Journal of Magnetic Resonance Imaging最新文献

Background: Elexacaftor/tezacaftor/ivacaftor (ETI) is a current standard therapy for pediatric cystic fibrosis (CF). Multiple-breath washout ¹²⁹Xe MRI (MBW Xe-MRI) is improved following 1 month of treatment. However, the utility of MBW Xe-MRI over extended ETI treatment and its comparison to single-breath Xe-MRI and pulmonary function tests (PFTs) in monitoring disease progression remains unclear.

Purpose: To compare MBW Xe-MRI and single-breath Xe-MRI in a small pediatric CF cohort at 1, 6, 12, and 24 months post-ETI initiation.

Study type: Prospective longitudinal cohort study.

Subjects: 14 participants (7 female, median age 15.5 [14, 17] years) with CF undergoing ETI.

Field strength/sequence: Xe-MRI using a gradient echo sequence at 3T.

Assessment: A total of 12 participants completed MBW Xe-MRI, single-breath Xe-MRI, and PFTs (spirometry, N₂ MBW) at ≥ 2 of 4 visits (1, 6, 12, and 24 months post-ETI). Fractional ventilation (FV) and FV coefficient of variation (CoV_FV) maps were calculated from MBW Xe-MRI. Ventilation defect percent (VDP) was calculated from single-breath Xe-MRI.

Statistical tests: Longitudinal changes were analyzed using a linear mixed-effects model (fixed effect: time, random intercept: participant). Significance via ANOVA F-test, p < 0.05. Intra-class correlation coefficients (ICC) were used to quantify between- and within-subject variability.

Results: Data completeness (total number of acquired data points divided by expected data points across 14 participants, 4 visits) was ≥ 75%. While PFTs/VDP remained stable over 24 months (ICC ≥ 0.93; linear mixed-effects model of time effect for ppFEV₁, LCI and VDP was not significant with p = 0.68, 0.13 and 0.12, respectively), CoV_FV demonstrated a small but significant increase (slope magnitude +0.001/month). Furthermore, two participants had elevated CoV_FV despite normal VDP. Finally, MBW Xe-MRI metrics showed higher within-subject variability than PFTs/VDP (ICC: FV = 0.41, CoV_FV = 0.55 vs. VDP/PFTs ≥ 0.92).

Data conclusion: CoV_FV may continue to evolve over 2 years in pediatric CF patients receiving ETI, particularly in individuals with persistent ventilation defects.

Evidence level: 1.

Stage of technical efficacy: 2.

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.