Magnetic Resonance Materials in Physics, Biology and Medicine最新文献

Objective: Liver regeneration after partial hepatectomy (PH) is markedly impaired in liver fibrosis, leading to serious complications. Non-invasive imaging methods for predicting regenerative capacity are crucial for preoperative planning and risk assessment. Gadobenate dimeglumine (Gd-BOPTA)-enhanced MRI at hepatobiliary phase has recently shown promise for assessing liver function. This study investigated the predictive value of Gd-BOPTA-enhanced MRI at hepatobiliary phase for liver regeneration in fibrotic rats.

Materials and methods: Thirty male Sprague-Dawley rats with experimentally induced liver fibrosis underwent Gd-BOPTA-enhanced MRI. The relative enhancement ratios of liver parenchyma (REL) and biliary system (REB) were quantified during the hepatobiliary phase. After 70% PH, the liver regeneration rate (LRR) was calculated on day 3 and 5. Stepwise multivariable linear regression was conducted to identify imaging and biochemical determinants of LRR.

Results: In fibrotic rats, the mean LRRs were 0.80 ± 0.10 (range, 0.64-1.01) and 1.06 ± 0.09 (range, 0.89-1.17) on day 3 and 5 after PH, respectively. Multivariable analysis identified REL (p = 0.002), REB (p = 0.026), and alanine aminotransferase (ALT; p = 0.040) as the strongest determinants of LRR on day 3 (Predicted LRR on day 3 = 0.368 + 1.332 × REL + 0.105 × REB - 0.001 × ALT(IU/l)). On day 5, REL (p < 0.001) and REB (p = 0.023) remained significant determinants of LRR (Predicted LRR on day 5 = 1.107 + 2.601 × REL - 0.173 × REB).

Discussion: Gd-BOPTA-enhanced MRI at hepatobiliary phase can effectively predict LRR on day 3 and 5 after partial hepatectomy in fibrotic rats.

Objective: This work investigated the performance of MRI Faraday cages (FCs) over the lifetime of clinical MRI systems, aiming to better inform an option to repurpose an existing FC when an MRI scanner is replaced.

Materials and methods: FC performance was measured at acceptance testing for 40 MRI systems and for a further 11 MRI systems of various ages. Results were compared with the MRI vendor's FC specification and with measurements made when the FCs were initially built.

Results: The majority of FCs, 63% (n = 25), had at least one measurement below specification at acceptance testing. However, no RF artefacts were observed on MR images. There were significant negative relationships between FC performance and age at the locations of the door and window (p < 0.001).

Discussion: FC performance can degrade between the time of FC manufacture and initial clinical MRI scanning. However, FC attenuation levels may need to be considerably less than specification values before external RF artefacts start appearing on MR images in practice. Further degradation of FC performance may occur over time, but this may be better addressed by maintenance on the MR exam room door rather than a much more costly and time-consuming replacement of the FC.

Objective: Quantitative Deuterium Metabolic Imaging, or DMI, is typically based on the natural abundance deuterium (²H) signal from water that is inherently present in all DMI data. The ²H level in water depends on many geographical and atmospheric factors, whereby the in vivo ²H level can be further modified through the administration and breakdown of deuterated substrates. For water to act as an internal concentration reference, the ²H enrichment needs to be determined on a regional or even per-subject basis.

Materials and methods: An NMR method is presented to quantitatively and robustly determine the ²H enrichment in water using dimethyl sulfoxide (DMSO) as an ¹H/²H internal reference. The method, employing a ¹H/²H ratio of water/DMSO ratios, is independent of the amount of water or reference. The method is readily implemented on any modern NMR spectrometer with signal acquisition based on simple, fully-relaxed pulse-acquire methods and standard NMR tubes.

Results: The double ratio method is validated on samples with known ²H enrichments and variations in ²H water content are demonstrated for bottled spring waters from across the United States, and for human blood plasma during infusions of deuterated glucose and acetate.

