Journal of Magnetic Resonance Imaging最新文献

Background: 0.55T systems offer unique advantages and may support expanded access to cardiac MRI.

Purpose: To assess the feasibility of 0.55T cardiac MR Fingerprinting (MRF), leveraging a deep image prior reconstruction to mitigate noise.

Study type: Phantom and prospective in vivo assessment.

Population: ISMRM/NIST MRI system phantom and 18 healthy subjects (11 female; ages 28 ± 8 years).

Field strength and sequences: MRF, modified Look-Locker inversion recovery (MOLLI), and T₂-prepared balanced steady state free precession (T₂-bSSFP) at 0.55T.

Assessment: MRF T₁ and T₂ maps were reconstructed using (1) a low-rank technique with sparse and locally low-rank regularization (SLLR-MRF) and (2) a deep image prior (DIP-MRF). Accuracy and precision of MRF and conventional sequences were evaluated in a phantom. In vivo performance of MRF was evaluated in the 18 healthy subjects, with 7 subjects also undergoing conventional mapping. Myocardial T₁ and T₂ values were compared among methods and image quality scored by three readers (2, 3, and 4 years of experience) on a 5-point scale.

Statistical tests: Linear regression, Bland-Altman, intraclass correlation coefficient, and one-way ANOVA with p < 0.05 considered significant.

Results: Mean measurements in the left ventricular septum were 671 ± 31 ms (MOLLI), 761 ± 147 ms (SLLR-MRF), and 686 ± 39 ms (DIP-MRF) for T₁, and 63.5 ± 5.7 ms (T₂-bSSFP), 47.5 ± 12.7 ms (SLLR-MRF), and 45.2 ± 4.5 ms (DIP-MRF) for T₂. Compared to conventional mapping, DIP-MRF exhibited significantly lower T₂ but no differences in T₁ (p > 0.99). Standard deviations within the myocardium were significantly lower with DIP-MRF compared to SLLR-MRF (39 vs. 147 ms for T₁ and 4.5 vs. 12.7 ms for T₂). Overall image quality ratings were significantly lower for SLLR-MRF (T₁: 2.3, T₂: 2.9), which were significantly lower compared to conventional mapping methods (T₁: 3.4, T₂: 3.9), and DIP-MRF (T₁: 3.8, T₂: 4.1) received higher scores.

Data conclusion: This study demonstrated the feasibility of cardiac MRF on a commercial 0.55T system, enabled by a deep image prior reconstruction for denoising.

Evidence level: 2.

Stage of technical efficacy: 1.

Background: Gadopiclenol is a high-relaxivity contrast agent enabling dose reduction while maintaining image quality. However, comparison with conventional agents remains limited in body MRI.

Purpose: To intra-individually compare half-dose gadopiclenol and standard-dose gadobenate for image quality and lesion conspicuity in abdominal MRI.

Study type: Retrospective.

Population: One hundred patients (55 men; mean age: 64 ± 14 years) who underwent both abdominal MRI with gadobenate (0.1 mmol/kg) and gadopiclenol (0.05 mmol/kg) on the same scanner within 12 months.

Field strength/sequence: 1.5T/3T, dynamic T1-weighted imaging pre-contrast, early arterial (EAP), late arterial (LAP), portal venous (PVP), and equilibrium phases (EP) using 3D fat-suppressed gradient echo sequence.

Assessment: Signal intensity of liver, pancreas, spleen, kidneys, aorta, portal vein, and abdominal lesions was measured on each phase except EAP. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and magnitude of contrast enhancement (ΔE) were calculated for organs. In lesions, lesion-to-background ratio (LBR) and ΔE were calculated. Subjective image quality and lesion conspicuity were assessed by three readers using a 5-point Likert scale.

Statistical tests: Paired t-test and Wilcoxon test. p < 0.05 indicated statistically significant results.

Results: Gadopiclenol yielded significantly higher CNR and SNR for pancreas, portal vein, and kidney in LAP. No significant differences in CNR (p: 0.372-0.858) and SNR (p: 0.433-0.936) were found in PVP. In EP, gadobenate showed higher hepatic CNR, while CNR and SNR of all other organs were comparable (p: 0.103-0.912). Gadopiclenol showed higher pancreatic ΔE in all enhanced phases. LBR and ΔE of 21 evaluated lesions were comparable across all phases (p: 0.100-0.821). No significant differences were observed in readers' perception of lesion enhancement (p: 0.059-0.957).

