Magnetic Resonance in Medicine最新文献

{"title":"Groupwise image registration with edge-based loss for low-SNR cardiac MRI.","authors":"Xuan Lei, Philip Schniter, Chong Chen, Rizwan Ahmad","doi":"10.1002/mrm.30486","DOIUrl":"https://doi.org/10.1002/mrm.30486","url":null,"abstract":"<p><strong>Purpose: </strong>The purpose of this study is to perform image registration and averaging of multiple free-breathing single-shot cardiac images, where the individual images may have a low signal-to-noise ratio (SNR).</p><p><strong>Methods: </strong>To address low SNR encountered in single-shot imaging, especially at low field strengths, we propose a fast deep learning (DL)-based image registration method, called Averaging Morph with Edge Detection (AiM-ED). AiM-ED jointly registers multiple noisy source images to a noisy target image and utilizes a noise-robust pre-trained edge detector to define the training loss. We validate AiM-ED using synthetic late gadolinium enhanced (LGE) images from the MR extended cardiac-torso (MRXCAT) phantom and free-breathing single-shot LGE images from healthy subjects (24 slices) and patients (5 slices) under various levels of added noise. Additionally, we demonstrate the clinical feasibility of AiM-ED by applying it to data from patients (6 slices) scanned on a 0.55T scanner.</p><p><strong>Results: </strong>Compared with a traditional energy-minimization-based image registration method and DL-based VoxelMorph, images registered using AiM-ED exhibit higher values of recovery SNR and three perceptual image quality metrics. An ablation study shows the benefit of both jointly processing multiple source images and using an edge map in AiM-ED.</p><p><strong>Conclusion: </strong>For single-shot LGE imaging, AiM-ED outperforms existing image registration methods in terms of image quality. With fast inference, minimal training data requirements, and robust performance at various noise levels, AiM-ED has the potential to benefit single-shot CMR applications.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144016891","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 T₂ mapping of lung parenchyma at 9.4 T: A feasibility study in three murine models of interstitial lung disease.","authors":"Grzegorz Kwiatkowski, Aleksandra Kaszlikowska, Laura Seldeslachts, Lauren Michiels, Tadeusz Pałasz, Uwe Himmelreich, Greetje Vande Velde, Stefan Chłopicki","doi":"10.1002/mrm.30534","DOIUrl":"https://doi.org/10.1002/mrm.30534","url":null,"abstract":"<p><strong>Purpose: </strong>To validate the feasibility of quantitative T₂ mapping as a novel, gadolinium-free, preclinical biomarker of interstitial lung disease (ILD).</p><p><strong>Methods: </strong>Quantitative T₂ mapping of lung parenchyma was obtained with multiple-slice multiple-echo readout. A mono-exponential model of magnetization decay was fit to the data to obtain parametric maps of T₂ relaxation time in four slices across whole lungs. The measurements were performed in three clinically relevant murine models ILD: acute lung injury due to endotoxemia, chronic recovery phase post-influenza infection, and bleomycin-induced interstitial lung fibrosis.</p><p><strong>Results: </strong>Quantitative maps of T₂ relaxation in healthy mice showed a mean value of 10.51 ± 0.56 ms. During ILD development, the mean T₂ increased up to threefold, showing high sensitivity to altered tissue water content due to augmented fraction of macromolecules in fibrosis or inflammation associated with disease progression.</p><p><strong>Conclusion: </strong>T₂ mapping of mouse lungs can be successfully applied at 9.4 T, offering quantitative insights through parametric T₂ mapping across various ILD models without requiring contrast agents. The proposed method for evaluating lung tissue damage is adaptable to other interstitial lung diseases.