Magnetic Resonance in Medicine最新文献

{"title":"Focus correction in MR thermography for increased targeting precision during focused ultrasound procedures.","authors":"Chang-Sheng Mei, Shenyan Zong, Bruno Madore, G Rees Cosgrove, Nathan J McDannold","doi":"10.1002/mrm.70089","DOIUrl":"https://doi.org/10.1002/mrm.70089","url":null,"abstract":"<p><strong>Purpose: </strong>Accurate targeting during MR-guided focused ultrasound (FUS) procedures is essential for effective treatment to be achieved. However, spatial discrepancies frequently arise between the planned target and the observed thermal hotspot on proton resonance frequency (PRF)-based MR thermometry because of temperature-induced artifacts. This study aims to correct such displacements caused by chemical shift and k-space center offset.</p><p><strong>Methods: </strong>Spatial misregistration was addressed using a two-step correction approach. The first step corrected pixel-wise displacements attributed to temperature-dependent resonance frequency shifts (chemical shift), based on local frequency offset maps. The second step compensated for TE errors induced by asymmetric phase gradients near the thermal focus, restoring accuracy in hotspot localization. Validation was performed in controlled phantom experiments, and the approach was retrospectively tested in vivo, in 121 sonications across seven essential tremor (ET) patients.</p><p><strong>Results: </strong>Phantom experiments demonstrated that spatial shifts up to approximately 1.5 mm could be effectively corrected. Clinical analysis showed a strong correlation (R² = 0.852) between temperature rise and spatial displacement, with a mean shift of 0.5 Mm per 10°C. Combined correction significantly reduced temperature estimation bias, with the mean error decreasing from -0.11°C to -0.05°C, as evaluated by Bland-Altman analysis.</p><p><strong>Conclusion: </strong>Temperature-related chemical shift and k-space offset substantially impact the spatial fidelity of PRF-based MR thermometry. The proposed correction framework improves thermal hotspot localization, enabling more accurate lesion targeting during FUS procedures.</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":"145138051","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":"MR sequence design to account for nonideal gradient performance.","authors":"Daniel J West, Felix Glang, Jonathan Endres, David Leitão, Moritz Zaiss, Joseph V Hajnal, Shaihan J Malik","doi":"10.1002/mrm.70093","DOIUrl":"https://doi.org/10.1002/mrm.70093","url":null,"abstract":"<p><strong>Purpose: </strong>MRI systems are traditionally engineered to produce close to idealized performance, enabling a simplified pulse sequence design philosophy. An example of this is control of eddy currents produced by gradient fields; usually these are compensated by pre-emphasizing demanded waveforms. This process typically happens invisibly to the pulse sequence designer, allowing them to assume achieved gradient waveforms will be as desired. Although convenient, this requires system specifications exposed to the end user to be substantially down-rated, as pre-emphasis adds an extra overhead to the waveforms. This strategy is undesirable for lower performance or resource-limited hardware. Instead, we propose an optimization-based method to design precompensated gradient waveforms that (i) explicitly respect hardware constraints and (ii) improve imaging performance by correcting k-space samples directly.</p><p><strong>Methods: </strong>Gradient waveforms are numerically optimized by including a model for system imperfections. This is investigated in simulation using an exponential eddy current model, then experimentally using an empirical gradient system transfer function on a 7T MRI system.</p><p><strong>Results: </strong>Our proposed method discovers solutions that produce negligible reconstruction errors while satisfying gradient system limits, even when classic pre-emphasis produces infeasible results. Substantial reduction in ghosting artifacts from echo-planar imaging was observed, including an average reduction of 77% in ghost amplitude in phantoms.