Magnetic Resonance in Medicine最新文献

{"title":"Acceleration of slice encoding for metal artifact correction at 0.55 T using hexagonal sampling.","authors":"Bahadır Alp Barlas, Kübra Keskin, Bochao Li, Brian A Hargreaves, Krishna S Nayak","doi":"10.1002/mrm.70077","DOIUrl":"https://doi.org/10.1002/mrm.70077","url":null,"abstract":"<p><strong>Purpose: </strong>To evaluate a hexagonal sampling approach for accelerated slice encoding for metal artifact correction (SEMAC) at 0.55 T. Contemporary mid-field systems (0.1 T-1.0 T) show tremendous potential for imaging near metal implants. However, the limited parallel-imaging options necessitate alternative methods for scan time reduction.</p><p><strong>Methods: </strong>We apply retrospective hexagonal undersampling to current state-of-the-art SEMAC with 2-fold generalized autocalibrating partially parallel acquisitions-based parallel imaging at 0.55 T. The hexagonal sampling approach results in an additional 50% scan time reduction. Feasibility is evaluated with phantom experiments involving spinal fixation and total hip arthroplasty hardware, and in vivo experiments involving patients with spinal fusions with varying compositions and 1 volunteer with a total hip arthroplasty.</p><p><strong>Results: </strong>Hexagonal sampling provides an additional 50% scan time reduction with compatible image quality. The two tradeoffs are (i) a small increase in signal void due to the loss of signal from one SEMAC spectral bin during post-acquisition filtering and (ii) position-dependent signal-to-noise-ratio reduction at locations close to the edge of the field of view in the phase-encoding direction.</p><p><strong>Conclusion: </strong>We demonstrate that hexagonal sampling can provide 50% scan time reduction in addition to generalized autocalibrating partially parallel acquisitions/parallel imaging for SEMAC at 0.55 T without introducing substantial artifacts. This may be a valuable mechanism for reducing scan time at 0.55 T and other midfield strengths, where parallel-imaging acceleration is limited.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145212975","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":"Optimized 3D UTE and ZTE MRI for high-resolution lung imaging: A comparative study.","authors":"Michael Carl, Jiaji Wang, James Lo, Jonathan H Chung, Jiang Du, Yajun Ma","doi":"10.1002/mrm.70100","DOIUrl":"https://doi.org/10.1002/mrm.70100","url":null,"abstract":"<p><strong>Purpose: </strong>To optimize and compare the performance of 3D UTE and zero echo time (ZTE) MRI sequences for high-resolution lung imaging at 3 T.</p><p><strong>Methods: </strong>UTE and ZTE sequences were optimized for lung imaging through phantom studies, and in vivo experiments. Imaging parameters, including bandwidth (BW) and flip angle (FA), were systematically assessed to identify the optimal settings for both sequences. A novel transient UTE sequence was introduced to enhance the SNR by allowing magnetization recovery during the respiratory wait period. Numerical simulations and in vivo experiments were conducted to compare the SNR performance of the proposed transient UTE with conventional steady-state UTE.</p><p><strong>Results: </strong>UTE imaging with a BW of ±125 kHz and an FA of 2° produced the sharpest lung images without noticeable artifacts. In contrast, ZTE imaging was optimal at a lower BW of ±62.5 kHz and an FA of 2°, but showed greater blurriness and more pronounced inhomogeneous excitation artifacts than UTE. The transient UTE sequence increased lung imaging SNR by approximately 11% to 20% compared to steady-state UTE without introducing obvious artifacts.</p><p><strong>Conclusion: </strong>UTE outperformed ZTE in terms of image sharpness and artifact reduction for lung imaging. The proposed transient UTE sequence further enhanced SNR, demonstrating the potential for improved lung MRI quality and diagnostic accuracy.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145192056","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":"Scalable spokes pTx pulses for 2D turbo-spin-echo imaging at 7 T.","authors":"Minghao Zhang, Christopher T Rodgers","doi":"10.1002/mrm.70068","DOIUrl":"https://doi.org/10.1002/mrm.70068","url":null,"abstract":"<p><strong>Purpose: </strong>Turbo spin echo (TSE) is important clinically. Unfortunately, 7 T TSE suffers from B₁ ⁺-induced signal dropouts. Magnitude-based parallel transmit (pTx) pulse design algorithms cannot enforce phase patterns complying with the Carr-Purcell-Meiboom-Gill conditions (90° phase shift between excitation and refocusing). We introduce scalable spokes pTx pulses for 7 T TSE imaging.</p><p><strong>Theory: </strong>We define scalable spokes pulses as having time-symmetric RF waveforms, antisymmetric in-plane gradients, and rephased subpulse slice-selection gradients. They produce flip angles that are approximately proportional to the applied voltage with voltage-independent phase patterns.