Feasibility of Myocardial Late Gadolinium Enhancement MRI at 5T versus 3T for Myocardial Fibrosis Assessment

Academic Background

Myocardial fibrosis is a common pathological feature of various cardiac diseases, and accurate assessment of myocardial fibrosis is crucial for diagnosis, treatment, and prognosis. Cardiac magnetic resonance imaging (MRI) is currently an important tool for evaluating myocardial structure and function, particularly the late gadolinium enhancement (LGE) technique, which can precisely visualize areas of myocardial fibrosis. The principle of LGE is based on the increased extracellular space and reduced capillary density in fibrotic regions, leading to prolonged retention of gadolinium contrast agents in these areas.

In recent years, ultra-high-field MRI devices, especially 5T MRI, have entered the market. Compared to traditional 3T MRI, 5T MRI has potential advantages in tissue contrast and signal-to-noise ratio (SNR). However, ultra-high-field MRI also faces several challenges in cardiac imaging, such as magnetic field inhomogeneity, increased radiofrequency energy deposition, and interference with electrocardiogram signals due to magnetohydrodynamic effects. Therefore, the feasibility and clinical value of 5T MRI in myocardial fibrosis assessment remain open questions.

Research Objective

This study aims to evaluate the feasibility of 5T myocardial LGE MRI in assessing myocardial fibrosis by comparing image quality and LGE quantification with reference-standard 3T myocardial LGE MRI.

Research Methods

Study Design and Participants

This prospective study adhered to the Declaration of Helsinki and was approved by the Ethics Committee of Peking Union Medical College Hospital. All participants provided written informed consent before enrollment. The study included patients who underwent 3T cardiac MRI between January 2023 and July 2023 and were diagnosed with myocardial fibrosis, followed by 5T MRI examinations between August 2023 and November 2023. Exclusion criteria included MRI contraindications (e.g., metal implants) or refusal to participate. Each participant received the same dose of gadolinium contrast agent.

Myocardial LGE MRI Examination

Participants were first examined on a 3T MRI scanner (Siemens Healthineers Magnetom Skyra) using an 18-channel body matrix coil and a 32-channel spine array coil. They were then re-examined on a 5T MRI scanner (United Imaging Healthcare UMR Jupiter) using an 8-channel volumetric transmit coil and a 24-channel body receive coil, along with the upper portion of a 48-channel spine receive coil. All sequences were electrocardiogram-triggered and performed during breath-holding. LGE images were acquired 10 minutes after intravenous administration of gadopentetate dimeglumine (0.15 mmol/kg) using a phase-sensitive inversion-recovery gradient-echo pulse sequence in long-axis and short-axis views.

Image Quality Assessment

LGE images were independently assessed by three radiologists (with 4, 12, and 19 years of cardiac MRI experience, respectively) using a Likert scale (1–5 points) to rate image quality. Additionally, signal intensities were measured in the LGE region, normal myocardium, left ventricular cavity, and pericardial fat, and SNR and contrast-to-noise ratio (CNR) were calculated.

LGE Quantification

LGE quantification was performed using dedicated software (CVI42, version 5.12), calculating the percentage of LGE area relative to the left ventricle.

Statistical Analysis

Statistical analyses were performed using SPSS software (version 26). Normally distributed data were expressed as mean and standard deviation, while non-normally distributed data were expressed as median and interquartile range. Continuous variables were compared using paired t-tests and Wilcoxon signed-rank tests. Bland-Altman analysis was used to assess inter-field agreement in SNR and CNR.

Results

Participant Characteristics

The study ultimately included 18 participants (mean age 49 ± 17 years, 9 males and 9 females), with a mean interval of 6.2 ± 2.3 months between 3T and 5T MRI examinations.

Safety Assessment

The specific absorption rate (SAR) values for all participants did not exceed the limits set by the International Electrotechnical Commission standard 60601-2-33. One patient experienced shortness of breath at the beginning of the examination and was unable to complete it, while the remaining participants reported no MRI-related adverse reactions.

Image Quality

The median image quality scores for 5T and 3T MRI were both 4.0 (p = 0.45), indicating no significant difference in subjective image quality. The SNR of 5T MRI was significantly higher than that of 3T MRI (median 183.7 vs. 125.8, p = 0.002). The CNR for normal myocardium and pericardial fat was also significantly higher in 5T MRI compared to 3T MRI (p < 0.001).

LGE Quantification

There was no significant difference in LGE quantification between 5T and 3T MRI (median 11.8% vs. 12.6%, p = 0.81), and the correlation between the two was excellent (r = 0.98, p < 0.001).

Discussion

This study is the first to evaluate the performance of 5T myocardial LGE MRI in assessing myocardial fibrosis and compare it with 3T MRI. The results show that 5T MRI has no significant difference in image quality and LGE quantification compared to 3T MRI, while SNR and CNR are significantly improved. These findings provide preliminary evidence for the clinical application of 5T MRI in myocardial fibrosis assessment.

The advantages of ultra-high-field MRI in cardiac imaging are mainly reflected in the improvement of SNR and CNR, which can be used to enhance spatial resolution, shorten acquisition time, and reduce respiratory and cardiac motion artifacts. Additionally, 5T MRI offers higher contrast in visualizing complex structures such as pericardial fat, which can improve the accuracy and reproducibility of myocardial fibrosis detection.

However, this study has some limitations, such as being a single-center study with a small sample size and a time interval between 3T and 5T MRI examinations. Future studies with larger sample sizes and randomized examination orders are needed to further validate the performance of 5T MRI.

Conclusion

5T myocardial LGE MRI is feasible for myocardial fibrosis assessment, with no significant difference in image quality and quantification compared to 3T MRI, and significantly improved SNR and CNR. This study provides important evidence for the clinical application of 5T MRI in cardiac imaging.

Research Highlights

1. Key Findings: 5T MRI demonstrates comparable image quality and quantification ability to 3T MRI in myocardial fibrosis assessment, with significantly improved SNR and CNR.
2. Significance: This study addresses the feasibility of ultra-high-field MRI in cardiac imaging, providing preliminary evidence for its clinical application.
3. Methodological Innovation: The study adopts a prospective design and ensures result reliability through rigorous image quality assessment and quantitative analysis.
4. Specificity of Study Population: The study focuses on patients with myocardial fibrosis, offering a new technical option for imaging assessment in this specific population.

Research Value

The scientific value of this study lies in its systematic evaluation of the performance of 5T MRI in myocardial fibrosis assessment, providing important evidence for its clinical application in cardiac imaging. The practical value is reflected in the potential of 5T MRI to improve image quality, shorten examination time, and reduce contrast agent dosage, making it a promising future option for cardiac MRI.