1.5 and 3T MRI systems.</p>\u0000 </section>\u0000 </div>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":"94 6","pages":"2632-2642"},"PeriodicalIF":3.0,"publicationDate":"2025-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144816997","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}