</p><p><strong>Conclusions: </strong>This work demonstrates numerical optimization of gradient waveforms, yielding substantially improved image quality when given a model for system imperfections. Although the method as implemented has limited flexibility, it could enable more efficient hardware use and may prove particularly important for maximizing performance of lower-cost systems.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145113671","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":"Optimization of pseudo-continuous arterial spin labeling for brain perfusion imaging in the intraoperative setting.","authors":"Carmen Sánchez-Albardíaz, Marta Calvo-Imirizaldu, Verónica Aramendía-Vidaurreta, Rebeca Echeverria-Chasco, Marta Vidorreta, Bartolomé Bejarano, Lain H Gonzalez-Quarante, Ana Aransay García, Cristina Honorato, Elena Cacho-Asenjo, Antonio Martinez-Simon, Maria A Fernández-Seara","doi":"10.1002/mrm.70088","DOIUrl":"https://doi.org/10.1002/mrm.70088","url":null,"abstract":"<p><strong>Purpose: </strong>Pseudo-continuous arterial spin labeling (PCASL) efficiency during intraoperative MRI is degraded due to large field inhomogeneities observed in some patients and lower arterial blood velocities induced by anesthesia. The purpose of this work was to maximize labeling efficiency during intraoperative MRI by optimizing PCASL parameters at 3 T.</p><p><strong>Methods: </strong>Effects of PCASL labeling pulse interval and gradient parameters on labeling efficiency were first investigated by numerical simulations based on Bloch equations. PCASL parameters were modified accordingly, considering hardware constraints, and evaluated experimentally. An experiment in healthy volunteers compared three labeling pulse intervals. In intraoperative brain tumor patients, different configurations were tested in two experiments: different labeling pulse intervals in patient experiment 1, and different labeling pulse interval and gradient average ( <math> <semantics> <mrow><msub><mi>G</mi> <mi>ave</mi></msub> </mrow> <annotation>$$ {G}_{ave} $$</annotation></semantics> </math> ) in experiment 2.</p><p><strong>Results: </strong>Numerical simulations showed that shortening the labeling pulse interval improved robustness of PCASL to off-resonance effects and that raising the <math> <semantics> <mrow><msub><mi>G</mi> <mi>ave</mi></msub> </mrow> <annotation>$$ {G}_{ave} $$</annotation></semantics> </math> increased labeling efficiency for lower blood velocity profiles. In healthy volunteers for large off-resonance, perfusion signal obtained with the labeling pulse interval of 600 μs was significantly higher than the one obtained with 1000 μs and 1400 μs (p-value < 0.001). In patients, a short labeling pulse interval of 600 μs and <math> <semantics> <mrow><msub><mi>G</mi> <mi>ave</mi></msub> </mrow> <annotation>$$ {G}_{ave} $$</annotation></semantics> </math> of 0.9 mT/m improved the quality of perfusion maps and significantly increased quantified cerebral blood flow values (p-value = 0.0078).</p><p><strong>Conclusion: </strong>Shortening the labeling pulse interval and increasing the gradient average improves PCASL efficiency in the intraoperative setting.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145086390","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":"Bidirectional crusher gradient method to estimate the labeling efficiency of pseudo-continuous arterial spin labeling MRI in mice.","authors":"Xiuli Yang, Yuguo Li, Adnan Bibic, Maria Guadalupe Mora Alvarez, Hanzhang Lu, Zhiliang Wei","doi":"10.1002/mrm.70086","DOIUrl":"https://doi.org/10.1002/mrm.70086","url":null,"abstract":"<p><strong>Purpose: </strong>To develop an experimental method for measuring the labeling efficiency of pseudo-continuous arterial spin labeling (pCASL) MRI in mice.</p><p><strong>Methods: </strong>We propose a method using bidirectional crusher gradients to modulate vascular signals in the azygos pericallosal artery (azPA) of the mouse brain, applied with and without pCASL labeling. The combination of corresponding signals allows the estimation of labeling efficiency. A series of studies were conducted to optimize post-labeling delay, labeling duration, TR, and slice thickness. The sensitivity of labeling efficiency measurements to changes in the labeling scheme was examined. Finally, a physiological challenge with 5% CO₂ was used to assess the potential effect of hypercapnia on labeling efficiency.