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144024787","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 pathway toward clinical translation of hyperpolarized [1,4-¹³C₂,2,3-d₂]fumarate as an imaging biomarker for early cellular necrosis in vivo.","authors":"Jonathan R Birchall, Pascal Wodtke, Ashley Grimmer, Esben S S Hansen, Lotte B Bertelsen, Nikolaj Bøgh, Marta Wylot, Maria J Zamora-Morales, Otso Arponen, Ines Horvat-Menih, Elizabeth C Latimer, Fung Tan, Evita Pappa, Johann Graggaber, Joseph Cheriyan, Kelly Holmes, Matthew J Locke, Helen Sladen, Joan Boren, Mikko I Kettunen, Anita Chhabra, Ian B Wilkinson, Christoffer Laustsen, Kevin Brindle, Mary A McLean, Ferdia A Gallagher","doi":"10.1002/mrm.30519","DOIUrl":"https://doi.org/10.1002/mrm.30519","url":null,"abstract":"<p><strong>Purpose: </strong>The detection of hyperpolarized carbon-13 (HP ¹³C)-fumarate conversion to ¹³C-malate using ¹³C-MRSI is a biomarker for early detection of cellular necrosis. Here, we describe the translation of HP ¹³C-fumarate as a novel human imaging agent, including the evaluation of biocompatibility and scaling up of the hyperpolarization methods for clinical use.</p><p><strong>Methods: </strong>Preclinical biological validation was undertaken in fumarate hydratase-deficient murine tumor models and controls. Safety and biocompatibility of ¹³C-fumarate was assessed in healthy rats (N = 18) and in healthy human volunteers (N = 9). The dissolution dynamic nuclear polarization process for human doses of HP ¹³C-fumarate was optimized in phantoms. Finally, 2D ¹³C-MRSI following injection of HP ¹³C-fumarate was performed in an ischemia-reperfusion porcine kidney model (N = 6).</p><p><strong>Results: </strong>Fumarate-to-malate conversion was reduced by 42%-71% in the knockdown murine tumor model compared to wildtype tumors. Twice-daily injection of ¹³C-fumarate in healthy rats at the maximum evaluated dose (120 mg/kg/day) showed no significant persistent blood or tissue effects. Healthy human volunteers injected at the maximum dose (3.84 mg/kg) and injection rate (5 mL/s) showed no statistically significant changes in vital signs or blood measurements 1 h post-injection. Spectroscopic evidence of fumarate-to-malate conversion was observed in the ischemic porcine kidney (0.96 mg/kg).</p><p><strong>Conclusion: </strong>HP ¹³C-fumarate has shown promise as a novel and safe hyperpolarized agent for monitoring cellular necrosis. This work provides the basis for future imaging of HP ¹³C-fumarate metabolism in humans.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144064104","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":"Engineering clinical translation of OGSE diffusion MRI.","authors":"Ante Zhu, Eric S Michael, Hua Li, Tim Sprenger, Yihe Hua, Seung-Kyun Lee, Desmond Teck Beng Yeo, Jennifer A McNab, Franciszek Hennel, Els Fieremans, Dan Wu, Thomas K F Foo, Dmitry S Novikov","doi":"10.1002/mrm.30510","DOIUrl":"https://doi.org/10.1002/mrm.30510","url":null,"abstract":"<p><p>Oscillating gradient spin echo (OGSE) diffusion MRI (dMRI) can probe the diffusive dynamics on short time scales ≲10 ms, which translates into the sensitivity to tissue microstructure at the short length scales <math> <semantics><mrow><mo>≲</mo> <mn>10</mn> <mspace></mspace> <mi>μ</mi></mrow> <annotation>$$ lesssim 10kern0.3em upmu $$</annotation></semantics> </math> m. OGSE-based tissue microstructure imaging techniques able to characterize the cell diameter and cellular density have been established in pre-clinical studies. The unique image contrast of OGSE dMRI has been shown to differentiate tumor types and malignancies, enable early diagnosis of treatment effectiveness, and reveal different pathophysiology of lesions in stroke and neurological diseases. Recent innovations in high-performance gradient human MRI systems provide an opportunity to translate OGSE research findings in pre-clinical studies to human research and the clinic. The implementation of OGSE dMRI in human studies has the promise to advance our understanding of human brain microstructure and improve patient care. Compared to the clinical standard (pulsed gradient spin echo), engineering OGSE diffusion encoding for human imaging is more challenging. This review summarizes the impact of hardware and human biophysical safety considerations on the waveform design, imaging parameter space, and image quality of OGSE dMRI. Here we discuss the effects of the gradient amplitude, slew rate, peripheral nerve stimulation, cardiac stimulation, gradient driver, acoustic noise and mechanical vibration, eddy currents, gradient nonlinearity, concomitant gradient, motion and flow, and signal-to-noise ratio. We believe that targeted engineering for safe, high-quality, and reproducible imaging will enable the translation of OGSE dMRI techniques into the clinic.