Magnetic Resonance in Medicine最新文献

{"title":"Accelerated EPR imaging using deep learning denoising","authors":"Irene Canavesi,&nbsp;Navin Viswakarma,&nbsp;Boris Epel,&nbsp;Alan McMillan,&nbsp;Mrignayani Kotecha","doi":"10.1002/mrm.30473","DOIUrl":"10.1002/mrm.30473","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>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>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>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>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>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>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>We demonstrate the application of deep learning techniques to EPRI denoising. Higher SNR will bring the EPRI technique one step closer to clinics.</p>\u0000 </section>\u0000 </div>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":"94 1","pages":"436-446"},"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":"Dynamic glucose enhanced imaging using direct water saturation","authors":"Linda Knutsson,&nbsp;Nirbhay N. Yadav,&nbsp;Sajad Mohammed Ali,&nbsp;David Olayinka Kamson,&nbsp;Eleni Demetriou,&nbsp;Anina Seidemo,&nbsp;Lindsay Blair,&nbsp;Doris D. Lin,&nbsp;John Laterra,&nbsp;Peter C. M. van Zijl","doi":"10.1002/mrm.30447","DOIUrl":"10.1002/mrm.30447","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>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 <i>(LW)</i> broadening of the direct water saturation (DS) curve of the water saturation spectrum (Z-spectrum) during and after glucose infusion (DS-DGE MRI).</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>To estimate the glucose-infusion-induced <i>LW</i> changes <i>(</i>Δ<i>LW)</i>, 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 Δ<i>LW</i>, a deep learning-based Lorentzian fitting approach was used on voxel-based DS spectra acquired before, during, and post-infusion. Area-under-the-curve <i>(AUC)</i> images, obtained from the dynamic Δ<i>LW</i> time curves, were compared qualitatively to perfusion-weighted imaging parametric maps.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>In simulations, Δ<i>LW</i> 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, Δ<i>LW</i> was approximately 1% in GM/WM, 5% to 20% for different tumor types, and 40% in CSF. The resulting DS-DGE <i>AUC</i> maps clearly outlined lesion areas.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>DS-DGE MRI is highly promising for assessing D-glucose uptake. Initial results in brain tumor patients show high-quality <i>AUC</i> maps of glucose-induced line broadening and DGE-based lesion enhancement similar and/or complementary to perfusion-weighted imaging.</p>\u0000 </section>\u0000 </div>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":"94 1","pages":"15-27"},"PeriodicalIF":3.0,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/mrm.30447","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":"OA","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":"A 128-channel receive array with enhanced signal-to-noise ratio performance for 10.5T brain imaging","authors":"Russell L. Lagore,&nbsp;Alireza Sadeghi-Tarakameh,&nbsp;Andrea Grant,&nbsp;Matt Waks,&nbsp;Edward Auerbach,&nbsp;Steve Jungst,&nbsp;Lance DelaBarre,&nbsp;Steen Moeller,&nbsp;Yigitcan Eryaman,&nbsp;Riccardo Lattanzi,&nbsp;Ilias Giannakopoulos,&nbsp;Luca Vizioli,&nbsp;Essa Yacoub,&nbsp;Simon Schmidt,&nbsp;Gregory J. Metzger,&nbsp;Xiaoping Wu,&nbsp;Gregor Adriany,&nbsp;Kamil Uğurbil","doi":"10.1002/mrm.30476","DOIUrl":"10.1002/mrm.30476","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>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>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>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>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>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>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>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>\u0000 </section>\u0000 </div>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":"93 6","pages":"2680-2698"},"PeriodicalIF":3.0,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/mrm.30476","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":"OA","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":"Positive susceptibility-based contrast imaging with dephased balanced steady-state free precession","authors":"Jonas Frederik Faust,&nbsp;Peter Speier,&nbsp;Axel Joachim Krafft,&nbsp;Sunil Patil,&nbsp;Ravi Teja Seethamraju,&nbsp;Mark E. Ladd,&nbsp;Florian Maier","doi":"10.1002/mrm.30421","DOIUrl":"10.1002/mrm.30421","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>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>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>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>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>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 &lt; 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>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusion</h3>\u0000 \u0000 <p>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>\u0000 </section>\u0000 </div>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":"94 1","pages":"59-72"},"PeriodicalIF":3.0,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/mrm.30421","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":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"<ArticleTitle xmlns:ns0=\"http://www.w3.org/1998/Math/MathML\"><ns0:math> <ns0:semantics> <ns0:mrow><ns0:msubsup><ns0:mi>B</ns0:mi> <ns0:mn>1</ns0:mn> <ns0:mo>+</ns0:mo></ns0:msubsup> </ns0:mrow> <ns0:annotation>$$ {mathrm{B}}_1^{+} $$</ns0:annotation></ns0:semantics> </ns0:math> mapping near metallic implants using turbo spin echo pulse sequences.","authors":"Iman Khodarahmi, Mary Bruno, Ran Schwarzkopf, Jan Fritz, Mahesh B Keerthivasan","doi":"10.1002/mrm.30491","DOIUrl":"https://doi.org/10.1002/mrm.30491","url":null,"abstract":"<p><strong>Purpose: </strong>To propose a B₁ ⁺ mapping technique for imaging of body parts containing metal hardware, based on magnitude images acquired with turbo spin echo (TSE) pulse sequences.