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Modified look-locker inversion recovery T1 mapping indices: assessment of accuracy and reproducibility between magnetic resonance scanners

Fabio S Raman1, Nadine Kawel-Boehm12, Neville Gai1, Melanie Freed3, Jing Han4, Chia-Ying Liu1, Joao AC Lima5, David A Bluemke16 and Songtao Liu16*

Author Affiliations

1 Radiology and Imaging Sciences, National Institutes of Health Clinical Center, 10 Center Drive, MSC-1182, Bethesda, MD 20892-1182, USA

2 Clinic of Radiology and Nuclear Medicine, University of Basel Hospital, Basel, Switzerland

3 New York University School of Medicine, New York, NY, USA

4 U.S. Food and Drug Administration, Rockville, MD, USA

5 Division of Cardiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA

6 Molecular Biomedical Imaging Laboratory, National Institute of Biomedical Imaging and Bioengineering, Bethesda, MD, USA

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Journal of Cardiovascular Magnetic Resonance 2013, 15:64  doi:10.1186/1532-429X-15-64

Published: 26 July 2013

Abstract

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.

Keywords:
T1 mapping; Partition coefficient (λ); Extracellular volume fraction (ECV); Diffuse myocardial fibrosis; Modified look-locker with inversion recovery (MOLLI)