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144000921","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 MR acoustic radiation force imaging (MR-ARFI) for human transcranial focused ultrasound.","authors":"Morteza Mohammadjavadi, Ryan T Ash, Gary H Glover, Kim Butts Pauly","doi":"10.1002/mrm.30539","DOIUrl":"https://doi.org/10.1002/mrm.30539","url":null,"abstract":"<p><strong>Purpose: </strong>MR acoustic radiation force imaging (MR-ARFI) is an exceptionally promising technique to non-invasively confirm targeting accuracy and estimate exposure of low-intensity transcranial focused ultrasound applications. Implementing MR-ARFI in the human brain has been hindered by (1) sensitivity to subject motion, and (2) insufficient SNR at low (<1.0 MPa) ultrasound pressures. The purpose of this study was to optimize human MR-ARFI to allow reduced ultrasound exposure while at the same time being robust to bulk and physiological motion.</p><p><strong>Methods: </strong>We developed a novel timeseries approach to MR-ARFI with a single-shot spiral-out MRI sequence and correction for respiratory and cardiac motion artifacts. An MR-compatible four-element 500 kHz focused ultrasound transducer was coupled to the head and targeted to 60 mm depth in five participants. During spiral scans, two 6 ms focused ultrasound pulses (0.5-0.9 MPa in situ) were delivered in on-off blocks of 25 time frames.</p><p><strong>Results: </strong>Our method generates ARFI maps that with correction are largely immune to bulk and pulsatile brain motion with reduced scan time (80 s per acquisition). Robust ARFI signals were observed at the expected target in four human participants, using low intensity ultrasound that does not produce significant tissue heating, confirmed both by simulation and MR thermometry.</p><p><strong>Conclusion: </strong>Single shot spiral MR-ARFI is motion robust in human applications, provides reduction in ultrasound exposure, and reduced scan time, enabling iteration for image-guided targeting. This provide persuasive proof-of-principle that MR-ARFI can be used as a tool to guide ultrasound-based precision neural circuit therapeutics.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144000740","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 muscle water T₂ mapping using RF phase-modulated 3D gradient echo imaging.","authors":"Eléonore Vermeulen, Pierre-Yves Baudin, Marc Lapert, Benjamin Marty","doi":"10.1002/mrm.30545","DOIUrl":"https://doi.org/10.1002/mrm.30545","url":null,"abstract":"&lt;p&gt;&lt;strong&gt;Purpose: &lt;/strong&gt;To propose a motion robust 3D sequence for water T&lt;sub&gt;2&lt;/sub&gt; ( &lt;math&gt; &lt;semantics&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt; &lt;msub&gt;&lt;mn&gt;2&lt;/mn&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;H&lt;/mi&gt; &lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt; &lt;mi&gt;O&lt;/mi&gt;&lt;/mrow&gt; &lt;/msub&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ mathrm{T}{2}_{{mathrm{H}}_2mathrm{O}} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; ) estimation in skeletal muscle tissues.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Methods: &lt;/strong&gt;A &lt;math&gt; &lt;semantics&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt; &lt;msub&gt;&lt;mn&gt;2&lt;/mn&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;H&lt;/mi&gt; &lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt; &lt;mi&gt;O&lt;/mi&gt;&lt;/mrow&gt; &lt;/msub&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ mathrm{T}{2}_{{mathrm{H}}_2mathrm{O}} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; estimation method is proposed, using 10 image volumes acquired with a partially spoiled gradient echo (pSPGR) sequence, varying