Longitudinal Validation of Quantitative T1 MRI Measurements: A Six-Year Multi-Site Analysis Using the ISMRM/NIST Reference System

Motivation: To assess the reliability of quantitative MRI T1 measurements over time and across multiple MRI centers. Goal(s): To evaluate the consistency of T1 relaxometry across eleven centers over six years using the ISMRM/NIST phantom. Approach: Inversion-recovery T1 mapping was conducted to assess intra- and inter-site variability, comparing results to reference standards. Results: T1 values consistently remained within ±5% of reference standards across sites and time, suggesting reliable, stable measurements. This supports the use of quantitative T1 mapping in routine clinical settings and multi-center studies for disease monitoring and treatment assessment. Impact: This study demonstrates that standardized T1 relaxometry protocols yield consistent and reproducible measurements of the ISMRM/NIST phantom across multiple MRI centers over six years, supporting the clinical applicability of quantitative MRI for multi-center disease monitoring and treatment evaluation.