Journal of Magnetic Resonance Imaging最新文献

Background: Lumbar disc herniation (LDH) causes compositional alterations within compressed nerve roots, resulting in low back pain (LBP). The ultrashort echo time magnetization transfer technique (UTE-MT) facilitates assessment of macromolecular changes in collagen- or myelin-rich tissues in nerve roots.

Purpose: To assess lumbar nerve root composition in LDH using UTE-MT.

Study type: Prospective.

Population: One hundred and seventy-six participants (age range, 20-89; 72 females) with LDH.

Field strength/sequence: 3T/UTE-MT, Carr-Purcell-Meiboom-Gill (CPMG).

Assessment: UTE-MT ratio (UTE-MTR) and T₂ value in compressed nerve roots (determined on axial T₂) were evaluated by UTE-MT and CPMG in LDH patients (L4/5-L5/S1). Additionally, pain and functionality were evaluated using the visual analog scale (VAS) and Oswestry Disability Index (ODI).

Statistical tests: Linear regression and Bland-Altman assessed UTE-MT reproducibility. One-way ANOVA assessed the statistical significance of UTE-MTR and T₂ measures between compressed and intact nerve roots. ROC and DCA evaluated diagnostic performance and clinical value of UTE-MTR and T₂ in discriminating between compressed and intact nerve roots. Linear regression correlated UTE-MTR and T₂ with pain and functionality scores. The p value < 0.05 was considered significant.

Results: Significant increases in UTE-MTR and decreases in T₂ values in compressed nerve roots compared to intact ones. High AUC values for UTE-MTR (0.912 at L4/5 and 0.900 at L5/S1) highlighted its superior ability to distinguish between compressed and intact nerve roots, outperforming T₂ (AUCs of 0.840 and 0.790, respectively) in cohort discrimination. Strong significant positive correlations were found between UTE-MTR and VAS (R² = 0.63) and ODI (R² = 0.62), while T₂ values showed moderate significant negative correlations with VAS (R² = 0.32) and ODI (R² = 0.32) for the measurement of the most severely compressed nerve roots (determined on axial T₂).

Data conclusion: UTE-MT technique can detect macromolecular alterations in the compressed nerve roots of patients diagnosed with LDH.

Level of evidence: 1:

Technical efficacy: Stage 2.

Background: Bleeding risk assessment of esophageal varices (EVs) is commonly performed in liver cirrhosis. However, existing approaches are often invasive or insufficient to fully capture bleeding risk.

Purpose: To investigate portal venous hemodynamics and vessel geometry associated with EVs severity in cirrhotic patients using four-dimensional flow MRI as a noninvasive approach to support clinical risk assessment.

Study type: Retrospective.

Population: One-hundred and four cirrhotic patients consisting of patients without EVs (Group 1, n = 48), with low-risk EVs (Group 2, n = 37), and high-risk EVs (Group 3, n = 19).

Field strength/sequence: 3 T, a three-directional, velocity-encoded gradient echo sequence with Cartesian k-space sampling.

Assessment: Flow rate, mean velocity, and fractional flow changes in main portal vein (PV); effective vessel diameter and vessel angle; and rotational flow including vorticity, helicity, helical flow intensity (h₂), localized normalized helicity, and vortex volume.

Statistical tests: One-way ANOVA with Tukey's post hoc test or Kruskal-Wallis followed by Conover's post hoc test. Receiver operating characteristic (ROC) curve analysis. Significance level set at p < 0.05.

Results: Significant group differences were observed for flow rate at the proximal PV (ε² = 0.05) and for mean PV velocity at both proximal (ε² = 0.13) and distal locations (η² = 0.11). In contrast, neither fractional portal venous flow nor vessel angle measurements differed across groups (p = 0.294 and all p ≥ 0.475, respectively). Among rotational flow biomarkers, vorticity differentiated Group 3 from both Groups 1 and 2 (Group 1: 17.86 ± 3.26 s^-1, Group 2: 16.65 ± 4.58 s^-1, Group 3: 13.59 ± 3.23 s^-1; η² = 0.15), with an area under the ROC curve of 0.77 (sensitivity = 0.79, specificity = 0.62).

Data conclusion: Rotational flow biomarkers may support current risk assessment in cirrhotic patients with high-risk EVs.

Evidence level: 4.

Technical efficacy: Stage 2.

Background: Major adverse cardiovascular events (MACE) are a leading cause of morbidity and mortality in patients with end-stage renal disease (ESRD). However, risk stratification and prognostic prediction remain limited.

Purpose: To assess the incremental prognostic value of combined left atrial (LA) and left ventricular (LV) strain in predicting MACE among ESRD patients receiving renal replacement therapy.

Study type: Prospective.

Population: Three hundred thirteen ESRD patients (mean age: 53.8 ± 14.0 years; 202 males) undergoing maintenance dialysis.

Field strength/sequence: Balanced steady-state free precession (bSSFP) cine sequence at 3.0 T.

Assessment: Myocardial strain was analyzed from bSSFP cine images using feature-tracking software (CVI42). LA strain components were reservoir (LARS), conduit (LAScd), and contractile (LASct) strain, and LV strain included global longitudinal (GLS), radial (GRS), and circumferential (GCS) strain. Patients were followed up via clinical records and MACE were documented. Prognostic models were constructed using multivariable Cox proportional hazards regression. The baseline prediction model of conventional cardiovascular risk factors was then compared with models incorporating LARS and GLS to assess incremental prognostic value.