the RF phase-cycling increment and prescribed flip angle. The complex signal evolution is fit with a bi-component water/fat model to extract &lt;math&gt; &lt;semantics&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt; &lt;msub&gt;&lt;mn&gt;2&lt;/mn&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;H&lt;/mi&gt; &lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt; &lt;mi&gt;O&lt;/mi&gt;&lt;/mrow&gt; &lt;/msub&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ mathrm{T}{2}_{{mathrm{H}}_2mathrm{O}} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; and account for B&lt;sub&gt;1&lt;/sub&gt; and fat fraction confounders. Accuracy and precision were evaluated using numerical simulations. Cartesian and radial implementations of the sequence were tested. In phantoms, results were compared with reference spectroscopic and multi-spin echo imaging techniques. Several in vivo experiments evaluated robustness to B&lt;sub&gt;1&lt;/sub&gt; field inhomogeneities, sensitivity to physiological and pathological variations in &lt;math&gt; &lt;semantics&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt; &lt;msub&gt;&lt;mn&gt;2&lt;/mn&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;H&lt;/mi&gt; &lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt; &lt;mi&gt;O&lt;/mi&gt;&lt;/mrow&gt; &lt;/msub&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ mathrm{T}{2}_{{mathrm{H}}_2mathrm{O}} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; on the thigh muscles.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Results: &lt;/strong&gt;In phantoms, &lt;math&gt; &lt;semantics&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt; &lt;msub&gt;&lt;mn&gt;2&lt;/mn&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;H&lt;/mi&gt; &lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt; &lt;mi&gt;O&lt;/mi&gt;&lt;/mrow&gt; &lt;/msub&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ mathrm{T}{2}_{{mathrm{H}}_2mathrm{O}} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; values were highly correlated with reference spectroscopy and multi spin echo values (R&lt;sup&gt;2&lt;/sup&gt; &gt; 0.8). In vivo, &lt;math&gt; &lt;semantics&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt; &lt;msub&gt;&lt;mn&gt;2&lt;/mn&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;H&lt;/mi&gt; &lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt; &lt;mi&gt;O&lt;/mi&gt;&lt;/mrow&gt; &lt;/msub&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ mathrm{T}{2}_{{mathrm{H}}_2mathrm{O}} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; values were correlated with reference values in healthy controls (R&lt;sup&gt;2&lt;/sup&gt; = 0.69) and pathological muscles (R&lt;sup&gt;2&lt;/sup&gt; = 0.87) and were not affected by B&lt;sub&gt;1&lt;/sub&gt; inhomogeneities (R&lt;sup&gt;2&lt;/sup&gt; = 0.06). In the tongue muscle, a significant reduction in the SD of &lt;math&gt; &lt;semantics&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt; &lt;msub&gt;&lt;mn&gt;2&lt;/mn&gt; &lt;mrow&gt;&lt;msub&gt;&lt;mi&gt;H&lt;/mi&gt; &lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt; &lt;mi&gt;O&lt;/mi&gt;&lt;/mrow&gt; &lt;/msub&gt; &lt;/mrow&gt; &lt;annotation&gt;$$ mathrm{T}{2}_{{mathrm{H}}_2mathrm{O}} $$&lt;/annotation&gt;&lt;/semantics&gt; &lt;/math&gt; values was observed using the radial compared to the Cartesian pSPGR sequence (-28%).&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Conclusion: &lt;/strong&gt;The proposed approach pro","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144024674","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":"Navigator-free multi-shot diffusion MRI via non-local low-rank reconstruction.","authors":"Yiming Dong, Xinyu Ye, Chang Li, Matthias J P van Osch, Peter Börnert","doi":"10.1002/mrm.30554","DOIUrl":"https://doi.org/10.1002/mrm.30554","url":null,"abstract":"<p><strong>Purpose: </strong>To develop a non-local low-rank (NLLR) reconstruction method for multi-shot EPI (ms-EPI) in DWI, addressing phase inconsistencies and noise issues while maintaining high spatial resolution in clinically feasible scan times.