</p><p><strong>Methods: </strong>Scalable spokes pulses were designed for a phantom. Scaling behavior was characterized via Bloch simulations. Performance in terms of TSE echo homogeneity was assessed by extended phase graph simulations using in vivo field maps. Performance was validated for TSE acquisitions in a phantom and in vivo. Hippocampal TSE imaging was performed for four subjects comparing circularly polarized (CP), RF shimming, and scalable spokes pulses.</p><p><strong>Results: </strong>Scalable spokes pTx pulses show similar scaling behavior to previously proposed 3D k_T-point pulses. Scalable three-spoke pulses decrease flip-angle RMS error across subjects compared to CP mode pulses (11% vs. 23% for 120° pulses). TSE images with these pulses recover signals in cerebellum and temporal lobes.</p><p><strong>Conclusion: </strong>Scalable spokes pTx pulses produce flip angles that vary approximately linearly with peak voltage while maintaining consistent spatial patterns of phase. Together with their spatial flip-angle homogeneity, these pulses enable high-fidelity 2D slice-by-slice TSE imaging at 7 T, albeit with reduced slice coverage with our choice of homogeneity target under the current vendor-provided specific absorption rate constraints on 7 T MRI scanners.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145192041","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":"A unipolar head gradient for high-field MRI without encoding ambiguity.","authors":"Markus Weiger, Johan Overweg, Franciszek Hennel, Emily Louise Baadsvik, Samuel Bianchi, Oskar Björkqvist, Roger Luechinger, Jens Metzger, Eric Seth Michael, Thomas Schmid, Lauro Singenberger, Urs Sturzenegger, Erik Oskam, Gerrit Vissers, Jos Koonen, Wout Schuth, Jeroen Koeleman, Martino Borgo, Klaas Paul Pruessmann","doi":"10.1002/mrm.70098","DOIUrl":"https://doi.org/10.1002/mrm.70098","url":null,"abstract":"<p><strong>Purpose: </strong>MRI gradients with a conventional, bipolar design generally face a trade-off among performance, encoding ambiguity, and radiofrequency selectivity used to circumvent said ambiguity. This problem is particularly limiting in cutting-edge brain imaging performed at field strengths ≥ 7 T and using high-performance head gradients.</p><p><strong>Methods: </strong>To address this issue, the present work proposes to fundamentally eliminate the encoding ambiguity in head gradients by using a unipolar z-gradient design that takes advantage of the signal-free range on one side of the imaging volume. This concept is demonstrated by implementation of a unipolar head gradient for operation at 7 T.</p><p><strong>Results: </strong>Imaging in phantoms and in vivo demonstrates elimination of backfolding due to encoding ambiguity. At the same time, the unipolar design achieves efficiency on par with conventional bipolar design, resulting in high amplitude and slew-rate performance.</p><p><strong>Conclusion: </strong>The prospect of gradient systems based on a unipolar design holds promise for all advanced neuroimaging that demands high gradient performance. It will make the greatest difference at 7 T and beyond, where the absence of ambiguity removes a key concern and constraint in terms of radiofrequency behavior and instrumentation.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145192064","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":"Optimized T₁-weighted MP-RAGE MRI of the brain at 0.55 T using variable flip angle coherent gradient echo imaging and deep learning reconstruction.","authors":"Oliver Bieri, Marcel Dominik Nickel, Claudia Weidensteiner, Philipp Madörin, Grzegorz Bauman","doi":"10.1002/mrm.70109","DOIUrl":"https://doi.org/10.1002/mrm.70109","url":null,"abstract":"<p><strong>Purpose: </strong>To propose and evaluate an optimized MP-RAGE protocol for rapid T₁-weighted imaging of the brain at 0.55 T.</p><p><strong>Methods: </strong>Incoherent and coherent steady state free precession (SSFP) RAGE kernels with constant and variable excitation angles were investigated in terms of the white matter SNR and the white matter-gray matter signal difference. Potential edge smearing from the transient signal readout was assessed based on a differential point spread function analysis. Finally, the prospects of a deep-learning reconstruction (DLR) method for accelerated MP-RAGE MRI of undersampled data were evaluated for the best performing variant.</p><p><strong>Results: </strong>MP-RAGE imaging with a variable flip angle (vFA) SSFP-FID kernel outperformed all other investigated variants. As compared to the standard MPRAGE sequence using a spoiled gradient echo kernel with constant flip angle, vFA SSFP-FID offered an average gain in the white matter SNR of 21% ± 2% and an average improvement for the white matter-gray matter signal difference for cortical gray matter of 47% ± 7%. The differential point spread function was narrowest for the spoiled gradient echo but slightly increased by 8% for vFA SSFP-FID. For vFA SSFP-FID, DLR offered a considerable decrease in the overall scan time from 5:17 min down to 2:46 min without noticeable image artifacts and degradations.