Magnetic Resonance in Medicine最新文献

{"title":"Magnetization transfer explains most of the T₁ variability in the MRI literature.","authors":"Jakob Assländer, Sebastian Flassbeck","doi":"10.1002/mrm.30451","DOIUrl":"10.1002/mrm.30451","url":null,"abstract":"<p><strong>Purpose: </strong>To identify the predominant source of the <math> <semantics> <mrow> <msub><mrow><mi>T</mi></mrow> <mrow><mn>1</mn></mrow> </msub> </mrow> <annotation>$$ {T}_1 $$</annotation></semantics> </math> variability described in the literature, which ranges from 0.6-1.1 s for brain white matter at 3 T.</p><p><strong>Methods: </strong>25 <math> <semantics> <mrow> <msub><mrow><mi>T</mi></mrow> <mrow><mn>1</mn></mrow> </msub> </mrow> <annotation>$$ {T}_1 $$</annotation></semantics> </math> -mapping methods from the literature were simulated with a mono-exponential and various magnetization-transfer (MT) models, each followed by mono-exponential fitting. A single set of model parameters was assumed for the simulation of all methods, and these parameters were estimated by fitting the simulation-based to the corresponding literature <math> <semantics> <mrow> <msub><mrow><mi>T</mi></mrow> <mrow><mn>1</mn></mrow> </msub> </mrow> <annotation>$$ {T}_1 $$</annotation></semantics> </math> values of white matter at 3 T. We acquired in vivo data with a quantitative magnetization transfer and three <math> <semantics> <mrow> <msub><mrow><mi>T</mi></mrow> <mrow><mn>1</mn></mrow> </msub> </mrow> <annotation>$$ {T}_1 $$</annotation></semantics> </math> -mapping techniques. The former was used to synthesize MR images that correspond to the three <math> <semantics> <mrow> <msub><mrow><mi>T</mi></mrow> <mrow><mn>1</mn></mrow> </msub> </mrow> <annotation>$$ {T}_1 $$</annotation></semantics> </math> -mapping methods. A mono-exponential model was fitted to the experimental and corresponding synthesized MR images.</p><p><strong>Results: </strong>Mono-exponential simulations suggest good inter-method reproducibility and fail to explain the highly variable <math> <semantics> <mrow> <msub><mrow><mi>T</mi></mrow> <mrow><mn>1</mn></mrow> </msub> </mrow> <annotation>$$ {T}_1 $$</annotation></semantics> </math> estimates in the literature. In contrast, MT simulations suggest that a mono-exponential fit results in a variable <math> <semantics> <mrow> <msub><mrow><mi>T</mi></mrow> <mrow><mn>1</mn></mrow> </msub> </mrow> <annotation>$$ {T}_1 $$</annotation></semantics> </math> and explain up to 62% of the literature's variability. In our own in vivo experiments, MT explains 70% of the observed variability.</p><p><strong>Conclusion: </strong>The results suggest that a mono-exponential model does not adequately describe longitudinal relaxation in biological tissue. Therefore, <math> <semantics> <mrow> <msub><mrow><mi>T</mi></mrow> <mrow><mn>1</mn></mrow> </msub> </mrow> <annotation>$$ {T}_1 $$</annotation></semantics> </math> in biological tissue should be considered only a semi-quantitative metric that is inherently contingent upon the imaging methodology, and comparisons between different <math> <semantics> <mrow> <msub><mrow><mi>T</mi></mrow> <mrow><mn>1</mn></mrow> </msub> </mrow> <annotation>$$ {T}_1 $$</annotation></semantics> </math> -mapping methods and th","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143649604","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":"Magnetization transfer imaging using non-balanced SSFP at ultra-low field.","authors":"Sharada Balaji, Neale Wiley, Adam Dvorak, Francesco Padormo, Rui P A G Teixiera, Megan E Poorman, Alex MacKay, Tobias Wood, Adam R Cassidy, Anthony Traboulsee, David K B Li, Irene Vavasour, Steven C R Williams, Sean C L Deoni, Emil Ljungberg, Shannon H Kolind","doi":"10.1002/mrm.30494","DOIUrl":"https://doi.org/10.1002/mrm.30494","url":null,"abstract":"<p><strong>Purpose: </strong>Ultra-low field MRI scanners have the potential to improve health care delivery, both through improved access in areas where there are few MRI scanners and allowing more frequent monitoring of disease progression and treatment response. This may be particularly true in white matter disorders, including leukodystrophies and multiple sclerosis, in which frequent myelin-sensitive imaging, such as magnetization transfer (MT) imaging, might improve clinical care and patient outcomes.</p><p><strong>Methods: </strong>We implemented an on-resonance approach to MT imaging on a commercial point-of-care 64 mT scanner using a non-balanced steady-state free precession sequence. Phantom and in vivo experiments were used to evaluate and optimize the sequence sensitivity and reproducibility, and to demonstrate in vivo performance and inter-site reproducibility.