Abstract
BackgroundT1 mapping is widely used today in CMR, however, it underestimates true T1 values and its measurement error is influenced by several acquisition parameters. The purpose of this study was the extraction of accurate T1 data through the utilization of comprehensive, parallel Simulations for QUAntifying RElaxation Magnetic Resonance constants (SQUAREMR) of the MOLLI pulse sequence on a large population of spins with physiologically relevant tissue relaxation constants.MethodsA CMR protocol consisting of different MOLLI schemes was performed on phantoms and healthy human volunteers. For every MOLLI experiment, the identical pulse sequence was simulated for a large range of physiological combinations of relaxation constants, resulting in a database of all possible outcomes. The unknown relaxation constants were then determined by finding the simulated signals in the database that produced the least squared difference to the measured signal intensities.ResultsSQUAREMR demonstrated improvement of accuracy in phantom studies and consistent mean T1 values and consistent variance across the different MOLLI schemes in humans. This was true even for tissues with long T1s and MOLLI schemes with no pause between modified-Look-Locker experiments.ConclusionsSQUAREMR enables quantification of T1 data obtained by existing clinical pulse sequences. SQUAREMR allows for correction of quantitative CMR data that have already been acquired whereas it is expected that SQUAREMR may improve data consistency and advance quantitative MR across imaging centers, vendors and experimental configurations. While this study is focused on a MOLLI-based T1-mapping technique, it could however be extended in other types of quantitative MRI throughout the body.
Highlights
T1 mapping is widely used today in cardiovascular magnetic resonance (CMR), it underestimates true T1 values and its measurement error is influenced by several acquisition parameters
The T1 mapping technique (MOLLI) and the acquisition parameter set used in the aforementioned multicenter study are listed [14] as limiting factors in terms of accuracy when compared to other setups [8, 10]
While this study is focused on a Modified Look-Locker inversion recovery (MOLLI)-based T1 mapping technique, it could be extended in other types of quantitative MRI throughout the body
Summary
T1 mapping is widely used today in CMR, it underestimates true T1 values and its measurement error is influenced by several acquisition parameters. The complex nature of the underlying physics involved and the multitude of parameters that affect image acquisition and post-processing do not allow for consistent reference T1 values of normal myocardium and blood across all methods. Examples of this inconsistency include recent studies on cardiac T1 mapping, which have reported different ranges of T1 values for normal myocardium and blood depending on the methods being used [3, 6, 11,12,13]. The T1 mapping technique (MOLLI) and the acquisition parameter set used in the aforementioned multicenter study are listed [14] as limiting factors in terms of accuracy when compared to other setups (different T1 mapping techniques, acquisition scheme, flip angle etc.) [8, 10]
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