</p><p><strong>Conclusions: </strong>At 0.55 T, a vFA MP-RAGE variant using an SSFP-FID kernel combined with a DLR method offers excellent prospects for rapid T₁-weighted whole brain imaging in less than 3 min with nearly 1 mm (1.12 × 1.17 × 1.25 mm³) isotropic resolution.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145192033","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":"Evaluation of an interleaved acquisition scheme for improved robustness of channel-wise relative B₁ ⁺ mapping at 7 T.","authors":"Nico Egger, Laurent Ruck, Sophia Nagelstraßer, Judith Schirmer, Saskia Wildenberg, Andreas Bitz, Jürgen Herrler, Sebastian Schmitter, Michael Uder, Armin Michael Nagel","doi":"10.1002/mrm.70101","DOIUrl":"https://doi.org/10.1002/mrm.70101","url":null,"abstract":"<p><strong>Purpose: </strong>The purpose was to evaluate, whether an interleaved acquisition scheme for a fast relative <math> <semantics> <mrow><msubsup><mi>B</mi> <mn>1</mn> <mo>+</mo></msubsup> </mrow> <annotation>$$ {mathrm{B}}_1^{+} $$</annotation></semantics> </math> mapping method at 7 T reduces the likelihood of errors from exceeding the linear flip angle (FA) regime compared to a conventional sequential acquisition.</p><p><strong>Methods: </strong>Simulations of a channel-wise relative <math> <semantics> <mrow><msubsup><mi>B</mi> <mn>1</mn> <mo>+</mo></msubsup> </mrow> <annotation>$$ {mathrm{B}}_1^{+} $$</annotation></semantics> </math> mapping sequence were performed for sequential and interleaved acquisition schemes at different reference voltages (≙ different FAs). The simulations were performed for a phantom, the heart and the prostate and were based on 7 T ground-truth (GT) <math> <semantics> <mrow><msubsup><mi>B</mi> <mn>1</mn> <mo>+</mo></msubsup> </mrow> <annotation>$$ {mathrm{B}}_1^{+} $$</annotation></semantics> </math> data acquired with an actual FA imaging sequence (phantom) or obtained from electromagnetic field simulations (heart/prostate). Acquisition schemes were evaluated based on their signal linearity by calculating a normalized mean FA error between simulated signal intensities and GT <math> <semantics> <mrow><msubsup><mi>B</mi> <mn>1</mn> <mo>+</mo></msubsup> </mrow> <annotation>$$ {mathrm{B}}_1^{+} $$</annotation></semantics> </math> data. Additionally, validation measurements of relative <math> <semantics> <mrow><msubsup><mi>B</mi> <mn>1</mn> <mo>+</mo></msubsup> </mrow> <annotation>$$ {mathrm{B}}_1^{+} $$</annotation></semantics> </math> maps with the sequential and interleaved acquisition schemes were acquired for the phantom.</p><p><strong>Results: </strong>Validation measurements showed a good agreement with the simulation results for both acquisition schemes and displayed stronger deviations to the GT <math> <semantics> <mrow><msubsup><mi>B</mi> <mn>1</mn> <mo>+</mo></msubsup> </mrow> <annotation>$$ {mathrm{B}}_1^{+} $$</annotation></semantics> </math> data for the sequential scheme. The quantitative evaluation yielded higher FA errors for the sequential acquisition scheme for all three regions and all simulated reference voltages. At the same level of error, mean signals were higher for the interleaved acquisition scheme in all cases. Differences between interleaved and sequential acquisition schemes were most pronounced in the steady-state.</p><p><strong>Conclusion: </strong>An interleaved acquisition of channel-wise relative <math> <semantics> <mrow><msubsup><mi>B</mi> <mn>1</mn> <mo>+</mo></msubsup> </mrow> <annotation>$$ {mathrm{B}}_1^{+} $$</annotation></semantics> </math> maps extends the range of the linear FA regime, reducing the likelihood of errors and increasing the robustness of the approach.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145192049","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":"T₁-weighted fMRI in mouse visual cortex using an iron oxide nanoparticle contrast agent and UTE imaging at 9.4 T.","authors":"Naman Jain, Saskia Bollmann, Kai-Hsiang Chuang, Jonathan R Polimeni, Markus Barth","doi":"10.1002/mrm.70103","DOIUrl":"10.1002/mrm.70103","url":null,"abstract":"<p><strong>Purpose: </strong>This study aims to investigate the feasibility of using T₁-weighted fMRI with an iron oxide nanoparticle contrast agent and UTE imaging at 9.4 T to measure functional hyperemia in the mouse visual cortex. The goal is to capture positive signal changes in both the parenchyma and pial surface, and to test whether surface vessels respond during neuronal activation.</p><p><strong>Method: </strong>The study involved scanning of nine mice after administration of iron oxide-based superparamagnetic contrast agent via the tail vein. Two functional imaging experiments were conducted: one to investigate the effect of TE on the functional response, and another to characterize the impact of higher resolution on UTE functional contrast. Regions of interest were defined in the parenchyma and pial surface of the visual cortex.