</p><p><strong>Results: </strong>From phantom experiments, T₁ and T₂ effects were determined to have a negligible effect on the differential MT weighting. MT ratio (MTR) values in white matter were 23.1 ± 1.0% from 10 healthy volunteers, with an average reproducibility coefficient of variation of 1.04%. Normal-appearing white matter MTR values in a multiple sclerosis participant (21.5 ± 6.2%) were lower, but with a similar spread of values, compared to an age-matched healthy volunteer (23.3 ± 6.2%).</p><p><strong>Conclusion: </strong>An on-resonance MT imaging approach was developed at 64 mT that can be performed in as little as 4 min. A semi-quantitative myelin-sensitive imaging biomarker at this field strength is available for assessing both myelination and demyelination.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143649606","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":"Simulated radiation levels and patterns of MRI without a Faraday shielded room.","authors":"Ehsan Kazemivalipour, Bastien Guerin, Lawrence L Wald","doi":"10.1002/mrm.30499","DOIUrl":"https://doi.org/10.1002/mrm.30499","url":null,"abstract":"<p><strong>Purpose: </strong>We characterize electromagnetic (EM) radiation patterns and levels in conventional MRI systems as a function of field strength and load symmetry, providing a framework for mitigation strategies allowing operation without a shielded room.</p><p><strong>Methods: </strong>We simulated the far-field radiation pattern and fields at a 10 m radius (|E|_10m and |B|_10m) for a solenoidal superconducting MRI with a body birdcage coil operated between 0.25T and 6.5T. Five load configurations probed the impact of load-symmetry, ranging from a sphere to a body load (least-symmetric). We also assessed simple layered EM absorbers at the bore-ends.</p><p><strong>Results: </strong>All configurations exceeded regulatory limits for realistic transmit levels. At 1.5T, a 300 V_rms RF-pulse is 2700-fold the |E|_10m limit. Field strength and load symmetry strongly modulate radiation patterns and levels. The radiated power increased by more than four orders of magnitude from 0.25T to 6.5T. Spherical load radiation transitioned from a peak gain at the bore-ends (0.25-0.5T) to a donut-shaped pattern, suggesting current loops around the bore (1 T-1.5T), back to bore-axis-directed gain, suggesting propagating waves along the bore (2T-6.5T). Transition patterns were seen between these regimes; uniform radiation at 0.75T and a combined donut/bore-directed pattern at 1.75T. Load asymmetry increased both strength and pattern asymmetry, with the body load having the highest and least symmetric radiation with the legs facilitating wave propagation at high-fields. A simple optimized layered absorber at scanner's service-end reduced 3T peak radiation by 11 dB.</p><p><strong>Conclusion: </strong>Radiation from unshielded scanners far exceeds regulatory limits, particularly at high-field. Mitigation strategies must address load-symmetry, field strength, and wave effects.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143649609","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 glucose enhanced imaging using direct water saturation.","authors":"Linda Knutsson, Nirbhay N Yadav, Sajad Mohammed Ali, David Olayinka Kamson, Eleni Demetriou, Anina Seidemo, Lindsay Blair, Doris D Lin, John Laterra, Peter C M van Zijl","doi":"10.1002/mrm.30447","DOIUrl":"10.1002/mrm.30447","url":null,"abstract":"<p><strong>Purpose: </strong>Dynamic glucose enhanced (DGE) MRI studies employ CEST or spin lock (CESL) to study glucose uptake. Currently, these methods are hampered by low effect size and sensitivity to motion. To overcome this, we propose to utilize exchange-based linewidth (LW) broadening of the direct water saturation (DS) curve of the water saturation spectrum (Z-spectrum) during and after glucose infusion (DS-DGE MRI).</p><p><strong>Methods: </strong>To estimate the glucose-infusion-induced LW changes (ΔLW), Bloch-McConnell simulations were performed for normoglycemia and hyperglycemia in blood, gray matter (GM), white matter (WM), CSF, and malignant tumor tissue. Whole-brain DS-DGE imaging was implemented at 3 T using dynamic Z-spectral acquisitions (1.2 s per offset frequency, 38 s per spectrum) and assessed on four brain tumor patients using infusion of 35 g of D-glucose. To assess ΔLW, a deep learning-based Lorentzian fitting approach was used on voxel-based DS spectra acquired before, during, and post-infusion. Area-under-the-curve (AUC) images, obtained from the dynamic ΔLW time curves, were compared qualitatively to perfusion-weighted imaging parametric maps.