</p><p><strong>Theory and methods: </strong>To encode the underlying B₁ ⁺, multiple (two to four) TSE image sets with various excitation and refocusing flip angles were acquired. To this end, the acquired signal intensities were matched to a database of simulated signals which was generated by solving the Bloch equations taking into account the exact sequence parameters. The retrieved B₁ ⁺ values were validated against gradient-recalled and spin echo dual angle methods, as well as a vendor-provided TurboFLASH-based mapping sequence, in gel phantoms and human subjects without and with metal implants.</p><p><strong>Results: </strong>In the absence of metal, phantom experiments demonstrated excellent agreement between the proposed technique using three or four flip angle sets and reference dual angle methods. In human subjects without metal implants, the proposed technique with three or four flip angle sets showed excellent correlation with the spin echo dual angle method. In the presence of metal, both phantoms and human subjects revealed a narrow range of B₁ ⁺ estimation with the reference techniques, whereas the proposed technique successfully resolved B₁ ⁺ near the metal. In select cases, the technique was implemented in conjunction with multispectral metal artifact reduction sequences and successfully applied for B₁ ⁺ shimming.</p><p><strong>Conclusion: </strong>The proposed technique enables resolution of B₁ ⁺ values in regions near metal hardware, overcoming susceptibility-related and narrow-range limitations of standard mapping techniques.</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":"143625485","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":"Denoising complex-valued diffusion MR images using a two-step, nonlocal principal component analysis approach","authors":"Xinyu Ye,&nbsp;Xiaodong Ma,&nbsp;Ziyi Pan,&nbsp;Zhe Zhang,&nbsp;Hua Guo,&nbsp;Kamil Uğurbil,&nbsp;Xiaoping Wu","doi":"10.1002/mrm.30502","DOIUrl":"10.1002/mrm.30502","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>To propose a two-step, nonlocal principal component analysis (PCA) method and demonstrate its utility for denoising complex diffusion MR images with a few diffusion directions.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>A two-step denoising pipeline was implemented to ensure accurate patch selection even with high noise levels and was coupled with data preprocessing for g-factor normalization and phase stabilization before data denoising with a nonlocal PCA algorithm. At the heart of our proposed pipeline was the use of a data-driven optimal shrinkage algorithm to manipulate the singular values in a way that would optimally estimate the noise-free signal. Our approach's denoising performances were evaluated using simulation and in vivo human data experiments. The results were compared with those obtained with existing local PCA-based methods.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>In both simulation and human data experiments, our approach substantially enhanced image quality relative to the noisy counterpart, yielding improved performances for estimation of relevant diffusion tensor imaging metrics. It also outperformed existing local PCA-based methods in reducing noise while preserving anatomic details. It also led to improved whole-brain tractography relative to the noisy counterpart.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusion</h3>\u0000 \u0000 <p>The proposed denoising method has the utility for improving image quality for diffusion MRI with a few diffusion directions and is believed to benefit many applications, especially those aiming to achieve high-quality parametric mapping using only a few image volumes.</p>\u0000 </section>\u0000 </div>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":"93 6","pages":"2473-2487"},"PeriodicalIF":3.0,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143615812","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":"T1234: A distortion-matched structural scan solution to misregistration of high resolution fMRI data.","authors":"Chung Kan, Rüdiger Stirnberg, Marcela Montequin, Omer Faruk Gulban, A Tyler Morgan, Peter A Bandettini, Laurentius Huber","doi":"10.1002/mrm.30480","DOIUrl":"10.1002/mrm.30480","url":null,"abstract":"<p><strong>Purpose: </strong>Registration of functional and structural data poses a challenge for high-resolution fMRI studies at 7 T. This study aims to develop a rapid acquisition method that provides distortion-matched, artifact-mitigated structural reference data.</p><p><strong>Methods: </strong>We introduce an efficient sequence protocol termed T1234, which offers adjustable distortions. This includes data that match distortions of functional data and data that are free of distortions. This approach involves a T₁-weighted 2-inversion 3D-EPI sequence with four combinations of read and phase encoding directions optimized for high-resolution fMRI. A forward Bloch model was used for T₁ quantification and protocol optimization. Fifteen participants were scanned at 7 T using both structural and functional protocols to evaluate the use of T1234.</p><p><strong>Results: </strong>Results from two protocols are presented. A fast distortion-free protocol reliably produced whole-brain segmentations at 0.8 mm isotropic resolution within 3:00-3:40 min. It demonstrates robustness across sessions, participants, and three different 7 T SIEMENS scanners. For a protocol with geometric distortions that matched functional data, T1234 facilitates layer-specific fMRI signal analysis with enhanced laminar precision.</p><p><strong>Conclusion: </strong>This structural mapping approach enables precise registration with fMRI data. T1234 has been successfully implemented, validated, and tested, and is now available to users at our center and at over 50 centers worldwide.</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":"143625403","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}