This study proposes a hybrid diffusion MRI reconstruction framework combining Diffusion Tensor Imaging (DTI) and the multi-compartment non-central Wishart (MNCW) mixture model. The proposed framework uses an empirically selected fractional anisotropy (FA) threshold of 0.75 as a heuristic to distinguish between single- and multi-fiber voxels, enabling adaptive selection of the most appropriate reconstruction model for each voxel. Synthetic diffusion MRI datasets containing single-, two-, and three-fiber configurations were generated using 82 diffusion-sensitizing gradient directions with Rician noise. Voxels with FA ≥ 0.75 were reconstructed using DTI, while voxels with FA < 0.75 were analyzed using the MNCW model. Angular error and clustering behavior were evaluated under different thresholds. The method was further validated using rat optic chiasm and human brain datasets. The proposed framework reduced incorrect single-fiber detections and produced fewer disoriented voxels in complex fiber configurations compared with the conventional mixture model. A clustering threshold of 17 ^∘ provided stable reconstruction without merging distinct fibers. Real data experiments demonstrated anatomically consistent reconstruction of white matter structures. The hybrid framework improves orientation estimation by selectively applying mixture modeling only in voxels likely to contain multiple fibers, reducing over-segmentation, improving stability, and lowering computational complexity.
Macromolecular (MM) signals overlap with metabolite signals, but MM content differences across age and brain region and their influences on brain metabolites quantification have remained elusive. While most studies assume universal MM content when assessing neurochemical levels, region- and age-related MM differences could result in inaccurate quantification of metabolites. This study assesses MM differences linked to specific brain regions and age by analyzing their influence on metabolite signal quantification in the primary motor cortex (M1) and thalamus. We created age- and region-specific MM basis sets measured using an inversion-recovery protocol at 7 T. In addition, we acquired short echo time (TE) spectra from M1 and thalamus in a separate cohort, and differences in the metabolite quantification results that arose from using age- or region-matched and unmatched basis sets were evaluated. Comparisons were made between a young group (22–34 years) and an elderly group (64–79 years) and across M1 or thalamus. We found significant differences in metabolite signals when using basis sets created from matched versus unmatched macromolecule spectra by age or region. Specifically, in M1, substituting the alternate same-region basis set significantly changed 7/12 metabolite signals in elderly spectra and 6/12 in young spectra. The effect was more evident when fitting young thalamic spectra with the elderly thalamic basis, where 11/12 metabolites signals changed. When the thalamic MM basis set was applied to M1 spectra, 11/12 metabolites signals shifted significantly in the young-M1 and 7/12 in the elderly-M1. Our study demonstrated the importance of age-specific and region-specific MM basis sets for accurate metabolite quantification.
Accelerated 3D non-Cartesian MRI presents unique challenges in balancing high-resolution reconstruction with computational and memory constraints. In this work, a novel, memory-efficient image reconstruction framework using score-based diffusion models tailored for highly undersampled 3D radial UTE acquisitions is proposed. The method leverages a volumetric extension of the NCSN++ architecture with efficient NUFFT operations and integrates a conjugate gradient-based data consistency mechanism within a predictor–corrector sampling scheme. This approach enables robust and high-fidelity reconstructions from as few as 4000 spokes—representing up to 50 × undersampling relative to Nyquist. Generalizable performance across knee, ankle, and out-of-distribution shoulder datasets is demonstrated and superior image quality compared to compressed sensing and conventional iterative methods, especially at high acceleration factors is shown. The proposed framework marks a significant step toward practical deployment of diffusion models in non-Cartesian MRI reconstruction.
Dynamic glucose-enhanced (DGE) MRI is an emerging imaging technique that provides information on sugar uptake with contributions from delivery (perfusion), transport (membrane permeability), and metabolism in vivo. DGE MRI contrast reflects changes in water magnetization caused by changes in sugar concentration, which can be detected through chemical exchange between water protons and sugar hydroxyl protons. Such contrast can be visualized using chemical exchange-sensitive saturation transfer (CEST), on- and off-resonance spin-lock (CESL), and T_2 relaxation-based approaches. These methods enable the use of biodegradable sugars as contrast agents, which are expected to have fewer side effects than conventional gadolinium-based MRI contrast agents and are more affordable and environmentally friendly. In this review, part of the special issue “New MR imaging techniques in Oncology,” we provide an overview of DGE MRI and its potential applications in brain tumor imaging. We introduce the physical principles underlying the contrast mechanisms and summarize current acquisition strategies and post-processing approaches, including quantification and kinetic modeling. Technical challenges such as small signal changes, motion sensitivity, and inhomogeneities in static ( B_0 ) and radiofrequency ( B_1 ) magnetic fields are discussed. Special attention is given to glucose physiology and pharmacokinetics, including administration methods. Throughout, we summarize preclinical and early patient studies in brain tumors and compare DGE MRI with other functional and molecular imaging techniques using MRI and PET. Finally, we discuss future directions for clinical translation, emphasizing the need for standardized protocols and improved acquisition and post-processing strategies.