</p><p><strong>Results: </strong>Upon systematic testing, optimal acquisition parameters included a labeling duration ≥1170 ms, a TR of 3 s, and an imaging slice thickness of 0.75 mm. To quantitatively estimate labeling efficiency, the bolus arrival time to azPA was required and found to be 209.2 ± 19.1 ms. Typical labeling efficiencies in mouse pCASL scans were 0.780 ± 0.048 (mean ± SD). Furthermore, hypercapnia was found to increase pCASL labeling efficiency.</p><p><strong>Conclusion: </strong>Our proposed method facilitates perfusion measurement using pCASL MRI by accounting for intersubject variations in labeling efficiency, offering great potential for applications in pathophysiological studies.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145080969","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":"<ArticleTitle xmlns:ns0=\"http://www.w3.org/1998/Math/MathML\">ISME-incoherent sampling of multi-echo data to minimize cardiac-induced noise in brain maps of <ns0:math> <ns0:semantics> <ns0:mrow><ns0:msubsup><ns0:mi>R</ns0:mi> <ns0:mn>2</ns0:mn> <ns0:mo>*</ns0:mo></ns0:msubsup> </ns0:mrow> <ns0:annotation>$$ {R}_2^{ast } $$</ns0:annotation></ns0:semantics> </ns0:math> and magnetic susceptibility.","authors":"Quentin Raynaud, Rita Oliveira, Nadège Corbin, Yaël Balbastre, Ruud B van Heeswijk, Antoine Lutti","doi":"10.1002/mrm.70087","DOIUrl":"https://doi.org/10.1002/mrm.70087","url":null,"abstract":"&lt;p&gt;&lt;strong&gt;Purpose: &lt;/strong&gt;Maps of the MRI parameters &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msubsup&gt;&lt;mi&gt;R&lt;/mi&gt; &lt;mn&gt;2&lt;/mn&gt; &lt;mo&gt;*&lt;/mo&gt;&lt;/msubsup&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {mathrm{R}}_2^{ast } $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; and magnetic susceptibility ( &lt;math&gt; &lt;semantics&gt;&lt;mrow&gt;&lt;mi&gt;χ&lt;/mi&gt;&lt;/mrow&gt; &lt;annotation&gt;$$ chi $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; ) enable the investigation of microscopic tissue changes in brain disease. However, cardiac-induced signal instabilities increase the variability of brain maps of &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msubsup&gt;&lt;mi&gt;R&lt;/mi&gt; &lt;mn&gt;2&lt;/mn&gt; &lt;mo&gt;*&lt;/mo&gt;&lt;/msubsup&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {mathrm{R}}_2^{ast } $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; and &lt;math&gt; &lt;semantics&gt;&lt;mrow&gt;&lt;mi&gt;χ&lt;/mi&gt;&lt;/mrow&gt; &lt;annotation&gt;$$ chi $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; . In this study, we introduce incoherent sampling of multi-echo data (ISME)-a sampling strategy that minimizes the level of cardiac-induced instabilities in brain maps of &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msubsup&gt;&lt;mi&gt;R&lt;/mi&gt; &lt;mn&gt;2&lt;/mn&gt; &lt;mo&gt;*&lt;/mo&gt;&lt;/msubsup&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {mathrm{R}}_2^{ast } $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; and &lt;math&gt; &lt;semantics&gt;&lt;mrow&gt;&lt;mi&gt;χ&lt;/mi&gt;&lt;/mrow&gt; &lt;annotation&gt;$$ chi $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; .&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Methods: &lt;/strong&gt;ISME uses phase-encoding gradients to shift the k-space frequency of the acquired data between consecutive readouts of a multi-echo train. As a result, the multi-echo data at a given k-space index are acquired at different phases of the cardiac cycle. We compare the variability of &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msubsup&gt;&lt;mi&gt;R&lt;/mi&gt; &lt;mn&gt;2&lt;/mn&gt; &lt;mo&gt;*&lt;/mo&gt;&lt;/msubsup&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {mathrm{R}}_2^{ast } $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; and &lt;math&gt; &lt;semantics&gt;&lt;mrow&gt;&lt;mi&gt;χ&lt;/mi&gt;&lt;/mrow&gt; &lt;annotation&gt;$$ chi $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; maps acquired with ISME and with standard multi-echo trajectories in N = 10 healthy volunteers. We investigate the effect of both trajectories on the spatial aliasing of pulsating MR signals and propose a weighted least-squares approach for the estimation of &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msubsup&gt;&lt;mi&gt;R&lt;/mi&gt; &lt;mn&gt;2&lt;/mn&gt; &lt;mo&gt;*&lt;/mo&gt;&lt;/msubsup&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {mathrm{R}}_2^{ast } $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; that accounts for the increase of the residuals with echo time.