BACKGROUND: Cardiovascular magnetic resonance (CMR) T1 mapping indices, such as 
T1 time and partition coefficient (λ), have shown potential to assess diffuse 
myocardial fibrosis. The purpose of this study was to investigate how scanner 
and field strength variation affect the accuracy and precision/reproducibility 
of T1 mapping indices.
METHODS: CMR studies were performed on two 1.5T and three 3T scanners. Eight 
phantoms were made to mimic the T1/T2 of pre- and post-contrast myocardium and 
blood at 1.5T and 3T. T1 mapping using MOLLI was performed with simulated heart 
rate of 40-100 bpm. Inversion recovery spin echo (IR-SE) was the reference 
standard for T1 determination. Accuracy was defined as the percent error between 
MOLLI and IR-SE, and scan/re-scan reproducibility was defined as the relative 
percent mean difference between repeat MOLLI scans. Partition coefficient was 
estimated by ΔR1myocardium phantom/ΔR1blood phantom. Generalized linear mixed 
model was used to compare the accuracy and precision/reproducibility of T1 and λ 
across field strength, scanners, and protocols.
RESULTS: Field strength significantly affected MOLLI T1 accuracy (6.3% error for 
1.5T vs. 10.8% error for 3T, p<0.001) but not λ accuracy (8.8% error for 1.5T 
vs. 8.0% error for 3T, p=0.11). Partition coefficients of MOLLI were not 
different between two 1.5T scanners (47.2% vs. 47.9%, p=0.13), and showed only 
slight variation across three 3T scanners (49.2% vs. 49.8% vs. 49.9%, p=0.016). 
Partition coefficient also had significantly lower percent error for precision 
(better scan/re-scan reproducibility) than measurement of individual T1 values 
(3.6% for λ vs. 4.3%-4.8% for T1 values, approximately, for pre/post blood and 
myocardium values).
CONCLUSION: Based on phantom studies, T1 errors using MOLLI ranged from 6-14% 
across various MR scanners while errors for partition coefficient were less 
(6-10%). Compared with absolute T1 times, partition coefficient showed less 
variability across platforms and field strengths as well as higher precision.