Gadolinium-based contrast agents (GBCAs) exhibit variable relaxivity, and accurate relaxivity assessment is essential both for technical characterization and for optimizing clinical protocols. While reference relaxometry sequences are considered the gold standard for T1 and T2 quantification, clinical T1/T2 mapping techniques are used in routine MRI despite known limitations. This study aimed to compare relaxivity measurements obtained with reference relaxometry and clinically available T1/T2 mapping sequences at 1.5 T, using Gadoteric acid and Gadopiclenol as test agents. A phantom containing multiple dilutions of Gadoteric acid (0.1–3.0 mM) and Gadopiclenol (0.05–1.5 mM) was scanned on a routine 1.5 T MRI system. T1 relaxivity was assessed with spin-echo, inversion recovery, and clinical mapping techniques, while T2 relaxivity was measured with multi-echo spin echo and clinical mapping protocols. Relaxivity constants were derived from linear fitting. Water and oil vials were included as reference samples to verify signal stability and fitting consistency. Clinical mapping sequences yielded relaxivity values broadly consistent with reference methods, although their performance varied depending on the T1/T2 range. MP2RAGE showed non-physiological behavior at high gadolinium concentrations (very short T1 values), MOLLI exhibited reduced precision for the shortest T1 values, and the cardiac T2 mapping sequence had to be excluded due to inconsistent measurements in vials with very short T2 values. As expected, Gadopiclenol demonstrated higher r₁ and r₂ relaxivity than Gadoteric acid across all techniques. Clinical T1/T2 mapping sequences can provide reliable relaxivity estimates over most of the relevant range but show predictable limitations at extreme relaxation times. Reference relaxometry remains the most accurate approach. Using two contrast agents with different relaxivity profiles allowed a robust comparison of the strengths and limitations of clinical versus reference relaxometry techniques. Gadopiclenol exhibited higher relaxivity than Gadoteric acid under phantom conditions, consistent with its potential for dose-efficient protocols, although any clinical dose reduction requires dedicated in vivo validation.
Operating an MR scanner for technical and clinical research requires multidisciplinary competencies beyond MR physics, including safety management and teamwork. Gamification, particularly educational escape rooms, has been associated with improved motivation, engagement and knowledge retention in health professional education. We developed an MR-physics-themed educational escape room for the 41st Annual Meeting of the ESMRMB. Designed for teams of four with a time limit of 25 min, the room reproduced the atmosphere of an MR control room. The five puzzles covered the Larmor equation, sequence composition, MR safety and acoustical identification of MR sequences. Custom ESP32 electronics allowed the puzzles to communicate in real time with each other and with the game master. The room ran without technical interruptions and was played by 39 teams (approximately 160 participants); 12 solved it (escape rate 31
Quantitative susceptibility mapping (QSM) is a semi-quantitative method, i.e., only differences in magnetic susceptibility can be quantified. The lack of a stable internal reference hampers longitudinal and systematic comparisons among subjects. In this study, a phase-based approach, enabling the use of an external reference, is proposed. By modeling the object geometry and analyzing the object-induced magnetic field distortion in the external reference, a relationship between the manifested phase and susceptibility was established. The proposed theoretical framework was validated using a numerical head phantom and 3 T MRI measurements, investigating five phantoms with different concentrations of gadolinium and one healthy volunteer. The derived theoretical relationship, together with accurate phase measurements, provided the absolute mean magnetic susceptibility of the object of interest. Excellent accuracy was demonstrated in the numerical head phantom. Encouraging, although somewhat underestimated, susceptibility results were obtained for the MRI phantom measurements. The relationship between measured and theoretical susceptibility values showed excellent correlation (r = 0.98, p = 0.004). The in vivo measurement yielded an absolute mean susceptibility of 0.02 ppm (relative to water). Feasibility and proof of concept were demonstrated, and the approach, in combination with conventional QSM, offers an alternative reference solution with potential to facilitate absolute QSM maps.