</p><p><strong>Results: </strong>In simulations, ΔLW was 1.3%, 0.30%, 0.29/0.34%, 7.5%, and 13% in arterial blood, venous blood, GM/WM, malignant tumor tissue, and CSF, respectively. In vivo, ΔLW was approximately 1% in GM/WM, 5% to 20% for different tumor types, and 40% in CSF. The resulting DS-DGE AUC maps clearly outlined lesion areas.</p><p><strong>Conclusions: </strong>DS-DGE MRI is highly promising for assessing D-glucose uptake. Initial results in brain tumor patients show high-quality AUC maps of glucose-induced line broadening and DGE-based lesion enhancement similar and/or complementary to perfusion-weighted imaging.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143649602","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":"Accelerated EPR imaging using deep learning denoising.","authors":"Irene Canavesi, Navin Viswakarma, Boris Epel, Alan McMillan, Mrignayani Kotecha","doi":"10.1002/mrm.30473","DOIUrl":"https://doi.org/10.1002/mrm.30473","url":null,"abstract":"<p><strong>Purpose: </strong>Trityl OXO71-based pulse electron paramagnetic resonance imaging (EPRI) is an excellent technique to obtain partial pressure of oxygen (pO₂) maps in tissues. In this study, we used deep learning techniques to denoise 3D EPR amplitude and pO₂ maps.</p><p><strong>Methods: </strong>All experiments were performed using a 25 mT EPR imager, JIVA-25®. The MONAI implementation of four neural networks (autoencoder, Attention UNet, UNETR, and UNet) was tested, and the best model (UNet) was then enhanced with joint bilateral filters (JBF). The training dataset was comprised of 227 3D images (56 in vivo and 171 in vitro), 159 images for training, 45 for validation, and 23 for testing. UNet with 1, 2, and 3 JBF layers was tested to improve image SNR, focusing on multiscale structural similarity index measure and edge sensitivity preservation. The trained algorithm was tested using acquisitions with 15, 30, and 150 averages in vitro with a sealed deoxygenated OXO71 phantom and in vivo with fibrosarcoma tumors grown in a hind leg of C3H mice.</p><p><strong>Results: </strong>We demonstrate that UNet with 2 JBF layers (UNet+JBF2) provides the best outcome. We demonstrate that using the UNet+JBF2 model, the SNR of 15-shot amplitude maps provides higher SNR compared to 150-shot pre-filter maps, both in phantoms and in tumors, therefore, allowing 10-fold accelerated imaging. We demonstrate that the trained algorithm improves SNR in pO₂ maps.</p><p><strong>Conclusions: </strong>We demonstrate the application of deep learning techniques to EPRI denoising. Higher SNR will bring the EPRI technique one step closer to clinics.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143649589","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":"Quantitative multislice and jointly optimized rapid CEST for in vivo whole-brain imaging.","authors":"Ouri Cohen, Robert J Young, Ricardo Otazo","doi":"10.1002/mrm.30488","DOIUrl":"https://doi.org/10.1002/mrm.30488","url":null,"abstract":"<p><strong>Purpose: </strong>To develop a quantitative multislice chemical exchange saturation transfer (CEST) schedule optimization and pulse sequence that reduces the loss of sensitivity inherent to multislice sequences.</p><p><strong>Methods: </strong>A deep learning framework was developed for simultaneous optimization of scan parameters and slice order. The optimized sequence was tested in numerical simulations against a random schedule and an optimized single-slice schedule. The scan efficiency of each schedule was quantified. Three healthy subjects were scanned with the proposed sequence. Regions of interest in white matter (WM) and gray matter (GM) were defined. The sequence was compared with the single-slice sequence in vivo and differences quantified using Bland-Altman plots. Test-retest reproducibility was assessed, and the Lin's concordance correlation coefficient (CCC) was calculated for WM and GM. Intersubject variability was also measured with the CCC. Feasibility of whole-brain clinical imaging was tested using a multislab acquisition in 1 subject.</p><p><strong>Results: </strong>The optimized multislice sequence yielded a lower mean error than the random schedule for all tissue parameters and a lower error than the optimized single-slice schedule for four of six parameters. The optimized multislice sequence provided the highest scan efficiency. In vivo tissue-parameter values obtained with the proposed sequence agreed well with those of the optimized single-slice sequence and prior studies. The average WM/GM CCC was 0.8151/0.7779 for the test-retest scans and 0.7792/0.7191 for the intersubject variability experiment.</p><p><strong>Conclusion: </strong>A multislice schedule optimization framework and pulse sequence were demonstrated for quantitative CEST. The proposed approach enables accurate and reproducible whole-brain quantitative CEST imaging in clinically relevant scan times.