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Results: &lt;/strong&gt;ISME reduces the variability of &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msubsup&gt;&lt;mi&gt;R&lt;/mi&gt; &lt;mn&gt;2&lt;/mn&gt; &lt;mo&gt;*&lt;/mo&gt;&lt;/msubsup&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {mathrm{R}}_2^{ast } $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; and &lt;math&gt; &lt;semantics&gt;&lt;mrow&gt;&lt;mi&gt;χ&lt;/mi&gt;&lt;/mrow&gt; &lt;annotation&gt;$$ chi $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; maps across repetitions by 25%/26%/21% and 24%/32%/23% in the cerebellum/brainstem/whole brain, respectively. With ISME, the spatial aliasing of pulsating MR signals is incoherent between raw echo images, leading to visually sharper &lt;math&gt; &lt;semantics&gt; &lt;mrow&gt;&lt;msubsup&gt;&lt;mi&gt;R&lt;/mi&gt; &lt;mn&gt;2&lt;/mn&gt; &lt;mo&gt;*&lt;/mo&gt;&lt;/msubsup&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ {mathrm{R}}_2^{ast } $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; maps. The proposed weighted least-squares ap","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145080986","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":"Free-breathing 3D pulmonary ventilation mapping at 0.55 T using stack-of-spiral out-in bSSFP.","authors":"Ziwei Zhao, Nam G Lee, Bilal Tasdelen, Xin Miao, Ye Tian, Bochao Li, Sophia X Cui, Krishna S Nayak","doi":"10.1002/mrm.70069","DOIUrl":"https://doi.org/10.1002/mrm.70069","url":null,"abstract":"<p><strong>Purpose: </strong>To develop a free-breathing pulmonary imaging technique that provides three-dimensional (3D) structural images and regional ventilation maps, and to evaluate its repeatability and accuracy compared with two-dimensional phase-resolved functional lung (PREFUL) and global tidal volume.</p><p><strong>Methods: </strong>A free-breathing 3D stack-of-spiral out-in (SOS out-in) balanced steady-state free precession (bSSFP) sequence with self-navigators was designed to achieve 2-mm isotropic resolution in 5 min. Respiratory-resolved images were reconstructed using spatial L1 wavelet and temporal finite-difference constraints. The 3D ventilation maps were generated based on Jacobian determinant of the estimated nonrigid deformations. Six healthy volunteers were scanned in supine and prone positions. Ventilation maps were compared with two-dimensional PREFUL from two matched slices. Test-retest repeatability was assessed using Bland-Altman analysis. Correlations among the proposed method, PREFUL, and global tidal volume were evaluated.</p><p><strong>Results: </strong>In healthy volunteers, the SOS out-in lung images provided sufficient vessel-parenchyma contrast and boundary sharpness to support accurate ventilation estimation. Regional ventilation measurements from 3D SOS out-in demonstrated good repeatability (relative differences < 10%). Ventilation maps from 3D SOS out-in strongly correlated with PREFUL on a slice-matched basis as well as with global tidal volume (R² > 0.7, p < 0.001).</p><p><strong>Conclusion: </strong>The proposed method provides high-quality respiratory-resolved structural images and 3D ventilation mapping in a single 5-min scan at 0.55 T. Ventilation measurements are sensitive, consistent, and in good agreement with PREFUL and spirometry.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145081017","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 pseudo-continuous arterial spin labeling angiography using a 3D-radial multi-spoke spoiled gradient-recalled sequence.","authors":"Andreas Petrovic, Martin Soellradl, Thomas W Okell, Andrew Gauden, Leon Lai, Shalini A Amukotuwa, Roland Bammer","doi":"10.1002/mrm.70015","DOIUrl":"https://doi.org/10.1002/mrm.70015","url":null,"abstract":"<p><strong>Purpose: </strong>Accurate identification of arterial feeders and draining veins is critical for treatment decision-making in patients with intracranial high-flow vascular lesions. Currently available MRI sequences lack the temporal and spatial resolution needed for this task. A novel time-resolved pseudo-continuous arterial spin labeling (ASL) angiography sequence with high spatial and temporal resolution was developed, and image quality metrics relevant to clinical performance were assessed.