</p><p><strong>Results: </strong>The administration of the contrast agent produced a bright-blood signal in the vasculature in structural MRI when using a UTE acquisition. Positive signal changes were observed at the shortest TE (0.164 ms) in voxels sampling both the parenchyma (0.22% ± 0.08%) and pial surface (0.26% ± 0.1%), providing evidence that UTE fMRI experiments can detect changes in both parenchymal and pial vessels. Measurements using longer TEs (≥1 ms) showed negative signal changes, as expected. Higher spatial resolution resulted in increased percent signal change at the pial surface, suggesting reduced partial volume effects.</p><p><strong>Conclusion: </strong>The findings demonstrate that T₁-weighted fMRI with UTE imaging and Superparamagnetic Iron Oxide nanoparticles captures positive signal changes across all vascular compartments, providing additional insights into the involvement of surface vessels during functional hyperemia.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145192012","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":"Two-point B₁ correction for CEST MRI by fusing voxel-wise interpolation and T₁W voxel-clustering.","authors":"Yifan Li, Wenxuan Chen, Yi Wang, Xiaolei Song","doi":"10.1002/mrm.70102","DOIUrl":"https://doi.org/10.1002/mrm.70102","url":null,"abstract":"&lt;p&gt;&lt;strong&gt;Purpose: &lt;/strong&gt;As a sensitive metabolic MRI technique, CEST images are easily contaminated by &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt;&lt;/msub&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {mathrm{B}}_1 $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; inhomogeneity due to strong dependence on saturation &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt;&lt;/msub&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {mathrm{B}}_1 $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; . We aim to develop an efficient and robust two-point &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt;&lt;/msub&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {mathrm{B}}_1 $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; -correction method.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Methods: &lt;/strong&gt;The proposed method only acquires CEST images under two saturation &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt;&lt;/msub&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {mathrm{B}}_1 $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; 's, { &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mrow&gt;&lt;mn&gt;1&lt;/mn&gt; &lt;mo&gt;,&lt;/mo&gt; &lt;mtext&gt;high&lt;/mtext&gt;&lt;/mrow&gt; &lt;/msub&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {mathrm{B}}_{1,mathrm{high}} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; , &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mrow&gt;&lt;mn&gt;1&lt;/mn&gt; &lt;mo&gt;,&lt;/mo&gt; &lt;mi&gt;low&lt;/mi&gt;&lt;/mrow&gt; &lt;/msub&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {mathrm{B}}_{1,mathrm{low}} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; }, with desired &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt;&lt;/msub&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {mathrm{B}}_1 $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; in between. Besides, voxel-wise Z- &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt;&lt;/msub&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {mathrm{B}}_1 $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; interpolation (branch A), we performed another Z- &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;T&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt;&lt;/msub&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {mathrm{T}}_1 $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; - &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt;&lt;/msub&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {mathrm{B}}_1 $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; calibration (branch B), which divided image voxels into bins according to the &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;T&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt;&lt;/msub&gt; &lt;mi&gt;w&lt;/mi&gt;&lt;/mrow&gt; &lt;annotation&gt;$$ {mathrm{T}}_1mathrm{w} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; image and fitted a Z- &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt;&lt;/msub&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {mathrm{B}}_1 $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; curve for each bin. To ensure each voxel adopts a better-corrected value, we fused the images corrected from both branches, according to a mask predicted by a retrospectively trained model. For validation, glutamate CEST (GluCEST) experiments of phantom and healthy volunteers were acquired on a 5T scanner. A total of 14 &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt;&lt;/msub&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {mathrm{B}}_1 $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; pairs from 2.4μT to 3.6μT were evaluated, with the 7- &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;B&lt;/mi&gt; &lt;mn&gt;1&lt;/mn&gt;&lt;/msub&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {mathrm{B}}_1 $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; -correction as gold standard.