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143634101","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":"Parallel detection of MRI and ¹H MRSI for multi-contrast anatomical and metabolic imaging.","authors":"Robin A de Graaf, Monique Thomas, Henk M De Feyter","doi":"10.1002/mrm.30501","DOIUrl":"10.1002/mrm.30501","url":null,"abstract":"<p><strong>Purpose: </strong>MRI and MRSI provide unique and complementary information on anatomy, structure, function, and metabolism. The default strategy for a combined MRI and MRSI study is a sequential acquisition of both modalities, leading to long scan times. As MRI and MRSI primarily detect water and metabolites, respectively, the small frequency difference between resonances can be exploited with frequency-selective RF pulses to achieve interleaved or parallel detection of MRI and MRSI, without an increase in total scan time.</p><p><strong>Methods: </strong>Here, we describe the pulse sequence modifications necessary to allow acquisition of T₁ and T₂-weighted MRI and B₀/B₁ mapping in parallel with MRSI. In general, the MRSI module, including water suppression, can be used unmodified. MRI methods are executed in 3D using 3- to 4-ms frequency-selective Gaussian RF pulses with acceleration along the third dimension through repetitive small-angle nutation or multi-spin-echo acquisitions.</p><p><strong>Results: </strong>Phantom experiments demonstrated artifact-free 3D MRIs. MRSIs in the absence or presence of MRI elements were identical in sensitivity and spectral resolution (line width) and showed consistent water suppression. Parallel MRI-MRSI was applied to the brains of tumor-bearing rats in vivo. High-contrast, high-sensitivity metabolic MRSI data at 8 μL nominal resolution was acquired in parallel with 3D T₁-weighted, T₂-weighted, and B₀/B₁-weighted MRIs for an overall scan duration of 30 min.</p><p><strong>Conclusion: </strong>Multi-contrast MRIs and MRSI can be acquired in parallel by utilizing the small frequency difference between water and metabolites. This opens the possibility for shorter overall scans times, or the acquisition of higher-resolution or additional contrast MRIs.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143625495","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":"Reproducibility of tailored and universal nonselective excitation pulses at 7 T for human cardiac MRI: A 3-year and an interday study.","authors":"Manuel Fernando Sánchez Alarcón, Sebastian Dietrich-Conzelmann, Jean Pierre Bassenge, Jeanette Schulz-Menger, Sebastian Schmitter, Christoph Stefan Aigner","doi":"10.1002/mrm.30495","DOIUrl":"https://doi.org/10.1002/mrm.30495","url":null,"abstract":"<p><strong>Purpose: </strong>Ultrahigh-field (UHF; ≥7 T) MRI is challenging due to spatially heterogeneous B₁ ⁺ profiles. This longitudinal study evaluates the reproducibility of three parallel-transmission excitation strategies to enable UHF cardiac MRI: vendor-supplied radiofrequency (RF) shim, subject-tailored kT-points pulses (TPs), and universal kT-points pulses (UPs).</p><p><strong>Methods: </strong>Six healthy subjects underwent 7 T MRI scans performed by different MR operators using a 32-element parallel-transmission body array at four time points over 3 years. A single UP was computed and applied to all subjects. TPs were computed individually for each scan and organized into four configurations. Each configuration was applied to all scans from each subject to analyze intrasubject variability. Reproducibility was assessed by comparing the coefficient of variation (CV) of simulated flip angles (FAs) within the heart volume across scan sessions.</p><p><strong>Results: </strong>TPs designed for a specific scan session yielded lower CVs (2-fold reduction) than UP. Applying TPs to other scan sessions of the same subject, however, resulted in approximately 40% higher CVs and lower FA uniformity compared with the UP. On average, the UP consistently achieved the most reproducible results across inter-year, inter-day, and same-operator studies, with CVs of approximately 12%.</p><p><strong>Conclusion: </strong>Although TPs showed advantages when tailored for a specific target volume, they struggled with long-term consistency and required lengthy calibration. The precomputed UP kT-points pulses proved to be the most consistent across all scans acquired in the 3 years by different operators, minimizing CV-data dispersion and maintaining FA uniformity.