Shortened Modified Look-Locker Inversion recovery (ShMOLLI) for clinical myocardial T1-mapping at 1.5 and 3 T within a 9 heartbeat breathhold

Abstract

BackgroundT1 mapping allows direct in-vivo quantitation of microscopic changes in the myocardium, providing new diagnostic insights into cardiac disease. Existing methods require long breath holds that are demanding for many cardiac patients. In this work we propose and validate a novel, clinically applicable, pulse sequence for myocardial T1-mapping that is compatible with typical limits for end-expiration breath-holding in patients.Materials and methodsThe Shortened MOdified Look-Locker Inversion recovery (ShMOLLI) method uses sequential inversion recovery measurements within a single short breath-hold. Full recovery of the longitudinal magnetisation between sequential inversion pulses is not achieved, but conditional interpretation of samples for reconstruction of T1-maps is used to yield accurate measurements, and this algorithm is implemented directly on the scanner. We performed computer simulations for 100 ms<T1 < 2.7 s and heart rates 40-100 bpm followed by phantom validation at 1.5T and 3T. In-vivo myocardial T1-mapping using this method and the previous gold-standard (MOLLI) was performed in 10 healthy volunteers at 1.5T and 3T, 4 volunteers with contrast injection at 1.5T, and 4 patients with recent myocardial infarction (MI) at 3T.ResultsWe found good agreement between the average ShMOLLI and MOLLI estimates for T1 < 1200 ms. In contrast to the original method, ShMOLLI showed no dependence on heart rates for long T1 values, with estimates characterized by a constant 4% underestimation for T1 = 800-2700 ms. In-vivo, ShMOLLI measurements required 9.0 ± 1.1 s (MOLLI = 17.6 ± 2.9 s). Average healthy myocardial T1 s by ShMOLLI at 1.5T were 966 ± 48 ms (mean ± SD) and 1166 ± 60 ms at 3T. In MI patients, the T1 in unaffected myocardium (1216 ± 42 ms) was similar to controls at 3T. Ischemically injured myocardium showed increased T1 = 1432 ± 33 ms (p < 0.001). The difference between MI and remote myocardium was estimated 15% larger by ShMOLLI than MOLLI (p < 0.04) which suffers from heart rate dependencies for long T1. The in-vivo variability within ShMOLLI T1-maps was only 14% (1.5T) or 18% (3T) higher than the MOLLI maps, but the MOLLI acquisitions were twice longer than ShMOLLI acquisitions.ConclusionShMOLLI is an efficient method that generates immediate, high-resolution myocardial T1-maps in a short breath-hold with high precision. This technique provides a valuable clinically applicable tool for myocardial tissue characterisation.

Non-contrast T1-mapping detects acute myocardial edema with high diagnostic accuracy: a comparison to T2-weighted cardiovascular magnetic resonance

“…As artifacts may cause falsely high or low T1 values, it is important to have methods for assessing the quality and robustness of T1-maps, such as those used in this study (see Additional file 1). ShMOLLI underestimates the true T1 value by 4 % but in a consistent manner [16]. Thus, when comparing T1 values measured by different T1-mapping techniques, corrected T1 values and thresholds should be used.…”

Cardiac Magnetic Resonance T1 Mapping in Cardiomyopathies

“…Modern in-line processing provides registration tools to reduce motion artifacts before the computation of final T1 maps (motion-corrected or "MoCo MOLLI") [27]. A shortened Modified Look-Locker inversion recovery (shMOLLI) with shorter breath-holds has been validated and recently applied for cardiomyopathies [28,29].…”

Assessment of Myocardial Fibrosis in Hypertrophic Cardiomyopathy by Cardiac Magnetic Resonance: Modalities and Clinical Applications

“…T1 maps can be obtained at different slice levels, typically by a series of short axis images at basal, mid ventricular and apical level of left ventricle. (Figure 2) More recently, the new short MOLLI sequences (Sh MOLLI), [39] that have shorter acquisition times and are less dependent on the heart rate, provide immediate T1 maps with high resolution in less time and with high precision.…”