Background: Cardiac magnetic resonance (MR) enables assessment of myocardial oxygenation without contrast media. However, how myocardial oxygen metabolism is altered in light chain cardiac amyloidosis (AL-CA) patients remains poorly understood.
Purpose: To leverage newly developed MR techniques for the evaluation of altered myocardial oxygen metabolism in AL-CA patients.
Study type: Prospective.
Subjects: Twenty participants: 10 AL-CA patients (8 males) and 10 healthy controls (HCs; 8 males).
Sequence: 3 T, cine imaging, T1 mapping, first-pass perfusion imaging, and asymmetric spin echo prepared (ASEprep) sequence.
Assessment: All subjects underwent cine imaging for left ventricular global longitudinal strain (LVGLS), pre- and post-contrast T1 mapping for extracellular volume (ECV), and ASEprep sequence for myocardial oxygen extraction fraction (mOEF) mapping. Myocardial blood flow (MBF) was derived from first-pass perfusion images, and myocardial oxygen consumption (MVO2) and myocardial external efficiency (MEE) were quantified.
Statistical tests: T-test, U test, Firth penalized logistic regression, a one-way analysis of variance, and correlation analysis.
Results: Compared with HCs, AL-CA patients demonstrated higher mOEF (0.66 ± 0.04 vs. 0.59 ± 0.02), native T1 (1395.4 ± 109.25 vs. 1236.97 ± 41.32), and ECV (40.39 ± 8.99 vs. 25.48 ± 2.03), but lower MBF (0.08[0.08, 0.12] vs. 0.13[0.11, 0.15]), MVO2 (0.06 ± 0.01 vs. 0.08 ± 0.01), and LVGLS (-13.34 ± 3.75 vs. -17.65 ± 1.78). MEE (63.2 ± 21.18 vs. 77.15 ± 19.68, p = 0.156) in AL-CA patients was reduced, whereas total MVO2 (6.25 ± 2.98 vs. 4.6 ± 1.27, p = 0.115) was increased, though not statistically significant. mOEF correlated strongly with LV mass (r = 0.72), moderately with ECV (r = 0.60), native T1 (r = 0.64), LVGLS (r = -0.52), and MBF (r = -0.65). MVO2 correlated moderately with ECV (r = -0.57), native T1 (r = -0.56), and LV mass (r = -0.60). MEE correlated strongly with LVEF (r = 0.78) and moderately with LVGLS (r = 0.59).
Data conclusion: Our pilot cardiac MR study demonstrated the feasibility of quantifying myocardial oxygenation and mechanical efficiency in AL-CA. Elevated mOEF and reduced MBF suggest microvascular dysfunction from amyloid infiltration, while impaired MEE and increased total MVO2 underscore metabolic-mechanical uncoupling.
Evidence level: 2.
Technical efficacy: Stage 1.
Background: Accurate plane positioning is important for high-quality cardiac MRI images but requires specialized training, limiting accessibility.
Purpose: To evaluate an automated plane positioning tool and compare it with manual planning.
Study type: Prospective.
Population: Fifty-seven healthy volunteers (28 males; median age 42 years) and 20 consecutive patients (15 males; median age 61 years) scheduled for clinical cardiac MRI.
Field strength/sequence: Steady state free precession cine sequence at 1.5 T.
Assessment: In volunteers, short-axis (SAX), 2-chamber (2CH), 3-chamber (3CH), and 4-chamber (4CH) cine images were acquired using both automated and manual prescription. Two blinded radiologists (5 and 6 years of clinical cardiac MRI experience) rated plane quality on a Likert scale (1 = nondiagnostic to 5 = excellent). Mean plane angle differences between manual and automated prescriptions were calculated. Left and right ventricular end-systolic volume (ESV), end-diastolic volume (EDV), stroke volume (SV), and ejection fraction (EF) were compared. In patients, the number of required manual corrections to automated prescriptions was recorded.
Statistical analysis: Wilcoxon matched-pairs signed rank tests and Bland-Altman analyses, significance level at p ≤ 0.05.
Results: Automated plane positioning was successful in all volunteers. Image plane quality did not differ significantly between automated (mean score 4.64) and manual prescription (4.62, p = 0.812). Mean angle differences were 6.7° ± 4.3° (SAX), 10.3° ± 5.8° (2CH), 8.9° ± 5.1° (3CH), and 8.0° ± 4.8° (4CH). Volumetric parameters showed no significant differences between both planning methods with mean biases being -0.5 mL, p = 0.305 (LVEDV), 0.5 mL, p = 0.683 (LVESV), -1.0 mL, p = 0.168 (LVSV) and 0.4%, and p = 0.215 (LVEF). In patients, 8.8% (7/80) of automatically prescribed planes required minor corrections; 91.2% (73/80) were accepted without adjustments.
Data conclusion: Automated plane positioning for cardiac MRI may provide high-quality images and accurate volumetric assessment comparable to manual planning.
Evidence level: 2.
Technical efficacy: Stage 2.
Background: Although quantitative MRI can provide objective biomarkers for brain maturation assessment, unpredictable fetal movement limits its application on fetuses.
Purpose: To evaluate single-shot multiple overlapping-echo detachment (MOLED) imaging for fetal brain T2 relaxometry and to quantify fetal brain maturation using T2 relaxation time.
Study type: Phantom and prospective in vivo assessment.
Subjects: T2 phantom and 52 fetuses (mean gestational age [GA], 30.94 ± 3.62 weeks; range, 23-37 weeks).
Field strength/sequence: 3T; half-Fourier acquisition single-shot turbo spin-echo (HASTE) and MOLED sequences.