</p><p><strong>Theory and methods: </strong>Single-shot EPI (ss-EPI) is widely used for DWI but suffers from geometric distortions and T₂* blurring. ms-EPI improves spatial resolution but introduces shot-to-shot phase variations requiring correction strategies. Traditional navigator-based approaches may increase acquisition time. Recent low-rank regularization reconstruction techniques, such as locally low-rank (LLR) methods, can estimate the phase errors but rely strictly on local neighborhood information along the shot dimension. The proposed NLLR method extends this framework by leveraging non-local patch matching by grouping similar image patches across spatially distant image locations, enhancing non-local redundancy exploitation for improved phase estimation and correction as well as noise suppression. The method was validated in simulations and in vivo experiments and compared to existing post-processing denoising and navigator-free approaches.</p><p><strong>Results: </strong>In simulation experiments, compared to post-processing denoising algorithms, NLLR demonstrated superior noise suppression and structural preservation across all metrics, even when reconstructing from a single diffusion direction. In the in-vivo experiments, NLLR outperformed conventional navigator-free approaches particularly regarding noise suppression. Fractional anisotropy maps reconstructed using NLLR exhibited improved visualization of fine structures with improved SNR, with performance differences becoming more pronounced at higher resolutions.</p><p><strong>Conclusion: </strong>The proposed NLLR approach provides an efficient and good solution for high-resolution DWI reconstruction, improving image quality while mitigating phase variations and noise.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143989311","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":"Evaluations of the Bloch fitting method for the analysis of acidoCEST MRI.","authors":"Tianzhe Li, Jorge de La Cerda, Renee L Tran, F William Schuler, Aikaterini Kotrotsou, Shu Zhang, Kyle M Jones, Priya N Trakru, Mark D Pagel","doi":"10.1002/mrm.30511","DOIUrl":"https://doi.org/10.1002/mrm.30511","url":null,"abstract":"<p><strong>Purpose: </strong>AcidoCEST MRI measures tumor extracellular pH by fitting chemical exchange saturation transfer (CEST) Z-spectra with modified Bloch-McConnell equations, known as a Bloch fitting method. We evaluated Bloch fitting with Z-spectra and T₁, T₂, B₁, and B₀ MR information with phantoms. We applied the Bloch fitting method to in vivo acidoCEST MRI of a preclinical tumor model.</p><p><strong>Methods: </strong>We studied 120 phantoms of iopamidol with a range of pH values, concentrations, and T₁ values. We collected 180 Z-spectra for each phantom, along with T₁, T₂, B₁, and B₀ measurements. The data were analyzed with the Bloch fitting method to estimate pH. AcidoCEST MRI was performed with five mice with 4T1 mammary carcinoma using the Bloch fitting method.</p><p><strong>Results: </strong>Bloch fitting generated accurate and precise pH estimates without also including experimental T₁, T₂, B₁, or B₀ values. Accurate and precise pH estimates of phantoms were achieved with 3-μT saturation power, ≥1-s saturation time, ≥15 mM of iopamidol, and temperature control of 37.0 ± 1.5°C. Similar to our phantom studies, fixing one or more fitting parameters did not significantly alter the extracellular pH estimates from acidoCEST MRI of a 4T1 tumor model, which estimated a tumor extracellular pH of 6.8.</p><p><strong>Conclusions: </strong>Although fixing Bloch fitting parameters with experimental measurements saved computation time, fixing these parameters did not significantly improve the accuracy or precision of measuring pH in phantoms or within in vivo tumors, Therefore, measurements of T₁, T₂, B₁, and/or B₀ are not needed for acidoCEST MRI.