Discussion: The presented double ratio method is a robust and practical tool to determine ²H water enrichment on individual subjects and/or specific geographic regions.

Objective: This study compared image quality and lipid suppression efficacy between 5 and 3 T MR systems for lower-extremity non-contrast enhanced magnetic resonance angiography (NCE-MRA) using an optimized 2D time-of-flight (TOF) sequence with spatially separated lipid pre-saturation (SLIP).

Materials and methods: Ten healthy volunteers underwent 2D TOF examination on lower limbs at both field strengths. The SLIP technique was evaluated across field strengths and compared with conventional CHESS to assess lipid suppression efficiency. Subjective scoring was used to assess vessel visualization and image quality, while quantitative analysis of vessel-to-muscle contrast ratios was performed. Statistical significance was determined using paired t-tests. Three patients with Peripheral Arterial Occlusive Disease (PAOD) were evaluated at 5 T and compared to computed tomography angiography (CTA) as the reference standard.

Results: The implementation of SLIP underscores the capability of increased field strength for more effective implementation of chemical shift-based lipid suppression technique. 5 T NCE MRA demonstrated higher Likert scores of radiologists' subjective evaluations of vessel delineation (5 T vs 3 T: 3.73 vs. 3.47, P < 0.001) and image quality (3.58 vs 3.27, P = 0.002) than 3 T. Vessel-to-background ratio (VBR) (14.87 ± 3.80 vs 10.07 ± 2.64, P < 0.001) and vessel contrast-to-background ratio (VCBR) were higher at 5 T (0.84 ± 0.11 vs 0.77 ± 0.12, P < 0 .001), indicating enhanced vessel delineation than 3 T.

Conclusion: 5 T NCE-MRA outperforms 3 T in visualizing lower limb vasculature, with enhanced lipid suppression and reduced in-plane saturation artifacts, offering a non-invasive alternative for peripheral vascular assessment.

Objective: Deuterium metabolic imaging (DMI) is an emerging MR technique providing non-invasive insights into glucose metabolism. Reliable concentration estimation depends on knowledge of tissue specific relaxation times. This study reports T₁ and T₂ relaxation time constants of deuterium-labeled water (HDO) and glucose (Glc) from the human liver and kidney at 7T.

Materials and methods: Twelve healthy volunteers (6f/6 m) were examined using k-space-reordered inversion-recovery and spin-echo DMI with non-Cartesian concentric-ring trajectory (CRT) sampling. Seven volunteers underwent oral ²H-Glc (0.8 g/kg body weight) administration. Data were averaged over organ-specific masks before spectral fitting. One volunteer was measured after oral D₂O (0.5 ml/kg body weight) administration.

Results: Faster longitudinal relaxation but similar transversal relaxation were observed for ²H-labeled Glc in the liver compared to kidney tissue (T₁^liver/kidney = 60 ± 4 ms/85 ± 18 ms, p = 0.016; T₂^liver/kidney = 31 ± 6 ms/35 ± 2 ms, p = 0.283). HDO exhibited significantly shorter liver relaxation times (T₁^liver/kidney = 218 ± 24 ms/324 ± 34 ms, p < 0.001; T₂^liver/kidney = 28 ± 4 ms/39 ± 6 ms, p < 0.001). D₂O loading improved voxelwise SNR enabling renal T₁/T₂ mapping of HDO.

Discussion: Hepatic and renal glucose homeostasis is often impaired in several pathophysiological conditions such as tumors, diabetes and metabolic dysfunction-associated steatotic liver disease. Using organ-specific ²H relaxation times increases the accuracy of concentration estimation and can help to improve the understanding of underlying metabolic processes in future abdominal DMI studies, which can help to push abdominal DMI towards clinical application.