Assessment: The accuracy, motion robustness, and repeatability of 8-s MOLED T2 relaxometry were assessed using motion-free and motion phantom acquisitions. In 15 fetuses, the MOLED scan was repeated within 5 min to assess scan-rescan repeatability. Regional T2 values were determined in fetal white matter (WM), deep gray matter (dGM) and brainstem, and their changes with GA evaluated.
Statistical tests: Bland-Altman analysis, linear regression analysis (Pearson correlation coefficient, r), coefficient of variation, repeated-measures analysis of variance, and intraclass correlation coefficient. p < 0.05 was considered statistically significant.
Results: Motion-free and motion phantom acquisitions demonstrated that MOLED T2 significantly agreed with reference T2 (r = 0.99). In vivo studies reported mean T2 values for all fetuses (WM, 215.20 ms; dGM, 145.82 ms; brainstem, 125.80 ms). Scan-rescan acquisitions showed non-significant mean T2 differences (bias < 1%; limits of agreement, -8.51% to +7.78%). Regional T2 values showed significant negative correlations (r, -0.85 to -0.60) with GA. The brainstem exhibited a significantly higher rate of GA-related T2 change (3.43 ms per week) than WM and dGM (2.19 and 2.89 ms per week, respectively).
Data conclusion: MOLED imaging appears to allow motion-robust, clinically feasible, and highly repeatable T2 measurements for the whole fetal brain in 8 s. Regional differences in T2 values and age-related T2 changes demonstrate its potential for quantifying in utero brain maturation.
Evidence level: 2.
Technical efficacy: Stage 1.
Background: Magnetic resonance elastography (MRE) has demonstrated potential in characterizing intracranial tumors, including glioblastoma. The influence of pathology on measurement consistency and interobserver agreement needs evaluation to promote MRE implementation as a quantitative biomarker.
Purpose: To assess repeatability and interobserver agreement of absolute and normalized magnitude of the complex shear modulus (|G*|), storage modulus (G'), and loss modulus (G″) in glioblastoma.
Study type: Prospective.
Population: Thirteen adults (5 male, 8 female, mean age 66.23 years) with histopathologically confirmed glioblastoma.
Field strength/sequence: 3 T MRI, modified single-shot spin-echo echo-planar imaging.
Assessment: Two same-session MRE acquisitions were performed with patient repositioning. The solid tumor component was independently segmented by 2 observers on contrast-enhanced T1-weighted images co-registered to MRE maps.
Statistical tests: Repeatability was assessed using the repeatability coefficient, coefficient of variation, and Bland-Altman plots, and interobserver agreement by the intraclass correlation coefficient. The Wilcoxon signed-rank test compared parameters and coefficients of variation between tumor-normal-appearing white matter and absolute and normalized measurements. Significance was set at 0.05.
Results: Tumor |G*| and G' showed repeatability coefficients of 0.07-0.08 kPa and 0.05 kPa, compared with 0.13 kPa (|G*|) and 0.15-0.16 kPa (G') for normalized measurements. Coefficients of variation in tumor regions were 1.42% ± 1.12%-1.60% ± 1.41% for |G*| and 1.19% ± 0.96%-2.08% ± 2.22% for G', significantly lower than normalized values (4.82% ± 4.49%-4.21% ± 4.27% for |G*|; 5.12% ± 5.04%-5.45% ± 4.53% for G'). Tumor |G*| and G' showed excellent interobserver agreement (intraclass correlation coefficients 0.97 and 0.95). Tumor G″ demonstrated higher variability than |G*| and G' (coefficients of variation 8.58% ± 7.69%-7.51% ± 6.73%), with no significant difference between absolute and normalized measurements (p = 0.14).
Data conclusion: Tumor |G*| and G' are the most repeatable metrics in glioblastoma. Normalization reduces measurement repeatability due to normal-appearing white matter variability. The small sample size (n = 13) limits generalizability.
Evidence level: 2.
Technical efficacy: Stage 2.
Background: MRI is performed under sedation for patients requiring immobility or for those already sedated for clinical management. Although specialist guidelines advocate for anesthesiologist-led care, non-anesthesiologist-led adult sedation is a common practice worldwide. Furthermore, the increase in risk attributable to sedation has not been quantified.
Purpose: To investigate MRI sedation practices in Japan to quantify associated risks and to identify key safety vulnerabilities.
Study type: Survey.
Subjects: Data were collected from 549 Japanese medical institutions.
Assessment: A web-based questionnaire was distributed to members of major Japanese radiological societies to assess institutional policies, sedation management practices, safety measures, and historical adverse events. The survey primarily concerned deep sedation and general anesthesia in adults but also encompassed questions on minimal-to-moderate sedation and pediatric sedation.
Statistical tests: Chi-squared test, Welch's t-test, Fisher's exact test were used. Odds ratios (ORs) were calculated based on the cumulative number of adverse events over 2 years to examine the increased risk from sedation. p < 0.05 was considered significant.
Results: Adult MRI sedation management is typically led by attending physicians (84%) with limited consultation from anesthesiologists for sedation (9.0%) or radiologists for scan indication (5.1%). Safety infrastructure was often inadequate, with MRI-compatible ventilators (48%) or syringe pumps (29%) and capnometers (24%). In an analysis combining both pediatric and adult data, the ORs for the total sedated group versus non-sedated group were 62 (95% confidence interval, 54-73) for peripheral capillary oxygen saturation drop, 48 (32-72) for respiratory arrest, 15 (8.0-28) for cardiac arrest, 6.7 (2.0-23) for physical trauma, and 8.9 (4.0-20) for projectile accidents.
Data conclusion: MRI examinations under sedation are associated with a substantially higher risk of adverse events. Developing and implementing a standardized protocol may mitigate these procedural risks.
Level of evidence: 4:
Stage of technical efficacy: 5.
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