Conclusion: Half-dose gadopiclenol provides comparable subjective image quality and lesion conspicuity to standard-dose gadobenate, with superior pancreatic, kidney, and portal vein enhancement in LAP, and similar performance in PVP and EP.

Level of evidence: 4:

Background: FDG-PET aids presurgical epilepsy evaluation but is limited by access and radiation exposure.

Purpose: To evaluate synthetic FDG-PET generated from T1-weighted imaging and resting-state fMRI metrics.

Study type: Retrospective.

Population: 481 participants underwent simultaneous FDG PET/MR. Internal cohort: 311 epilepsy patients split into training/validation/internal test sets (n = 249/31/31; age 18.79 ± 16.33/22.20 ± 11.21/21.65 ± 17.62 years; male/female 145/104, 13/18, 22/9). External cohort: 115 temporal lobe epilepsy patients (age 25.36 ± 10.95 years; male/female 68/47) and 55 healthy controls (age 27.62 ± 5.82 years; male/female 24/31); 92 had surgery with 1-year outcome.

Field strength: Hybrid PET/MR at 3.0 T; gradient-echo T1WI, echo-planar imaging and resting-state BOLD gradient-echo EPI.

Assessment: Performance was assessed using SSIM, PSNR, MSE, NRMSE, SUVR correlation, and Bland-Altman analysis. Three blinded readers performed visual quality grading and detection of temporal lobe hypometabolism. Hippocampal radiomics was used for classification of hippocampal sclerosis and Engel outcome.

Statistical tests: t-tests, chi-square tests, Pearson correlation, Kolmogorov-Smirnov tests, DeLong tests, and false discovery rate correction.

Results: Excellent/Good visual ratings occurred in 82.8% (166/201), with Fleiss' κ = 0.42. SSIM was 0.98 ± 0.01 (internal) and 0.97 ± 0.01 (external); PSNR was 66.66 ± 1.25 and 64.16 ± 1.83, respectively. SUVR correlation with ground-truth PET was r = 0.94 (internal) and r = 0.89 (external); Bland-Altman bias was -0.02 (95% limits of agreement: -0.22 to 0.18) internally and -0.00002 (95% limits: -0.35 to 0.35) externally. Detection accuracy for temporal hypometabolism was 90.3% (internal; κ = 0.735) and 87.1% (external; κ = 0.758). Radiomics AUCs using synthetic PET were 0.72 (95% CI: 0.62-0.83) for hippocampal sclerosis versus healthy controls and 0.77 (95% CI: 0.67-0.87) for Engel IA versus IB-IV; DeLong tests versus ground-truth PET were non-significant (p = 0.56 and p = 0.48).

Conclusion: Multisequence MRI-based synthetic PET showed high agreement with ground-truth PET across image-quality and quantitative SUVR metrics, providing a PET-like metabolic surrogate when FDG-PET is unavailable or impractical.

Level of evidence: Evidence Level 3.

Stages of technical efficacy: Stage 3.

Background: Impaired myocardial microvascular function may promote cardiac remodeling (CR) and myocardial fibrosis (MF), increasing cardiovascular risks in athletes. Early assessment of myocardial microcirculatory perfusion presents potential for improving athlete care.

Purpose: To evaluate the characteristics of myocardial microvascular function in athletes using resting cardiac MRI first-pass perfusion.

Study type: Prospective.

Population: One hundred and eighty-six athletes (median age 24 years, range 18-57; 167 males; mean 10 h/week exercise for 5 years) and 43 controls (median age 25 years, range 21-56; 35 males; < 3 h/week exercise).

Field strength/sequence: Balanced steady-state free precession, gradient echo sequence, and phase sensitive inversion recovery late gadolinium enhancement sequences at 3.0 T.

Assessment: CR was defined as any cardiac parameters exceeding the 99th percentile upper reference limits. MF was visually evaluated by three independent radiologists. Left ventricular resting first-pass perfusion parameters were assessed and compared across different groups. A predictive model was developed to screen athletes with and without CR/MF.