</p><p><strong>Methods: </strong>Ten volunteers and eight patients with intracranial high-flow vascular lesions underwent a brain MRI protocol, augmented with the new sequence with multi-spoke (1-3) readouts and dynamic, sliding-window reconstruction. For each of the acquisitions, image quality was assessed using a 5-point Likert scale, as well as SNR and SNR efficiency. Spatial and temporal resolution and acquisition time were compared with standard-of-care sequences used to assess high-flow vascular lesions.</p><p><strong>Results: </strong>The time-resolved angiographic sequence achieved high isotropic spatial resolution (0.68 mm³), comparable to time of flight (TOF) MRA, but higher than that of contrast-enhanced (CE)-MRA, and a higher temporal resolution (200 ms) than CE-MRA. Multi-spoke acquisitions demonstrated a significant increase in SNR and SNR efficiency compared to single-spoke acquisitions while maintaining an overall high image quality rating and at a 31% reduced scan time relative to the single-spoke variant.</p><p><strong>Conclusion: </strong>This study demonstrated the clinical feasibility of a novel time-resolved ASL sequence using a multi-spoke 3D-radial readout with a vessel-signal optimized flip angle sweep. Sufficient SNR, superior spatial and temporal resolution to CE-MRA, and a comparable spatial resolution to TOF MRA were achieved in a clinically reasonable acquisition time.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145081041","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":"Contrast-optimized basis functions for self-navigated motion correction in quantitative MRI.","authors":"Elisa Marchetto, Sebastian Flassbeck, Andrew Mao, Jakob Assländer","doi":"10.1002/mrm.70090","DOIUrl":"10.1002/mrm.70090","url":null,"abstract":"<p><strong>Purpose: </strong>The long scan times of quantitative MRI techniques make them vulnerable to motion artifacts. For MR-Fingerprinting-like approaches, this problem can be addressed with self-navigated retrospective motion correction based on reconstructions in a singular value decomposition (SVD) subspace. However, the SVD promotes high signal intensity in all tissues, which limits the contrast between tissue types and ultimately reduces the accuracy of registration. The purpose of this paper is to rotate the subspace for maximum contrast between two types of tissue and improve the accuracy of motion estimates.</p><p><strong>Methods: </strong>A subspace is derived that promotes contrasts between brain parenchyma and CSF, achieved through the generalized eigendecomposition of mean autocorrelation matrices, followed by a Gram-Schmidt process to maintain orthogonality. We tested our motion correction method on 85 scans with varying motion levels, acquired with a 3D hybrid-state sequence optimized for quantitative magnetization transfer imaging.</p><p><strong>Results: </strong>A comparative analysis shows that the contrast-optimized basis significantly improves the parenchyma-CSF contrast, leading to more accurate motion estimates and reduced artifacts in the quantitative maps.</p><p><strong>Conclusion: </strong>The proposed contrast-optimized subspace improves the accuracy of the motion estimation.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12464935/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145081001","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":"Transcranial Doppler ultrasound validation of BOLD-fMRI cerebral blood flow relationship.","authors":"Genevieve Hayes, Joana Pinto, Sierra Sparks, Daniel P Bulte","doi":"10.1002/mrm.70091","DOIUrl":"https://doi.org/10.1002/mrm.70091","url":null,"abstract":"<p><strong>Purpose: </strong>A precise understanding of the interplay between cerebral blood flow (CBF) and blood oxygen level-dependent (BOLD) fMRI signals is essential for advancing cerebrovascular research. Although calibrated BOLD approaches often rely on arterial spin labelling (ASL) to estimate CBF, alternative validation using transcranial Doppler ultrasound (TCD) has not been explored. This study aims to determine whether a simplified hemodynamic model and linear regression can accurately characterize the relationship between TCD-derived CBF velocity and BOLD-fMRI responses during a ramp CO₂ stimulus. We hypothesized that both models would provide robust fits within the moderate partial pressure of end-tidal carbon dioxide (PETCO₂) and BOLD signal ranges tested.