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144008166","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":"Three-dimensional high-resolution T₁ mapping and perfusion imaging in the normal and ischemic rat brain with hyperpolarized [2-¹³C]tertiary-butyl alcohol.","authors":"Mauricio Contreras, Cody Callahan, Gopal Varma, Aaron K Grant","doi":"10.1002/mrm.30535","DOIUrl":"https://doi.org/10.1002/mrm.30535","url":null,"abstract":"<p><strong>Purpose: </strong>To develop methods for three-dimensional relaxometry and quantitative perfusion imaging using hyperpolarized [2-¹³C]tertiary-butyl alcohol (TBA) in the rat brain under normal and ischemic conditions at 9.4 T. TBA is a freely diffusible tracer that readily traverses the blood-brain barrier, resulting in high tissue signal and long residence times.</p><p><strong>Methods: </strong>A hybrid method consisting of rapid two-dimensional imaging of the arterial input followed by slower three-dimensional variable tip-angle balanced steady state free-precession imaging of the brain is implemented. Image data are analyzed to extract the signal amplitude and T_1,2 decay rates. Knowledge of the tracer's kinetics in tissue is used to determine blood flow.</p><p><strong>Results: </strong>Effective T₁ relaxation rates in the rat brain range from about 15 to 20s. T₂ ranges from about 60 to 250 ms, with the shortest relaxation times found in the brainstem. In ischemic regions, the effective T₁ relaxation time is prolonged due to slower washout, whereas T₂ is largely unchanged. The technique yields flow rates in cortical gray matter ranging from 140 mL/100 g/min in normal brains to less than 30 mL/100 g/min in ischemic cases.</p><p><strong>Conclusion: </strong>Hyperpolarized TBA provides sufficient sensitivity and tissue residence time to enable three-dimensional mapping of relaxation and blood flow at 1.2-1.5-mm³ isotropic resolution in the rat brain. The technique has adequate signal-to-noise ratio in tissue with restricted flow. Raw images of the tracer can be acquired at 0.48 mm³ isotropic resolution and signal-to-noise ratio of about 13 in cortical gray matter.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144033758","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":"Model-based self-supervised learning for quantitative assessment of myocardial oxygen extraction fraction and myocardial blood volume.","authors":"Qi Huang, Haoteng Tang, Keyan Wang, Ran Li, Cihat Eldeniz, Natalie Nguyen, Thomas H Schindler, Linda R Peterson, Yang Yang, Yan Yan, Jingliang Cheng, Pamela K Woodard, Jie Zheng","doi":"10.1002/mrm.30555","DOIUrl":"https://doi.org/10.1002/mrm.30555","url":null,"abstract":"<p><strong>Purpose: </strong>To develop a model-driven, self-supervised deep learning network for end-to-end simultaneous mapping of myocardial oxygen extraction fraction (mOEF) and myocardial blood volume (MBV).</p><p><strong>Methods: </strong>An asymmetrical spin echo-prepared sequence was used to acquire mOEF and MBV images. By integrating a physical model into the training process, a self-supervised learning (SSL) pattern can be regulated. A loss function consisted of the mean squared error, plus cosine similarity was used to improve the performance of network predictions for estimating mOEF and MBV simultaneously. The SSL network was trained and evaluated using simulated data with ground truths and human data in vivo from 10 healthy subjects and 10 patients with myocardial infarction.</p><p><strong>Results: </strong>In the simulation study, the SSL method demonstrated the ability of generating relatively accurate mOEF, MBV, and ΔB maps simultaneously. In the in vivo study, healthy volunteers had an average mOEF of 0.6-0.7 and MBV of 0.11-0.13, comparable to literature-reported values. In the myocardial infarction regions, the average mOEF and MBV in 5 tested patients reduced to 0.45 ± 0.09 and 0.09 ± 0.02, which were significantly lower (p < 0.001) than those in normal regions (0.67 ± 0.04 and 0.13 ± 0.01, respectively).</p><p><strong>Conclusion: </strong>This work has demonstrated the initial feasibility of generating mOEF and MBV maps simultaneously by a model-driven, self-supervised learning method.</p>","PeriodicalId":18065,"journal":{"name":"Magnetic Resonance in Medicine","volume":" ","pages":""},"PeriodicalIF":3.0,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143969345","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}