Statistical tests: Univariate analysis and Pearson coefficient were used. Area under the receiver operating characteristic curve (AUC) was used to assess the performance of the predictive model. A p < 0.05 was considered significant.

Results: Athletes exhibited lower upslope (2.12 [1.72; 2.56] vs. 2.77 [1.94; 3.22]) and maximum signal intensity (MaxSI) (20.8 [18.3; 23.6] vs. 29.5 [26.8; 33.0]), longer time to maximum signal intensity (TTM) (35.1 [31.0; 47.7] vs. 29.5 [26.8; 33.0] s) than controls. Male athletes with CR and/or MF showed lower upslope (1.54 [1.29; 1.96] vs. 1.94 [1.62; 2.43]) and MaxSI (18.0 [15.5; 21.7] vs. 21.2 [19.0; 23.5]), higher TTM (40.3 [31.5; 53.9] vs. 34.5 [29.0; 44.0] s) than those without. These perfusion parameters of athletes showed a negative correlation with global T2 mapping, QRS and corrected QT interval (r = -0.210 to -0.292). The AUC for the prediction model of CR and/or MF was 0.837.

Data conclusion: Athletes showed lower resting myocardial perfusion than controls, especially in those with CR and/or MF, suggesting an association between perfusion reduction and CR/MF.

Evidence level: 1.

Technical efficacy: Stage 2.

Background: Autism Spectrum Disorder (ASD) presents with early neurodevelopmental alterations in preschool children, yet comprehensive characterization using multimodal quantitative MRI remains limited in this age group.

Purpose: To investigate voxel-wise brain microstructural differences in preschool ASD through integrated analysis of cerebral perfusion, multiparametric relaxometry, and magnetic susceptibility.

Study type: Prospective case-control.

Population: Twenty nine-children with ASD (age 2-6 years; 23 males/6 females) and 25 age-/sex-matched healthy controls (HC).

Field strength/sequence: 3.0 T MRI; high-resolution 3D-T1WI, quantitative susceptibility mapping (QSM), synthetic MRI (SyMRI), 3D pseudo-continuous arterial spin labeling (3D-pCASL).

Assessment: Clinical assessments included the Gesell Developmental Schedules (GDS) and Childhood Autism Rating Scale (CARS). Imaging analysis consisted of voxel-wise whole-brain assessment of QSM, T1/T2/PD, and cerebral blood flow (CBF) maps.

Statistical tests: General linear models with cluster-based thresholding were applied for group comparison; Spearman's rank correlation with Bonferroni correction was used for clinical associations; and receiver operating characteristic (ROC) analysis with Delong's test was performed to compare diagnostic performance based on the areas under the curve (AUCs).

Results: Compared to HC, children with ASD showed decreased QSM values in the left superior/middle frontal gyri (SFG/MFG; cluster = 212 voxels, peak T = 5.55, p < 0.001). They also had reduced T1 relaxation times in bilateral SFG/MFG/precentral/postcentral gyri (four clusters: 315-750 voxels, peak T = 5.11-5.88, all p < 0.001). QSM values in the left SFG/MFG correlated positively with fine motor scores (r = 0.630, p < 0.001), while T1 values in the bilateral precentral/postcentral gyri correlated with gross motor scores (right: r = 0.548, p = 0.002; left: r = 0.461, p = 0.012). ROC analysis showed high diagnostic accuracy for both QSM (left SFG/MFG AUC = 0.858) and T1 values (left SFG/MFG AUC = 0.905; bilateral precentral/postcentral gyri AUC = 0.892-0.908).

Data conclusion: Preschool ASD demonstrates prefrontal iron deficiency (reduced QSM) and sensorimotor myelination alterations (decreased T1), which correlate with motor deficits and show high diagnostic efficacy.

Evidence level: 2.

Technical efficacy: Stage 2.

Overview of metabolism that can be probed with hyperpolarized tracers. Pyruvate lies at an important fate of metabolism with several different products offering insights into several enzymes. The labeling position of choice determines the metabolites able to be measured. Fumarate and malate are two important intermediaries in the TCA cycle where measurement offers an insight into cellular death. By Khan and Laustsen (310–327).