Prediction of cartilage structural properties through MRI could allow earlier detection of joint pathologies, such as osteoarthritis. Bovine patellar cartilage samples (n = 12) were imaged using magnetic resonance fingerprinting, followed by histological examination of proteoglycan content and collagen fiber anisotropy. The relaxation time maps and raw signal data were then used for training Gaussian process regression (GPR) models to predict the histology results. Proteoglycan content was predicted by the GPR models with high accuracy (median r = 0.81, σ = 0.08 and NRMSE = 11.7
Identify and quantify physiological sources of variability in hyperpolarized 129Xe gas-exchange MRI and present a dose-delivery workflow that promotes repeatable lung inflation and alveolar pressure during imaging. A modular 129Xe dose-delivery and monitoring system was developed with two configurations: a remotely actuated flow/volume-monitoring device used to evaluate pre-dose lung inflation, and a pressure-sensing mouthpiece used with conventional delivery to estimate alveolar pressure during breath-hold. In Cohort A (n = 12), standard coaching was evaluated by quantifying how pre-dose lung volumes deviated from the target of functional residual capacity (FRC). In Cohort B (n = 14), 129Xe spectroscopy under normal, Mueller, and Valsalva breath-hold maneuvers was used to quantify the extent to which alveolar pressure modulates RBC:Membrane (RBC:M) and RBC oscillation amplitude. In Cohort A, coaching drove subjects in 70
To assess the feasibility of performing quantitative in vivo tissue sodium concentration measurements in the skin with MRI using a sodium-tuned single-loop transmit/receive surface coil at 3 T. Proton and sodium imaging of skin at the lower back was performed in 17 healthy volunteers on a clinical 3 T system using an anisotropic (1 x 1 x 10 mm) 3D cones sequence. B1 mapping via the double-angle method was used to account for spatial variation in transmit and receive sensitivity. Apparent tissue sodium concentration (aTSC) was estimated relative to a concurrently imaged phantom of known concentration. The mean and standard deviation of B1-corrected aTSC across all subjects were 28 ± 7 mM, approximately 63
OBJECTIVE:Parallel imaging is ubiquitous in MRI, enabling higher spatial and/or temporal resolution. However, successful unfolding is contingent on robust and accurate estimation of relative coil sensitivities, which often involves computation times that preclude online deployment. We present a computationally efficient method of robustly estimating coil sensitivities, and reconstructing under-sampled images using a data-driven regularised SENSE formalism that is commensurate with online deployment for Cartesian k-space acquisitions. MATERIALS AND METHODS:The proposed image reconstruction method via Multiple Orthogonal Reference Sensitivity Encoding (MORSE) estimates multiple sensitivities per voxel to address issues, such as rapidly varying sensitivities, chemical shift artefact, or insufficient fields of view. It simultaneously provides a data-driven regularisation term for noise control providing inherent adaptability to diverse imaging contexts. RESULTS:MORSE has been successfully deployed in multiple neuroimaging studies at both 3T and 7T, including functional studies of autobiographical memory processing, visual and auditory perception, and quantitative MRI studies of neurodegenerative diseases including Huntington's, Alzheimer's and Parkinson's. Exemplar image reconstructions are presented and compared with GRAPPA, ENLIVE, ESPIRiT and LORAKS. We also showcase application of MORSE outside of the brain via application in liver and knee imaging. MORSE consistently produced high-quality, artefact-free images with reconstruction times feasible for online deployment. DISCUSSION:The proposed method of sensitivity estimation and unfolding regularisation is flexible and robust. It is made available to the community in open-source as a library of functions within the vendor-agnostic Gadgetron image reconstruction framework.
To evaluate an accelerated free-breathing three-dimensional stack-of-radial MRI technique of liver proton density fat fraction (PDFF) and $${\text{R}}_{2}^{*}$$ R 2 ∗ quantification on retrospectively undersampled pediatric patient data. A newly developed compressed sensing reconstruction with multidimensional regularization was evaluated on undersampled data in 21 clinical pediatric subjects at 1.5 T with respect to the reference-standard self-gating reconstruction on oversampled data (700 radial views per slice). PDFF and $${\text{R}}_{2}^{*}$$ R 2 ∗ maps were calculated using the proposed method with fully sampled and undersampled radial views (352 and 176) and compared to reference-standard results using Bland-Altman analysis (reported as [mean difference; lower, upper limits of agreement]). Practical equivalence was evaluated using Bayesian posterior analysis with region of practical equivalence (ROPE) at ± 3% for PDFF and ± 10 s −1 for $${\text{R}}_{2}^{*}$$ R 2 ∗ . Echo images, PDFF and $${\text{R}}_{2}^{*}$$ R 2 ∗ maps reconstructed using the proposed method had reduced image artifacts. Bland-Altman plots showed that the proposed method using 176 views had lower biases, [-0.7;-2.4,1.0]% for PDFF and [-5.3;-25.5,14.9] s −1 for $${\text{R}}_{2}^{*}$$ R 2 ∗ , compared to the reference method using 352 views: [0.8; -0.6, 2.1]% for PDFF and [-9.2;-51.9,33.4] s −1 for $${\text{R}}_{2}^{*}$$ R 2 ∗ . Bayesian posterior analysis revealed that our proposed method using 176 views was practically equivalent to the reference method using 700 views with 100% within the PDFF ROPE and with 98.25% within the $${\text{R}}_{2}^{*}$$ R 2 ∗ ROPE. An acceleration factor of 4 and an approximate acquisition time saving of 67% shorter could be achieved. The proposed method may allow accelerated free-breathing liver PDFF and $${\text{R}}_{2}^{*}$$ R 2 ∗ mapping in pediatric subjects in approximately 1 min.