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143625433","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 128-channel receive array with enhanced signal-to-noise ratio performance for 10.5T brain imaging.","authors":"Russell L Lagore, Alireza Sadeghi-Tarakameh, Andrea Grant, Matt Waks, Edward Auerbach, Steve Jungst, Lance DelaBarre, Steen Moeller, Yigitcan Eryaman, Riccardo Lattanzi, Ilias Giannakopoulos, Luca Vizioli, Essa Yacoub, Simon Schmidt, Gregory J Metzger, Xiaoping Wu, Gregor Adriany, Kamil Uğurbil","doi":"10.1002/mrm.30476","DOIUrl":"10.1002/mrm.30476","url":null,"abstract":"<p><strong>Purpose: </strong>To develop and characterize a 128-channel head array for brain imaging at 10.5 T, evaluate signal-to-noise ratio (SNR) relative to ultimate intrinsic SNR (uiSNR) and lower field strengths, and demonstrate human brain anatomical and functional imaging with this unique magnetic field and high-channel-count array.</p><p><strong>Methods: </strong>The coil consists of a 16-channel self-decoupled loop transmit/receive (16Tx/Rx) array with a 112-loop receive-only (Rx) insert. Interactions between the 16Tx/Rx array and the 112Rx insert were mitigated using coaxial cable traps placed every 1/16 of a wavelength on each feed cable, locating most preamplifier boards outside the transmitter field, and miniaturizing those placed directly on individual coils.</p><p><strong>Results: </strong>The effect of the 112Rx insert on the circumscribing 16Tx/Rx array was minimized, leading to similar transmit field maps obtained experimentally with and without the 112Rx array in place and by electromagnetic simulations of the 16Tx/Rx array alone. The 128-channel array captured 77% of uiSNR centrally. Significantly higher 1/g-factor values across the whole brain was achieved compared with 7 T. Excellent SNR, high parallel-imaging performance, and minimal Tx-Rx interactions collectively facilitated acquisition of high-quality, high-resolution, proof-of-concept functional and anatomical images, including with power-demanding sequences in the human brain.</p><p><strong>Conclusions: </strong>Counterintuitive to expectations based on magnetic fields less than or equal to 7 T, the higher channel counts provided SNR gains centrally, capturing about 80% uiSNR. The fraction of uiSNR achieved centrally in 64Rx, 80Rx, and 128Rx arrays suggested that a plateau was being reached at 80%. At this plateau, B₀-dependent SNR gains for 10.5 T relative to 7 T were approximately linear to quadratic for the periphery and the center, respectively.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143625490","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":"Positive susceptibility-based contrast imaging with dephased balanced steady-state free precession.","authors":"Jonas Frederik Faust, Peter Speier, Axel Joachim Krafft, Sunil Patil, Ravi Teja Seethamraju, Mark E Ladd, Florian Maier","doi":"10.1002/mrm.30421","DOIUrl":"https://doi.org/10.1002/mrm.30421","url":null,"abstract":"<p><strong>Purpose: </strong>Dephasing gradients can be introduced within a variety of gradient-echo pulse sequences to delineate local susceptibility changes (\"White-Marker\" phenomenon), e.g., for the visualization of metallic interventional devices which are otherwise difficult to display. We investigated dephased balanced steady-state free precession (d-bSSFP) and compared it with similar contrast techniques: dephased RF-spoiled fast low-angle shot (d-FLASH) and dephased steady-state free precession (d-SSFP).</p><p><strong>Methods: </strong>A signal model was formulated to describe the positive contrast in d-bSSFP. For the example of an MR-compatible aspiration needle, the positive contrast artifact appearance was theoretically derived, and the model was verified in a water phantom at B₀ = 0.55 T. Model accuracy was evaluated by comparing the measured artifact size (for TEs between 3.4 ms and 50 ms) and the signal magnitude to the model prediction.</p><p><strong>Results: </strong>While positive contrast artifacts for d-FLASH and d-SSFP are axisymmetric with respect to the generating object, for d-bSSFP, a point-symmetric susceptibility artifact arises for a cylindrical needle due to the characteristic signal formation. The observed d-bSSFP artifact size was in accordance with the model (error < 1 mm). Measured (predicted) cumulated artifact signal was 1.13 ± 0.07 (1.27) times higher and 5.9 ± 0.4 times higher than the d-SSFP and d-FLASH cumulated artifact signal, respectively. In contrast to d-SSFP, the d-bSSFP artifact was robust against banding artifacts.</p><p><strong>Conclusion: </strong>d-bSSFP contrast is well described by the introduced model. Positive contrast artifacts show higher cumulated signal magnitude, symmetry, and homogeneity compared with d-FLASH and d-SSFP and can therefore improve device visualization and potentially device localization.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143615814","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}