</p><p><strong>Methods: </strong>Twenty-five healthy participants underwent two sessions. In session 1, right middle cerebral artery velocity (MCAv) was acquired using clinical TCD. In session 2, 3 T BOLD-fMRI data were collected. Both sessions used a ramp PETCO₂ protocol with deep breaths followed by 5% and 10% CO₂. Data processing included motion correction, spatial smoothing, fieldmap correction, high-pass filtering, and PETCO₂ alignment with smoothed MCAv (MCA <math> <semantics> <mrow><mover><mi>v</mi> <mo>‾</mo></mover> </mrow> <annotation>$$ overline{v} $$</annotation></semantics> </math> ) and BOLD signals from the right parietal lobe. A simplified hemodynamic model and linear regression were applied to assess the MCA <math> <semantics> <mrow><mover><mi>v</mi> <mo>‾</mo></mover> </mrow> <annotation>$$ overline{v} $$</annotation></semantics> </math> -BOLD relationship, with model performance evaluated by R².</p><p><strong>Results: </strong>Final analysis included 21 participants. The hemodynamic model produced consistent fits (R² ≥ 0.69). Linear regression showed strong agreement between MCA <math> <semantics> <mrow><mover><mi>v</mi> <mo>‾</mo></mover> </mrow> <annotation>$$ overline{v} $$</annotation></semantics> </math> and BOLD (R² = 0.759).</p><p><strong>Conclusion: </strong>Both modeling approaches successfully linked TCD-derived MCA <math> <semantics> <mrow><mover><mi>v</mi> <mo>‾</mo></mover> </mrow> <annotation>$$ overline{v} $$</annotation></semantics> </math> and BOLD-fMRI responses during hypercapnia. These findings support the use of TCD as a complementary surrogate for CBF in BOLD calibration and cerebrovascular research.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145081046","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":"3D Cartesian ultrashort double half-echo imaging of the lung parenchyma for water density imaging.","authors":"Richard B Thompson, Christopher Keen, Richard Coulden, Hefin Jones, Robert W Stobbe, Justin G Grenier","doi":"10.1002/mrm.30615","DOIUrl":"https://doi.org/10.1002/mrm.30615","url":null,"abstract":"<p><strong>Purpose: </strong>Develop and illustrate a 3D double half-echo Cartesian UTE method for spin-density weighted imaging of the lung parenchyma and calculation of lung water density (LWD).</p><p><strong>Methods: </strong>A 3D gradient-echo pulse sequence was modified to acquire half-echoes, to enable UTEs (TE/TR = 145 μs/1.2 ms), with an acquired resolution of 3.125 mm by 3.125 mm by 5 mm. Breath-hold (12.9 s) and free-breathing (94 s) acquisitions, using a center of k-space navigator, were compared to a previously validated yarnball UTE sequence (1.5T/2.89T). Apparent SNR in the lung parenchyma was measured for all in-vivo acquisitions. Illustrative clinical cases included heart failure and sarcoidosis with a comparison to CT images.</p><p><strong>Results: </strong>Lung image quality and calculated LWD was similar for all compared methods at 1.5T and 2.89T for breath-hold and free-breathing acquisitions (N = 10, p > 0.05), with no visible artifacts. The mean lung parenchyma SNR values were 18.4 ± 1.4, 21.8 ± 1.7 and 15.1 ± 1.0 for 1.5T free-breathing, 2.89T free-breathing and 2.89T breath-hold, respectively, and 20.7 ± 1.1 for yarnball acquisitions (2.89T), with corresponding average LWD values of 26.7 ± 2.9%, 27.1 ± 2.5%, 27.1 ± 2.1% and 27.7 ± 2.7%. MRI LWD images and CT scans yielded similar image contrast and normalized signal intensity units. All Cartesian UTE images were reconstructed on the scanner without the requirement for gridding.</p><p><strong>Conclusions: </strong>A double half-echo Cartesian UTE pulse sequence provides water-density weighted images of the lung parenchyma in a breath-hold or short free-breathing acquisition with sufficient signal to noise for quantification of LWD at 1.5T or 2.89T.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145069924","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}