To determine the feasibility of anatomical neuroimaging studies using 0.55 T MRI. MPRAGE images with 1 mm isotropic resolution were acquired from a cohort of five healthy subjects using both 0.55 T and 3 T scanners, including repeat scans of each subject at each field strength. The 0.55 T images were denoised to mitigate the effects of high resolution and low-field strength. All scans were analyzed using BrainSuite and FreeSurfer image analysis software, which performs operations including tissue classification, region segmentation/labeling, and thickness/volume measurements for different brain regions. Regional cortical thickness measurements and regional brain volume measurements were compared, and test–retest repeatability at each field strength was evaluated. For both image analysis software tools, we observed reasonably good correlations between field strengths for cortical thickness measures and regional brain volume measures. Test-retest repeatability analysis suggests that experimental variability was generally higher at 0.55 T than at 3 T, although the amount of difference was dependent on the specific measure being considered and the software tool that was used. While our sample size was small which limits the strength of the conclusions we can draw, this small-scale pilot study suggests the potential feasibility of certain types of anatomical neuroimaging studies at 0.55 T (especially those involving volume measurements), assuming that appropriate adjustments are made to account for increased experimental variability at this field strength.
INTRODUCTION:The intra-voxel incoherent motion (IVIM) effect is an additional signal attenuation in in-vivo diffusion-weighted MRI due to blood microcirculation. The dependence of this effect on diffusion time is of high interest because it may inform about the architecture of blood vessels in perfusion studies and help optimizing diffusion scans to avoid the IVIM bias. This dependence is derived here using capillary blood trajectories obtained by realistic flow simulations in capillary bed samples of mouse brain cortex derived from two-photon microscopy. METHODS:Using the gaussian phase approximation, NMR signal attenuation due to IVIM is derived for pulsed-gradient diffusion sequences at different diffusion times and for sequences with flow-compensated gradient shapes by calculating the product of the gradient moment spectra with the spectral density of the simulated blood velocity autocorrelation function. RESULTS AND DISCUSSION:The results suggest that the microcirculation underlying the IVIM effect in the brain cannot be faithfully depicted by the commonly used models of diffusive or ballistic flow, but rather as a correlated random motion with a correlation time in the range of 60-120 ms. Consequently, the correlation time appears to be an interesting, MRI-accessible endpoint to characterize microcirculation. Further, the flow compensation as a means of suppressing the IVIM effect in diffusion measurements may not be fully effective.
Radiology, particularly superconducting MRI, accounts for a significant share of healthcare energy consumption. We aimed to achieve zero-emission MR imaging by combining a permanent-magnet MRI with a solar energy system. We installed a 30-kW peak rooftop solar array on an energy-efficient building. We used a permanent-magnet MRI system with a 0.4 T field strength, 25 mT gradients, and a 55 T/m/s slew rate. We installed a 22 kWh LiFePO4 battery for short-term energy storage. A smart consumer controller routed solar energy as the primary source. Surplus solar energy was fed into the power grid. If solar production was too low, energy was purchased from the grid. In the event of a grid failure with no available solar energy, a high-voltage DC generator would supply grid energy. Energy consumption and solar energy production were analyzed from January 2024 to December 2025. Total energy consumption in 2025 was 22,992 kWh. Total energy production in 2025 was 30,823 kWh. Total grid feed in 2025 was 16,364 kWh. Total energy retrieved from the grid in 2025 was 8948 kWh. From May to August 2025, the practice operated grid independent for more than 94
To investigate the influence of gadolinium-based contrast agent (GBCA) administration on breast lesions’ signal intensities on diffusion-weighted images and its derived ADC maps acquired 2 min after GBCA administration. An intra-patient analysis was performed. 110 lesions > 5 mm in 93 patients, visible on screening and pre-operative MRI scans at 1.5 T and 3.0 T, were included. Pre-contrast and post-contrast DWI were acquired with single-shot spin-echo echo-planar imaging (SSh-SE-EPI) with b0, b50, b150, and b800 diffusion weightings. 2D regions of interest were drawn. Each b value was separately analyzed regarding signal intensities on DWI. Furthermore, ADC values were compared based on the pairs b0–b800 and b150–b800. The comparison between pre- and post-contrast DWIs was investigated within and between different groups (overall, malignant/benign, and at 1.5/3.0 T). The Wilcoxon-signed rank test and independent Student T test were used when appropriate. P < 0.01 was considered as statistically significant. Overall, and for malignant and benign lesions separately, a significant change after contrast administration in signal intensity was observed at each specific b value, irrespective of the use of 1.5 T or 3.0 T. The effect of contrast administration was overall notably different when comparing b0 (+ 9.4