Objective: Structural MRI-based regional volumes are widely used for Alzheimer's disease (AD) classification, but inter-individual variability in intracranial volume (ICV) introduces confounding. Traditional adjustment methods use region-of-interest (ROI)/ICV ratios or residual adjustment during pre-processing, yet no consensus exists on the optimal method. This study tests whether explicitly including ICV as a covariate (ROI + ICV) improves classification compared with ratio, residual adjustment, and the unadjusted baseline.

Materials and methods: T1-weighted MRIs from ADNI1 (n = 1423) and MIRIAD (n = 69) were processed with FreeSurfer to extract eight AD-related ROI volumes and ICV. Four feature configurations (ROI-only, ROI/ICV, Residual ROI, ROI + ICV) were benchmarked across six classifiers for cognitive normal (CN)-AD, CN-mild cognitive impairment (MCI), and MCI-AD. Performance was assessed with AUROC and F1 using Friedman and post hoc tests. In addition, feature attribution was examined with permutation importance and SHAP.

Results: ROI + ICV consistently produced the largest performance gains over ROI-only in CN-AD and CN-MCI, outperforming ratio and residual adjustment across most classifiers. These improvements generalized to the independent MIRIAD dataset. SHAP analyses showed that the directional effect of ICV reversed across strategies: under ratio or residual adjustment, larger ICV decreased AD probability, whereas in ROI + ICV, larger ICV increased it. This highlights ICV's contextual influence on model decisions.

Discussion: Pre-processing-based adjustments do not fully remove ICV effects and can distort ROI-ICV relationships. Explicit covariate inclusion avoids these issues and yields more consistent, generalizable improvements. Thus, ICV should be modeled rather than removed, making ROI + ICV the preferred default ICV-handling strategy for MRI-based AD classification.

Objective: To quantify the T₁ relaxation times at 7T for key abdominal organs and tissues, including the liver, kidney, spleen, and skeletal paraspinal muscles.

Materials and methods: T₁ mapping was performed on a 7T whole-body scanner with a parallel transmission (pTx) system in five healthy volunteers. Static pTx (B₁⁺ shimming) was applied to maximize B₁⁺ magnitude in the target region. For each T₁ map, data were collected using eight snapshot gradient-echo inversion recovery sequences during breath holding. Voxel-wise T₁ values were calculated based on DICOM data using exponential model fitting.

Results: Mean abdomen T₁ values and corresponding coefficients of variation across the group were: 1829 ± 60 ms, 3.3% for the kidney cortex; 2619 ± 83 ms, 3.2% for the kidney medulla; 1378 ± 48 ms, 3.5% for the liver; 1954 ± 28 ms, 1.4% for the skeletal paraspinal muscle; 1770 ± 36 ms, 2.0% for the spleen.

Conclusion: In this study, we quantified the T₁ relaxation times at 7T for key abdominal organs and tissues, including the liver, kidney, spleen, and skeletal paraspinal muscle. To achieve this, pTx was applied to mitigate B₁⁺ dropouts in the target regions. The B₁⁺ insensitive snapshot gradient-echo inversion recovery method was utilized to acquire accurate and reproducible T₁ maps.

Objective: This review aims to summarize the research progress of magnetic resonance imaging (MRI)-based deep learning ( DL) in meningiomas, analyze its advantages, limitations, and key issues in clinical translation, provide technical references for relevant medical researchers and clinicians, thereby promoting the faster and more standardized application of DL in clinical diagnosis and treatment, and ultimately benefiting patients.

Background: The early detection and accurate grading and classification of meningiomas are crucial for formulating personalized treatment plans. DL has achieved breakthrough progress in the field of meningioma imaging analysis. By adopting objective and quantitative analysis methods, it effectively overcomes the limitation of traditional diagnostic methods that rely on subjective human visual judgment, opening up broad prospects for the precise diagnosis and treatment of meningiomas.

Methods: The literature search and selection process for this review was conducted as follows: Search period: 1 January 2019 to 31 October 2024; Databases searched: PubMed, Web of Science, and Embase; Search string: (("meningioma" OR "meningiomas") AND ("magnetic resonance imaging" OR "MRI") AND ("deep learning" OR "convolutional neural network" OR "CNN" OR "transformer" OR "neural network" OR "neural networks")).

