Magnetic Resonance in Medicine最新文献

{"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}

{"title":"Self-supervised denoising diffusion probabilistic models for abdominal DW-MRI.","authors":"Serge Didenko Vasylechko, Andy Tsai, Onur Afacan, Sila Kurugol","doi":"10.1002/mrm.30536","DOIUrl":"https://doi.org/10.1002/mrm.30536","url":null,"abstract":"<p><strong>Purpose: </strong>To improve the quality of abdominal diffusion-weighted MR images (DW-MRI) when acquired using single-repetition (NEX = 1) protocols, and thereby increase apparent diffusion coefficient (ADC) map accuracy and lesion conspicuity at high b-values. We aim to reduce the effect of blurring due to motion that obscures small lesions when averaging multiple repetition images at each b-value, which is the current clinical standard.</p><p><strong>Methods: </strong>We propose a self-supervised denoising diffusion probabilistic model (ssDDPM) to improve DW-MRI quality given noisy single-repetition acquisitions in pediatric abdominal scans. The ssDDPM is designed for multi-b-value DW-MRI and incorporates diffusion signal decay model (i.e., ADC model) constraints into its loss term. The model is trained to denoise single-repetition images from multiple b-values while ensuring that the output adheres to the signal decay model. Training was performed on a dataset of 120 pediatric subjects with liver tumors. The performance of ssDDPM was compared with non-local means (NLM) filtering and deep image prior (DIP) denoising techniques. These techniques have the capability to denoise single repetition images unlike the other techniques in literature that requires multiple direction or repetition images. Evaluation included qualitative radiologist's image quality assessment, receiver operating characteristic (ROC) analysis for lesion detection, and ADC fitting accuracy compared with motion-free, breath-hold reference data.</p><p><strong>Results: </strong>The ssDDPM demonstrated superior performance over comparison methods in terms of image quality, lesion conspicuity, and ADC map accuracy in NEX = 1 images. It received higher scores in radiologist assessments and showed better lesion discrimination in ROC analysis. Additionally, ssDDPM provided more precise and accurate ADC estimates when compared with the motion-free, breath-hold reference data.</p><p><strong>Conclusion: </strong>The ssDDPM effectively reduces motion related deblurring and enhances the quality of DW-MRI images by directly denoising single-repetition (NEX = 1) images while respecting signal decay model constraints. This method improves the assessment of pediatric liver lesions, offering a more accurate and efficient diagnostic tool with reduced scan times, when compared with current clinical practice and other denoising techniques.</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":"144015470","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 virtual biopsy of in vivo pH and metabolism using PRESS and semi-LASER MRS of hyperpolarized ¹³C nuclei.","authors":"Wolfgang Gottwald, Luca Nagel, Martin Grashei, Sebastian Bauer, Nadine Setzer, Florian Gaksch, Sandra Sühnel, Jason G Skinner, Rickmer Braren, Irina Heid, Geoffrey J Topping, Franz Schilling","doi":"10.1002/mrm.30544","DOIUrl":"https://doi.org/10.1002/mrm.30544","url":null,"abstract":"<p><strong>Purpose: </strong>To develop and evaluate sequences for multi-voxel magnetic resonance spectroscopy using hyperpolarized molecules.</p><p><strong>Methods: </strong>A standard single voxel PRESS sequence was extended to acquire multiple voxels consecutively. Its SNR was compared against a 2D FID-CSI with both ¹H and hyperpolarized ¹³C nuclei in phantoms and in a healthy mouse at 7T. This sequence was also used to determine tumor pH and metabolic activity in an endogenous murine pancreatic ductal adenocarcinoma model. Furthermore, a semi-LASER sequence, using adiabatic full passage RF pulses for refocusing, was implemented. Multi-voxel PRESS and semi-LASER were then compared in healthy mice for measuring metabolic activity and pH using hyperpolarized [1-¹³C]pyruvate and [1,5-¹³C₂]Z-OMPD, respectively.</p><p><strong>Results: </strong>Multi-voxel PRESS and semi-LASER detected ¹³C metabolites in mouse kidneys and endogenous pancreatic ductal adenocarcinoma (PDAC) tumors with SNR comparable to that of standard 2D FID-CSI. They enable fast MRS with a high spectral resolution that is highly customizable to recover spectra from regions not coverable by a single CSI slice.</p><p><strong>Conclusion: </strong>For the first time, we show hyperpolarized MRS using multi-voxel PRESS and semi-LASER sequences for hyperpolarized ¹³C-labeled molecules. By implementing a semi-LASER sequence using adiabatic full passage refocusing pulses, RF saturation was reduced. Semi-LASER allows flexible overlapping of voxel refocusing planes, while for PRESS, signal from these regions is attenuated.</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":"144006865","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 susceptibility mapping in magnetically inhomogeneous tissues.","authors":"Thomas Jochmann, Fahad Salman, Michael G Dwyer, Niels Bergsland, Robert Zivadinov, Jens Haueisen, Ferdinand Schweser","doi":"10.1002/mrm.30537","DOIUrl":"https://doi.org/10.1002/mrm.30537","url":null,"abstract":"<p><strong>Purpose: </strong>Conventional quantitative susceptibility mapping (QSM) methods rely on simplified physical models that assume isotropic and homogeneous tissue properties, leading to artifacts and inaccuracies in biological tissues. This study aims to develop and evaluate DEEPOLE, a deep learning-based method that incorporates macroscopically nondipolar Larmor frequency shifts into QSM to enhance the quality and accuracy of susceptibility maps.</p><p><strong>Methods: </strong>DEEPOLE integrates the QUASAR model into a deep convolutional neural network to account for frequency contributions neglected by conventional QSM. We trained DEEPOLE using synthesized data reflecting realistic power spectrum distributions. Its performance was evaluated against traditional QSM algorithms-including deep learning QSM, QUASAR (quantitative susceptibility and residual mapping), morphology-enabled dipole inversion (MEDI), fast nonlinear susceptibility inversion (FANSI), and superfast dipole inversion (SDI)-using realistic digital brain models with and without microstructure effects, as well as in vivo human brain data. Quantitative assessments focused on susceptibility estimation accuracy, artifact reduction, and anatomical consistency.</p><p><strong>Results: </strong>In digital brain models, DEEPOLE outperformed conventional QSM methods by producing susceptibility maps with fewer artifacts and greater quantitative accuracy, especially in regions affected by microstructure effects. In vivo, DEEPOLE generated more anatomically consistent susceptibility maps and mitigated artifacts such as inhomogeneities and streaking, providing improved susceptibility estimates in deep gray matter and white matter.</p><p><strong>Conclusion: </strong>Incorporating macroscopically nondipolar Larmor frequency shifts into QSM through DEEPOLE improves the quality and accuracy of susceptibility maps. This methodological advancement enhances the reliability of susceptibility measurements, particularly in studies of neurodegenerative and demyelinating conditions where macroscopically nondipolar contributions are substantial.</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":"144024769","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}