To develop a dynamic contrast-enhanced (DCE) MRI protocol for imaging the aortic wall of abdominal aortic aneurysms (AAAs), and to investigate the repeatability and clinical correlation of novel biomarkers for rupture risk assessment. A dedicated DCE protocol with black-blood contrast was applied to 20 patients with AAA, of which 16 underwent a second scan 6 months later. Semiquantitative DCE-derived parameters in the aneurysm wall were calculated, assessed for test–retest repeatability using within-subject coefficient of variation (wCV), and correlated with clinical measures (aneurysm diameter and growth rate) using Spearman’s rank correlation. The developed protocol allows for accurate delineation of the aortic wall and calculation of semiquantitative DCE-derived parameters. The maximum enhancement (ME) and area under the curve (AUC) demonstrated good stability with wCVs of 14
The magnetically induced displacement force on nearby ferromagnetic objects has injured and killed people. The "quench" button dissipates the magnetic field by forcing the wire from the superconducting to the resistive state and its use in such situations should be unquestioned. Unfortunately, recent events demonstrate a reluctance to initiate a quench, perhaps because of the expense and down-time involved and the shock of confronting a rare and dire situation. Reports from various adverse incidents involving quenches also suggest a need to improve the awareness of what might happen during a quench. This review highlights relevant attributes of superconducting magnets (e.g. possible reasons for a quench, field attributes during the quench, various failure mechanisms that may occur etc.), the quench button, quench pipe, cryogen safety, and the quench sequence of events. Furthermore, it is necessary to be prepared for a rare gaseous helium release, including a nearby second safety-trained assistant, as people have been injured, incapacitated, or killed either by physical contact with a super-cooled object, hypoxia, or asphyxiation. In this regard, the development of "cryogenless" magnets demonstrates significant safety benefits. A selection of Food and Drug Administration (FDA) "Manufacturer and User Facility Device Experience" (MAUDE) incident reports illustrate these various situations, and device recalls also identify and resolve various potential, or realized, hazards, such as magnet explosions due to over-pressure and accidental cryogen release mechanisms. All users of MRI equipment must recognize when it is necessary to initiate a quench, what happens when a quench goes awry, and be prepared with quick decisions and actions. However, with small ferromagnetic objects or other non-critical situations, there may be alternative non-quench solutions. Understanding prior incidents prepares us for what might happen in a future incident and is a motivation for additional safety procedure development and training activities.
To evaluate how data acquisition and post-processing choices influence ultrashort echo time (UTE)–based characterization of the short-T2* compositional structure of the Achilles tendon. Ten healthy volunteers (33.3 ± 6.9 years) underwent Achilles tendon MRI using a multi-echo, time-interleaved UTE sequence. T2* data were analyzed with and without fat suppression using two models: (i) a bi-component decay with two water pools and (ii) a tri-component decay including two water components and one fat component. The effect of magnitude versus complex fitting on compositional estimates was also assessed. Three Achilles tendon regions were analyzed: insertion (INS), mid-portion (MID), and muscle–tendon junction (MTJ). Estimated short vs. long T2* components differed significantly depending on the use of fat suppression (p < 0.001 for all tendon regions) and fitting method (magnitude vs. complex) (pINS = 0.002, pMID < 0.001, pMTJ < 0.001). T2* time constants were comparatively stable, particularly in the MID part (p > 0.05). The fitting method affected short T2* component in the MTJ (pMTJ = 0.032) and long T2* component in the INS and MTJ (pINS = 0.025, pMTJ < 0.017). Non-fat-suppressed vs. fat-suppressed (FS) strategy and fitting approach substantially affect bi-component T2* quantification of the Achilles tendon, limiting comparability of UTE-based metrics. Tri-component modeling provides a more realistic description of tendon signal and may improve sensitivity to pathological changes. Further studies in patients are needed.