Conclusions: The application of DL in meningioma research marks that medical imaging diagnosis has entered a new intelligent stage. By providing doctors with more objective and accurate diagnostic basis, it facilitates the formulation of personalized treatment plans, thereby improving patients' treatment outcomes and quality of life. The continuous breakthroughs of DL in the field of meningiomas indicate that the future of medical imaging diagnosis will be more intelligent and precise.

Objective: To investigate the physiological factors affecting the timing of late arterial phase imaging in gadolinium-ethoxybenzyl-diethylenetriamine-pentaacetic acid-enhanced MRI (EOB-MRI), with a focus on contrast transit times.

Methods: This retrospective study included 122 patients who underwent EOB-MRI between April and September 2024. Contrast transit times from the right atrium to the left ventricle (RA-LV time) and to the celiac artery (RA-CeA time) were measured using real-time bolus-tracking images. Using vascular enhancement patterns, the late arterial phase timing was visually assessed and categorized as Early, Appropriate, or Delayed. Differences among the imaging timing groups were analyzed using analysis of variance (ANOVA) and post hoc Welch's t tests with Holm correction, with a significance threshold of p < 0.05.

Results: Mean RA-LV times (mean ± SD, range) were 7.0 ± 1.1 s (5.0-9.0 s), 5.2 ± 0.9 s (4.0-8.0 s), and 4.7 ± 0.6 s (4.0-6.0 s) for the Early, Appropriate, and Delayed groups, respectively; significant differences were observed between Early vs. Appropriate (p < 0.001) and Appropriate vs. Delayed (p = 0.02). Correspondingly, RA-CeA times were 12.4 ± 2.0 s (10.0-15.0 s), 8.9 ± 1.8 s (5.0-14.0 s), and 7.7 ± 1.1 s (6.0-10.0 s), respectively, with significant differences between Early vs. Appropriate (p < 0.001) and Appropriate vs. Delayed (p = 0.001). Additionally, significant differences in sex and height were observed between the Early and Appropriate groups (p < 0.01). No other variables showed significant differences.

Conclusion: Contrast transit times significantly affect the appropriateness of late arterial phase imaging in EOB-MRI. Incorporating individualized transit time assessment alongside conventional bolus tracking may improve the consistency of late arterial phase acquisition and enhance the performance for diagnosing hepatic tumors.

In-cell nuclear magnetic resonance (NMR) spectroscopy has emerged as a leading technique in structural biology, providing atomic-level insights into the structures, dynamics, and interactions of biomolecules within their native cellular environments. By bridging the gap between conventional in vitro studies and the complexity of living systems, in-cell NMR enables direct observation of biomolecular behavior under near-physiological conditions. This review highlights recent methodological advances that have expanded the scope and feasibility of in-cell NMR. Innovations in isotopic labeling, including selective incorporation strategies, have enhanced spectral resolution and sensitivity. Optimized delivery approaches, such as microinjection and electroporation, facilitate efficient introduction of labeled biomolecules into diverse cell types. The use of cryogenically cooled probes and high-field magnets further improves signal detection, enabling the study of low-abundance targets. We discuss key applications, including protein folding, conformational dynamics, biomolecular interaction networks, and nucleic acid structural rearrangements. In addition, in-cell NMR has proven invaluable for drug discovery, providing mechanistic insights into intracellular drug-target interactions. Despite these advances, challenges remain, including spectral overlap from endogenous components, low intracellular concentrations, and maintaining cell viability during extended experiments. Future developments integrating cryo-electron microscopy (cryo-EM), mass spectrometry (MS), hyperpolarization techniques, and advanced labeling strategies promise to enhance sensitivity, resolution, and applicability, solidifying in-cell NMR as an indispensable tool for probing biomolecular function in living cells.