Technical challenges in establishing local native T1 reference ranges in cardiac MRI: a critical review

Establishing local reference ranges for native T1 in healthy myocardium is critical in cardiac magnetic resonance imaging (CMR) for the accurate detection of myocardial fibrosis and other tissue abnormalities. However, native T1 measurements vary widely and are sensitive to technical factors such as the magnetic field strength, static magnetic field (B0) and radiofrequency (B1) homogeneities, differences in MRI scanners across various vendors, imaging protocols, and specific acquisition parameters employed. These variabilities have consequently hindered the direct comparison of T1 values across different studies and centers. This review aims to evaluate the main technical challenges and methodological inconsistencies that impact the establishment of local native T1 reference ranges in CMR, and review proposals for mitigation, harmonization, and standardization strategies designed to enhance comparability across CMR platforms. A comprehensive literature search was conducted focusing on myocardial native T1 mapping using the modified Look-Locker inversion recovery (MOLLI) technique and its variants, as well as on alternative T1 mapping sequences like ShMOLLI, SASHA, SMART1Map, and SAPPHIRE. Reported native T1 values in healthy myocardium were found to be inconsistent across studies, driven by differences in the magnetic field strength, static magnetic field (B0), and radiofrequency (B1) homogeneities, and vendor-specific hardware and software configurations. Standardization of T1 mapping protocols, including standardized imaging parameters and vendor-specific reference adjustment, is therefore necessary to improve the comparability and reliability of myocardial T1 values across CMR centers. In addition, a robust quality assurance (QA) program and effective quality control (QC) measures are pivotal in ensuring the reliability and consistency of the measurements. KEY POINTS: Question How do technical factors and scanner-specific variabilities hinder the establishment of reliable local native T1 reference ranges for accurate myocardial tissue characterization? Findings Standardization of acquisition parameters, vendor-specific benchmarks, and robust quality assurance programs effectively minimize inter-scanner variability, ensuring reliable and comparable native myocardial T1 measurements across centers. Critical relevance statement This review identifies technical drivers of T1 variability and proposes a standardization framework, enabling clinicians to establish accurate local reference ranges and improve diagnostic comparability across diverse platforms in clinical radiology practice.