Statistical tests: Cox proportional hazards regression identified predictors of MACE, and model performance was evaluated using C-index, Akaike and Bayesian information criteria (AIC/BIC), and Kaplan-Meier analysis. p < 0.05 was considered significant.

Results: During a median follow-up of 16.93 months, 61 patients developed MACE. LARS (hazard ratio (HR) 0.90, 95% confidence interval (CI) 0.87-0.94) and LV GLS (HR 1.21, 95% CI 1.08-1.36) were independent predictors. The Cox model incorporating both LARS and LV GLS showed improved discrimination compared with the clinical risk factor model (C-index 0.79 vs. 0.70). Stratification by both LA and LV strain markers significantly improved MACE prediction (log-rank: p < 0.001).

Data conclusion: The integration of LA and LV strain offered superior prognostic value for MACE prediction in ESRD patients, enabling refined risk stratification beyond traditional measures.

Evidence level: 2.

Technical efficacy: Stage 3.

Background: Although deep learning reconstruction (DLR) has been shown to improve image quality in MRI, its impact on quantitative physiologic parameters derived from diffusion-weighted imaging (DWI) and dynamic susceptibility contrast (DSC) perfusion in brain tumor imaging remains unclear.

Purpose: To evaluate the impact of DLR on quantitative parameters derived from DWI and DSC in patients with brain tumors.

Study type: Retrospective.

Subjects: Sixty-two patients (33 male) with post-radiation brain metastasis.

Field strength/sequence: 3.0 T; T2, FLAIR, T1WI, DWI, DSC perfusion, and contrast-enhanced T1WI.

Assessment: DWI and DSC images were reconstructed at three DLR levels (high, medium, and low). Agreement between original and DLR images for apparent diffusion coefficient (ADC), cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), and time to peak (TTP) was assessed using the coefficient of variation, repeatability coefficient (RC), and concordance correlation coefficient. For DSC time-series, signal-to-noise ratio, root mean square error (RMSE), and mean absolute error (MAE) were computed within tumor masks. DWI comparisons used mean signal intensity at b = 0 and b = 1000.

Statistical tests: Paired t-tests compared ADC, relative CBV, and DWI signals. RMSE and MAE were compared using repeated-measures analysis of variance. Significance was set at p < 0.05.

Results: ADC (p = 0.955-0.979) and CBV (p = 0.341-0.708), CBF (p = 0.684-0.983), and MTT (p = 0.403-0.971) values showed no significant differences between original and DLR images, while high-level DLR showed significantly higher TTP than original images. RCs demonstrated high reproducibility across DLR levels for ADC (21.78-22.20), CBV (0.88-0.96), CBF (27.98-34.18), MTT (1.26-1.50), and TTP (3.40-3.99). DSC analysis showed the best noise reduction with high-level DLR (lowest RMSE, 254.62 and MAE, 253.18 of DSC) without compromising CBV quantification.

Data conclusion: DLR effectively reduced noise in DWI and DSC while preserving quantitative accuracy of ADC, CBV, CBF, and MTT. DLR may enable robust physiological MRI when applied in brain tumor imaging.

Level of evidence: 3:

Technical efficacy: Stage 3.

Magnetic resonance imaging (MRI) has emerged as a noninvasive technique for probing the electrical properties of biological tissues: electrical conductivity and relative permittivity. This review focuses on the electrical conductivity and provides a comprehensive overview of applications across both low- and high-frequency regimes. At low frequencies (below 1 MHz), conductivity mapping primarily reflects tissue microstructure and ionic composition. In contrast, at high frequencies (around 100 MHz), tissue conductivity primarily reflects ionic composition. First, we summarize the theoretical foundations, technical developments, and reconstruction algorithms that underpin conductivity imaging, highlighting advances in magnetic resonance electrical impedance tomography, current density imaging, and electrical properties tomography. The main part of the article discusses preclinical and clinical applications, demonstrating the potential and possible roles of conductivity imaging in clinical settings, along with current challenges and emerging applications. Finally, we outline future directions toward integrating conductivity imaging into routine MRI protocols, with the potential to enhance diagnostic precision and therapeutic monitoring. EVIDENCE LEVEL: 1. TECHNICAL EFFICACY: Stage 3.

Whole-body magnetic resonance imaging (WB-MRI) has attracted attention recently for multi-organ assessment. Although there is a body of literature on diagnostic performance as well as recommendations for use in particular high-risk subpopulations who require whole-body surveillance, WB-MRI has also entered the consumer market as a screening tool for average-risk individuals. For this latter purpose, there are proposed health-related benefits as well as controversies about the potential benefits and harms. The multi-disease screening of asymptomatic, average-risk groups with MRI, often with very low pre-test probability of clinically significant lesions or with limited detectability of disorders on imaging, signifies a major divergence from conventional screening principles. In some scenarios, it is plausible that WB-MRI improves disease detection and improves health outcomes, while lessening the inconvenience of multiple tests that each evaluate for a single-disease. However, the testing efficiency, clinical utility, and cost-effectiveness of large-scale implementation of screening WB-MRI are not established. In this narrative review, we highlight potential strengths and drawbacks based on the limited evidence to date. Awareness of the pathway for rigorous assessment of potential benefits and harms and current gaps in evidence may better guide research and inform implementation as interest in screening WB-MRI evolves. LEVEL OF EVIDENCE: 5. TECHNICAL EFFICACY: Stage 2.