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Results: &lt;/strong&gt;Across glutamate phantom","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145138077","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":"Design and performance of a toroidal radiofrequency volume coil with intrinsic electromagnetic interference rejection for low-field portable Halbach-based MRI systems.","authors":"Jules Vliem, Chloe Najac, Beatrice Lena, Andrew Webb, Irena Zivkovic","doi":"10.1002/mrm.70095","DOIUrl":"https://doi.org/10.1002/mrm.70095","url":null,"abstract":"<p><strong>Purpose: </strong>One of the intrinsic limitations of low-field MRI is low signal-to-noise ratio, which can be further reduced by electromagnetic interference (EMI) due to the lack of a Faraday shielded room. To address this issue, we propose a novel radiofrequency (RF) coil design that is inherently less sensitive to EMI while maintaining high receive sensitivity.</p><p><strong>Methods: </strong>The proposed coil structure is based on an anapole (toroidal) design and consists of six rings, each containing four continuous wires wound around an elliptical three-dimensional-printed former. The wire in the entire structure is uninterrupted. This coil is designed for use in systems with an axial B₀ field direction. The performance of the proposed RF coil was evaluated on a Halbach array system designed for neuroimaging and operating at 47 mT and compared with a widely used spiral head coil.</p><p><strong>Results: </strong>The noise level achieved by the proposed toroidal coil in combination with a belt wrapped around the subjects and grounded to the scanner was comparable to that of the widely used spiral head coil when combined with a grounding belt and passive aluminum shielding. The coil transmit and receive efficiency was comparable to the efficiency of the spiral head coil.</p><p><strong>Conclusion: </strong>The proposed RF coil inherently reduces the effect of EMI, potentially removing or reducing the need for passive shielding or external/internal sensors for EMI reduction in postprocessing.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145138088","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":"Scanner-based real-time automated volumetry reporting of the fetus, amniotic fluid, placenta, and umbilical cord for fetal MRI at 0.55T.","authors":"Sara Neves Silva, Alena Uus, Hadi Waheed, Simi Bansal, Kamilah St Clair, Wendy Norman, Jordina Aviles Verdera, Daniel Cromb, Tomas Woodgate, Milou van Poppel, Johannes K Steinweg, Jacqueline Matthew, Kuberan Pushparajah, David Lloyd, Vanessa Kyriakopoulou, Dimitris Siassakos, Anna David, Joseph V Hajnal, Lisa Story, Mary A Rutherford, Jana Hutter","doi":"10.1002/mrm.70097","DOIUrl":"https://doi.org/10.1002/mrm.70097","url":null,"abstract":"<p><strong>Purpose: </strong>This work aims to enable real-time automated intra-uterine volumetric reporting and fetal weight estimation for fetal MRI, deployed directly on the scanner.</p><p><strong>Methods: </strong>A multi-region segmentation nnUNet was trained on 146 images of 73 fetal subjects (coronal and axial orientations) for the parcellation of the fetal head, fetal body, placenta, amniotic fluid, and umbilical cord from whole uterus bSSFP stacks. A reporting tool was then developed to integrate the segmentation outputs into an automated report, providing volumetric measurements, fetal weight estimations, and z-score visualizations. The complete pipeline was subsequently deployed on a 0.55T MRI scanner, enabling real-time inference and fully automated reporting in the duration of the acquisition.</p><p><strong>Results: </strong>The segmentation pipeline was quantitatively and retrospectively evaluated on 36 stacks of 18 fetal subjects and demonstrated sufficient performance for all labels, with high scores ( <math> <semantics><mrow><mo>></mo></mrow> <annotation>$$ > $$</annotation></semantics> </math> 0.98) for the fetus, placenta, and amniotic fluid, and 0.91 for the umbilical cord. The prospective evaluation of the scanner deployment step was successfully performed on 50 cases, with the regional volumetric reports available directly on the scanner.</p><p><strong>Conclusions: </strong>This work demonstrated the feasibility of multi-regional intra-uterine segmentation, fetal weight estimation, and automated reporting in real-time. This study provides a robust baseline solution for the integration of fully automated scanner-based measurements into fetal MRI reports.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145138086","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}